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Wild, Martin. "Enlightening Global Dimming and Brightening". Bulletin of the American Meteorological Society 93, n.º 1 (enero de 2012): 27–37. http://dx.doi.org/10.1175/bams-d-11-00074.1.
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Tanaka, Katsumasa, Atsumu Ohmura, Doris Folini, Martin Wild y Nozomu Ohkawara. "Is global dimming and brightening in Japan limited to urban areas?" Atmospheric Chemistry and Physics 16, n.º 21 (11 de noviembre de 2016): 13969–4001. http://dx.doi.org/10.5194/acp-16-13969-2016.
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Abstract. Worldwide observations indicate secular trends of all-sky surface solar radiation on a decadal time scale, termed global dimming and brightening. Accordingly, the observed surface radiation in Japan generally shows a strong decline until the end of the 1980s and then a recovery until around 2000. Because a substantial number of measurement stations are located within or close to populated areas, one may speculate that the observed trends are strongly influenced by local air pollution and are thus not of large-scale significance. This hypothesis poses a serious question as to what regional extent the global dimming and brightening are significant: are the global dimming and brightening truly global phenomena, or regional, or even only local? Our study focused on 14 meteorological observatories that measured all-sky surface solar radiation, zenith transmittance, and maximum transmittance. On the basis of municipality population time series, historical land use maps, recent satellite images, and actual site visits, we concluded that eight stations have been significantly influenced by urbanization, with the remaining six stations being left pristine. Between the urban and rural areas, no marked differences were identified in the temporal trends of the aforementioned meteorological parameters. Our findings suggest that global dimming and brightening in Japan occurred on a large scale, independently of urbanization.
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Stanhill, Gerald. "A perspective on global warming, dimming, and brightening". Eos, Transactions American Geophysical Union 88, n.º 5 (30 de enero de 2007): 58. http://dx.doi.org/10.1029/2007eo050007.
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Hatzianastassiou, Nikolaos, Eleftherios Ioannidis, Marios-Bruno Korras-Carraca, Maria Gavrouzou, Christos D. Papadimas, Christos Matsoukas, Nikolaos Benas, Angeliki Fotiadi, Martin Wild y Ilias Vardavas. "Global Dimming and Brightening Features during the First Decade of the 21st Century". Atmosphere 11, n.º 3 (21 de marzo de 2020): 308. http://dx.doi.org/10.3390/atmos11030308.
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Downward surface solar radiation (SSR) trends for the first decade of the 2000s were computed using a radiative transfer model and satellite and reanalysis input data and were validated against measurements from the reference global station networks Global Energy Balance Archive (GEBA) and Baseline Surface Radiation Network (BSRN). Under all-sky conditions, in spite of a somewhat patchy structure of global dimming and brightening (GDB), an overall dimming was found that is weaker in the Northern than in the Southern Hemisphere (−2.2 and −3.1 W m−2, respectively, over the 2001–2009 period). Dimming is observed over both land and ocean in the two hemispheres, but it is more remarkable over land areas of the Southern Hemisphere. The post-2000 dimming is found to have been primarily caused by clouds, and secondarily by aerosols, with total cloud cover contributing −1.4 W m−2 and aerosol optical thickness −0.7 W m−2 to the global average dimming of −2.65 W m−2. The evaluation of the model-computed GDB against BSRN and GEBA measurements indicates a good agreement, with the same trends for 65% and 64% of the examined stations, respectively. The obtained model results are in line with other studies for specific world regions and confirm the occurrence of an overall solar dimming over the globe during the first decade of 21st century. This post-2000 dimming has succeeded the global brightening observed in the 1990s and points to possible impacts on the ongoing global warming and climate change.
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Wang, Kaicun, Robert E. Dickinson, Qian Ma, John A. Augustine y Martin Wild. "Measurement Methods Affect the Observed Global Dimming and Brightening". Journal of Climate 26, n.º 12 (15 de junio de 2013): 4112–20. http://dx.doi.org/10.1175/jcli-d-12-00482.1.
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Abstract Surface incident solar radiation G determines our climate and environment, and has been widely observed with a single pyranometer since the late 1950s. Such observations have suggested a widespread decrease between the 1950s and 1980s (global dimming), that is, at a rate of −3.5 W m−2 decade−1 (or −2% decade−1) from 1960 to 1990. Since the early 1990s, the diffuse and direct components of G have been measured independently, and a more accurate G has been calculated by summing these two measurements. Data from this summation method suggest that G increased at a rate of 6.6 W m−2 decade−1 (3.6% decade−1) from 1992 to 2002 (brightening) at selected sites. The brightening rates from these studies were also higher than those from a single pyranometer. In this paper, the authors used 17 years (1995–2011) of parallel measurements by the two methods from nearly 50 stations to test whether these two measurement methods of G provide similar long-term trends. The results show that although measurements of G by the two methods agree very well on a monthly time scale, the long-term trend from 1995 to 2011 determined by the single pyranometer is 2–4 W m−2 decade−1 less than that from the summation method. This difference of trends in the observed G is statistically significant. The dependence of trends of G on measurement methods uncovered here has an important implication for the widely reported global dimming and brightening based on datasets collected by different measurement methods; that is, the dimming might have been less if measured with current summation methods.
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Wang, Y. W. y Y. H. Yang. "China's dimming and brightening: evidence, causes and hydrological implications". Annales Geophysicae 32, n.º 1 (28 de enero de 2014): 41–55. http://dx.doi.org/10.5194/angeo-32-41-2014.
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Abstract. There is growing evidence that, corresponding to global dimming and brightening, surface solar radiation and sunshine hours over China have undergone decadal fluctuations during the 1960s–2000s. The results of a number of these analyses are, however, very different. In this study, we synthesize reliable results and conclusively address recent advances and insufficiencies in studies on dimming and brightening in China. A temporally and spatially prevalent dimming trend is noted in surface solar radiation, direct solar radiation and sunshine hours since the 1960s. Meanwhile, the changing trend in diffuse solar radiation is less pronounced. Increasing anthropogenic aerosol loading is regarded as the most plausible explanation for China's dimming. The brightening trend since 1990, which mainly occurs in southeastern China and in the spring season, is weak and insignificant. The reverse in the solar radiation trend is associated with climate change by cloud suppression and slowdown in anthropogenic emissions. The future solar radiation trend in China could largely depend on the development of air quality control. Other potential driving factors such as wind speed, water vapor and surface albedo are also non-negligible in specific regions of China. Hydrological implications of dimming and brightening in China lack systematic investigation. However, the fact that solar radiation and pan evaporation trends in China track a similar curve in 1990 further suggests that the pan evaporation paradox could be partly resolved by changes in solar radiation.
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Ohring, George, Shabtai Cohen, Joel Norris, Alan Robock, Yinon Rudich, Martin Wild y Warren Wiscombe. "Global Dimming and Brightening: International Workshop of the Israel Science Foundation on Global Dimming and Brightening; Ein Gedi, Israel, 10-14 February 2008". Eos, Transactions American Geophysical Union 89, n.º 23 (3 de junio de 2008): 212. http://dx.doi.org/10.1029/2008eo230008.
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Liepert, Beate, Martin Wild y Ellsworth Dutton. "Comment on “A perspective on global warming, dimming, and brightening”". Eos, Transactions American Geophysical Union 88, n.º 45 (6 de noviembre de 2007): 473. http://dx.doi.org/10.1029/2007eo450011.
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Parding, Kajsa M., Beate G. Liepert, Laura M. Hinkelman, Thomas P. Ackerman, Knut-Frode Dagestad y Jan Asle Olseth. "Influence of Synoptic Weather Patterns on Solar Irradiance Variability in Northern Europe". Journal of Climate 29, n.º 11 (24 de mayo de 2016): 4229–50. http://dx.doi.org/10.1175/jcli-d-15-0476.1.
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Abstract Observations have revealed strong variability of shortwave (SW) irradiance at Earth’s surface on decadal time scales, referred to as global dimming and brightening. Previous studies have attributed the dimming and brightening to changes in clouds and atmospheric aerosols. This study assesses the influence of atmospheric circulation on clouds and SW irradiance to separate the influence of “natural” SW variability from direct and, to some extent, indirect aerosol effects. The focus is on SW irradiance in northern Europe in summer and spring because there is little high-latitude SW irradiance during winter. As a measure of large-scale circulation the Grosswetterlagen (GWL) dataset, a daily classification of synoptic weather patterns, is used. Empirical models of normalized SW irradiance are constructed based on the GWL, relating the synoptic weather patterns to the local radiative climate. In summer, a temporary SW peak in the 1970s and subsequent dimming is linked to variations in the synoptic patterns over Scandinavia, possibly related to a northward shift in the North Atlantic storm track. In spring, a decrease of anticyclonic and increase of cyclonic weather patterns over northern Europe contributes to the dimming from the 1960s to 1990. At many sites, there is also a residual SW irradiance trend not explained by the GWL model: a weak nonsignificant residual dimming from the 1950s or 1960s to around 1990, followed by a statistically significant residual brightening. It is concluded that factors other than the large-scale circulation (e.g., decreasing aerosol emissions) also play an important role in northern Europe.
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Lin, Jia Lin y Tao Tao Qian. "Solar Energy and Global Climate Change". Advanced Materials Research 875-877 (febrero de 2014): 1767–70. http://dx.doi.org/10.4028/www.scientific.net/amr.875-877.1767.
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Previous studies have shown that the solar energy input to the earth system underwent significant decadal variations at individual surface energy budget stations, with a global dimming from 1950s to 1980s, but a global brightening from 1980s to 2000s, and a mixed tendency at different locations thereafter. Here we use a new global gridded solar irradiance dataset to show that the previous results from individual stations represent well the regional means but not the global mean or hemisphere means. The global mean has a decadal variation that is quite different from the individual station results reported in previous studies, which comes from the fact that the southern hemisphere mean has an opposite trend with the northern hemisphere mean. No long-term global dimming trend is found associated with global warming
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Schmidt, Gavin A., Anastasia Romanou y Beate Liepert. "Further comment on “A perspective on global warming, dimming, and brightening”". Eos, Transactions American Geophysical Union 88, n.º 45 (6 de noviembre de 2007): 473. http://dx.doi.org/10.1029/2007eo450012.
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Hu, Qi, Xueqing Ma, Huayun He, Feifei Pan, Qijin He, Binxiang Huang y Xuebiao Pan. "Warming and Dimming: Interactive Impacts on Potential Summer Maize Yield in North China Plain". Sustainability 11, n.º 9 (5 de mayo de 2019): 2588. http://dx.doi.org/10.3390/su11092588.
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Global warming and dimming/brightening have significant implications for crop systems and exhibit regional variations. It is important to clarify the changes in regional thermal and solar radiation resources and estimate the impacts on potential crop production spatially and temporally. Based on daily observation data during 1961–2015 in the North China Plain (NCP), the impacts of climate change associated with climate warming and global dimming/brightening on potential light–temperature productivity (PTP) of summer maize were assessed in this study. Results show that the NCP experienced a continuous warming and dimming trend in maize growing season during the past 55 years, and both ATT10 and solar radiation had an abrupt change in the mid-1990s. The period of 2000–2015 was warmer and dimmer than any other previous decade. Assuming the maize growing season remains unchanged, climate warming would increase PTP of summer maize by 4.6% over the period of 1961–2015, which mainly occurred in the start grain filling–maturity stage. On the other hand, as negative contribution value of solar radiation to the PTP was found in each stage, dimming would offset the increase of PTP due to warming climate, and lead to a 15.6% reduction in PTP in the past 55 years. This study reveals that the changes in thermal and solar radiation have reduced the PTP of summer maize in the NCP. However, the actual maize yield could benefit more from climate warming because solar radiation is not a limiting factor for the current low production level.
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Zhao, N., X. Zeng y H. Sun. "Impact of global dimming on reference evapotranspiration in Hai River basin, China". Proceedings of the International Association of Hydrological Sciences 368 (7 de mayo de 2015): 287–92. http://dx.doi.org/10.5194/piahs-368-287-2015.
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Abstract. Global radiation can impact the surface energy balance and hydrological cycle. This study analysed changes in global radiation in Hai River basin, China during 1960 to 2012. Global radiation decreased significantly from 1960 to 1989 and increased from 1990 to 2012, which has been described as “from dimming to brightening”. Sunshine duration was used as a proxy index where radiation records were unavailable. Results showed that sunshine duration (for 45 stations) show a significant decreasing trend from 1960 to 2012, which was a little different to global radiation (for 6 stations) during the brightening phase. Penman-Monteith model was used for estimating trends of reference evapotranspiration. The consistency of temporal and spatial variations in sunshine duration and reference evapotranspiration was examined during the periods 1960−1989 and 1990−2012. The results showed that the annual reference evapotranspiration trend was consistent with the sunshine duration trend (both were decreasing for 37 of the 45 stations) during 1960 to 1989, followed by an upward trend (for 26 of the 45 stations) from 1990, while the annual sunshine duration indicated a downward trend (for all 45 stations) during the whole period 1960−2012. Overall, global dimming could be the dominant factor for the decreased reference evapotranspiration from 1960 to 1989, while the increased reference evapotranspiration from 1990 to 2012 could be driven by other meteorological variables, especially global warming.
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Müller, Björn, Martin Wild, Anton Driesse y Klaus Behrens. "Rethinking solar resource assessments in the context of global dimming and brightening". Solar Energy 99 (enero de 2014): 272–82. http://dx.doi.org/10.1016/j.solener.2013.11.013.
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He, Yanyi, Kaicun Wang, Chunlüe Zhou y Martin Wild. "A Revisit of Global Dimming and Brightening Based on the Sunshine Duration". Geophysical Research Letters 45, n.º 9 (5 de mayo de 2018): 4281–89. http://dx.doi.org/10.1029/2018gl077424.
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Stanhill, Gerald. "Reply to Comments on “A perspective on global warming, dimming, and brightening”". Eos, Transactions American Geophysical Union 88, n.º 45 (6 de noviembre de 2007): 473. http://dx.doi.org/10.1029/2007eo450013.
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Brazel, Anthony y Roger Tomalty. "Shortwave Irradiance (1950 to 2020): Dimming, Brightening, and Urban Effects in Central Arizona?" Climate 9, n.º 9 (28 de agosto de 2021): 137. http://dx.doi.org/10.3390/cli9090137.
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The objective of this study was to evaluate long-term change in shortwave irradiance in central Arizona (1950–2020) and to detect apparent dimming/brightening trends that may relate to many other global studies. Global Energy Budget Archives (GEBA) monthly data were accessed for the available years 1950–1994 for Phoenix, Arizona and other selected sites in the Southwest desert. Monthly data of the database called gridMET were accessed, a 4-km gridded climate data based on NLDAS-2 and available for the years 1979–2020. Three Agricultural Meteorological Network (AZMET) automated weather stations in central Arizona have observed hourly shortwave irradiance over the period 1987–present. Two of the rural AZMET sites are located north and south of the Phoenix Metropolitan Area, and another site is in the center of the city of Phoenix. Using a combination of GEBA, gridMET, and AZMET data, annual time series demonstrate dimming up to late 1970s, early 1980s of −30 W/m2 (−13%), with brightening changes in the gridMET data post-1980 of +9 W/m2 (+4.6%). An urban site of the AZMET network showed significant reductions post-1987 up to 2020 of −9 W/m2 (3.8%) with no significant change at the two rural sites.
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Wild, Martin y Edgar Schmucki. "Assessment of global dimming and brightening in IPCC-AR4/CMIP3 models and ERA40". Climate Dynamics 37, n.º 7-8 (16 de noviembre de 2010): 1671–88. http://dx.doi.org/10.1007/s00382-010-0939-3.
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Kvalevåg, Maria M. y Gunnar Myhre. "Human Impact on Direct and Diffuse Solar Radiation during the Industrial Era". Journal of Climate 20, n.º 19 (1 de octubre de 2007): 4874–83. http://dx.doi.org/10.1175/jcli4277.1.
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Abstract In this study the direct and diffuse solar radiation changes are estimated, and they contribute to the understanding of the observed global dimming and the more recent global brightening during the industrial era. Using a multistream radiative transfer model, the authors calculate the impact of changes in ozone, NO2, water vapor, CH4, CO2, direct and indirect aerosol effects, contrails, and aviation-induced cirrus on solar irradiances at the surface. The results show that dimming is most pronounced in central Africa, Southeast Asia, Europe, and northeast America. Human activity during the industrial era is calculated and accounts for a decrease in direct solar radiation at the surface of up to 30 W m−2 (30%–40%) and an increase in diffuse solar radiation of up to 20 W m−2. The physical processes that lead to the changes in direct and diffuse solar radiation are found to be remarkably different and the authors explain which mechanisms are responsible for the observed changes.
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Cavanagh, Patrick y Stuart Anstis. "Diamond Patterns: Cumulative Cornsweet Effects and Motion-Induced Brightening". i-Perception 9, n.º 4 (julio de 2018): 204166951877069. http://dx.doi.org/10.1177/2041669518770690.
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A Cornsweet edge creates the perception of a step in surface lightness between two adjacent regions of identical mean luminance due to a gradient on both sides. We might imagine that in a concatenated set of these gradients, the lightness steps would accumulate, but they do not. However, a diamond pattern, with each diamond filled with an identical luminance gradient does give a cumulative Cornsweet effect. Here, we offer an illumination explanation for why the cumulative effect is visible in the diamonds but not in the basic ramp grating and we demonstrate that when the diamonds drift, they produce a strong brightening effect (depending on the direction of the motion) and a dimming aftereffect. These effects are consistent with the local luminance gradients and not with the global lightness shift of the cumulative Cornsweet effect.
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Stjern, Camilla W., Jón Egill Kristjánsson y Aksel Walløe Hansen. "Global dimming and global brightening-an analysis of surface radiation and cloud cover data in northern Europe". International Journal of Climatology 29, n.º 5 (abril de 2009): 643–53. http://dx.doi.org/10.1002/joc.1735.
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Moseid, Kine Onsum, Michael Schulz, Trude Storelvmo, Ingeborg Rian Julsrud, Dirk Olivié, Pierre Nabat, Martin Wild et al. "Bias in CMIP6 models as compared to observed regional dimming and brightening". Atmospheric Chemistry and Physics 20, n.º 24 (22 de diciembre de 2020): 16023–40. http://dx.doi.org/10.5194/acp-20-16023-2020.
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Abstract. Anthropogenic aerosol emissions have increased considerably over the last century, but climate effects and quantification of the emissions are highly uncertain as one goes back in time. This uncertainty is partly due to a lack of observations in the pre-satellite era, making the observations we do have before 1990 additionally valuable. Aerosols suspended in the atmosphere scatter and absorb incoming solar radiation and thereby alter the Earth's surface energy balance. Previous studies show that Earth system models (ESMs) do not adequately represent surface energy fluxes over the historical era. We investigated global and regional aerosol effects over the time period 1961–2014 by looking at surface downwelling shortwave radiation (SDSR). We used observations from ground stations as well as multiple experiments from eight ESMs participating in the Coupled Model Intercomparison Project Version 6 (CMIP6). Our results show that this subset of models reproduces the observed transient SDSR well in Europe but poorly in China. We suggest that this may be attributed to missing emissions of sulfur dioxide in China, sulfur dioxide being a precursor to sulfate, which is a highly reflective aerosol and responsible for more reflective clouds. The emissions of sulfur dioxide used in the models do not show a temporal pattern that could explain observed SDSR evolution over China. The results from various aerosol emission perturbation experiments from DAMIP, RFMIP and AerChemMIP show that only simulations containing anthropogenic aerosol emissions show dimming, even if the dimming is underestimated. Simulated clear-sky and all-sky SDSR do not differ greatly, suggesting that cloud cover changes are not a dominant cause of the biased SDSR evolution in the simulations. Therefore we suggest that the discrepancy between modeled and observed SDSR evolution is partly caused by erroneous aerosol and aerosol precursor emission inventories. This is an important finding as it may help interpret whether ESMs reproduce the historical climate evolution for the right or wrong reason.
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Wandji Nyamsi, William, Antti Lipponen, Arturo Sanchez-Lorenzo, Martin Wild y Antti Arola. "A hybrid method for reconstructing the historical evolution of aerosol optical depth from sunshine duration measurements". Atmospheric Measurement Techniques 13, n.º 6 (11 de junio de 2020): 3061–79. http://dx.doi.org/10.5194/amt-13-3061-2020.
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Abstract. A novel method has been developed to estimate aerosol optical depth (AOD) from sunshine duration (SD) measurements under cloud-free conditions. It is a physically based method serving for the reconstruction of the historical evolution of AOD during the last century. In addition to sunshine duration data, it requires daily water vapor and ozone products as inputs taken from the ECMWF 20th century reanalysis ERA-20C, available at the global scale over the period 1900–2010. Surface synoptic cloud observations are used to identify cloud-free days. For 16 sites over Europe, the accuracy of the estimated daily AOD, and its seasonal variability, is similar to or better than those from two earlier methods when compared to AErosol RObotic NETwork measurements. In addition, it also improves the detection of the signal from massive aerosol events such as important volcanic eruptions (e.g., Arenal and Fernandina Island in 1968, El Chichón in 1982 and Pinatubo in 1992). Finally, the reconstructed AOD time series are in good agreement with the dimming/brightening phenomenon and also provide preliminary evidence of the early-brightening phenomenon.
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Wang, Zhiguo, Junzhu Du y Na Zhao. "Impact of global dimming/brightening on estimating Angström-Prescott parameters based on geographically weighted regression in China". IOP Conference Series: Earth and Environmental Science 634 (5 de febrero de 2021): 012006. http://dx.doi.org/10.1088/1755-1315/634/1/012006.
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Qian, Cheng, Congbin Fu y Zhaohua Wu. "Changes in the Amplitude of the Temperature Annual Cycle in China and Their Implication for Climate Change Research". Journal of Climate 24, n.º 20 (15 de octubre de 2011): 5292–302. http://dx.doi.org/10.1175/jcli-d-11-00006.1.
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Abstract Climate change is not only reflected in the changes in annual means of climate variables but also in the changes in their annual cycles (seasonality), especially in the regions outside the tropics. In this study, the ensemble empirical mode decomposition (EEMD) method is applied to investigate the nonlinear trend in the amplitude of the annual cycle (which contributes 96% of the total variance) of China’s daily mean surface air temperature for the period 1961–2007. The results show that the variation and change in the amplitude are significant, with a peak-to-peak annual amplitude variation of 13% (1.8°C) of its mean amplitude and a significant linear decrease in amplitude by 4.6% (0.63°C) for this period. Also identified is a multidecadal change in amplitude from significant decreasing (−1.7% decade−1 or −0.23°C decade−1) to significant increasing (2.2% decade−1 or 0.29°C decade−1) occurring around 1993 that overlaps the systematic linear trend. This multidecadal change can be mainly attributed to the change in surface solar radiation, from dimming to brightening, rather than to a warming trend or an enhanced greenhouse effect. The study further proposes that the combined effect of the global dimming–brightening transition and a gradual increase in greenhouse warming has led to a perceived warming trend that is much larger in winter than in summer and to a perceived accelerated warming in the annual mean since the early 1990s in China. It also notes that the deseasonalization method (considering either the conventional repetitive climatological annual cycle or the time-varying annual cycle) can also affect trend estimation.
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Yamasoe, Marcia Akemi, Nilton Manuel Évora Rosário, Samantha Novaes Santos Martins Almeida y Martin Wild. "Fifty-six years of surface solar radiation and sunshine duration over São Paulo, Brazil: 1961–2016". Atmospheric Chemistry and Physics 21, n.º 9 (3 de mayo de 2021): 6593–603. http://dx.doi.org/10.5194/acp-21-6593-2021.
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Abstract. A total of 56 years (1961–2016) of daily surface downward solar irradiation, sunshine duration, diurnal temperature range and the fraction of the sky covered by clouds in the city of São Paulo, Brazil, were analysed. The main purpose was to contribute to the characterization and understanding of the dimming and brightening effects on solar global radiation in this part of South America. As observed in most of the previous studies worldwide, in this study, during the period between 1961 and the early 1980s, a negative trend in surface solar irradiation was detected in São Paulo, characterizing the occurrence of a dimming effect. Sunshine duration and the diurnal temperature range also presented negative trends, in opposition to the positive trend observed in the cloud cover fraction. However, a brightening effect, as observed in western industrialized countries in more recent years, was not observed. Instead, for surface downward irradiation, the negative trend persisted, with a trend of −0.13 MJ m−2 per decade, with a p value of 0.006, for the 56 years of data and in consonance with the cloud cover fraction increasing trend, but not statistically significant, of 0.3 % per decade (p value = 0.198). The trends for sunshine duration and the diurnal temperature range, by contrast, changed signal, as confirmed by a piecewise linear regression model. Some possible causes for the discrepancy are discussed, such as the frequency of fog occurrence, urban heat island effects, horizontal visibility (as a proxy for aerosol loading variability) and greenhouse gas concentration increase. Future studies on the aerosol effect are planned, particularly with higher temporal resolution, as well as modelling studies, to better analyse the contribution of each possible cause.
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Feister, U., J. Junk y M. Woldt. "Long-term solar UV radiation reconstructed by Artificial Neural Networks (ANN)". Atmospheric Chemistry and Physics Discussions 8, n.º 1 (10 de enero de 2008): 453–88. http://dx.doi.org/10.5194/acpd-8-453-2008.
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Abstract. Artificial Neural Networks (ANN) are efficient tools to derive solar UV radiation from measured meteorological parameters such as global radiation, aerosol optical depths and atmospheric column ozone. The ANN model has been tested with different combinations of data from the two sites Potsdam and Lindenberg, and used to reconstruct solar UV radiation at eight European sites by more than 100 years into the past. Annual totals of UV radiation derived from reconstructed daily UV values reflect interannual variations and long-term patterns that are compatible with variabilities and changes of measured input data, in particular global dimming by about 1980–1990, subsequent global brightening, volcanic eruption effects such as that of Mt. Pinatubo, and the long-term ozone decline since the 1970s. Patterns of annual erythemal UV radiation are very similar at sites located at latitudes close to each other, but different patterns occur between UV radiation at sites in different latitude regions.
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Loew, Alexander, Axel Andersson, Jörg Trentmann y Marc Schröder. "Assessing Surface Solar Radiation Fluxes in the CMIP Ensembles". Journal of Climate 29, n.º 20 (23 de septiembre de 2016): 7231–46. http://dx.doi.org/10.1175/jcli-d-14-00503.1.
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Abstract Earth system models are indispensable tools in climate studies. The Coupled Model Intercomparison Project (CMIP) is a coordinated effort of the Earth system modeling community to intercompare existing models. An accurate simulation of surface solar radiation fluxes is of major importance for the accuracy of simulations of the near-surface climate in Earth system models. The present study provides a quantitative assessment of the accuracy and multidecadal changes of surface solar radiation fluxes for model results from two phases of CMIP. The entire archives of phase 5 of CMIP (CMIP5) and its predecessor phase 3 (CMIP3) are analyzed for present-day climate conditions. A relative model ranking is provided, and its uncertainty is quantified using different global observational records. It is shown that the choice of an observational dataset can have a major influence on relative model ranking between CMIP models. However the multidecadal variability of surface solar radiation fluxes, also known as global “dimming” or “brightening,” is largely underestimated by the CMIP models.
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Feister, U., J. Junk, M. Woldt, A. Bais, A. Helbig, M. Janouch, W. Josefsson et al. "Long-term solar UV radiation reconstructed by ANN modelling with emphasis on spatial characteristics of input data". Atmospheric Chemistry and Physics 8, n.º 12 (23 de junio de 2008): 3107–18. http://dx.doi.org/10.5194/acp-8-3107-2008.
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Abstract. Artificial Neural Networks (ANN) are efficient tools to derive solar UV radiation from measured meteorological parameters such as global radiation, aerosol optical depths and atmospheric column ozone. The ANN model has been tested with different combinations of data from the two sites Potsdam and Lindenberg, and used to reconstruct solar UV radiation at eight European sites by more than 100 years into the past. Special emphasis will be given to the discussion of small-scale characteristics of input data to the ANN model. Annual totals of UV radiation derived from reconstructed daily UV values reflect interannual variations and long-term patterns that are compatible with variabilities and changes of measured input data, in particular global dimming by about 1980/1990, subsequent global brightening, volcanic eruption effects such as that of Mt. Pinatubo, and the long-term ozone decline since the 1970s. Patterns of annual erythemal UV radiation are very similar at sites located at latitudes close to each other, but different patterns occur between UV radiation at sites in different latitude regions.
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García, R. D., E. Cuevas, O. E. García, V. E. Cachorro, P. Pallé, J. J. Bustos, P. M. Romero-Campos y A. M. de Frutos. "Reconstruction of global solar radiation time series from 1933 to 2013 at the Izaña Atmospheric Observatory". Atmospheric Measurement Techniques 7, n.º 9 (25 de septiembre de 2014): 3139–50. http://dx.doi.org/10.5194/amt-7-3139-2014.
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Abstract. This paper presents the reconstruction of the 80-year time series of daily global solar radiation (GSR) at the subtropical high-mountain Izaña Atmospheric Observatory (IZO) located in Tenerife (The Canary Islands, Spain). For this purpose, we combine GSR estimates from sunshine duration (SD) data using the Ångström–Prescott method over the 1933/1991 period, and GSR observations directly performed by pyranometers between 1992 and 2013. Since GSR measurements have been used as a reference, a strict quality control has been applied based on principles of physical limits and comparison with LibRadtran model. By comparing with high quality GSR measurements, the precision and consistency over time of GSR estimations from SD data have been successfully documented. We obtain an overall root mean square error (RMSE) of 9.2% and an agreement between the variances of GSR estimations and GSR measurements within 92%. Nonetheless, this agreement significantly increases when the GSR estimation is done considering different daily fractions of clear sky (FCS). In that case, RMSE is reduced by half, to about 4.5%, when considering percentages of FCS > 40% (~ 90% of days in the testing period). Furthermore, we prove that the GSR estimations can monitor the GSR anomalies in consistency with GSR measurements and, then, can be suitable for reconstructing solar radiation time series. The reconstructed IZO GSR time series between 1933 and 2013 confirms change points and periods of increases/decreases of solar radiation at Earth's surface observed at a global scale, such as the early brightening, dimming and brightening. This fact supports the consistency of the IZO GSR time series presented in this work, which may be a reference for solar radiation studies in the subtropical North Atlantic region.
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García, R. D., E. Cuevas, O. E. García, V. E. Cachorro, P. Pallé, J. J. Bustos, P. M. Romero-Campos y A. M. de Frutos. "Re-construction of global solar radiation time series from 1933 to 2013 at the Izaña Atmospheric Observatory". Atmospheric Measurement Techniques Discussions 7, n.º 4 (25 de abril de 2014): 4191–227. http://dx.doi.org/10.5194/amtd-7-4191-2014.
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Abstract. This paper presents the re-construction of the 80 year time series of daily global shortwave downward radiation (SDR) at the subtropical high-mountain Izaña Atmospheric Observatory (IZO, Spain). For this purpose, we combine SDR estimates from sunshine duration (SD) data using the Ångström–Prescott method over the 1933/1991 period, and SDR observations directly performed by pyranometers between 1992 and 2013. Since SDR measurements have been used as a reference, a strict quality control has been applied, when it was not possible data have been re-calibrated by using the LibRadtran model. By comparing to high quality SDR measurements, the precision and consistency over time of SDR estimations from SD data have successfully been documented. We obtain a overall root mean square error (RMSE) of 9.2% and an agreement between the variances of SDR estimations and SDR measurements within 92% (correlation coefficient of 0.96). Nonetheless, this agreement significantly increases when the SDR estimation is done considering different daily fractions of clear sky (FCS). In that case, RMSE is reduced by half, up to about 4.5%, when considering percentages of FCS > 40% (90% of days in the testing period). Furthermore, we prove that the SDR estimations can monitor the SDR anomalies in consistency with SDR measurements and, then, can be suitable for re-constructing solar radiation time series. The re-constructed IZO global SDR time series between 1933 and 2013 confirms discontinuities and periods of increases/decreases of solar radiation at Earth's surface observed at a global scale, such as the early brightening, dimming and brightening. This fact supports the consistency of the IZO SDR time series presented in this work, which may be a reference for solar radiation studies in the subtropical North Atlantic region.
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Bodas-Salcedo, A., M. A. Ringer y A. Jones. "Evaluation of the Surface Radiation Budget in the Atmospheric Component of the Hadley Centre Global Environmental Model (HadGEM1)". Journal of Climate 21, n.º 18 (15 de septiembre de 2008): 4723–48. http://dx.doi.org/10.1175/2008jcli2097.1.
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Abstract The partitioning of the earth radiation budget (ERB) between its atmosphere and surface components is of crucial interest in climate studies as it has a significant role in the oceanic and atmospheric general circulation. An analysis of the present-day climate simulation of the surface radiation budget in the atmospheric component of the new Hadley Centre Global Environmental Model version 1 (HadGEM1) is presented, and the simulations are assessed by comparing the results with fluxes derived from satellite data from the International Satellite Cloud Climatology Project (ISCCP) and ground measurements from the Baseline Surface Radiation Network (BSRN). Comparisons against radiative fluxes from satellite and ground observations show that the model tends to overestimate the surface incoming solar radiation (Ss,d). The model simulates Ss,d very well over the polar regions. Consistency in the comparisons against BSRN and ISCCP-FD suggests that the ISCCP-FD database is a good test for the performance of the surface downwelling solar radiation in climate model simulations. Overall, the simulation of downward longwave radiation is closer to observations than its shortwave counterpart. The model underestimates the downward longwave radiation with respect to BSRN measurements by 6.0 W m−2. Comparisons of land surface albedo from the model and estimates from the Moderate Resolution Imaging Spectroradiometer (MODIS) show that HadGEM1 overestimates the land surface albedo over deserts and over midlatitude landmasses in the Northern Hemisphere in January. Analysis of the seasonal cycle of the land surface albedo in different regions shows that the amplitude and phase of the seasonal cycle are not well represented in the model, although a more extensive validation needs to be carried out. Two decades of coupled model simulations of the twentieth-century climate are used to look into the model’s simulation of global dimming/brightening. The model results are in line with the conclusions of the studies that suggest that global dimming is far from being a uniform phenomenon across the globe.
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Wang, Zhiguo, Na Zhao y Zhongrun Hou. "Solar dimming or brightening in the upper reaches of the Yangtze River Basin under 1.5 °C and 2 °C global warming targets?" IOP Conference Series: Earth and Environmental Science 675, n.º 1 (1 de febrero de 2021): 012037. http://dx.doi.org/10.1088/1755-1315/675/1/012037.
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Radionov, V. F., Е. N. Rusina y E. Е. Sibir. "Long-term variability of annual sums of total and absorbed solar radiation in the Аrctic". Arctic and Antarctic Research, n.º 3 (30 de septiembre de 2017): 39–50. http://dx.doi.org/10.30758/0555-2648-2017-0-3-39-50.
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Variability of total (Q) and absorbed (Q – R) radiation after the year 2000 at some Russian Arctic stations in comparison with the long-term variability of these characteristics since the beginning of observations and until 1992 was investigated. As estimating parameters, the normalized by multiyear averages for 1961–1990 of anomalies of annual sums of total and absorbed radiation were chosen. We have analyzed the variability of total cloudiness and integral optical thickness characterizing transparency of the atmosphere as the factors producing the largest influence on total radiation incoming to the land surface. The integral optical thickness of the atmosphere in the Arctic after 2000 was most likely determined by specifics of air pollutants coming to the Arctic atmosphere and was significantly higher in the western Arctic area, than in the eastern one. After 2000 practically at all stations considered, the income of total radiation appeared to be below the multiyear average. Significant by the absolute value, but different by the sign, changes of absorbed radiation were recorded. The long-term periods of decrease and the subsequent increase of the incoming solar radiation observed at the European stations and called as “global dimming and global brightening” were not revealed at the Russian Arctic actinometric stations.
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Bartholomeus, R. P., J. H. Stagge, L. M. Tallaksen y J. P. M. Witte. "How over 100 years of climate variability may affect estimates of potential evaporation". Hydrology and Earth System Sciences Discussions 11, n.º 9 (24 de septiembre de 2014): 10787–828. http://dx.doi.org/10.5194/hessd-11-10787-2014.
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Abstract. Hydrological modeling frameworks require an accurate representation of evaporation fluxes for appropriate quantification of e.g. the soil moisture budget, droughts, recharge and groundwater processes. Many frameworks have used the concept of potential evaporation, often estimated for different vegetation classes by multiplying the evaporation from a reference surface ("reference evaporation") with crop specific scaling factors ("crop factors"). Though this two-step potential evaporation approach undoubtedly has practical advantages, the empirical nature of both reference evaporation methods and crop factors limits its usability in extrapolations and non-stationary climatic conditions. In this paper we assess the sensitivity of potential evaporation estimates for different vegetation classes using the two-step approach when calibrated using a non-stationary climate. We used the past century's time series of observed climate, containing non-stationary signals of multi-decadal atmospheric oscillations, global warming, and global dimming/brightening, to evaluate the sensitivity of potential evaporation estimates to the choice and length of the calibration period. We show that using empirical coefficients outside their calibration range may lead to systematic differences between process-based and empirical reference evaporation methods, and systematic errors in estimated potential evaporation components. Such extrapolations of time-variant model parameters are not only relevant for the calculation of potential evaporation, but also for hydrological modeling in general, and they may limit the temporal robustness of hydrological models.
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Bartholomeus, R. P., J. H. Stagge, L. M. Tallaksen y J. P. M. Witte. "Sensitivity of potential evaporation estimates to 100 years of climate variability". Hydrology and Earth System Sciences 19, n.º 2 (24 de febrero de 2015): 997–1014. http://dx.doi.org/10.5194/hess-19-997-2015.
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Abstract. Hydrological modeling frameworks require an accurate representation of evaporation fluxes for appropriate quantification of, e.g., the water balance, soil moisture budget, recharge and groundwater processes. Many frameworks have used the concept of potential evaporation, often estimated for different vegetation classes by multiplying the evaporation from a reference surface ("reference evaporation") by crop-specific scaling factors ("crop factors"). Though this two-step potential evaporation approach undoubtedly has practical advantages, the empirical nature of both reference evaporation methods and crop factors limits its usability in extrapolations under non-stationary climatic conditions. In this paper, rather than simply warning about the dangers of extrapolation, we quantify the sensitivity of potential evaporation estimates for different vegetation classes using the two-step approach when calibrated using a non-stationary climate. We used the past century's time series of observed climate, containing non-stationary signals of multi-decadal atmospheric oscillations, global warming, and global dimming/brightening, to evaluate the sensitivity of potential evaporation estimates to the choice and length of the calibration period. We show that using empirical coefficients outside their calibration range may lead to systematic differences between process-based and empirical reference evaporation methods, and systematic errors in estimated potential evaporation components. Quantification of errors provides a possibility to correct potential evaporation calculations and to rate them for their suitability to model climate conditions that differ significantly from the historical record, so-called no-analog climate conditions.
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Matsoukas, C., N. Benas, N. Hatzianastassiou, K. G. Pavlakis, M. Kanakidou y I. Vardavas. "Potential evaporation trends over land between 1983–2008: driven by radiative or turbulent fluxes?" Atmospheric Chemistry and Physics Discussions 11, n.º 4 (8 de abril de 2011): 10935–72. http://dx.doi.org/10.5194/acpd-11-10935-2011.
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Abstract. We model the Penman potential evaporation (PE) over all land areas of the globe for the 25-year period 1983–2008, relying on radiation transfer models (RTMs) for the shortwave and longwave fluxes. Penman's PE is determined by two factors: available energy for evaporation and ground to atmosphere vapour transfer. Input to the PE model and RTMs comprises satellite cloud and aerosol data, as well as data from reanalyses. PE is closely linked to pan evaporation, whose trends have sparked controversy in the community, since the factors responsible for the observed pan evaporation trends are not determined with consensus. Our particular interest is the temporal evolution of PE, and the provided insight to the observed trends of pan evaporation. We examine the interannual trends of PE and various related physical quantities, such as net solar flux, net longwave flux, water vapour saturation deficit and wind speed. Our findings are the following: Global warming has led to a larger water vapour saturation deficit. Global dimming/brightening cycles in the last 25 years slightly increased the available energy for evaporation. PE trends seem to follow closely the trends of energy availability and not the trends of the atmospheric capability for vapour transfer, almost everywhere on the globe, with trends in the Northern hemisphere significantly larger than in the Southern. These results support the hypothesis that secular changes in the radiation fluxes, and not vapour transfer considerations, are responsible for potential evaporation trends.
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Wild, Martin, Atsumu Ohmura, Christoph Schär, Guido Müller, Doris Folini, Matthias Schwarz, Maria Zyta Hakuba y Arturo Sanchez-Lorenzo. "The Global Energy Balance Archive (GEBA) version 2017: a database for worldwide measured surface energy fluxes". Earth System Science Data 9, n.º 2 (23 de agosto de 2017): 601–13. http://dx.doi.org/10.5194/essd-9-601-2017.
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Abstract. The Global Energy Balance Archive (GEBA) is a database for the central storage of the worldwide measured energy fluxes at the Earth's surface, maintained at ETH Zurich (Switzerland). This paper documents the status of the GEBA version 2017 dataset, presents the new web interface and user access, and reviews the scientific impact that GEBA data had in various applications. GEBA has continuously been expanded and updated and contains in its 2017 version around 500 000 monthly mean entries of various surface energy balance components measured at 2500 locations. The database contains observations from 15 surface energy flux components, with the most widely measured quantity available in GEBA being the shortwave radiation incident at the Earth's surface (global radiation). Many of the historic records extend over several decades. GEBA contains monthly data from a variety of sources, namely from the World Radiation Data Centre (WRDC) in St. Petersburg, from national weather services, from different research networks (BSRN, ARM, SURFRAD), from peer-reviewed publications, project and data reports, and from personal communications. Quality checks are applied to test for gross errors in the dataset. GEBA has played a key role in various research applications, such as in the quantification of the global energy balance, in the discussion of the anomalous atmospheric shortwave absorption, and in the detection of multi-decadal variations in global radiation, known as global dimming and brightening. GEBA is further extensively used for the evaluation of climate models and satellite-derived surface flux products. On a more applied level, GEBA provides the basis for engineering applications in the context of solar power generation, water management, agricultural production and tourism. GEBA is publicly accessible through the internet via http://www.geba.ethz.ch. Supplementary data are available at https://doi.org/10.1594/PANGAEA.873078.
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Matsoukas, C., N. Benas, N. Hatzianastassiou, K. G. Pavlakis, M. Kanakidou y I. Vardavas. "Potential evaporation trends over land between 1983–2008: driven by radiative fluxes or vapour-pressure deficit?" Atmospheric Chemistry and Physics 11, n.º 15 (1 de agosto de 2011): 7601–16. http://dx.doi.org/10.5194/acp-11-7601-2011.
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Abstract. We model the Penman potential evaporation (PE) over all land areas of the globe for the 25-yr period 1983–2008, relying on radiation transfer models (RTMs) for the shortwave and longwave fluxes. Penman's PE is determined by two factors: available energy for evaporation and ground to atmosphere vapour transfer. Input to the PE model and RTMs comprises satellite cloud and aerosol data, as well as data from reanalyses. PE is closely linked to pan evaporation, whose trends have sparked controversy in the community, since the factors responsible for the observed pan evaporation trends are not determined with consensus. Our particular interest is the temporal evolution of PE, and the provided insight to the observed trends of pan evaporation. We examine the decadal trends of PE and various related physical quantities, such as net solar flux, net longwave flux, water vapour saturation deficit and wind speed. Our findings are the following: Global warming has led to a larger water vapour saturation deficit. The periods 1983–1989, 1990–1999, and 2000–2008 were characterised by decreasing, increasing, and slightly decreasing PE, respectively. In these last 25 yr, global dimming/brightening cycles generally increased the available energy for evaporation. PE trends seem to follow more closely the trends of energy availability than the trends of the atmospheric capability for vapour transfer, at most locations on the globe, with trends in the Northern hemisphere significantly larger than in the Southern. These results support the hypothesis that global potential evaporation trends are attributed primarily to secular changes in the radiation fluxes, and secondarily to vapour transfer considerations.
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Przybylak, R., P. N. Svyashchennikov, J. Uscka-Kowalkowska y P. Wyszyński. "Solar Radiation in the Arctic during the Early Twentieth-Century Warming (1921–50): Presenting a Compilation of Newly Available Data". Journal of Climate 34, n.º 1 (enero de 2021): 21–37. http://dx.doi.org/10.1175/jcli-d-20-0257.1.
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AbstractThe early twentieth-century warming (ETCW), defined as occurring within the period 1921–50, saw a clear increase in actinometric observations in the Arctic. Nevertheless, information on radiation balance and its components at that time is still very limited in availability, and therefore large discrepancies exist among estimates of total solar irradiance forcing. To eliminate these uncertainties, all available solar radiation data for the Arctic need to be collected and processed. Better knowledge about incoming solar radiation (direct, diffuse, and global) should allow for more reliable estimation of the magnitude of total solar irradiance forcing, which can help, in turn, to more precisely and correctly explain the reasons for the ETCW in the Arctic. The paper summarizes our research into the availability of solar radiation data for the Arctic. An important part of this work is its detailed inventory of data series (including metadata) for the period before the mid-twentieth century. Based on the most reliable data series, general solar conditions in the Arctic during the ETCW are described. The character of solar radiation changes between the ETCW and present times, in particular after 2000, is also analyzed. Average annual global solar radiation in the Russian Arctic during the ETCW was slightly greater than in the period 1964–90 (by about 1–2 W·m−2) and was markedly greater than in the period 2001–19 (by about 16 W·m−2). Our results also reveal that in the period 1920–2019 three phases of solar radiation changes can be distinguished: a brightening phase (1921–50), a stabilization phase (1951–93), and a dimming phase (after 2000).
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Makowski, K., M. Wild y A. Ohmura. "Diurnal temperature range over Europe between 1950 and 2005". Atmospheric Chemistry and Physics 8, n.º 21 (13 de noviembre de 2008): 6483–98. http://dx.doi.org/10.5194/acp-8-6483-2008.
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Abstract. It has been widely accepted that diurnal temperature range (DTR) decreased on a global scale during the second half of the twentieth century. Here we show however, that the long-term trend of annual DTR has reversed from a decrease to an increase during the 1970s in Western Europe and during the 1980s in Eastern Europe. The analysis is based on the high-quality dataset of the European Climate Assessment and Dataset Project, from which we selected approximately 200 stations covering the area bordered by Iceland, Algeria, Turkey and Russia for the period 1950 to 2005. We investigate national and regional annual means as well as the pan-European mean with respect to trends and reversal periods. 17 of the 24 investigated regions including the pan-European mean show a statistical significant increase of DTR since 1990 at the latest. Of the remaining 7 regions, two show a non-significant increase, three a significant decrease and two no significant trend. Changes in DTR are affected by both surface shortwave and longwave radiation, the former of which has undergone a change from dimming to brightening in the period considered. Consequently, we discuss the connections between DTR, shortwave radiation and sulfur emissions which are thought to be amongst the most important factors influencing the incoming solar radiation through the primary and secondary aerosol effect. We find reasonable agreement between trends in SO2 emissions, radiation and DTR in areas affected by high pollution. Consequently, we conclude that the trends in DTR could be mostly determined by changes in emissions and the associated changes in incoming solar radiation.
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Makowski, K., M. Wild y A. Ohmura. "Diurnal temperature range over Europe between 1950 and 2005". Atmospheric Chemistry and Physics Discussions 8, n.º 2 (9 de abril de 2008): 7051–84. http://dx.doi.org/10.5194/acpd-8-7051-2008.
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Abstract. It has been widely accepted that diurnal temperature range (DTR) decreased on a global scale during the second half of the twentieth century. Here we show however, that the long-term trend of annual DTR has reversed from a decrease to an increase during the 1970s in Western Europe and during the 1980s in Eastern Europe. The analysis is based on the high-quality dataset of the European Climate Assessment and Dataset Project, from which we selected approximately 200 stations, covering the area from Iceland to Algeria and from Turkey to Russia for 1950 to 2005. We investigate national and regional annual means as well as the pan-European mean with respect to trends and reversal periods. 17 of the 24 investigated regions including the pan-European mean show a statistical significant increase since 1990 at the latest. Of the remaining 7 regions, 2 show a non-significant increase, 3 a significant decrease and the remaining 2 no significant trend. The long-term change in DTR is governed by both surface shortwave and longwave radiation, the former of which has undergone a change from dimming to brightening. Consequently, we discuss the connections between DTR, shortwave radiation and sulfur emissions which are thought to be amongst the most important factors influencing the incoming solar radiation through the primary and secondary aerosol effect. We find reasonable agreement between trends in SO2 emissions, radiation and DTR in areas affected by high pollution. Consequently, we conclude that the long-term trends in DTR are mostly determined by changes in emissions and the associated changes in incoming solar radiation.
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Kinne, Stefan. "Aerosol radiative effects with MACv2". Atmospheric Chemistry and Physics 19, n.º 16 (29 de agosto de 2019): 10919–59. http://dx.doi.org/10.5194/acp-19-10919-2019.
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Abstract. Monthly global maps for aerosol properties of the Max Planck Aerosol Climatology version 2 (MACv2) are applied in an offline radiative transfer model to determine aerosol radiative effects. This model setup cannot address rapid adjustments by clouds, but current evidence suggests their contribution to be small when compared to the instantaneous radiative forcing. Global maps are presented to detail the regional and seasonal variability associated with (annual) global averages. Radiative effects caused by the aerosol presence (direct effects) and by aerosol modified clouds (indirect effects) are examined. Direct effects are determined for total aerosol, anthropogenic aerosol and extracted individual aerosol components. Indirect effects cover the impact of reduced cloud drop sizes by anthropogenic aerosol. Present-day global annual radiative effects for anthropogenic aerosol yield (1) a climate cooling of −1.0 W m−2 at the top of the atmosphere (TOA); (2) a surface net-flux reduction of −2.1 W m−2; and, by difference; (3) an atmospheric effect of +1.1 W m−2. This atmospheric solar heating is almost entirely a direct effect. On a global basis, indirect effects (−0.65 W m−2) dominate direct effects (−0.35 W m−2) for the present-day climate response at the TOA, whereas the present-day surface radiative budget is more strongly reduced by direct effects (−1.45 W m−2) than by indirect effects (−0.65 W m−2). Natural aerosols are on average less absorbing and larger in size. However, their stronger solar TOA cooling efficiency is offset by a non-negligible infrared (IR) greenhouse warming efficiency. In the sum the global average annual direct forcing efficiencies (per unit AOD) for natural and anthropogenic aerosol are similar: −12 W m−2 per unit AOD for all-sky conditions and −24 W m−2 per unit AOD for clear-sky conditions. The present-day direct TOA impact by all soot (BC) is +0.55 W m−2, when globally and annually averaged. Between +0.25 and +0.45 W m−2 of that can be attributed to anthropogenic sources, depending on assumptions for the preindustrial BC reference state. Similarly, the preindustrial fine-mode reference uncertainty has a strong influence not just on the direct effect but even more on the indirect effect. Present-day aerosol TOA forcing is estimated to stay within the −0.7 to −1.6 W m−2 range (with the best estimate at −1.0 W m−2). Calculations with scaled temporal changes to anthropogenic AOD from global modeling indicate that the global annual aerosol forcing has not changed much over the last decades, despite strong shifts in regional maxima for anthropogenic AOD. These regional shifts explain most solar insolation (brightening or dimming) trends that have been observed by ground-based radiation data.
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Koch, Dorothy, Susanne E. Bauer, Anthony Del Genio, Greg Faluvegi, Joseph R. McConnell, Surabi Menon, Ronald L. Miller et al. "Coupled Aerosol-Chemistry–Climate Twentieth-Century Transient Model Investigation: Trends in Short-Lived Species and Climate Responses". Journal of Climate 24, n.º 11 (1 de junio de 2011): 2693–714. http://dx.doi.org/10.1175/2011jcli3582.1.
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Abstract The authors simulate transient twentieth-century climate in the Goddard Institute for Space Studies (GISS) GCM, with aerosol and ozone chemistry fully coupled to one another and to climate including a full dynamic ocean. Aerosols include sulfate, black carbon (BC), organic carbon, nitrate, sea salt, and dust. Direct and BC-snow-albedo radiative effects are included. Model BC and sulfur trends agree fairly well with records from Greenland and European ice cores and with sulfur deposition in North America; however, the model underestimates the sulfur decline at the end of the century in Greenland. Global BC effects peak early in the century (1940s); afterward the BC effects decrease at high latitudes of the Northern Hemisphere but continue to increase at lower latitudes. The largest increase in aerosol optical depth occurs in the middle of the century (1940s–80s) when sulfate forcing peaks and causes global dimming. After this, aerosols decrease in eastern North America and northern Eurasia leading to regional positive forcing changes and brightening. These surface forcing changes have the correct trend but are too weak. Over the century, the net aerosol direct effect is −0.41 W m−2, the BC-albedo effect is −0.02 W m−2, and the net ozone forcing is +0.24 W m−2. The model polar stratospheric ozone depletion develops, beginning in the 1970s. Concurrently, the sea salt load and negative radiative flux increase over the oceans around Antarctica. Net warming over the century is modeled fairly well; however, the model fails to capture the dynamics of the observed midcentury cooling followed by the late century warming. Over the century, 20% of Arctic warming and snow–ice cover loss is attributed to the BC-albedo effect. However, the decrease in this effect at the end of the century contributes to Arctic cooling. To test the climate responses to sulfate and BC pollution, two experiments were branched from 1970 that removed all pollution sulfate or BC. Averaged over 1970–2000, the respective radiative forcings relative to the full experiment were +0.3 and −0.3 W m−2; the average surface air temperature changes were +0.2° and −0.03°C. The small impact of BC reduction on surface temperature resulted from reduced stability and loss of low-level clouds.
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Wang, Kai, Hong Ye, Feng Chen, Yongzhu Xiong y Cuiping Wang. "Urbanization Effect on the Diurnal Temperature Range: Different Roles under Solar Dimming and Brightening*". Journal of Climate 25, n.º 3 (1 de febrero de 2012): 1022–27. http://dx.doi.org/10.1175/jcli-d-10-05030.1.
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Abstract Based on the 1960–2009 meteorological data from 559 stations across China, the urbanization effect on the diurnal temperature range (DTR) was evaluated in this study. Different roles of urbanization were specially detected under solar dimming and solar brightening. During the solar dimming time, both urban and rural stations showed decreasing trends in maximum temperature (Tmax) because of decreased radiation, suggesting that the dimming effects are not only evident in urban areas but also in rural areas. However, minimum temperature (Tmin) increased more substantially in urban areas than in rural areas during the dimming period, resulting in a greater decrease in the DTR in the urban areas. When the radiation reversed from dimming to brightening, the change in the DTR became different. The Tmax increased faster in rural areas, suggesting that the brightening could be much stronger in rural areas than in urban areas. Similar trends of Tmin between urban and rural areas appeared during the brightening period. The urban DTR continued to show a decreasing trend because of the urbanization effect, while the rural DTR presented an increasing trend. The remarkable DTR difference in the urban and rural areas showed a significant urbanization effect in the solar brightening time.
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Xia, X. "A closer looking at dimming and brightening in China during 1961–2005". Annales Geophysicae 28, n.º 5 (17 de mayo de 2010): 1121–32. http://dx.doi.org/10.5194/angeo-28-1121-2010.
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Abstract. This study investigates dimming and brightening of surface solar radiation (SSR) during 1961–2005 in China as well as its relationships to total cloud cover (TCC). This is inferred from daily ground-based observational records at 45 pyranometer stations. A statistical method is introduced to study contributions of changes in the frequency of TCC categories and their atmospheric transparency to the secular SSR trend. The surface records suggest a renewed dimming beyond 2000 in North China after the stabilization in the 1990s; however, a slight brightening appears beyond 2000 in South China. Inter-annual variability of SSR is negatively correlated with that of TCC, but there is a positive correlation between decadal variability of SSR and TCC in most cases. The dimming during 1961–1990 is exclusively attributable to decreased atmospheric transparency, a portion of which is offset by TCC frequency changes in Northeast and Southwest China. The dimming during 1961–1990 in Northwest and Southeast China primarily results from decreased atmospheric transparency under all sky conditions and the percentage of dimming stemming from TCC frequency changes is 11% in Northwest and 2% in Southeast China. Decreased atmospheric transparencies during 1991–2005 in North China in most cases lead to the dimming. TCC frequency changes also contribute to the dimming during this period in North China. This feature is more pronounced in summer and winter when TCC frequency changes can account for more than 80% of dimming. In South China, increased atmospheric transparencies lead to the brightening during 1991–2005. A substantial contribution by TCC frequency changes to the brightening is also evident in spring and autumn.
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Yang, Su, Xiaolan L. Wang y Martin Wild. "Causes of Dimming and Brightening in China Inferred from Homogenized Daily Clear-Sky and All-Sky in situ Surface Solar Radiation Records (1958–2016)". Journal of Climate 32, n.º 18 (16 de agosto de 2019): 5901–13. http://dx.doi.org/10.1175/jcli-d-18-0666.1.
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AbstractThis paper presents a study on long-term surface solar radiation (SSR) changes over China under clear- and all-sky conditions and analyzes the causes of the “dimming” and “brightening.” To eliminate the nonclimatic signals in the historical records, the daily SSR dataset was first homogenized using quantile-matching (QM) adjustment. The results reveal rapid dimming before 2000 not only under all-sky conditions, but also under clear-sky conditions, at a decline rate of −9.7 ± 0.4 W m−2 decade−1 (1958–99). This is slightly stronger than that under all-sky conditions at −7.4 ± 0.4 W m−2 decade−1, since the clear-sky dimming stopped 15 years later. A rapid “wettening” of about 40-Pa surface water vapor pressure (SWVP) from 1985 to 2000 was found over China. It contributed 2.2% to the SSR decline under clear-sky conditions during the whole dimming period (1958–99). Therefore, water vapor cannot be the main cause of the long-term dimming in China. After a stable decade (1999–2008), an intensive brightening appeared under the clear-sky conditions at a rate of 10.6 ± 2.0 W m−2 decade−1, whereas a much weaker brightening (−0.8 ± 3.1 W m−2 decade−1) has been observed under all-sky conditions between 2008 and 2016. The remarkable divergence between clear- and all-sky trends in recent decades indicates that the clouds played two opposite roles in the SSR changes during the past 30 years, by compensating for the declining SSR under the cloud-free conditions in 1985–99 and by counteracting the increasing SSR under cloud-free conditions in 2008–16. Aerosols remain as the main cause of dimming and brightening over China in the last 60 years, although the clouds counteract the effects of aerosols after 2000.
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Bosten, J. M. y D. I. A. MacLeod. "Mechanisms of the dimming and brightening aftereffects". Journal of Vision 13, n.º 6 (21 de mayo de 2013): 11. http://dx.doi.org/10.1167/13.6.11.
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Bosten, J. y D. MacLeod. "Mechanisms of the dimming and brightening after-effects". Journal of Vision 11, n.º 11 (23 de septiembre de 2011): 376. http://dx.doi.org/10.1167/11.11.376.
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Gorley, Bob. "Global dimming". Weather 60, n.º 6 (1 de junio de 2005): 174. http://dx.doi.org/10.1256/wea.23.05.
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