Dissertationen: „Rainfall characteristics“

1

Phakula, Steven. „Modelling seasonal rainfall characteristics over South Africa“. Diss., University of Pretoria, 2016. http://hdl.handle.net/2263/60851.

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Aspects of seasonal forecast skill using global climate models (GCMs) are assessed over South Africa. The GCMs output is configured to predict low and high number of rainfall days exceeding predefined threshold values for the summer rainy seasons and to predict the rainfall totals of the onset of the rainy seasons for eight homogeneous rainfall regions of South Africa. Using canonical correlation analysis (CCA) as statistical downscaling tool the forecast skill levels of both coupled ocean-atmosphere and uncoupled atmospheric models are determined through retro-actively generated hindcasts. Both approaches have skill in predicting the low and high number of rainfall days exceeding predefined threshold values for the summer rainy seasons as well as rainfall totals of onset of the rainy seasons for the homogeneous rainfall regions. In addition to the forecast verification results, CCA pattern analysis is also performed to determine the dominating atmospheric circulation systems predicted to be controlling rainfall variations for the seasons of interest. CCA pattern analysis for both the GCMs indicate that when there are anomalously negative (positive) predicted 850hPa geopotential heights over South Africa, there are anomalously wet (dry) rainfall conditions over the most part of South Africa for the different seasons of interest. This work has paved the way for the operational production of seasonal rainfall characteristics over South Africa.
Dissertation (MSc)--University of Pretoria, 2016.
Geography, Geoinformatics and Meteorology
MSc
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Angelis, Carlos Frederico de. „Rainfall characteristics over tropical and subtropical South America“. Thesis, University of Birmingham, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.410573.

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3

Gamoyo, Majambo Jarumani. „Rainfall variability characteristics over the East African coast“. Master's thesis, University of Cape Town, 2012. http://hdl.handle.net/11427/10571.

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Includes bibliographical references.
This study explores inter-annual rainfall variability over the East African coast region (Kenya and Tanzania) for the period 1980-2010 and focuses on dry and wet spell characteristics during the two rainy seasons. The atmospheric and ocean conditions associated with the rainfall variability are also considered. Extreme occurrences of rainfall variable can result in droughts and floods which in turn may lead to socioeconomic disruptions. East Africa is highly dependent and vulnerable to the amounts and timing of rainfall.

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4

Liu, An. „Influence of rainfall and catchment characteristics on urban stormwater quality“. Thesis, Queensland University of Technology, 2011. https://eprints.qut.edu.au/48324/1/An_Liu_Thesis.pdf.

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This thesis presents the outcomes of a comprehensive research study undertaken to investigate the influence of rainfall and catchment characteristics on urban stormwater quality. The knowledge created is expected to contribute to a greater understanding of urban stormwater quality and thereby enhance the design of stormwater quality treatment systems. The research study was undertaken based on selected urban catchments in Gold Coast, Australia. The research methodology included field investigations, laboratory testing, computer modelling and data analysis. Both univariate and multivariate data analysis techniques were used to investigate the influence of rainfall and catchment characteristics on urban stormwater quality. The rainfall characteristics investigated included average rainfall intensity and rainfall duration whilst catchment characteristics included land use, impervious area percentage, urban form and pervious area location. The catchment scale data for the analysis was obtained from four residential catchments, including rainfall-runoff records, drainage network data, stormwater quality data and land use and land cover data. Pollutants build-up samples were collected from twelve road surfaces in residential, commercial and industrial land use areas. The relationships between rainfall characteristics, catchment characteristics and urban stormwater quality were investigated based on residential catchments and then extended to other land uses. Based on the influence rainfall characteristics exert on urban stormwater quality, rainfall events can be classified into three different types, namely, high average intensity-short duration (Type 1), high average intensity-long duration (Type 2) and low average intensity-long duration (Type 3). This provides an innovative approach to conventional modelling which does not commonly relate stormwater quality to rainfall characteristics. Additionally, it was found that the threshold intensity for pollutant wash-off from urban catchments is much less than for rural catchments. High average intensity-short duration rainfall events are cumulatively responsible for the generation of a major fraction of the annual pollutants load compared to the other rainfall event types. Additionally, rainfall events less than 1 year ARI such as 6- month ARI should be considered for treatment design as they generate a significant fraction of the annual runoff volume and by implication a significant fraction of the pollutants load. This implies that stormwater treatment designs based on larger rainfall events would not be feasible in the context of cost-effectiveness, efficiency in treatment performance and possible savings in land area needed. This also suggests that the simulation of long-term continuous rainfall events for stormwater treatment design may not be needed and that event based simulations would be adequate. The investigations into the relationship between catchment characteristics and urban stormwater quality found that other than conventional catchment characteristics such as land use and impervious area percentage, other catchment characteristics such as urban form and pervious area location also play important roles in influencing urban stormwater quality. These outcomes point to the fact that the conventional modelling approach in the design of stormwater quality treatment systems which is commonly based on land use and impervious area percentage would be inadequate. It was also noted that the small uniformly urbanised areas within a larger mixed catchment produce relatively lower variations in stormwater quality and as expected lower runoff volume with the opposite being the case for large mixed use urbanised catchments. Therefore, a decentralised approach to water quality treatment would be more effective rather than an "end-of-pipe" approach. The investigation of pollutants build-up on different land uses showed that pollutant build-up characteristics vary even within the same land use. Therefore, the conventional approach in stormwater quality modelling, which is based solely on land use, may prove to be inappropriate. Industrial land use has relatively higher variability in maximum pollutant build-up, build-up rate and particle size distribution than the other two land uses. However, commercial and residential land uses had relatively higher variations of nutrients and organic carbon build-up. Additionally, it was found that particle size distribution had a relatively higher variability for all three land uses compared to the other build-up parameters. The high variability in particle size distribution for all land uses illustrate the dissimilarities associated with the fine and coarse particle size fractions even within the same land use and hence the variations in stormwater quality in relation to pollutants adsorbing to different sizes of particles.

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Szyniszewska, Anna Maria. „Determining the daily rainfall characteristics from the monthly rainfall totals in central and northeastern Thailand“. [Gainesville, Fla.] : University of Florida, 2009. http://purl.fcla.edu/fcla/etd/UFE0025162.

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6

NHAT, Le Minh. „Development of Intensity-Duration-Frequency Relationships Based on Scaling Characteristics of Rainfall Extremes“. 京都大学 (Kyoto University), 2008. http://hdl.handle.net/2433/124493.

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7

Oliveira, Rômulo Augusto Jucá. „Characteristics and error modeling of GPM satellite rainfall estimates during CHUVA campaign in Brazil“. Instituto Nacional de Pesquisas Espaciais (INPE), 2017. http://urlib.net/sid.inpe.br/mtc-m21b/2017/05.22.17.16.

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Studies that investigate and evaluate the quality, limitations and uncertainties of satellite rainfall estimates are fundamental to assure the correct and successful use of these products in applications, such as climate studies, hydrological modeling and natural hazard monitoring. Over regions of the globe that lack in situ observations, such studies are only possible through intensive field measurement campaigns, which provide a range of high quality ground measurements, e.g., CHUVA (Cloud processes of tHe main precipitation systems in Brazil: A contribUtion to cloud resolVing modeling and to the GlobAl Precipitation Measurement) and GoAmazon (Observations and Modeling of the Green Ocean Amazon) over the Brazilian Amazon during 2014/2015. This study aims to assess the uncertainty of the Global Precipitation Measurement (GPM) satellite constellation in representing the main characteristics of precipitation over different regions of Brazil. The Integrated Multi-satellitE Retrievals for GPM (IMERG) (level-3) and the Goddard Profiling Algorithm (GPROF) (level-2) algorithms are evaluated against ground-based radar observations, specifically, the S-band weather radar from the Amazon Protection National System (SIPAM) and the X-band dual polarization weather radar (X-band CHUVA radar) as references. The space-based rainfall estimates, based on active microwave (e.g., TRMM-PR and GPM-DPR [at Ku-band] radars) are also used as references. The results for the CHUVA-Vale campaign suggest that GPROF has relatively good agreement (spatial distribution and accumulated rainfall), especially for convective rain cases, due the significant presence of ice scattering. However, the intensity and volume of light/moderate rains is overestimated and performance related to light/heavy rains (underestimated) are intrinsically linked to convectivestratiform rainfall occurrences over the study region. For the study over the Central Amazon Region (CHUVA-GoAmazon), results showed that during the wet season, IMERG, which uses the GPROF2014 rainfall retrieval from the GPM Microwave Imager (GMI) sensor, significantly overestimates the frequency of heavy rainfall volumes at around 00:0004:00 UTC and 15:0018:00 UTC. This overestimation is particularly evident over the Negro, Solimões and Amazon rivers due to the poorlycalibrated algorithm over water surfaces. On the other hand, during the dry season, the IMERG product underestimates mean precipitation in comparison to the S-band SIPAM radar, mainly due to the fact that isolated convective rain cells in the afternoon are not detected by the satellite precipitation algorithm. The study based on verification of GPM level 2 by traditional and object-based analysis shows that volume and occurrence of heavy rainfall are underestimated, a good agreement of GPROF2014 for TMI and GMI versus TRMM PR and GPM DPR (Ku band) rainfall retrievals, respectively, was noted. Such most evident good performances were found through continuous and categorical analyses, especially during the wet season, where the number of objects and larger areas were observed. The larger object area seen by GPROF2014(GMI) compared to DPR (Ku band) was directly linked to the structure of vertical profiles of the precipitanting systems and the presence of bright band was the main source of uncertainty on the estimation of precipitation area and intensity. The results via error modeling, through the Precipitation Uncertainties for Satellite Hydrology (PUSH) framework, demonstrated that the PUSH model was suitable for characterizing the error from the IMERG algorithm when applied to S-band SIPAM radar estimates. PUSH could efficiently predict the error distribution in terms of spatial and intensity distributions. However, an underestimation (overestimation) of light satellite rain rates was observed during the dry (wet) period, mainly over the river. Although the estimated error showed a lower standard deviation than the observed error, they exhibited good correlations to other, especially in capturing the systematic error along the Negro, Solimões and Amazon rivers, especially during the wet season.
Estudos que investigam e avaliam a qualidade, limitações e incertezas das estimativas de precipitação de satélites são fundamentais para assegurar o uso correto e bem-sucedido desses produtos em aplicações, como estudos climáticos, modelagem hidrológica e monitoramento de desastres naturais. Em regiões do globo que não possuem observações in situ, esses estudos apenas são possíveis através de campanhas intensivas de medição de campo, que oferecem uma gama de medições de superfície de alta qualidade, por exemplo, CHUVA (Cloudprocesses of tHe main precipitation systems in Brazil: A contribUtion to cloud re-solVing modeling and to the GlobAl Precipitation Measurement) e GoAmazon (Observations and Modeling of the Green Ocean Amazon) sobre a Amazônia Brasileira durante 2014/2015. Este estudo tem como objetivo avaliar as incertezas provenientes da constelação de satélites do Global Precipitation Measurement (GPM) em representar as principais características da precipitação em diferentes regiões do Brasil. Os algoritmos Integrated Multi-satellitE Retrievals for GPM (IMERG) (level-3) e Goddard Profiling Algorithm (GPROF) (level-2) são avaliados em contraste as observações de radares meteorológicos, especificamente, do Sistema Nacional de Proteção da Amazônia (SIPAM) e o radar meteorológico banda X de dupla polarização (X-band CHUVA radar) como referência. As estimativas de precipitação, baseadas em radares de microondas ativos (por exemplo, radares TRMM-PR e GPM-DPR [na banda Ku]) também são utilizadas como referência. Os resultados da campanha CHUVA-Vale sugerem que o GPROF possui uma boa concordância (distribuição espacial e precipitação acumulada), especialmente para casos de chuva convectiva, devido à presença significativa de espalhamento por gelo. No entanto, a intensidade e volume de chuvas leves/moderadas é superestimada e um desempenho (subestimado) relacionado às chuvas fracas/intensas diretamente ligado às ocorrências de chuvas convectivasestratiformes na região do estudo. Para o estudo da região da Amazônia Central (CHUVA-GoAmazon), os resultados mostraram que, durante a estação chuvosa, o IMERG, que utiliza as estimativas de precipitação do GPROF2014 a partir do sensor GPM Microwave Imager (GMI), superestima significativamente a freqüência de chuvas intensas em torno de 00:00-04:00 UTC e 15:00-18:00 UTC. Essa superestimativa é particularmente evidente nos rios Negro, Solimões e Amazonas devido ao algoritmo apresentasse erroneamente calibrado sobre as superfícies de água. Por outro lado, durante a estação seca, o produto IMERG subestima a precipitação média em comparação com o radar banda-s do SIPAM, principalmente devido ao fato de que células convectivas isoladas à tarde não são detectadas por tal algoritmo. O estudo baseado na verificação das estimativas do GPM Level 2 por abordagens tradicional e baseada em objeto mostra que, embora a subestimiativa do volume e ocorrência de chuvas intensas, foi observada uma boa concordância do GPROF2014 (TMI e GMI) versus TRMM PR e GPM DPR (Ku band), Respectivamente. Tais evidentes melhores desempenhos foram encontrados através de análises contínua e categórica, especialmente durante a estação chuvosa, onde o maior número e maiores áreas de objetos foram observados. As maiores áreas, observadas pelo GPROF2014 (GMI) comparada ao DPR (banda Ku) esteve diretamente ligada à estrutura de perfis verticais dos sistemas de precipitantes e a presença de banda brilhante foi a principal fonte de incerteza na estimativa da área e intensidade de precipitação. Os resultados referentes à modelagem do erro, através da ferramenta Precipitation Uncertainties for Satellite Hydrology (PUSH), as análises demonstraram que o modelo PUSH foi adequado para caracterizar o erro do algoritmo IMERG quando aplicado às estimativas de radar banda S do SIPAM. O modelo PUSH pôde prever eficientemente a distribuição de erro em termos espaciais e de intensidade. No entanto, observou-se uma subestimativa (superestimativa) das taxas de chuva fracas do satélite durante o período seco (chuvoso), especialmente ao longo do rio. Embora o erro estimado tenha apresentado menor desvio padrão do que o erro observado, eles apresentaram boas correlações entre si, especialmente na captura do erro sistemático ao longo dos rios Negro, Solimões e Amazonas, especialmente durante a estação chuvosa.

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Boening, Kathryn Margaret. „Impacts of Green Infrastructure Practices and Rainfall Characteristics on Sewershed Hydrology and Water Quality“. The Ohio State University, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=osu1595352797878418.

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9

Crawford, T. „Future climate change : modelling the implications of shifts in rainfall characteristics for runoff in Northern Ireland“. Thesis, Queen's University Belfast, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.479249.

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10

Diaz, de Arends Miriam Leonarda. „Ecophysiology and phenology of very dry tropical forest trees : effects of soil characteristics, rainfall and irrigation“. Thesis, University of Cambridge, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.624548.

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11

Zheng, Tingting. „Mathematical modeling of soil erosion by rainfall and shallow overland flow“. Thesis, Loughborough University, 2011. https://dspace.lboro.ac.uk/2134/9144.

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New analytical and numerical solutions are developed to both the kinematic approximation to the St Venant equations and the Hairsine-Rose (HR) soil erosion model in order to gain a better physical understanding of soil erosion and sediment transport in shallow overland flow. The HR model is unique amongst physically based erosion models in that it is the only one that: considers the entire distribution of the soil s sediment size classes, considers the development of a layer of deposited non-cohesive sediment having different characteristics to the original underlying cohesive soil and considers separately the erosion processes of rainfall detachment, runoff entrainment and gravitational deposition. The method of characteristics and the method of lines were used to develop both the analytical and numerical solutions respectively. These solutions were obtained for boundary and initial conditions typical of those used in laboratory flume experiments along with physically realistic constant and time dependent excess rainfall rates. Depending on the boundary and initial conditions, interesting new solutions of the kinematic wave equation containing expansion waves, travelling shocks as well as solutions which split into an upslope and downslope drying profiles were found. Numerical solutions of the HR model were applied to the experimental flume data of Polyakov and Nearing (2003) obtained under flow conditions which periodically cycled between net erosion and net deposition conditions. While excellent agreement was found with suspended sediment data, the analysis suggested that an additional transport mechanisms, traditionally not included in soil erosion models, was occurring. While the inclusion of bed-load transport improved the ii overall model prediction, it was still not sufficient. Subsequent asymptotic analysis then showed that the interaction of the flow with an evolving bed morphology was in fact far more important than bed load transport. A very interesting finding from this work showed that the traditional criterion of validating sediment transport model based solely on suspended sediment data was not sufficient as reliable predictions could be obtained even when important transport mechanisms were neglected. Experimental plots of sediment discharge or suspended sediment concentration against water discharge in overland flow have been shown to contain significant hysteresis between the falling and rising limbs of the discharge hydrograph. In the final Chapter, the numerical solution developed for the complete system of soil erosion and kinematic flow was used to show that it was possible for the HR model to simulate three of the four hysteresis loops identified in the literature. Counter clock-wise loops, clock-wise loops and figure 8 loops could all be produced as a result of starting with different initial conditions, being mi(x; 0) = 0, mi(x; 0) = pimt and mi(x; 0) = 0:5pimt respectively. This is the first time that these types of hysteresis loops have been produced by any erosion model. The generation of these hysteresis loops are physically explainable in terms of sediment availability and is consistent with data obtained on the field scale.

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Alias, Noraliani Binti. „First flush behaviour in urban residential catchments“. Thesis, Queensland University of Technology, 2013. https://eprints.qut.edu.au/63811/1/Noraliani_Alias_Thesis.pdf.

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The current state of knowledge in relation to first flush does not provide a clear understanding of the role of rainfall and catchment characteristics in influencing this phenomenon. This is attributed to the inconsistent findings from research studies due to the unsatisfactory selection of first flush indicators and how first flush is defined. The research study discussed in this thesis provides the outcomes of a comprehensive analysis on the influence of rainfall and catchment characteristics on first flush behaviour in residential catchments. Two sets of first flush indicators are introduced in this study. These indicators were selected such that they are representative in explaining in a systematic manner the characteristics associated with first flush. Stormwater samples and rainfall-runoff data were collected and recorded from stormwater monitoring stations established at three urban catchments at Coomera Waters, Gold Coast, Australia. In addition, historical data were also used to support the data analysis. Three water quality parameters were analysed, namely, total suspended solids (TSS), total phosphorus (TP) and total nitrogen (TN). The data analyses were primarily undertaken using multi criteria decision making methods, PROMETHEE and GAIA. Based on the data obtained, the pollutant load distribution curve (LV) was determined for the individual rainfall events and pollutant types. Accordingly, two sets of first flush indicators were derived from the curve, namely, cumulative load wash-off for every 10% of runoff volume interval (interval first flush indicators or LV) from the beginning of the event and the actual pollutant load wash-off during a 10% increment in runoff volume (section first flush indicators or P). First flush behaviour showed significant variation with pollutant types. TSS and TP showed consistent first flush behaviour. However, the dissolved fraction of TN showed significant differences to TSS and TP first flush while particulate TN showed similarities. Wash-off of TSS, TP and particulate TN during the first 10% of the runoff volume showed no influence from corresponding rainfall intensity. This was attributed to the wash-off of weakly adhered solids on the catchment surface referred to as "short term pollutants" or "weakly adhered solids" load. However, wash-off after 10% of the runoff volume showed dependency on the rainfall intensity. This is attributed to the wash-off of strongly adhered solids being exposed when the weakly adhered solids diminish. The wash-off process was also found to depend on rainfall depth at the end part of the event as the strongly adhered solids are loosened due to impact of rainfall in the earlier part of the event. Events with high intensity rainfall bursts after 70% of the runoff volume did not demonstrate first flush behaviour. This suggests that rainfall pattern plays a critical role in the occurrence of first flush. Rainfall intensity (with respect to the rest of the event) that produces 10% to 20% runoff volume play an important role in defining the magnitude of the first flush. Events can demonstrate high magnitude first flush when the rainfall intensity occurring between 10% and 20% of the runoff volume is comparatively high while low rainfall intensities during this period produces low magnitude first flush. For events with first flush, the phenomenon is clearly visible up to 40% of the runoff volume. This contradicts the common definition that first flush only exists, if for example, 80% of the pollutant mass is transported in the first 30% of runoff volume. First flush behaviour for TN is different compared to TSS and TP. Apart from rainfall characteristics, the composition and the availability of TN on the catchment also play an important role in first flush. The analysis confirmed that events with low rainfall intensity can produce high magnitude first flush for the dissolved fraction of TN, while high rainfall intensity produce low dissolved TN first flush. This is attributed to the source limiting behaviour of dissolved TN wash-off where there is high wash-off during the initial part of a rainfall event irrespective of the intensity. However, for particulate TN, the influence of rainfall intensity on first flush characteristics is similar to TSS and TP. The data analysis also confirmed that first flush can occur as high magnitude first flush, low magnitude first flush or non existence of first flush. Investigation of the influence of catchment characteristics on first flush found that the key factors that influence the phenomenon are the location of the pollutant source, spatial distribution of the pervious and impervious surfaces in the catchment, drainage network layout and slope of the catchment. This confirms that first flush phenomenon cannot be evaluated based on a single or a limited set of parameters as a number of catchment characteristics should be taken into account. Catchments where the pollutant source is located close to the outlet, a high fraction of road surfaces, short travel time to the outlet, with steep slopes can produce high wash-off load during the first 50% of the runoff volume. Rainfall characteristics have a comparatively dominant impact on the wash-off process compared to the catchment characteristics. In addition, the pollutant characteristics also should be taken into account in designing stormwater treatment systems due to different wash-off behaviour. Analysis outcomes confirmed that there is a high TSS load during the first 20% of the runoff volume followed by TN which can extend up to 30% of the runoff volume. In contrast, high TP load can exist during the initial and at the end part of a rainfall event. This is related to the composition of TP available for the wash-off.

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Gusli, Sikstus. „Effect of methods of wetting and rainfall characteristics on crusting and hardsetting of a red-brown earth“. Title page, abstract and table of contents only, 1995. http://web4.library.adelaide.edu.au/theses/09PH/09phg982.pdf.

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Includes bibliographical references. The beneficial effects of tillage are often negated in Australian soils by poor aggregate structural stability. If irrigation or rain falls on exposed freshly tilled soil, crusting or harsetting often develops on drying. Rainfall intensity, kinetic energy, rate of wetting, antecedent water content and soil management history have been implicated in aggregate breakdown.

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Jobin, Erik. „An Urban Rainfall Storm Flood Severity Index“. Thèse, Université d'Ottawa / University of Ottawa, 2013. http://hdl.handle.net/10393/24124.

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Extreme rainfall statistics are important for the design and management of the water resource infrastructure. The standard approach for extreme rainfall event severity assessment is the Intensity-Duration-Frequency (IDF) method. However, this approach does not consider the spatial context of rainfall and consequently does not properly describe rainfall storm severity, nor rarity. This study provides a critical account of the current standard practice and presents an approach that takes into consideration both the spatial context of rainfall storms, and indirectly incorporates runoff to produce a representative approach to assessing urban rainfall storm severity in terms of flood potential. A stepwise regression analysis was performed on a dataset of individual rainfall storm characteristics to best represent documented basement floodings in the City of Edmonton. Finally, the urban rainfall storm flood severity index was shown to be most representative of the documented basement floodings' severity when compared to that of the IDF method.

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Toba, T., und T. Ohta. „An observational study of the factors that influence interception loss in boreal and temperate forests“. Elsevier, 2005. http://hdl.handle.net/2237/6939.

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Little, Kathryn Leigh. „Using Electrical Resistivity Imaging to Relate Surface Coal Mining Valley Fill Characteristics to Effluent Stream Quality“. Thesis, Virginia Tech, 2018. http://hdl.handle.net/10919/94131.

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Surface coal mining has altered Appalachian landscapes, affecting water quality and aquatic ecology. Valley fills created from excess overburden are prominent features of many mined landscapes. Increased total dissolved solids (TDS), as measured by its surrogate specific conductance (SC), is a significant water quality concern related to the exposure of fresh mineral surfaces to weathering in valley fills. Specific conductance levels in waters draining Appalachian mined areas are highly variable, yet the causes for this variability are not well known. Here we sought to improve understanding of such variability by investigating the interior subsurface structure and hydrologic flowpaths within a series of valley fills and relating that to valley fill characteristics such as age and construction method. We used electrical resistivity imaging (ERI) to investigate the subsurface structure of four valley fills in two dimensions. We combined ERI with artificial rainfall to investigate the location and transit time of hydrologic preferential infiltration flowpaths through the fills. Finally, we used our ERI results in conjunction with SC data from effluent streams to improve understanding of SC relationship to fill flowpaths and characteristics. ERI results indicated considerable variability in substrate type and widespread presence of preferential infiltration flowpaths among the valley fills studied. We estimated an average preferential flowpath length of 6.6 meters, average transit time of 1.4 hours, and average velocity of 5.1 m/h or 0.14 cm/s through preferential infiltration flowpaths. ERI successfully distinguished fills constructed using methods of conventional loose-dump and experimental controlled-material compacted-lift construction. Conventional fills had greater ranges of subsurface resistivity, indicating a wider range of substrate types and/or more variable moisture content. Conventional fills also showed more accumulation of water within the fill during artificial rainfall, possibly indicating more quick/deep preferential infiltration flowpaths than in the experimental fill. Relationships between other fill characteristics as well as stream effluent SC were not related in a statistically significant way to fill structure or flowpaths. ERI appears to be a robust non-invasive technique that provides reliable information on valley fill structure and hydrology, and experimental compacted-lift valley fill construction produces significantly altered hydrologic response, which in turn affects downstream SC.
MS

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Haule, Kallisto L. „The influence of rainfall distribution, landscape positions and soil characteristics on the evaluation of land resources for rainfed agriculture in Tanzania“. Thesis, University of Reading, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.358213.

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Chen, Liping. „Soil Characteristics Estimation and Its Application in Water Balance Dynamics“. Thesis, University of North Texas, 2008. https://digital.library.unt.edu/ark:/67531/metadc9789/.

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This thesis is a contribution to the work of the Texas Environmental Observatory (TEO), which provides environmental information from the Greenbelt Corridor (GBC) of the Elm Fork of the Trinity River. The motivation of this research is to analyze the short-term water dynamic of soil in response to the substantial rainfall events that occurred in North Texas in 2007. Data collected during that year by a TEO soil and weather station located at the GBC includes precipitation, and soil moisture levels at various depths. In addition to these field measurements there is soil texture data obtained from lab experiments. By comparing existing water dynamic models, water balance equations were selected for the study as they reflect the water movement of the soil without complicated interrelation between parameters. Estimations of water flow between soil layers, infiltration rate, runoff, evapotranspiration, water potential, hydraulic conductivity, and field capacity are all obtained by direct and indirect methods. The response of the soil at field scale to rainfall event is interpreted in form of flow and change of soil moisture at each layer. Additionally, the analysis demonstrates that the accuracy of soil characteristic measurement is the main factor that effect physical description. Suggestions for model improvement are proposed. With the implementation of similar measurements over a watershed area, this study would help the understanding of basin-scale rainfall-runoff modeling.

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Silva, Gerald Norbert Souza da. „Regionalização automatizada de parâmetros de modelos chuva-vazão integrada a um sistema de informações geográficas“. Universidade Federal da Paraíba, 2012. http://tede.biblioteca.ufpb.br:8080/handle/tede/5466.

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Made available in DSpace on 2015-05-14T12:09:08Z (GMT). No. of bitstreams: 1 arquivototal.pdf: 7934601 bytes, checksum: 83089393956abb6b7fa32c5295791684 (MD5) Previous issue date: 2012-03-30
Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES
A major difficulty for studies of small hydrological watersheds is the lack of good quality time series of hydrologic data, mainly because the flow rates in small watersheds are not monitored. Another important issue is that available rainfall runoff models are almost always developed focusing on watersheds of medium and large scale. Regionalization studies have become an important tool to attempt to overcome these limitations. Suitable in most of the hydrological studies is the regionalization of rainfall runoff-model parameters by using specific characteristics of a watershed. A tool was developed in a Geographic Information System which automatically gets the physical characteristics of watersheds from a digital elevation model by selecting the outlet and then generating the rainfall runoff model parameters with neural networks. This study uses data from small dams in the semi-arid region of northeastern Brazil. The developed methodology is applied using target watersheds for the parameter estimation. The results show that the developed tool can be very useful for rainfall runoff estimation in small watersheds.
Uma das maiores dificuldades para os estudos de pequenas bacias hidrográficas é a falta de séries históricas de dados hidrológicos, principalmente porque a fluviometria em pequenas bacias hidrográficas não é monitorada. Outra questão importante é que, os modelos chuva-vazão disponíveis quase sempre são desenvolvidos com foco em bacias de médio e grande porte. Estudos de regionalização se tornaram uma ferramenta importante para tentar superar essas limitações. A regionalização de parâmetros de modelos chuva-vazão, usando características específicas das bacias hidrográficas, é adequada para a maioria dos estudos hidrológicos. Uma ferramenta foi desenvolvida em um Sistema de Informação Geográfica, que determina automaticamente as características físicas das bacias hidrográficas a partir de um modelo digital de elevação, e, em seguida, gera os parâmetros do modelo chuva-vazão com redes neurais artificiais. Este trabalho usa dados de pequenas barragens na região semiárida do Nordeste do Brasil. A metodologia desenvolvida é aplicada e avaliada utilizando também o método da bacia meta para a estimativa dos parâmetros. Os resultados mostram que a ferramenta desenvolvida pode ser muito útil para o estudo da relação chuva-vazão em bacias hidrográficas de pequeno porte.

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Kloppers, Pierre-Louis. „Investigating the relationships between wheat-specific rainfall characteristics, large-scale modes of climate variability and wheat yields in the Swartland region, South Africa“. Master's thesis, University of Cape Town, 2014. http://hdl.handle.net/11427/13214.

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Includes bibliographical references.
Wheat producers in the South Western Cape (SWC) of South Africa need to cope with biophysical and socio-economic systems exposing farmers to a multidimensional decision- making environment. The rain fed wheat production in the Swartland region is highly susceptible to the interannual variability of winter rainfall. Producers, therefore, need relevant climatic information to identify ways to improve profitability and to make sound economic decisions. Seasonal forecasting has the potential to provide wheat producers with invaluable information regarding the climatic conditions. However, due to the complex nature of the atmospheric dynamics associated with winter rainfall in South Africa, seasonal forecasting models have been found to have very little skill in predicting the variability of winter rainfall. Such a shortfall has created a gap for which this study has attempted to bridge. This study aimed to investigate the relationship between wheat-specific rainfall characteristics, large-scale modes of climate variability and wheat yields in the Swartland region to assess whether these relationships could provide useful climatic information to the wheat farmers. Six wheat-specific rainfall characteristics (total rainfall ; number of wet days ; number of ‘good’ rainfall events; number of heavy rainfall events; percentage ‘good’ rainfall ; and the number of dry dekads ) on various time scales (winter; seasonal; monthly and dekadal) were correlated against wheat yield records over a 17 year period from 1994 to 2010. From this analysis, the distribution and timing of the rainfall throughout the wheat growing season (April to September) emerged as an important determinant of wheat yield. An accurate statistical wheat prediction model was created using farmer stipulated rainfall- wheat yield thresholds. Three teleconnections (El Niño-Southern Oscillation [ENSO], Antarctic Oscillation [AAO] and South Atlantic sea surface temperatures [SSTs]) represented by eight climate indices (Nino 3.4 Index, Ocean Nino Index [ONI], Southern Oscillation Index [SOI], AAO index, Southern Annular Mode Index [SAM], South Atlantic Dipole Index [SADI], South Western Atlantic SST Index [SWAI] and South Central Atlantic SST Index [SCAI]), were correlated against wheat yield data over a 17 year period from 1994 to 2010. The relationships between the three teleconnections and wheat yield in the Swartland were established. Teleconnection-wheat yield correlations were found to be limited, with regards to the application of this information to farmers, due to the lack of a comprehensive understanding of the dynamics of how the three teleconnections influence the local climate and, therefore, the wheat yield in the Swartland. The eight climate indices, representing the three teleconnections, were correlated against the six wheat-specific rainfall characteristic indices from each of the three study areas over the period from 1980 to 2012. The state of ENSO during the first half of the year was shown to be correlated with rainfall characteristics during both the first (April to July) and second (July to September) halves of the wheat growing season; however, these correlations differ ed in their sign. Correlations suggested a negative phase of AAO was associated with above normal rainfall throughout the year across the Swartland region. Sea surface temperatures in the central South Atlantic during March to October showed significant negative correlations with rainfall during the latter half of the wheat growing season (July to October) across the Swartland region. This study presented evidence supporting the plausibility and validity for the use of the state of large-scale modes of variability in the prediction of wheat-specific rainfall characteristics and aggregated yields in the Swartland region. This has the potential to provide useful information to wheat farmers in the Swartland to aid in their decision making process

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Karlina. „ASSESSMENT OF HYDRO-METEOROLOGICAL DROUGHTS RELATED TO ENSO IN LOMBOK AND SUMATRA ISLANDS, INDONESIA“. Kyoto University, 2018. http://hdl.handle.net/2433/231991.

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付記する学位プログラム名: グローバル生存学大学院連携プログラム
Kyoto University (京都大学)
0048
新制・課程博士
博士(工学)
甲第21058号
工博第4422号
新制||工||1687(附属図書館)
京都大学大学院工学研究科社会基盤工学専攻
(主査)教授寶馨, 教授堀智晴, 准教授佐山敬洋
学位規則第4条第1項該当

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Krois, Joachim, Achim Schulte, Vigo Edwin Pajares und Moreno Carlos Cerdan. „Temporal and spatial characteristics of rainfall patterns in the Northern Sierra of Peru – A case study for La Niña to El Niño transitions from 2005 to 2010“. Pontificia Universidad Católica del Perú. Centro de Investigación en Geografía Aplicada, 2014. http://repositorio.pucp.edu.pe/index/handle/123456789/119763.

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The climatic conditions of the northern Sierra of Peru are marked by the interaction of different macro- to mesoscale climatic features such as the El Niño Southern Oscillation (ENSO) or Mesoscale Convective Complexes (MCCs) and the seasonally shifting Intertropical Convergence Zone (ITCZ), but also by local scale climatic features such as inhomogeneous topography and local wind fields. The region under investigation, located in the vicinity of the South America Continental Water Divide (CWD), provides the opportunity to study interactions of western and eastern disturbances in a high mountain environment and their effects on rainfall variability. In general, rainfall variability is related to diurnal convection patterns, enhanced by valley breeze systems and modulated by local scale wind anomalies. Spillover of low-level air masses of Pacific origin passing over the Andean ridges is frequent. Although direct effects of ENSO on high Andean rainfall variability are in debate, our findings show that the majority of rain gauges used in this study follow an El Niño/dry and a La Niña/wet signal. However, high elevation areas on the western escarpment of the Andes benefit from abundant nocturnal rainfall that partly offsets the rainfall deficits during El Niño. Our data suggest that the spatial extent of this easterly wet pulse is limited to areas located above 3000 m asl. ENSO cycles contribute to rainfall variability near the CWD in the northern Sierra of Peru by modulating the seasonal rainfall regime and causing a positive temperature anomaly.
Las condiciones climáticas de la sierra norte del Perú están marcadas por la interacción de diferentes rasgos climáticos a escalas macro y meso, tal como el fenómeno ENSO o los Complejos Convectivos a Meso-escala (MCC) y la estacionalmente móvil Zona de Interconvergencia Intertropical (ITCZ), pero también por rasgos climáticos a escala local tales como la heterogeneidad topográfica y los campos de vientos locales. La zona de estudio se ubica en las cercanías de la divisoria de aguas continentales de Sudamérica (CWD), provee la oportunidad de estudiar las interacciones de las disturbancias occidental y oriental en un ambiente de alta montaña y sus efectos en la variabilidad de las precipitaciones. En general la variabilidad de las precipitaciones se relaciona con patrones de convección diurna, reforzada por los sistemas de brisas de valle y modulada por anomalías de vientos a escala local. El desplazamiento de masas de aire a baja altura provenientes del Pacífico que remontan los Andes es frecuente. Aunque los efectos directos del ENSO en la variabilidad de las precipitaciones andinas está todavía en debate, nuestras investigaciones muestran que la mayoría de las mediciones hechas para este estudio siguen una señal El Niño/seco y La Niña/húmedo. Sin embargo, las zonas altas de lasescarpas occidentales de los Andes se benefician de abundante lluvia nocturna que parcialmente completa los déficits de precipitaciones durante El Niño. Nuestros datos sugieren que la cobertura espacial de este pulso húmedo del Este se limita a áreas que se ubican encima de los 3000 msnm. Los ciclos ENSO contribuyen a la variabilidad de las precipitaciones cerca del CWD en la sierra norte del Perú mediante la modulación del régimen estacional de lluvias que causa una anomalía de temperatura positiva.

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Gitau, Wilson. „Diagnosis and predictability of intraseasonal characteristics of wet and dry spells over equatorial east Africa“. Phd thesis, Université de Bourgogne, 2010. http://tel.archives-ouvertes.fr/tel-00794889.

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Most of Eastern Africa has arid and semi-arid climate with high space-time variability in rainfall. The droughts are very common in this region, and often persist for several years, preceded or followed by extreme floods. Most of the livelihoods and socio-economic activities however remain rain-dependent leading to severe negative impacts during the periods of occurrence of climate extremes. It has been noted that one extreme event was capable of reversing national economic growth made over a period of several years. Thus no sustainable development can be attained in eastern Africa without effective mainstreaming of climate information in the development policies, plans and programmes. Many past studies in the region have focused on rainfall variability at seasonal, annual and decadal scales. Very little work has been done at intraseasonal timescale that is paramount to most agricultural applications. This study aims at filling this research gap, by investigating the structure of rainfall season in terms of the distribution of wet and dry spells and how this distribution varies in space and time at interannual time scale over Equatorial Eastern Africa. Prediction models for use in the early warning systems aimed at climate risk reduction were finally developed. The specific objectives of the study include, delineate and diagnose the some aspects of the distribution of the wet and dry spells at interannual timescale; investigate the linkages between the aspects of the distribution of wet and dry spells identified and dominant large scale climate fields that drive the global climate; and assess the predictability of the various aspects of wet and dry spells for the improvement of the use in the early warning systems of the region.Several datasets spanning a period of 40 years (1961 - 2000) were used. The data included gauged daily rainfall amount for the three Eastern Africa countries namely Kenya, Uganda, and Tanzania; Hadley Centre Sea Surface Temperature (SST); re-analysis data and radiosonde observations from Nairobi (Kenya) and Bangui (Central Africa Republic) upper air stations. The indices of El Niño-Southern Oscillation (ENSO), Indian Ocean Dipole and SST gradients which constituted the predefined predictors were also used [...]

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Tessema, Selome M. „Hydrological modeling as a tool for sustainable water resources management: a case study of the Awash River Basin“. Licentiate thesis, KTH, Miljöbedömning och -förvaltning, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-33617.

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The growing pressure on the world‘s fresh water resources is enforced by population growth that leads to conflicts between demands for different purposes. A main concern on water use is the conflict between the environment and other purposes like hydropower, irrigation for agriculture and domestic and industry water supply, where total flows are diverted without releasing water for ecological conservation. As a consequence, some of the common problems related to water faced by many countries are shortage, quality deterioration and flood impacts. Hence, utilization of integrated water resources management in a single system, which is built up by river basin, is an optimum way to handle the question of water. However, in many areas, when planning for balancing water demands major gaps exist on baseline knowledge of water resources. In order to bridge these gaps, hydro-logical models are among the available tools used to acquire adequate understanding of the characteristics of the river basin. Apart from forecasting and predicting the quantity and quality of water for decision makers, some models could also help in predicting the impacts of natural and anthropogenic changes on water resources and also in quantifying the spatial and temporal availability of the resources. However, main challenges lie in choosing and utilizing these models for a specific basin and managerial plan. In this study, an analysis of the different types of models and application of a selected model to characterize the Awash River basin, located in Ethiopia, is presented. The results from the modeling procedure and the performance of the model are discussed. The different possible sources of uncertainties in the modeling process are also discussed. The results indicate dissimilar predictions in using different methods; hence proper care must be taken in selecting and employing available methods for a specific watershed prior to presenting the results to decision makers.
QC 20110516

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Madhyastha, Karthik. „Scaling Characteristics Of Tropical Rainfall“. Thesis, 2012. http://etd.iisc.ernet.in/handle/2005/2584.

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We study the space-time characteristics of global tropical rainfall. The data used is from the Tropical Rainfall Measuring Mission (TRMM) and spans the years 2000-2009. Using anomaly fields constructed by removing a single mean and by subtracting the climatology of the ten year dataset, we extract the dominant modes of variability of tropical rainfall from an Empirical Orthogonal Function (EOF) analysis. To our knowledge, this is the first attempt at applying the EOF formal-ism to high spatio-temporal resolution global tropical rainfall. Spatial patterns and temporal indices obtained from the EOF analysis with single annual mean removed show large scale patterns associated with the seasonal cycle. Even though the seasonal cycle is dominant, the principal component (PC) time series show fluctuations at subseasonal scales. When the climatological mean is removed, spatial patterns of the dominant modes resemble features associated with tropical intraseasonal variability (ISV). Correspondingly, the signature of a seasonal cycle is relatively suppressed, and the PCs have prominent fluctuations at subseasonal scales. The significance of the leading EOFs is demonstrated by means of a novel ratio plot of the variance captured by the leading EOFs to the variance in the data. This shows that, in regions of high variability (which go hand in hand with high rainfall), the EOF/PC pairs capture a fair amount of the variance (up to 20% for the first EOF/PC pair) in the data. We then pursue an EOF analysis of the finest data resolution available. In particular, we per-form a regional analysis (a global analysis is beyond our present computational resources) of the tropics with 0.25◦×0.25◦, 3-hourly data. The regions we focus on are the Indian region, the Maritime Continent and South America. The spatial patterns obtained reveal a rich hierarchical structure to the leading modes of variability in these regions. Similarly, the PCs associated with these leading spatial modes show variability all the way from 90 days to the diurnal scale. With the results from EOF analysis in hand, we quantify the multiscale spatio-temporal structures encountered in our study. In particular, we examine the power spectra of the PCs and EOFs. A robust feature of the space and time spectra is the distribution of energy or variance across a range of scales. On the temporal front, aside from a seasonal and diurnal peaks, the variance scales as a power-law from a few days to the 90 day period. Similarly, below the planetary scale, from approximately 5000 km to 200 km the spatial spectrum also follows a power-law. Therefore, when trying to understand the variability of tropical rainfall, all scales are important, and it is difficult to justify a focus on isolated space and time scales.

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陳正炎. „Effect of rainfall on the characteristics“. Thesis, 1998. http://ndltd.ncl.edu.tw/handle/39378933318593628786.

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„Changes in rainfall characteristics and reflectivity-rainfall rate relationships in Hong Kong“. 2011. http://library.cuhk.edu.hk/record=b5894868.

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Lau, Stephen Po Wing.
"August 2011."
Thesis (M.Phil.)--Chinese University of Hong Kong, 2011.
Includes bibliographical references (leaves 62-66).
Abstracts in English and Chinese.
List of figures --- p.vi
List of tables --- p.ix
Chapter Chapter 1: --- Background --- p.1
Chapter Chapter 2: --- Changes in Rainfall Characteristics in Hong Kong --- p.3
Chapter 2.1 --- Introduction --- p.3
Chapter 2.2 --- Data --- p.5
Chapter 2.3 --- Method --- p.6
Chapter 2.3.1 --- Linear Regression Analysis --- p.8
Chapter 2.3.2 --- Empirical Mode Decomposition --- p.9
Chapter 2.4 --- Result --- p.12
Chapter 2.4.1 --- Rainfall Rate Categories --- p.12
Chapter 2.4.2 --- Rainfall Events Statistics --- p.20
Chapter 2.4.3 --- Diurnal Variation --- p.26
Chapter 2.4.4 --- Rainfall Rate Distribution --- p.30
Chapter Chapter 3: --- Reflectivity-rainfall Rate Relationships in Hong Kong --- p.33
Chapter 3.1 --- Introduction --- p.33
Chapter 3.2 --- Data --- p.35
Chapter 3.3 --- Method --- p.37
Chapter 3.3.1 --- Linear Regression Analysis --- p.37
Chapter 3.4 --- Result --- p.38
Chapter 3.4.1 --- Comparison of Rainfall Rate from Various Sources --- p.39
Chapter 3.4.2 --- Raindrop Size Distributions under Various Classification Schemes --- p.42
Chapter 3.4.3 --- Z-R Relationships Derived from Various Sources --- p.48
Chapter Chapter 4: --- Conclusion --- p.58
Bibliography --- p.62

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Wang, Jyun-Kai, und 王郡鍇. „Examination of Influence of Rainfall Characteristics on“. Thesis, 2009. http://ndltd.ncl.edu.tw/handle/yc3p7h.

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碩士
國立嘉義大學
土木與水資源工程學系研究所
97
The examination of influence of rainfall characteristics, including rainfall amount, rainfall duration, and rainfall pattern, on shallow landslides due to the dissipation of matric suction is conducted in this study. Four representative rainfall patterns including the uniform, advanced, intermediate, and delayed rainfalls are adopted. The results show that not only the occurrence of shallow landslide but also the failure depth and the time to failure are affected by the rainfall characteristics. The different rainfall patterns seem to have the identical minimum landslide-triggering rainfall amount. There is a rainfall duration threshold for landslide occurrence for a rainfall with larger than the minimum landslide-triggering rainfall amount. For each rainfall pattern the rainfall duration threshold for landslide occurrence decreases to constant with the increase of rainfall amount. The uniform rainfall has the least rainfall duration threshold for landslide occurrence, followed by the advanced rainfall, and then the intermediated rainfall. For each rainfall pattern the failure depths and the times to failure from various rainfall durations with constant rainfall amount could be largely different. In addition, the differences of the failure depths and the times to failure between various rainfall patterns with the identical amount and duration of rainfall could be also significant. It can be concluded that, as compared with the occurrence of shallow landslide, the failure depth and the time to failure are more sensitive to the rainfall characteristics. Hence, it needs more accurate rainfall prediction data to achieve reliable estimation of the failure depth and the time to failure in comparison with evaluating the occurrence of shallow landslide.

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LIN, CHI-WEN, und 林琦雯. „Impact of Rainfall Characteristics on Landslide Assessment“. Thesis, 2016. http://ndltd.ncl.edu.tw/handle/40673841495690442535.

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碩士
長榮大學
土地管理與開發學系碩士班
104
About two-thirds of Taiwan’s total area is covered by mountains and hills. Coupled with the global climate change, rainfall-induced landslides often occur and lead to human causalities and properties loss. Therefore, the assessment of rainfall-induced landslides is indeed an important task. The study areas in this research are the Tsengwen and Nanhua Dam watershed in the southern Taiwan. The FORMOSAT satellite images before and after the years 2009-2013 (including 7 typhoons and rainfall events) were acquired and used. The Genetic Adaptive Neural Network (GANN) was implemented in the analysis techniques for the interpretation of satellite images and to obtain surface information and hazard log data. The scope of the impact of different rainfall stations in the study area was estimated using Thiessen's Polygon Method to explore the characteristics of rainfall. The relationship between the pattern, amount, and duration of rainfall and location and scale of landslide was also explored. The results of image classification show that the average value of coefficient of agreement is 0.75 at medium-high level. The rainfall patterns are classified into 5 types using 72-hour rainfall duration for each rainfall station: pre-peak, central-peak, post-peak, twin-peak, and tri-peak. The results also show that when the accumulated rainfall is small, rainfall pattern affect the number and scale of landslides. When the accumulated rainfall is large, there is no correlation between rainfall patterns and landslides. Furthermore, regardless rainfall patterns most landslide sites occur in slope between 20˚ and 40˚. Pre-peak and central-peak rainfall-induced landslides sites occur in slope between 20˚ and 30˚. The other rainfall-induced landslides sites occur in slope between 30˚ and 40˚. Moreover, in the case of the same accumulated rainfall, the elevations of landslides induced by pre-peak and central-peak are much higher than those induced by the others.

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Chang, Chan-Hua, und 張展華. „Characteristics of Annual rainfall and Maximum one day rainfall in Kao-Ping Area“. Thesis, 2003. http://ndltd.ncl.edu.tw/handle/58162691719786829098.

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碩士
國立屏東科技大學
水土保持系
91
Five frequency analysis methods were used in this study for the Maximum one day rainfall and annual from the data issued by Central Weather Bureau(CWB) of weather observation station in December, 2000(5th edition) and data in annual book about 188 weather observation stations of CWB in Kaohsiung and Pingtung. As the results of analysis shown, it is suggested to use Pearson type Ⅲ method for predicting frequency analysis of annual rainfall in Kaohsiung City, Kaohsiung County, Pingtung County, and the whole region of Kaohsiung and Pingtung; for the Maximum one day rainfall,Log Natural Distribution for predicting frequency analysis is suggested to use in Kaohsiung City, Log Pearson type Ⅲ method in Kaohsiung County, Pingtung County, and the whole region of Kaohsiung and Pingtung. Based on the distributions from applicable theories, the most applicable theory for each station was found. Then, use the hydrological frequency analysis to estimate the hydrological parameters of 5-yr, 20-yr, 25-yr, 50-yr and 100-yr, and draw the rainfall contour map accordingly for the reference for different requirements. The rainfall contour map shows that the rainfall increases as the elevation increases, but it is hard to estimate the increase rate. By taking each village, town, city and district as the regional units, the frequency regression equations, R squares and standard deviations were obtained, which can provide the relevant engineers an easy way to obtain the hydrological parameters for the reference of construction design. As for the relationship of rainfalls and elevations of station, it can be found from the results of this study that the more the year number of record, the closer the relationship between the average annual rainfall and the maximum one day rainfall. Therefore, as the year number of record increases, the reliability of the hydrological frequency analysis increases. However, the average annual rainfall and the maximum one day rainfall increase as the elevation of the stations increases, but there is no fixed increase trend. The average annual rainfall and maximum one day rainfall have no conspicuous relationship with the elevations of the stations. Especially, the relationship of the maximum one day rainfall and the elevation is worse.

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KANG-LINGSHEN und 沈岡陵. „Rainfall characteristics for anisotropic conductivity of soil slope“. Thesis, 2013. http://ndltd.ncl.edu.tw/handle/82567248652454101368.

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碩士
國立成功大學
資源工程學系碩博士班
101
The stability of slopes decreases due to the suction decreases occurring with rainfall infiltration. Traditional studies of slope stability have used a general limit equilibrium method to calculate the safety factors and to determine whether a slope is safe. However, sometimes the failure of slope may occur even though the safety factor is more than unity (FS 〉 1) because the input soil parameters are considered to be the mean value for slope stability analysis. As a result, when many parameters are used in analysis, the level of uncertainty increases. The probability approach used to study geotechnical issues offers a systematic way to treat uncertainties, especially in the case of slope stability problems. In this study, probability analysis is used to evaluate the stability of unsaturated soil slopes. The geological formation of residual soils is mostly in distinctive layers that may have different hydraulic conductivity (ks) in different directions. Furthermore much of the research on this topic has assumed the ks to be isotropic. Therefore, in this thesis, the effect of anisotropic of ks on the slope seepage under the condition of rainfall infiltration is examined. In this study, the finite element computer program Geo-Studio is used to simulate the process of rainwater infiltrate to the slope. The pore-water pressure results evaluated from seepage analysis (SEEP/W) are imported into the slope stability program (SLOPE/W). In order to quantify the slope stability results probabilistically, the soil strength parameters are provided with a range. The results of the designed case study indicated that in the case of sand, the rainfall pattern controlled the time for the occurrence of instability of the slope under consideration. The rate of decrease in safety factor versus time was found to be faster in the case of the advanced pattern, followed by the normal and delayed patterns. The results for the anisotropic ratio of hydraulic conductivity indicated that when the anisotropic ratios become higher, the reduction in the reliability index is insignificant. Cases for the sand slope under different rainfall intensities (I) were designed. It was found that while the ks was greater than I, the reliability index decreased immediately, and there was also a decrease in the reliability index by nearly a quarter because the event after 6 hours remained stable. When, the ks was less than I, the reliability index stayed at the beginning level. About 7 hours later, there was found to be a marked downward trend. The reliability index fell by 65%. In the other case, the simulation results indicated that when the ks was less than I, the percentage probability of the occurrence of a landslide was larger than when the ks was greater than I. Finally, in the cases of anisotropic ks, the stability of the high ratio soil slopes was not found to be sensitive to the reliability index variation during the simulation period. Moreover, when the ks was greater than I, the stability of the slope decreased earlier than was the case in the opposite situation.

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CHENG, SHI-CHI, und 陳世墀. „Studies on the characteristics of one-day rainfall and one-hour rainfall intensity in Taiwan“. Thesis, 1987. http://ndltd.ncl.edu.tw/handle/6m9j9s.

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Ratan, Ram. „Changes In The Duration-Depth Characteristics Of Indian Monsoon Rainfall During 1951-2000“. Thesis, 2009. http://hdl.handle.net/2005/941.

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Several previous studies have found that various characteristics of the Indian monsoon rainfall have shown secular changes over the past century. In this study, using a gridded (1degree) daily rainfall dataset, we analyse the spatio-temporal characteristics of the intensity and duration of monsoon (June through September) rainfall for secular changes over the last 50 years. The characteristics of the duration of rain events are described by wet and dry spells. A wet/dry spell is defined as a period of consecutive days with rainfall above/below a particular threshold. We choose to use a threshold that is a function of the local climatological mean, given the spatial heterogeneity of mean monsoon rainfall. The wet and dry spells are then divided into three categories: short [1 to 7 days], moderate [8 to 10 days], long [11 and more days] and analysed for changes over the past 50 years [19512000]. We find that while the number of short duration wet spells show a significant increase over the last 50 years (~15% change), the number of long duration wet spells show a significant decrease (~25%). Furthermore, while the numbers of short duration dry periods have shown a significant increase, the moderate and long duration dry spells do not shown an appreciable change. This increase and decrease in the short and long duration wet spells offset each other and consequently the total number of rainy days during the season has not shown any significant change over the past 50 years. In addition to the duration of wet and dry spells, we also analysed for changes in the accumulated rainfall of the short, medium and long duration wet spells. Our analysis suggests that while the depth of accumulated rainfall in short duration wet spells has shown a significant increase (~20%), the depth of rain in the long duration spells has shown a significant decrease (~30%) in the past fifty years.

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Lu, CHING HONE, und 呂俊弘. „Study of Characteristics of Rainfall Lag Type Tank Model“. Thesis, 1998. http://ndltd.ncl.edu.tw/handle/02255018316047237794.

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Yung-ShengChue und 邱永昇. „Rainfall-Induced Landslide Potential and Landslide Distribution Characteristics Assessment“. Thesis, 2016. http://ndltd.ncl.edu.tw/handle/3uadpd.

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Kuo, Chun-Chang, und 郭峻菖. „The temporal variation of regional rainfall characteristics in Taiwan“. Thesis, 2009. http://ndltd.ncl.edu.tw/handle/29325167554087748302.

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碩士
逢甲大學
水利工程與資源保育研究所
97
This article was designed to examine the rainfall variations of the whole source in two selected rivers of the four areas in Taiwan, and furthermore investigated to what extent the rainfall and the rainfall characteristics influence Taiwan under the climate change. This article indicated that the amount of the yearly rainfall data was decreased from the north to the south parts in the west area, and besides it was decreased from the south to the north parts in the east area. The amount of rainfall extremes events was gradually increased in every area in Taiwan, however the annual rainy day revealed decreasingly. The results demonstrated that the future rainfall pattern in Taiwan will make the rainfall duration shorten. Significantly, the wet season of the west area may become the season between April and September, and what was more, the wet season of the east area may respectively become the periods between May and October, June and November as well as July and December. Nevertheless, the annual maximum two-daily rainstorm depth contributed to an increasing trend in Taiwan. Moreover, the optimum probability all revealed the extreme distribution in the analysis of the annual maximum two-daily rainfall frequency. In contrast to the annual maximum daily rainfall frequency, only a half showed the extreme distribution. Accordingly, the author concluded that the extreme distribution should be often used in the optimum probability distribution when designing the rainfall frequency in Taiwan.

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Chang, Wan-Ling, und 張琬鈴. „Statistical Characteristics of Long Term Rainfall at Taipei Station“. Thesis, 2008. http://ndltd.ncl.edu.tw/handle/68010127835756409222.

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碩士
華梵大學
環境與防災設計學系碩士班
96
The aim of this paper is to study the characteristics of long term variations of rainfall distribution and changes of rainfall amount for Taipei weather station of Central Weather Bureau. Annual and monthly and different 30 years rainfall data as the statistical data from 1900 to 2006 are used in this paper. These data are analyzed by the statistical distribution method for different period in order to discuss in this paper. The results are shown the statistical distribution of annual rainfall is more symmetrical. Normal and Gamma distributions both can describe the annual rainfall; but the monthly rainfall distribution is more suitable by the Gamma distribution. The five-year moving average of monthly rainfall in the year after 1980 are shown that the observed rainfall of February, April, August and September is apparently higher than the total mean. The rainy days present the reduced tendency generally and the rainfall intensity present increased. The Probability of Gamma distribution for recently 30 years annual rainfall data is obvious different from other different periods of 30 years. The curve of Gamma distribution moves to right forward location. It appears that the mode and mean of annual rainfall increase but its probability decreases. In recently 30 years monthly rainfall data revealed that the probability of monthly heavy rainfall, which it described by the Gamma distribution, has a tendency to increase except for the January, March and July. The increase rate is most obvious shown in February and September.

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38

Lu, Shu Min, und 盧淑敏. „Study on rainfall characteristics for upstream in Lanyang-hsi watershed“. Thesis, 1994. http://ndltd.ncl.edu.tw/handle/40992277053335355432.

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39

Guo, Bao-Cheng, und 郭保成. „Application of Grey Theory to Analyze the Characteristics of Rainfall“. Thesis, 2007. http://ndltd.ncl.edu.tw/handle/65278024252593597293.

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碩士
國立屏東科技大學
畜產系所
95
Rainfall is the natural resource that human keeps of life. It is also the important agriculture resource in Taiwan. Human depends on it more and more. However, a natural phenomenon is exist many uncertain factors. Therefore, rainfall don’t allowed to control by human easily. This research applies a series of Grey System Theory Method to analyze the south-west area of Taiwan. It analyzes the rainfall characteristics and the trend of the future in Pingtung especially. It refers to the water resource policy which to establish and perform in the future. This research is divides into three parts. The first part applies Class Ratio Method of Grey System Theory to supplement rainfall data. It compares with Interpolation Method and Normal Ratio Method. While station locates a mountain area, Class Ratio Method is more well than Interpolation Method and Normal Ratio Method. The second part applies Grey Relation Method to analyze rainfall factors in the south-west area of Taiwan. It related to the geographic and climatic condition. It isn't controlled by the degree of humidity factor completely. The results shown that wind velocity and elevation has higher relativity of rainfall in the south-west area. The third part applies Topological analysis and Grey Prediction Model GM（1,1）to forecast the variety of rainfall that 5 year in the future in Pingtung. The annual rainfall compares with the average annual rainfall will be reduced. The few rainfall condition of the plain area in the west will concentrates more, and the annual rainfall of the mountain area in the east will enlarges the margin.

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40

Feng, Ya-Chien, und 馮雅茜. „The precipitation characteristics of autumn torrential rainfall event in northern Taiwan“. Thesis, 2007. http://ndltd.ncl.edu.tw/handle/09664314949642842020.

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碩士
國立中央大學
大氣物理研究所
95
Precipitation characteristics of the torrential rainfall event on 10th Sep. 2006 in northern Taiwan will be discussed in this thesis. The maximum daily accumulated rainfall was 556 mm at Zhuzihu. The heavist rainfall took place during 06-12UTC. The data collected by NCU dual-polarimetric radar and RCWF radar are mainly used to analyze mesoscale features, such as space-time distribution of precipitation, possible mechanisms, as well as microphysics characteristics. In synoptic scale, a continental high in China and a low locating on Bashi Channel influenced Taiwan. They caused a low level convergent zone in the north-eastern area of Taiwan. Because the continental high moved out of China and it turned to westerly on high level, the climate character was categorized to early autumn. The horizontal reflectivity patterns were diverse. Convections moved from east to west. Statistic result shows that the strong reflectivity dispersed to three areas, northeastern sea of Taiwan, Mt. Datun and Tamsui River estuary. The environment provided favorable conditions for these precipitation systems, such as convergence and terrain upslope enhancement. From dual-polarization data, shallow convections were embedded in large and long-lasting stratiform system. ZDR was increasing as height decreasing. Within near saturated environment, the bigger drops in lower level indicated that precipitation may be enhanced by collision and coalescence. Using dual-polarization radar data to retrieve raindrop size distribution, and combing kinematics analysis, we could prescribe a simple microphysics conceptual model. The long-lasting stratiform system continuously provided droplets to low level convections in a wide spread region. Wherever there is more upward motion, more vapor would condense. A wider spread of DSD set up the stage of seeder-feeder mechanism.

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41

Li, Ya-Chuan, und 李雅娟. „The Analysis of Climatological Characteristics of Non-typhoon Rainfall in Taiwan“. Thesis, 2006. http://ndltd.ncl.edu.tw/handle/37745781646216174240.

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碩士
國立臺灣大學
土木工程學研究所
94
The main rainfall type of Taiwan can be divided into a typhoon rain and monsoon rain. The overall rainfall that typhoon brings yearly depends on the actual times of invasion. This research mainly discussed the '' non-typhoon rainfall '' , and expected to analyze the relation among the variations of the change of geopotential height in the entire environment, the corresponding change of airflow surrounding Taiwan, and the transition of rainfall type of Taiwan caused by he variation of airflow. We use the 85 stations of daily rainfall observation in Taiwan, the data of 850 hpa airflow surrounding Taiwan (117.5°-125°E、20°-27.5°N), and the data of 850 hpa geopotential height within this area (90°-170°E、0°-60°N) from 1980 to 2004 in this research. Four methods are used in this research. First, we extracted the typhoon rainfall. Second, the Principle Components Analysis. Third, the analysis of cumulation anomaly. Finally, we tried to find the relation among three climatology and anomalies, the geopotential height, the airflow and the rainfall of the duration of moist-rain or drought. This research reveals three important results. First, the yearly arithmetic mean of rainfall in Taiwan is about 2400mm. The typhoon rainfall accounts for around 23 %, 38% at most (in 2004) and 3 % at least (1983). This means a huge variation over years. Consequently, when analyzing the long-term characteristics of rainfall, it is suggested to discuss these two types separately. Second, three principle components of rainfall are derived by using the principle components analysis. The first one displays a positive coefficient in Taiwan, especially in South-east. The second one is a positive coefficient in North-west with a negative value in South-east, and the third is a positive value in West with a negative value in East. Finally, there is a considerately good relation between geopotential height and rainfall from the duration of moist-rain or drought, e.g., the geopotential height varies with the positive coefficients of different principle components to show a positive anomaly during the drought. This research has explored the relation among geopotential height, airflow in the entire environment and rainfall. In the future, we expect to use this index as an estimation criteria of yearly or seasonal change of non-typhoon rainfall in Taiwan after development and examination.

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42

Yu, An-gi, und 游安吉. „Use radar data analysis the convective structure characteristics of rainfall system“. Thesis, 1996. http://ndltd.ncl.edu.tw/handle/46763365528873329373.

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43

Lu, Yu-Tien, und 盧瑜典. „Influence of Rainfall Infiltration on Hydrologic Characteristics of Unsaturated Colluvium Soil“. Thesis, 2013. http://ndltd.ncl.edu.tw/handle/64113223404945594927.

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碩士
國立臺灣科技大學
營建工程系
101
Taiwan has many colluvium soil slope located in the water catchment area, as a result, the stability of slope may decrease due to the high rainfall intensity brought by typhoon. In some cases, the colluvium slope may even fails putting lives and properties at high risk. Therefore, how to prevent such disaster occurring in the slope region is an important issue. The objective of this research is to investigate the influence of rainfall infiltration on hydrologic characteristics of unsaturated colluvium soil. This study, first summarized field monitoring results from previous field monitoring works by Hsiao(2011) at Sha Lun Tsai colluvium soil slope near Shihmen reservoir. The studied data include rainfall amount, matric suction, permeability, evapotranspiration and temperature. Subsequently, a series of numerical analyses were conducted using GeoStudio software, including the SEEP/W seepage analysis, and SLOPE/W slope stability analysis. The results from this study show that matric suction change in the field are mainly affected by rainfall infiltration. Numerical simulation can provide valuable insights of unsaturated soil at the time of rainfall infiltration in transient analysis results, such as pressure head, total head, volumetric water content, pore water pressure, and matric suction. For example, when the rainfall intensity is 30mm/hr, the impact of rainfall infiltration on the matric suction depth is about 2m when the water table is low. The influence of rainfall infiltration on the matric suction depth about increaces to 3m when the water table is high. In addition, the matric suction and the wetting front exhibit interactive relationship, the wetting front stops development when the matric suction increases; wetting front

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44

Huang, Po-Yuan, und 黃柏元. „Analysis of Spatiotemporal Characteristics of Typhoon Rainfall for Laonong River Basin“. Thesis, 2014. http://ndltd.ncl.edu.tw/handle/13073595376134184548.

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碩士
淡江大學
水資源及環境工程學系碩士班
102
Taiwan is among the most active tropical cyclone regions in the world. There are several typhoons hit Taiwan every year. Especially in 2009, typhoon Morakot brought a significant disaster in Taiwan. Due to the serious damages caused by typhoons, it is necessary to explore the characteristics of typhoons. In order to understand the characteristics of rainfall of typhoon, the method of empirical mode decomposition (EMD) in Hilbert-Huang transform (HHT), able to consider the non-linear and non-stationary nature of signal, is adopted in this study. On the other hand, the method of empirical orthogonal function (EOF) analysis, usually used in atmospheric sciences, is also employed to analyze the spatiotemporal characteristics of typhoon rainfall. In addition, the data of Laonong River Basin is taken for example to investigate the temporal and spatial distribution of typhoon rainfall. According to the analysis results of 10 typhoons in Laonong River Basin, it shows that the expansion coefficients associated with the EOF can reflect the variation of typhoon rainfall with time appropriately. In addition, the spatial distribution of rainfall can be depicted clearly by the first few spatial modes of EOF. By overlapping the map of EOF isopleth and the map of potential debris flow torrent, or the landslide potential map, we can easily identify where the high-risk hazard areas are. The results in this study can be used as an indicator for risk management and as a tool to develop practical strategies for disaster prevention, such as mitigation of landslides and debris flow.

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45

Lee, Po-Feng, und 李柏鋒. „Applying Spatial and Rainfall Characteristics of Basins in Improving Runoff Estimation“. Thesis, 2003. http://ndltd.ncl.edu.tw/handle/98137521860944847714.

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碩士
國立臺灣大學
地理環境資源學研究所
91
Since the first announcement of the “Rational formula” by Kuichling (1889), rational formula is profoundly used in estimate peak flow rate in watershed. It also can be used in the basin lacking of rainfall-runoff records if we can decide appropriately on each parameter. Although the rational formula is easy to use, but there are different hydrological and geomorphic characteristics in each watershed. How to decide the correlation between these characteristics and parameters will have a directly influence on the values of estimation. This study will discuss the relation between the runoff estimation and the spatial and rainfall characteristics, and apply these characteristics in improving runoff estimation. This study applies the GIS technique to found the spatial characteristic indices of the basin（basin area, A、percent impervious area, Imp、shape index, M、scatteration, Rc、length ratio, RL） and analyze the rainfall characteristics of each rainfall event（rainfall amount, P、rainfall intensity, I、peak duration ratio, T、kurtosis coefficient, β）. Meanwhile, the indices are used to correlation analysis with estimation error and runoff coefficient and to establish the model of rational formula by regression analysis. The study results discuss the relation between the runoff estimation and the spatial and rainfall characteristics ,and establish the regression equation of error（E） and indices: E = 62.703－91.368* M－55.128*Rc + 92.9* RL－44.075*T— 1.927*β＋0.165*I R = 0.51 and the regression equation of runoff coefficient（C）and indices: Co = －0.11 + 1.123* M + 0.186* Rc－0.73 RL + 0.73*CN + 0.0004*P R = 0.56 The verified results indicate that the MB% of the regression equation of error is 11.4% and the MB% of the regression equation of runoff coefficient is -9.6%. The verified results are accepted and these improved models achieve the goal that improving the error of runoff estimation and runoff coefficient.

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46

LIN, QI-YUAN, und 林啟源. „An analysis of rainfall characteristics for debris-flow events in Taiwan“. Thesis, 1991. http://ndltd.ncl.edu.tw/handle/38557769612517346987.

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47

Hou, Tung-Chao, und 侯統昭. „Characteristics of Landslides and Rainfall in the Tseng-Wen Reservoir Watershed“. Thesis, 2012. http://ndltd.ncl.edu.tw/handle/60708092590580180183.

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碩士
國立屏東科技大學
水土保持系所
100
Construction of Tseng-Wen reservoir is to solve the problem of lack of water resources in order to supply for the Chia-Nan plain region, because of the intense rainfall events such as typhoons and heavy rainfall, makes a large amount of landslides occurred in the upstream areas of the reservoir watersheds, causing the sediment siltation serious, reduce storage capacity and shorten the life of a reservoir. Therefore, It is an important work at understand characteristics of Landslides and landslide potential of Tseng-Wen reservoir watershed, help improve within sediment prevention benefits in the watershed and extend the operating life of the reservoir. Therefore, this study collect the landslides at 10 games of the typhoon and torrential rain between 2001~2010 to analysis the spatial and temporal variations of landslides. and using GIS technique to build the landslides database, Explore the Effects of the landslide of by potential factor (slope, aspect, elevation, geology, soils, land use) and triggering factors (rainfall). In addition, we also using the dangerous value method to discussed the landslide potential in the study. 　　Result shows that the spatial and temporal variations of landslides in the Tseng-Wen reservoir watershed. Before Typhoon Morakot, the landslide rate is remain below 1%, after Typhoon Morakot, makes a large amount of landslides occurred in the watershed, cause the landslide rate increased to 3.07%. Then, there are continue to decrease year by year trend. Result shows that the magnitude and frequency distribution of landslides, there are in line with the exponential relationship. By contrast, the frequency of small-scale landslides occurred more than the large-scale landslides, and lead to large-scale landslides occurred mainly by rainfall. The results show that the landslide caused in mainly take place in the upstream areas of the watersheds, it mostly happened at the height of 500~1,250meters, and the slope grade is at 27°~43°, and with increasing slope landslide rate is also enhanced. In addition, a large number of landslides also occurred in the enlarged area of former landslide zone and the headward erosion zone. 　　Result shows that the characteristics of landslides and rainfall. After Typhoon Morakot, the rainfall conditions induced collapse due to the Slope Stability reduce both collapse more, should be followed downward correction as appropriate. This research use Daogi formula to estimate the landslide rate in this watershed. It is advice may be given the average rainstorm of one day replace the average accumulated rainfall of watershed, and the critical rainfall may be given 130mm~250mm. This result is more in line with the characteristics of the watershed and the typhoons rainfall. 　　The dangerous value method to analyst the weights of landslide factors are land use, soil, slope, geology, rainfall, elevation and aspect respectively. The results show that the reasonable land use can reduce the possibility of landslide. A simple test result shows that the dangerous value method can predict landslide well. By using the multi-tempral landslide layers, the accuracy of the landslide potential maps can be compared, The analytical results show the predict landslide precisely where 70.48% landslide fall on the high susceptibility zone. Finally the analytical results can effective application to watershed management planning and preliminary forecast of disaster prevention.

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48

Martinez, Carlos J. „Seasonal Climatology, Variability, Characteristics, and Prediction of the Caribbean Rainfall Cycle“. Thesis, 2021. https://doi.org/10.7916/d8-byp7-1b34.

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The Caribbean is a complex region that heavily relies on its seasonal rainfall cycle for its economic and societal needs. This makes the Caribbean especially susceptible to hydro-meteorological disasters (e.g., droughts and floods), and other weather/climate risks. Therefore, effectively predicting the Caribbean rainfall cycle is valuable for the region. The efficacy of predicting the Caribbean rainfall cycle is largely dependent on effectively characterizing the climate dynamics of the region. However, the dynamical processes and climate drivers that shape the seasonal cycle are not fully understood, as previous observational studies show inconsistent findings as to what mechanisms influence the mean state and variability of the cycle. These inconsistencies can be attributed to the limitations previous studies have when investigating the Caribbean rainfall cycle, such as using monthly or longer resolutions in the data or analysis that often mask the seasonal transitions and regional differences of rainfall, and investigating the Caribbean under a basin-wide lens rather than a sub-regional lens. This inhibits the ability to accurately calculate and predict subseasonal-to-seasonal (S2S) rainfall characteristics in the region. To address these limitations and inconsistencies, the research in this thesis examines the seasonal climatology, variability, and characteristics of the Caribbean rainfall cycle under a sub-regional and temporally fine lens in order to investigate the prediction of the cycle. Regional variations and dynamical processes of the Caribbean annual rainfall cycle are assessed using (1) a principal component analysis across Caribbean stations using daily observed precipitation data; and, (2) a moisture budget analysis. The results show that the seasonal cycle of rainfall in the Caribbean hinges on three main facilitators of moisture convergence: the Atlantic Intertropical Convergence Zone (ITCZ), the Eastern Pacific ITCZ, and the North Atlantic Subtropical High (NASH). A warm body of sea-surface temperatures (SSTs) in the Caribbean basin known as the Atlantic Warm Pool (AWP) and a low-level jet centered at 925hPa over the Caribbean Sea known as the Caribbean Low-Level Jet (CLLJ) modify the extent of moisture provided by these main facilitators. The interactions of these dynamical processes are responsible for shaping the seasonal components of the annual rainfall cycle: The Winter Dry Season (WDS; mid-November to April); the Early-Rainy Season (ERS; mid-April to mid-June); an intermittent relatively dry period known as the mid-summer drought, (MSD; mid-June to late August), and the Late-Rainy Season (LRS; late August to late November). Five geographical sub-regions are identified in the Caribbean Islands, each with its unique set of dynamical processes, and consequently, its unique pattern of rainfall distribution throughout the rainy season: Northwestern Caribbean, the Western Caribbean, the Central Caribbean, the Central and Southern Lesser Antilles, and Trinidad and Tobago and Guianas. Convergence by sub-monthly transients contributes little to Caribbean rainfall. The wettest and driest Caribbean ERS and LRS years’ are then explored by conducting the following: (1) a spatial composite of rainfall using the daily rainfall data; and, (2) spatial composites of SSTs, sea-level pressure (SLP), and mean flow moisture convergence and transports using monthly data. The ERS and LRS are impacted in distinctly different ways by two different, and largely independent, large-scale phenomena, external to the region: a SLP dipole mode of variability in the North Atlantic known as the North Atlantic Oscillation (NAO), and the El Nino Southern Oscillation (ENSO). Dry ERS years are associated with a persistent dipole of cold and warm SSTs over the Caribbean Sea and Gulf of Mexico, respectively, that are caused by a preceding positive NAO state. This setting involves a wind-evaporation-SST (WES) feedback expressed in enhanced trade winds and consequently, moisture transport divergence over all of the Caribbean, except in portions of the Northwestern Caribbean in May. A contribution from the preceding winter cold ENSO event is also discernible during dry ERS years. Dry LRS years are due to the summertime onset of an El Niño event, developing an inter-basin SLP pattern that moves moisture out of the Caribbean, except in portions of the Northwestern Caribbean in November. Both large-scale climate drivers would have the opposite effect during their opposite phases leading to wet years in both seasons. Existing methodologies that calculate S2S rainfall characteristics were not found to be suitable for a region like the Caribbean, given its complex rainfall pattern; therefore, a novel and comprehensive method is devised and utilized to calculate onset, demise, and MSD characteristics in the Caribbean. When applying the method to calculate S2S characteristics in the Caribbean, meteorological onsets and demises, which are calculated via each year’s ERS and LRS mean thresholds, effectively characterize the seasonal evolution of mean onsets and demises in the Caribbean. The year-to-year variability of MSD characteristics, and onsets and demises that are calculated by climatological ERS and LRS mean thresholds resemble the variability of seasonal rainfall totals in the Caribbean and are statistically significantly correlated with the identified dynamical processes that impact each seasonal component of the rainfall cycle. Finally, the seasonal prediction of the Caribbean rainfall cycle is assessed using the identified variables that could provide predictive skill of S2S rainfall characteristics in the region. Canonical correlation analysis is used to predict seasonal rainfall characteristics of station-averaged sub-regional frequency and intensity of the ERS and LRS wet days, and magnitude of the MSD. Predictor fields are based on observations from the ERA-Interim reanalysis and GCM output from the North America Multi-Model Ensemble (NMME). Spearman Correlation and Relative Operating Characteristics are applied to assess the forecast skill. The use of SLP, 850-hPa zonal winds (u850), vertically integrated zonal (UQ), and meridional (VQ) moisture fluxes show comparable, if not better, forecast skill than SSTs, which is the most common predictor field for regional statistical prediction. Generally, the highest ERS predictive skill is found for the frequency of wet days, and the highest LRS predictive skill is found for the intensity of wet days. Rainfall characteristics in the Central and Eastern Caribbean have statistically significant predictive skill. Forecast skill of rainfall characteristics in the Northwestern and Western Caribbean are lower and less consistent. The sub-regional differences and consistently significant skill across lead times up to at least two months can be attributed to persistent SST/SLP anomalies during the ERS that resemble the North Atlantic Oscillation pattern, and the summer-time onset of the El Niño-Southern Oscillation during the LRS. The spatial pattern of anomalies during the MSD bears resemblance to both the ERS and LRS spatial patterns. The findings from this thesis provide a more comprehensive and complete understanding of the climate dynamics, variability, and annual mean state of the Caribbean rainfall cycle. These results have important implications for prediction, decision-making, modeling capabilities, understanding the genesis of hydro-meteorological disasters, investigating rainfall under other modes of variability, and Caribbean impact studies regarding weather risks and future climate.

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49

Chen, Yuan-Jung, und 陳垣榮. „Relationship between rainfall return period and landslide characteristics in a watershed“. Thesis, 2015. http://ndltd.ncl.edu.tw/handle/09819095636978531064.

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碩士
國立中興大學
水土保持學系所
103
Previous studies on the collapses indicated that the weak geology condition and extreme rainfall are the main reasons of landslide. However, it was unable to explain the neighboring non-failure site, which the similar geological condition. Frequency of landslide event is always inversely proportional to the landslide scale, and therefore return period and scale should be distinguished. In addition, landslides in the watershed could be categorized by the occurrence locations i.e. near-riverbank and off-riverbank landslide, which are not only caused different mechanism but also different landslide scale. Near-riverbank landslides are mainly affected by a stream, whereas off-riverbank landslides are usually influenced by rainfall intensity. Thus, the relationship between the collapse location characteristics and different rainfall return periods is relatively important to explore. Chen-You-Lan watershed was selected as the study area due to numerous landslides. The events of Typhoon Herb, Toraji and Morakot, which caused more serious disasters, were selected to estimate rainfall return period and extract the each newly collapses. According to the terrain and land use of landslide sites, the collapse sites can be classified as headstream, river, road and cultivation categories. In addition, the spatial distribution and trend relationships for the collapse site and the correspondent scale were also well discussed under the different return periods. The results showed that rainfall return period of the selected events is quite different although the rainfall intensity is similar. Typhoon Herb has the highest return period (100-yr) followed by Typhoon Toraji (60-yr) and Typhoon Morakot (24-yr), respectively. Typhoon herb also caused the largest amount of collapse area and volume, which implies the noticeable factor for the collapse scale is rainfall return period. There were only 10% of the recurrent landslides occurred during the tested Typhoon events. It was found that there are about 67.88% and 33.22% recurrent landslide occurred at the sites of near-riverbank and off-riverbank respectively. There exists an 80% of collapse areas occurred at near-riverbank and 20% of that happened at the off-riverbank. This phenomenon indicated that the extreme rainfall event could trigger most of new born landslides in the watershed, and the return period of an extreme event could be used as effective indicator to estimate the potential collapse and its scale.

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50

Hung-ChingYang und 楊宏慶. „Influence of Rainfall Intensity and Slope Characteristics on Slope Stability Analysis“. Thesis, 2012. http://ndltd.ncl.edu.tw/handle/30236453887959959231.

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碩士
國立成功大學
資源工程學系碩博士班
100
The rainfall is the most important factor in slope stability, and the rainfall infiltration is affected by the behavior of soil in the unsaturated zone. The unsaturated state is very common in nature, but the analysis of unsaturated zone is very difficult, therefore, we use the Slope/w and Seep/w modules in the Geo-Studio program to simulate slope stability and rainfall infiltration. In this study, we change rainfall intensity and slope condition to get the relationship between factor of safety and time, and discuss the influence of rainfall intensity and slope characteristics on slope stability. In the study, we discuss the different nature of slope, such as slope material, slope angle, slope height, the groundwater table deep and rainfall patterns. Results indicated that the slope becomes more danger when the slope angle, slope height and rainfall intensity increase, and the hydraulic conductivity of the material determines the impact of the rainfall on slope stability. It has less influence than the rainfall intensity on slope stability when we change the depth of groundwater table depth. In the part of rainfall patterns, the results show that it has great connection between slope stability and occurrence of peak rainfall intensity. In this study, we also discuss the slope failure at the Shanher Stream and the Xiao Lin village, and analysis the slope failure time which are induced by the rainfall. In the case of Xiao Lin village, the simulation result of failure time has an error of one hour, and the result of Shanher Stream is quite consistent with the actual failure time.

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Dissertationen zum Thema „Rainfall characteristics“

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