Dissertations / Theses: 'Potential vorticity'

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Birkett, Hannah Rachel. "Reduced upper-tropospheric potential vorticity." Thesis, University of Reading, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.299301.

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Berrisford, Paul. "Potential vorticity in extratropical cyclones." Thesis, University of Reading, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.233686.

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Davis, Christopher A. (Christopher Alfred). "Cyclogenesis diagnosed with potential vorticity." Thesis, Massachusetts Institute of Technology, 1990. http://hdl.handle.net/1721.1/51476.

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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric and Planetary Sciences, 1990.
Includes bibliographic references (p. 188-194).
by Christopher A. Davis.
Ph.D.

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Boss, Emmanuel. "Dynamics of potential vorticity fronts /." Thesis, Connect to this title online; UW restricted, 1996. http://hdl.handle.net/1773/11031.

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Neves, Alberto P. C. "Unbalanced frontogenesis with constant potential vorticity." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 1996. http://handle.dtic.mil/100.2/ADA326390.

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Thesis (M.S. in Meteorology and Physical Oceanography) Naval Postgraduate School, December 1996.
Thesis advisor(s): Roger T. Williams, Melinda S. Peng. "December 1996." Includes bibliographical references (p. 75-76). Also available online.

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Wang, Yuhui. "The potential vorticity budget of mean winter anomalies." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape9/PQDD_0029/MQ55097.pdf.

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Wang, Yuhui 1970. "The potential vorticity budget of mean winter anomalies /." Thesis, McGill University, 1999. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=29930.

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NCEP reanalyses have been used to compute the climatological isentropic potential vorticity (IPV) budget at the 315K level for 39 winters and for those winters with a North Atlantic Oscillation (NAO) as well as winters with a Pacific/North American (PNA) pattern.
The climatology shows two main IPV sources, each being upstream of the two main centers of positive PV on the east coasts of North America and Asia. The results for the winters with a NAO (PNA) anomaly show, in particular, that the mean-winter IPV anomalies associated with these patterns also have upstream sources. The importance of the latter is not as clear as that of the continential sources that maintain the climatological centers.
The mean-winter IPV advection that balances the IPV sources/sinks is composed of the advection by the time-mean flow and by the transient eddies (decomposed into high- and low-frequency components), where the former is the dominant component. The latter are found to produce a negative feedback in that they act to reduce the amplitude of the IPV anomaly. For the NAO anomaly, low-frequency transient advection is more important, while high-frequency transient advection is more statistically significant for the PNA anomaly. Both the high and low-frequency advection have comparable contributions in maintaining the climatological distribution of the stationary eddy IPV.

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Norton, Warwick Alexander. "Balance and potential vorticity inversion in atmospheric dynamics." Thesis, University of Cambridge, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.293018.

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Huo, Zonghui. "Numerical prediction and potential vorticity diagnosis of extratropical cyclones." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp02/NQ29963.pdf.

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Huo, Zonghui. "Numerical prediction and potential vorticity diagnosis of extratropical cyclones." Thesis, McGill University, 1996. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=42058.

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By combining numerical simulations with different diagnostic tools, this thesis examines the various aspects of two explosively deepening cyclones--the superstorm of March 12-14 1993 and a storm that occurred during the Intensive Observation Period 14 (IOP-14) of the Canadian Atlantic Storm Program (CASP). Using conventional observations, the general aspects of the storms are documented and the dynamical and physical mechanisms are discussed. Then the life cycles are simulated with the Canadian Regional Finite-Element model. To improve the model initial conditions, a methodology is proposed on the basis of potential vorticity thinking, and is tested to be successful in the simulation of the March 1993 superstorm. Using the successful simulations as control runs, a series of numerical sensitivity experiments are conducted to study the impacts of model physics on the development of the two rapidly deepening cyclones.
The deepening mechanisms of both storms are examined within the context of PV thinking, i.e., using piecewise potential vorticity inversion diagnostics. In both cases, the upper-level PV anomalies contribute the most to the surface cyclone, followed by the lower-level thermal anomalies and diabatic heating related moist PV anomaly. It is found that a favorable phase tilt between the upper- and lower-level PV anomalies allows a mutual interaction between them, in which the circulations associated with the upper-level anomalies enhance the lower-level anomalies, which in turn feedback positively into the upper-level PV anomalies. In addition to the vertical interactions, there also exist lateral interactions between the upper-level PV anomalies for the March 1993 superstorm. The upper-level PV features (troughs) are isolated with the piecewise PV inversion. By removing or changing the intensity of the trough in the initial conditions, the RFE model is integrated to examine the impact of each trough and its interaction with the other trough on the superstorm development.

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Woollings, Tim. "Entropy and potential vorticity in dynamical core atmosphere models." Thesis, University of Reading, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.412174.

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12

Beare, Robert J. "Potential vorticity sensitivity maps and the predictability of cyclones." Thesis, University of Reading, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.394128.

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Levine, Andrew S. "Intensity changes or recurving typhoons from a potential vorticity perspective." Thesis, University of Hawaii at Manoa, 2003. http://hdl.handle.net/10125/6980.

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Potential vorticity (PV) interactions are evaluated in fourteen recurving typhoons to assess its usefulness as a forecast tool for intensity change. PV fields are derived from the large scale data in the ECMWF Global Advanced Operational Analysis data set. A deformation of the 1 potential vorticity unit contour around the typhoon on the 330 K isentropic surface coincides with the weakening of three typhoons, and may prove to be a useful forecast guideline for all recurving typhoons. Five typhoons have a trough with high PV on the 345 K isentropic surface approach within 10° radial distance. For these five typhoons, PV is not useful for forecasting intensity in isolation from other variables. The PV fields are too subtle by themselves to show a significant difference among typhoons which intensify, weaken or remain steady. Because of this, vertical shear of the horizontal wind and maximum potential intensity (MPI) are included with PV to examine intensity changes. Vertical shear of the horizontal wind calculated between 850-200 hPa in an intensifying typhoon is ≤ 15 mis, while shear in a weakening typhoon is ≥ 25 m/s. Shear increases as a PV anomaly propagates closer to the typhoon center. Weakening is associated with the upper PV anomaly passing within 50 from the center of the typhoon. When over fairly constant sea surface temperature (change of ≤ 1 °C ), two typhoons close to their MPI weakened. The typhoon which was far from its MPI intensified. Guidelines for forecasting intensity change using these parameters are presented.
x, 84 leaves

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Demirtas, Meral. "Sensitivity of short-range forecasts to local potential vorticity modifications." Thesis, University of Reading, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.339513.

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Ahmadi-Givi, Farhang. "The role of latent heat release in an explosive extratropical cyclogenesis." Thesis, University of Reading, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.269965.

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Cerrai, Diego. "Moisture and potential vorticity in medicanes: theoretical approach and case studies." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2015. http://amslaurea.unibo.it/8743/.

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Da poco più di 30 anni la comunità scientifica è a conoscenza dell’occasionale presenza di strutture cicloniche con alcune caratteristiche tropicali sul Mar Mediterraneo, i cosiddetti medicane. A differenza dei cicloni baroclini delle medie latitudini, essi posseggono una spiccata simmetria termica centrale che si estende per gran parte della troposfera, un occhio, talvolta privo di nubi, e una struttura nuvolosa a bande spiraleggianti. Ad oggi non esiste ancora una teoria completa che spieghi la loro formazione ed evoluzione. La trattazione di questa tesi, incentrata sull’analisi dei campi di vorticità potenziale e di umidità relativa, è sviluppata nell’ottica di una miglior comprensione delle dinamiche alla mesoscala più rilevanti per la nascita dei medicane. Lo sviluppo di tecniche avanzate di visualizzazione dei campi generati dal modello WRF, quali l’animazione tridimensionale delle masse d’aria aventi determinate caratteristiche, ha permesso l’individuazione di due zone di forti anomalie di due campi derivati dalla vorticità potenziale in avvicinamento reciproco, intensificazione e mutua interazione nelle ore precedenti la formazione dei medicane. Tramite la prima anomalia che è stata chiamata vorticità potenziale secca (DPV), viene proposta una nuova definizione di tropopausa dinamica, che non presenta i problemi riscontrati nella definizione classica. La seconda anomalia, chiamata vorticità potenziale umida (WPV), individua le aree di forte convezione e permette di avere una visione dinamica dello sviluppo dei medicane alle quote medio-basse. La creazione di pseudo immagini di vapore acqueo tramite la teoria del trasferimento radiativo e la comparazione di queste mappe con quelle effettivamente misurate nei canali nella banda del vapore acqueo dai sensori MVIRI e SEVIRI dei satelliti Meteosat hanno da un lato confermato l’analisi modellistica, dall’altro consentito di stimare gli errori spazio-temporali delle simulazioni. L’utilizzo dei dati di radianza nelle microonde, acquisiti dai sensori AMSU-B e MHS dei satelliti NOAA, ha aggiunto ulteriori informazioni sia sulle intrusioni di vorticità potenziale che sulla struttura degli elementi convettivi presenti sul dominio, in modo particolare sulla presenza di ghiaccio in nube. L’analisi dettagliata di tre casi di medicane avvenuti nel passato sul Mar Mediterraneo ha infine consentito di combinare gli elementi innovativi sviluppati in questo lavoro, apportando nuove basi teoriche e proponendo nuovi metodi di indagine non solo per lo studio di questi fenomeni ma anche per un’accurata ricerca scientifica su ciclogenesi di altro tipo.

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Du, Jun. "On the Mei-Yu front and the associated potential vorticity anomaly." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/tape15/PQDD_0013/NQ35150.pdf.

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Gesser, Ryan Alan. "A quasi-geostrophic potential vorticity diagnosis of the March 1993 superstorm." Thesis, Georgia Institute of Technology, 1997. http://hdl.handle.net/1853/26249.

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Agusti-Panareda, Anna. "A potential vorticity perspective on the extratropical transition of tropical cyclones." Thesis, University of Reading, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.409060.

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20

Kirk-Davidoff, Daniel Bernard 1968. "The implications of potential vorticity homogenization for climate and climate sensitivity." Thesis, Massachusetts Institute of Technology, 1998. http://hdl.handle.net/1721.1/17447.

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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 1998.
Includes bibliographical references (p. 128-132).
by Daniel Bernard Kirk-Davidoff.
Ph.D.

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21

Mohebalhojeh, Ali Reza. "Balance and potential vorticity inversion in models of atmosphere-ocean dynamics." Thesis, University of Cambridge, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.621675.

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Morrison, Anne Inglis. "Observations of oceanic potential vorticity and its relationship with other tracers." Thesis, University of Southampton, 1999. https://eprints.soton.ac.uk/42141/.

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Driven by interest in measuring the oceanic velocity field from space, sea surface temperature (SST) has been suggested as a proxy for potential vorticity (PV), which may then be inverted to give velocity. However, little is known about the relationships between PV and other water mass tracers, as these have not previously been thoroughly examined. In this thesis, the inter-relationships between PV, SST, potential temperature and salinity in three quite different frontal regions of the ocean are investigated. The regions studied were in the North-east Atlantic, the Sargasso Sea and the Bellingshausen Sea (Southern Ocean). The only earlier work known in this field was by Fischer et al. (1989), which found a near-linear relationship between PV and isopycnic potential temperature on a shallow isopycnal in the North Atlantic. This relationship was also evident in climatological values of PV and temperature in the North Atlantic. The results from the three regions considered in this thesis vary considerably, and are believed to be due to different frontal dynamics and water mass formation mechanisms. All the North-east Atlantic results are in close agreement, despite differences in measurement scales and the year of survey. The reasons for different relationships occurring are examined. Theories for setting PV and tracer values are investigated, and in particular the models of Woods (1985) and Spall (1995) are found to explain the relationships found in the North-east Atlantic and Sargasso Sea, respectively. However, a combination of these models, applied to different scales of motion, is needed to explain the Bellingshausen Sea results. Preliminary work is carried out using a one-dimensional computer model to follow the development of the relationship in the north-east Atlantic.

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Koller, J. "Potential Vorticity Evolution in the Co-orbital Region of Embedded Protoplanets." Los Alamos, N.M. : Oak Ridge, Tenn. : Los Alamos National Laboratory ; distributed by the Office of Scientific and Technical Information, U.S. Dept. of Energy, 2004. http://www.osti.gov/servlets/purl/836124-uO0DBZ/native/.

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Thesis (Ph.D.); Submitted to the Department of Physics and Astronomy, Rice University, Houston, TX (US); 1 Sep 2004.
Published through the Information Bridge: DOE Scientific and Technical Information. "LA-14149-T" J. Koller. US DOE (US) 09/01/2004. Report is also available in paper and microfiche from NTIS.

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Wardle, Richard M. "Representation of eddies in climate models by a potential vorticity flux." Thesis, Massachusetts Institute of Technology, 1999. http://hdl.handle.net/1721.1/58540.

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Thesis (Ph. D.)--Joint Program in Physical Oceanography (Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences; and the Woods Hole Oceanographic Institution), February 1999.
Includes bibliographical references (p. 170-177).
This thesis addresses the parameterization of the heat and momentum transporting properties of eddy motions for use in three-dimensional, primitive equation, z-coordinate atmosphere and ocean models. Determining the transport characteristics of these eddies is fundamental to understanding their effect on the large-scale ocean circulation and global climate. The approach is to transform the primitive equations to yield the altered 'transformed Eulerian mean' (TEM) equations. The assumption is made that the eddy motions obey quasigeostrophic dynamics while the mean flow obeys the primitive equations. With this assumption, the TEM framework leads to the eddies appearing as one term, which acts as a body force in the momentum equations. This force manifests itself as a flux of potential vorticity (PV) - a quantity that incorporates both eddy momentum and heat transporting properties. Moreover, the dynamic velocities are those of the residual mean circulation, a much more relevant velocity for understanding heat and tracer transport. Closure for the eddy PV flux is achieved through a flux-gradient relationship, which directs the flux down the large scale PV gradient. For zonal flows, care is taken to ensure that the resulting force does not generate any net momentum, acting only to redistribute it. Neglect of relative vorticity fluxes in the PV flux yields the parameterization scheme of Gent and McWilliams. The approach is investigated by comparing a zonally-averaged parameterized model with a three dimensional eddy-resolving calculation of flow in a stress-driven channel. The stress at the upper surface is communicated down the water column to the bottom by eddy form drag. Moreover, lateral eddy momentum fluxes act to strengthen and sharpen the mean flow, transporting eastward momentum up its large scale gradient. Both the vertical momentum transfer and lateral, upgradient momentum transfer by eddies, are captured in the parameterized model. The advantages of this approach are demonstrated in two further zonal cases: 1) the spin-down of a baroclinic zone, and 2) the atmospheric jet stream. The time mean TEM approach and the eddy PV flux closure are explored in the context of an eddy-resolving closed basin flow which breaks the zonal symmetry. Decomposition of eddy PV fluxes into components associated with advective and dissipative effects suggest that the component associated with eddy flux divergence, and therefore forcing of the mean flow, is mainly directed down the large scale gradient and can be parameterized as before. Thus, the approach can be used to capture eddy transport properties for both zonal mean and time mean flows. The PV flux embodies both the eddy heat and momentum fluxes and so presents a more unified picture of their transferring properties. It therefore provides a powerful conceptual and practical framework for representing eddies in numerical models of the atmsophere and ocean.
by Richard M. Wardle.
Ph.D.

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Judt, Falko. "Convectively-Generated Potential Vorticity in Rainbands and Secondary Eyewall Formation in Hurricanes." Scholarly Repository, 2009. http://scholarlyrepository.miami.edu/oa_theses/214.

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Concentric eyewall formation and eyewall replacement cycles are intrinsic processes that determine the intensity of a tropical cyclone, as opposed to purely environmental factors such as wind shear or the ocean heat content. Although extensive research has been done in this area, there is not a single widely accepted theory on the formation of secondary eyewall structures. Many previous studies focused on dynamic processes in the inner core of a tropical cyclone that would precede and ultimately lead to the formation of a secondary eyewall. Hurricanes Katrina and Rita in 2005 were frequently sampled by research aircraft which gathered a copious amount of data. During this time, Rita developed a secondary eyewall which eventually replaced the original eyewall. This thesis will investigate the formation of a secondary eyewall with particular emphasis on the rainband region, as observations show that an outer principal rainband transformed into the secondary ring. A high resolution, full physics model (MM5) initialized with global model forecast fields correctly predicted the secondary eyewall formation in Rita. The model output will be used to investigate both Katrina and Rita in terms of their PV generation characteristics since PV and vorticity maxima correlate well with wind maxima that accompany the eyewall and rainbands. Furthermore, dynamical processes such as vortex Rossby wave (VRW) activity in the inner core region will be analyzed. Comparison of the differences in the two storms might shed some light on dynamics that can lead to structure changes. Comparison of the model data with aircraft observation is used to validate the results. Doppler radar derived wind fields will be used to calculate the vertical vorticity. The vorticity field is closely related to PV and thus a manifestation of the PV generation process in the rainband. The investigation has shown that Rita?s principal rainband features higher PV generation rates at radii beyond 80 km. Both the azimuthal component and the projection of asymmetric PV generated by convection onto the azimuthal mean connected with the principal band are hypothesized to be of importance for the formation of the secondary eyewall. VRW were found not to be important for the initial formation of the ring but might enhance convective activity once the outer eyewall contracts.

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Cheng, William Y. Y. "Potential vorticity analysis of a multiple frontal cyclogenesis event during CASP II." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape11/PQDD_0005/MQ44148.pdf.

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Boerlage, Andrew P. "A description of tropical cyclone recurvature in terms of isentropic potential vorticity." Thesis, Monterey, California. Naval Postgraduate School, 1989. http://hdl.handle.net/10945/26964.

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Marble, Douglas Craig. "A model analysis of potential vorticity on isopycnal surfaces for the global ocean." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 1993. http://handle.dtic.mil/100.2/ADA275047.

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Thesis (M.S. in Meteorology and Physical Oceanography) Naval Postgraduate School, September 1993.
Thesis advisor(s): Semtner, Albert J. "September 1993." Bibliography: p. 33-35. Also available online.

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Bermejo, Rodolfo. "Analysis of a Galerkin-Characteristic algorithm for the potential vorticity-stream function equations." Thesis, University of British Columbia, 1990. http://hdl.handle.net/2429/30561.

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In this thesis we develop and analyze a Galerkin-Characteristic method to integrate the potential vorticity equations of a baroclinic ocean. The method proposed is a two stage inductive algorithm. In the first stage the material derivative of the potential vorticity is approximated by combining Galerkin-Characteristic and Particle methods. This yield a computationally efficient algorithm for this stage. Such an algorithm consists of updating the dependent variable at the grid points by cubic spline interpolation at the foot of the characteristic curves of the advective component of the equations. The algorithm is unconditionally stable and conservative for Δt = O(h). The error analysis with respect to L² -norm shows that the algorithm converges with order O(h); however, in the maximum norm it is proved that for sufficiently smooth functions the foot of the characteristic curves are superconvergent points of order O(h⁴ /Δt). The second stage of the algorithm is a projection of the Lagrangian representation of the flow onto the Cartesian space-time Eularian representation coordinated with Crank-Nicholson Finite Elements. The error analysis for this stage with respect to L²-norm shows that the approximation component of the global error is O(h²) for the free-slip boundary condition, and O(h) for the no-slip boundary condition. These estimates represent an improvement with respect to other estimates for the vorticity previously reported in the literature. The evolutionary component of the global error is equal to K(Δt² + h), where K is a constant that depends on the derivatives of the advective quantity along the Characteristic. Since the potential vorticity is a quasi-conservative quantitiy, one can conclude that K is in general small. Numerical experiments illustrate our theoretical results for both stages of the method.
Science, Faculty of
Mathematics, Department of
Graduate

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Campa, Jana [Verfasser]. "Potential vorticity and moisture in extratropical cyclones : climatology and sensitivity experiments / Jana Campa." Mainz : Universitätsbibliothek Mainz, 2013. http://d-nb.info/1038204593/34.

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Rozak, Edward J. "Potential Vorticity Streamers as Precursors to Tropical Cyclone Genesis in the Western Pacific." Thesis, Monterey, California. Naval Postgraduate School, 2012. http://hdl.handle.net/10945/6863.

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The term tropical transition (TT) is used to describe the formation of a tropical cyclone from an extratropical precursor. The overarching goal of this thesis is to re-examine TT in the western North Pacific. This is accomplished via the synthesis of a subjective climatology of all tropical cyclones (TCs) from 20022008 and a case study analysis of ensemble prediction data for the particularly intriguing event of TS 16W in September of 2008. The climatological analysis indicated that TT events represented 14% of all TCs during the study period. The maximum frequency of TT events occurred in the late summer / early fall. The resulting storm systems tended to form farther to the north than non-TT events and were found to be relatively weak and short- lived. The results of the case study analysis lend credence to the earlier finding that the genesis pathway of TS 16W exhibited a two-stage evolution. The first stage involved the forcing of near-continuous deep convection by a tropopause-level potential vorticity (PV) anomaly. The second stage involved the rearrangement of the upper-level PV structure via diabatic processes, resulting in a necessary reduction of vertical wind shear.

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Cooper, Ian Michael. "The role of surface and diffusive processes on potential vorticity in atmospheric fronts." Thesis, University of Reading, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.306836.

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Davenport, Robert T. "Potential vorticity analysis of low level thunderstorm dynamics in an idealized supercell simulation." Thesis, Monterey, Calif. : Naval Postgraduate School, 2009. http://edocs.nps.edu/npspubs/scholarly/theses/2009/Mar/09Mar%5FDavenport.pdf.

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Thesis (M.S. in Meteorology)--Naval Postgraduate School, March 2009.
Thesis Advisor(s): Nuss, Wendell A. "March 2009." Description based on title screen as viewed on April 23, 2009. Author(s) subject terms: Potential Vorticity, Severe Weather, Supercell, Weather Research and Forecasting Model, Advanced WRF. Includes bibliographical references (p. 43-47). Also available in print.

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Twitchett, Arwen Fay. "Predictability and dynamics of potential vorticity streamers and connections to high impact weather." Thesis, University of Leeds, 2012. http://etheses.whiterose.ac.uk/2582/.

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Narrow potential vorticity (PV) intrusions across the tropopause (PV streamers) are interconnected with surface high- and low- pressure systems and frequently present during high-impact weather in the mid-latitudes. They often form during the breaking of Rossby waves (observed as large meanders of the jet stream), and occur at the end of the wave life cycle. Extreme weather events are likely to increase in the future due to global warming and climate change, so, enhanced knowledge about the main infuences on these events is crucial for early warning systems. This thesis explores the location and relationship between upper- (troughs and PV streamers) and lower- (cyclones and anticyclones) level features impacting the United Kingdom during heavy precipitation days. It then investigates the genesis of preceding Rossby waves and initiation of PV streamer formation related to heavy precipitation cases. Finally, the predictability of these features is analysed through an assessment of forecasting skill in the European Centre for Medium-Range Weather Forecasts (ECMWF deterministic models as well as the THORPEX Interactive Grand Global Ensemble (TIGGE) prediction system through the use of a novel feature-based error method. Stratospheric PV streamers were found to be present during UK heavy precipitation cases 88% of the time in summer, 85% in autumn, 72% in spring and 63% in winter. They are the dominant in influence on heavy precipitation for the UK in summer as well as in autumn in combination with cyclones. Cyclones are located to the north-west of the UK during all of the seasons with highest frequency in winter and least in summer. Anticyclones also have an impact on UK precipitation by steering systems further north in the winter. The results vary regionally, with western and northern areas characterized by orographic in influences. Eastern Scotland has the most consistent pattern of stratospheric streamer involvement, and the combination of upper-level and orographic effects create uplift of moist air leading to heavy precipitation events. Remarkably, spring has the most variance in the distribution of upper- and lower-level features with evidence of a distinct east/west split across the country. Cyclone and anticyclone pairings dominate in the west, while stratospheric and tropospheric streamer coupling enhances precipitation in the east. Rossby waves preceding the events are triggered from 3 to 7 days in advance, with some seasonal variations. The trigger points range from the Pacific Ocean basin, throughout North America to the western Atlantic Ocean. The waves then proceed across the North Atlantic, where PV streamers are initiated. Triggers located to the west (or behind) the PV streamer lead to enhanced ridges and LC1 or anticyclonic streamer types, while triggers to the east (ahead of the streamer) increase the likelihood of LC2 or cyclonic streamer types. Influences to the east are the most common form of trigger closely followed by streamers forming from recirculated stratospheric air (for example when a parcel of air re-attaches to the stratosphere). PV streamers are generally represented well in short forecast lead times (1-2 days) with a growth in structural and location errors as lead time increases. An interesting result of the feature error method was the identification of significantly lower PV mean and maximum amplitudes (by as much as -3.5PVU) especially in the upper eastern flank of the streamer. This could be due to insfficient influx of high PV air into the streamer and would benefitt from further investigation. In associated heavy precipitation forecasts, TIGGE ensemble members with more accurate rainfall prediction have consistently better PV streamer representation than those who under-predicted the precipitation. The evidence indicates that improved understanding and prediction of PV streamers can lead to better predictability of heavy precipitation and thus an enhancement in early warning systems.

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Henderson, John M. "An application of potential vorticity inversion to the position forecast problem of Hurricane Opal." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp04/mq29714.pdf.

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Hall, Melinda M. "Horizontal and vertical structure of velocity, potential vorticity and energy in the gulf stream." Thesis, Online version, 1985. http://hdl.handle.net/1912/3150.

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Henderson, John M. 1972. "An application of potential vorticity inversion to the position forecast problem of hurricane Opal /." Thesis, McGill University, 1997. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=27339.

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Accurate forecasting of hurricane motion is required to prepare for hurricane landfall. The underpredicted acceleration of Hurricane Opal by the National Centers for Environmental Prediction's (NCEP) operational eta model during landfall and over-land passage is investigated using quasi-geostrophic potential vorticity (QGPV) inversion. We identify and explain model errors in the evironmental steering flow using a systematic procedure including removal of Opal's cyclonic circulation that builds upon previous work.
The eastern ridge associated with the anticyclonic QGPV was persistently forecasted too weak and too distant from Opal, though the forecast of this feature improved at shorter ranges. The anticyclonic contribution to the retrieved flow increased from $-$11% of the observed vector (inhibiting the motion) to 15% (aiding the motion). This increase of 3.8 m s$ sp{-1}$ is alone sufficient to explain the slow forecast.
The eta forecasts likely did not sufficiently resolve the advection downstream of storm outflow and subsequent ridge building. This error propagated through the forecast cycle and prevented phase-locking with the ridge and increased flow. Representation of the ridge improved following advection of the outflow over the more dense U.S. upper air network.
This study emphasizes the need for accurate upper-air analyses and offers a real-time application of QGPV inversion that decomposes the steering flow. The need for further research into the intimate relationship between storm intensity and subsequent storm track is stated.

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38

Weijenborg, Christian [Verfasser]. "Characteristics of Potential Vorticity anomalies associated with mesoscale extremes in the extratropical troposphere / Christian Weijenborg." Bonn : Universitäts- und Landesbibliothek Bonn, 2016. http://d-nb.info/1109879911/34.

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Nakamura, Mototaka. "Characteristics of potential vorticity mixing by breaking Rossby waves in the vicinity of a jet." Thesis, Massachusetts Institute of Technology, 1994. http://hdl.handle.net/1721.1/11730.

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Thesis (Sc. D.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 1995.
Includes bibliographical references (p. 248-253).
by Mototaka Nakamura.
Sc.D.

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40

Wu, Chun-Chieh. "Understanding hurricane movement from a potential vorticity perspective : a numerical model and an observational study." Thesis, Massachusetts Institute of Technology, 1993. http://hdl.handle.net/1721.1/57832.

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McTaggart-Cowan, R. "A potential vorticity component-based study of the extratropical transitions of hurricanes Danielle and Earl (1998)." Thesis, McGill University, 2003. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=19557.

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This thesis documents a study of the simultaneous North Atlantic extratropical transition (ET) and intensification (ET/R) of ox-hurricanes Danielle and Earl (1998), with the goal of identifying the midlatitude and remnant tropical cyclone (TC) features germane to the ET/R process. Using potential vorticity (PV) based diagnostics and an extension of piecewise PV inversion techniques that accounts for atmospheric water, the initial conditions of the Mesoscale Compressible Community model are altered by the individual removal of possible forcing features. Results from ensuing sensitivity tests are compared to the control simulation and changes in the structure and/or the intensity of ET/R are diagnosed. It is found that the existence of a trough upstream of the remnant TC is a necessary forcing for redevelopment and that larger north-south trough amplitudes result in stronger vortex reintensification. Transitions occurring in the equatorward entrance region of a baroclinic jet are likely to undergo baroclinic mode redevelopment, whereas those taking place in the poleward exit region of the jet usually take on tropical mode characteristics. Baroclinic mode storms are insensitive to the structure of the TC remnant; tropical mode redevelopment, however, rely heavily on both the circulation and the moisture associated with the ex-tropical feature. Considered pragmatically, the results of this study amount to a list of the key ingredients necessary for the ET/R of the storms studied, which will be of use in the forecasting of similar events. A broader application of the findings in the context of current ET research yields insight into both the dynamics and thermodynamics of these extreme events.

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Hood, L. L., and B. E. Soukharev. "Interannual Variations of Total Ozone at Northern Midlatitudes Correlated with Stratospheric EP Flux and Potential Vorticity." AMER METEOROLOGICAL SOC, 2005. http://hdl.handle.net/10150/623351.

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At northern midlatitudes over the 1979–2002 time period, column ozone trends are observed to have maximum negative amplitudes in February and March. Here, the portion of the observed ozone interannual variability and trends during these months that can be attributed to two specific dynamical transport processes is estimated using correlative and regression methods. In approximate agreement with a recent independent study, 18%–25% of the observed maximum negative trend is estimated to be due to long-term changes in the diabatic (Brewer–Dobson) circulation driven by global-scale changes in planetary wave [Eliassen–Palm (EP) flux] forcing. In addition, 27%–31% of the observed maximum midlatitude trend during these months is estimated to be due to long-term changes in local nonlinear synoptic wave forcing as deduced from correlated interannual variations of zonal mean ozone and Ertel’s potential vorticity. Like long-term decreases in the Brewer–Dobson circulation, this trend component reflects an overall net increase in the polar vortex strength, which is associated with increased numbers of anticyclonic, poleward-breaking Rossby waves at northern midlatitudes. Together, these components can explain approximately 50% of the observed maximum negative column ozone trend and interannual variance at northern midlatitudes in February and March. The combined empirical model also approximately simulates a leveling off or slight increase in column ozone anomalies that has been observed for some months and latitudes since the mid-1990s.

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Morris, Christopher M. "Using potential vorticity to characterize the forcing of a coastally trapped wind reversal along the California coast." Thesis, Monterey, California: Naval Postgraduate School, 2015. http://hdl.handle.net/10945/45230.

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Approved for public release; distribution is unlimited
Using the Climate Forecast System Reanalysis (CFSR) dataset, the synoptic environment of six historical coastally trapped wind reversals (CTWR) along the California coast is examined. Building on the Mass and Bond climatology of 1996, the study uses potential vorticity (PV) as a proxy for the coastal jet and seeks to characterize the forcing of the CTWRs by analyzing their 950-mb potential vorticity plumes. The study also pursues the ability to separate geostrophically-balanced wind reversals synonymous with synoptic systems from unbalanced wind reversals (CTWRs) by taking advantage of the invertibility of PV and using the inversion technique outlined in the August 1991 issue of Monthly Weather Review by Christopher Davis and Kerry Emanuel. The study then applied the methodology to data from July/August 2012/2013 in order to uncover possible CTWRs. The primary findings of this study are as follows: 1) the potential vorticity maximum generated through the offshore flow of the coastal jet is required to move off shore and establish an across-coast PV gradient in order for a CTWR to form/propagate northward of Point Conception and 2) the Davis Emanuel PV inversion technique yielded mixed results, heavily influenced by diurnal effects and subjected to instability due to topographical interactions.

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Reilly, Daniel Hunt. "On the role of upper-tropospheric potential vorticity advection in tropical cyclone formation : case studies from 1991." Thesis, Massachusetts Institute of Technology, 1992. http://hdl.handle.net/1721.1/54988.

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Iwabe, Clara Miho Narukawa. "Ciclones secundários no Sudoeste do Atlântico Sul: climatologia e simulação numérica." Universidade de São Paulo, 2012. http://www.teses.usp.br/teses/disponiveis/14/14133/tde-08042013-180829/.

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Os ciclones secundários são sistemas que ainda não são bem definidos e, assim, são fenômenos de difícil previsibilidade, necessitando de mais estudos para identificar os sinais que disparam seu desenvolvimento. Neste estudo realizou-se um levantamento climatológico e estudo numérico de ciclogênese secundária no sudoeste do Oceano Atlântico Sul com o objetivo de obter informações sobre a atuação destes sistemas e entender os processos dinâmicos envolvidos no seu desenvolvimento. Para o período entre 1980 e 2010, a climatologia mostra que uma média de 3,9 sistemas secundários se forma por ano no Oceano Atlântico Sul. Estes sistemas ocorrem com maior e menor frequência nos meses frios e quentes, respectivamente. Dois tipos distintos de ciclones secundários foram encontrados. TIPO1 que se forma a leste e na região da frente quente do ciclone primário. Estes sistemas se desenvolvem sob advecção quente nos baixos níveis e pouca influência de anomalias de vorticidade potencial (VP) de altos níveis; TIPO2 se desenvolve a oeste/noroeste do ciclone primário onde predomina forte advecção fria em baixos níveis. No entanto, fluxos de calor e umidade intensos contribuem para aquecer a baixa troposfera e em altos níveis são forçados por anomalias de VP. Simulações numéricas com o modelo Weather Research and Forecasting (WRF) indicam os fluxos de calor sensível e latente na superfície como mecanismos de intensificação dos ciclones secundários TIPO1 e TIPO2, sendo o fluxo de calor latente mais importante no abaixamento de pressão destes sistemas. Os experimentos numéricos mostram que o ciclone do TIPO2 não se desenvolve na ausência de anomalia de VP, enquanto que o TIPO1 se desenvolve mais fraco e atrasado no tempo. A análise por separação de fatores indica que a anomalia de VP e algum outro mecanismo não relacionado aos fatores avaliados nas simulações tiveram papel disparador no ciclone do TIPO1, enquanto a interação da anomalia de VP com os fluxos de superfície atuou como intensificador. No TIPO2, o desenvolvimento ocorreu unicamente pela atuação da anomalia de VP, a qual também agiu como um intensificador juntamente com os fluxos de calor e umidade, bem como os processos de interação entre estes dois fatores.
Secondary cyclones are systems that are not well defined yet and they are difficult to predict, requiring further studies to identify the signals that trigger their development. In this study we carried out a climatology and numerical study of secondary cyclogenesis over the southwestern South Atlantic Ocean in order to obtain information about these systems and understand the dynamic processes involved in its development. The climatology for the period 1980-2010 shows that an average of 3.9 secondary systems per year develops in the southwestern South Atlantic Ocean. These systems occur with more and less frequency in the colder and warmer months, respectively. Two distinct types of secondary cyclones were found. TYPE1 forms eastward and over the warm front region of the primary cyclone. These systems develop due to warm advection at lower levels and relatively weak influence of potential vorticity (PV) anomalies at upper levels. TYPE2 develops westward/northwestward of the primary cyclone where strong cold advection predominates at lower levels. However, in this type, the lower troposphere is heated due to intense heat and moisture fluxes and at upper levels it is forced by PV anomalies. Numerical simulations using the Weather Research and Forecasting model (WRF) indicate that the sensible and latent heat fluxes on surface act as intensification mechanisms for both TYPE1 and TYPE2 secondary cyclones and that the latent heat flux influences more on decreasing the pressure in these systems. The numerical experiments show that the cyclone TYPE2 does not develop in the absence of PV anomalies, while the TYPE1 does, but it is relatively weaker and delayed in time. Factors separation analysis indicates that the PV anomaly and some other mechanism unrelated to the factors evaluated in the simulations have a triggering role in the development of the secondary cyclone TYPE1, while the interaction of PV anomaly with surface fluxes acted to intensify the cyclone. The TYPE2 development occurred solely due to PV anomaly, which also acted to intensifying together with heat/moisture fluxes on surface as well as the interaction processes of these two factors.

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Mansuripur, M. "Comment on Jackson's analysis of electric charge quantization due to interaction with Dirac's magnetic monopole." ELSEVIER SCIENCE BV, 2016. http://hdl.handle.net/10150/622958.

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In J.D. Jackson's Classical Electrodynamics textbook, the analysis of Dirac's charge quantization condition in the presence of a magnetic monopole has a mathematical omission and an all-too-brief physical argument that might mislead some students. This paper presents a detailed derivation of Jackson's main result, explains the significance of the missing term, and highlights the close connection between Jackson's findings and Dirac's original argument. (C) 2016 Sharif University of Technology. All rights reserved.

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Vich, Ramis Maria del Mar. "Design of ensemble prediction systems based on potential vorticity perturbations and multiphysics. Test for western Mediterranean heavy precipitation events." Doctoral thesis, Universitat de les Illes Balears, 2012. http://hdl.handle.net/10803/84075.

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L'objectiu principal d'aquesta tesi és millorar l'actual capacitat de predicció de fenòmens meteorològics de pluja intensa potencialment perillosos a la Mediterrània occidental. Es desenvolupen i verifiquen tres sistemes de predicció per conjunts (SPC) que tenen en compte incerteses presents en els models numèrics i en les condicions inicials. Per generar els SPC s'utilitza la connexió entre les estructures de vorticitat potencial (VP) i els ciclons, a més de diferents esquemes de parametrització física. Es mostra que els SPC proporcionen una predicció més hàbil que la determinista. Els SPC generats pertorbant les condicions inicials han obtingut millor puntuació en verificacions estadístiques. Els resultats d'aquesta tesi mostren la utilitat i la idoneïtat dels mètodes de predicció basats en la pertorbació d'estructures de VP de nivells alts, precursors de les situacions ciclòniques. Els resultats i estratègies presentats pretenen ser un punt de partida per a futurs estudis que facin ús d'aquests mètodes.
The main goal of this thesis is to improve the current prediction skill of potentially hazardous heavy precipitation weather events in the western Mediterranean region. We develop and test three different ensemble prediction systems (EPSs) that account for uncertainties present in both the numerical models and the initial conditions. To generate the EPSs we take advantage of the connection between potential vorticity (PV) structures and cyclones, and use different physical parameterization schemes. We obtain an improvement in forecast skill when using an EPS compared to a determinist forecast. The EPSs generated perturbing the initial conditions perform better in the statistical verification scores. The results of this Thesis show the utility and suitability of forecasting methods based on perturbing the upper-level precursor PV structures present in cyclonic situations. The results and strategies here discussed aim to be a basis for future studies making use of these methods.

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Baumgart, Marlene Annette [Verfasser]. "Processes governing the amplification of forecast errors and forecast uncertainty in a quantitative potential-vorticity framework / Marlene Annette Baumgart." Mainz : Universitätsbibliothek Mainz, 2020. http://d-nb.info/1211123510/34.

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Hardy, Sam. "The 23-26 September 2012 UK floods : influence of diabatic processes and upper-level forcing on cyclone development." Thesis, University of Manchester, 2017. https://www.research.manchester.ac.uk/portal/en/theses/the-2326-september-2012-uk-floods-influence-of-diabatic-processes-and-upperlevel-forcing-on-cyclone-development(7331bff8-e536-4446-bacf-701aca158c2b).html.

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The thesis comprises two separate journal articles that together form a coherent body of work. In this thesis, the key physical processes responsible for the 23-26 September 2012 UK floods are investigated using a case study approach. The cyclone responsible for the floods developed near the Azores on 20¬-22 September following the interaction between an equatorward-moving potential vorticity (PV) streamer and tropical storm Nadine. Convectively-driven latent heat release associated with the developing cyclone reduced upper-level PV and resulted in the fracture of the PV streamer into a discrete anomaly as the cyclone intensified. In Paper 1, convection-permitting model simulations and diabatic heating rate and PV tendency calculations along trajectories demonstrate that deposition heating strongly reduced upper-level PV in the vicinity of the PV streamer, contributing to its fracture into a discrete anomaly. The cyclone deepened further over the UK on 23-26 September, ahead of a second upper-level PV anomaly. In Paper 2, sensitivity simulations of the storm are presented. PV inversion is used to modify the strength and position of the PV anomaly in the initial conditions and to examine whether the event could have been even more extreme with different upper-level forcing. Results show that quasigeostrophic forcing for ascent ahead of the PV anomaly contributed to the maintenance of the rainfall band over the UK. Counterintuitively however, strengthening the upper-level forcing produced a shallower cyclone with lower rainfall totals. Instead of moving eastward over the UK to interact with the cyclone, the strengthened anomaly rotated cyclonically around a large-scale trough over Iceland, resulting in a fragmented rainfall band. The counterintuitive results suggest that the verifying analysis represents almost the highest-impact scenario possible for this flooding event.

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Lee, Irene W. 1977. "An analytic examination of the effect of the stratosphere on surface climate through the method of piecewise potential vorticity inversion." Thesis, Massachusetts Institute of Technology, 2003. http://hdl.handle.net/1721.1/17677.

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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 2003.
Includes bibliographical references (leaves 75-77).
An analytic study was performed to examine the effect of the stratosphere on the surface of the earth. The method of piecewise potential vorticity inversion was employed in the diagnosis of the magnitude of and dynamics behind the stratosphere-surface link in both the transient and stationary cases. The potential vorticity inversion results in both the transient and stationary models indicated that the stratosphere possesses a significant effect at the surface of the earth. It was determined that, compared to the stratosphere as a whole, it was primarily the lower stratosphere that had the most significant impact at the surface of the earth. The results of this analytic study therefore indicate that in modeling the surface of the earth, the dynamics detailed here between the lower stratosphere and surface must be included for the modeled surface weather or climate simulations to be accurate.
by Irene W. Lee.
S.M.

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Dissertations / Theses on the topic 'Potential vorticity'

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