Dissertations / Theses: 'Large-scale atmospheric circulation'

1

Larson, Kristin Ann. "Tropical climate sensitivities : clouds, water vapor, radiation and large-scale circulation /." Thesis, Connect to this title online; UW restricted, 2002. http://hdl.handle.net/1773/10015.

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Peters, Matthew E. "Moist convection and the large scale tropical circulation /." Thesis, Connect to this title online; UW restricted, 2005. http://hdl.handle.net/1773/6773.

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3

Brandefelt, Jenny. "Atmospheric circulation regimes and climate change." Doctoral thesis, Stockholm : Dept. of Meteorology, Stockholm University, 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-530.

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4

Zhou, Guidi [Verfasser]. "Extratropical Sea Surface Temperature Impacts on Large-Scale Atmospheric Circulation / Guidi Zhou." Kiel : Universitätsbibliothek Kiel, 2016. http://d-nb.info/1081659904/34.

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5

Smolinski, Kelly Katherine. "Interrelationships Among Large-Scale Atmospheric Circulation Regimes and Surface Temperature Anomalies in the North American Arctic." Thesis, Georgia Institute of Technology, 2004. http://hdl.handle.net/1853/5026.

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The focus of this study is to examine the mechanisms involved in the interactions among large-scale atmospheric circulation patterns and how they are related to surface air temperature anomalies in the North American Arctic. Historical temperature data sets of Fairbanks, Alaska and Montreal, Quebec have been analyzed with respect to large-scale atmospheric circulation index data sets to investigate surface temperature anomalies in winter during the period 1960 to 2002.

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6

Huff, Russell. "Melt anomalies on the Greenland Ice Sheet and large scale modes of atmospheric circulation." Connect to online resource, 2007. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:3256466.

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7

Albuquerque, Cavalcanti Iracema Fonseca de. "Large scale disturbances in the southern hemisphere tropospheric circulation-model experiments and analyses of observed data." Thesis, University of Reading, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.305030.

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Kerimoglu, Onur. "Influence Of Large Scale Atmospheric Systems On Hydorology And Ecology Of Turkish Lakes." Master's thesis, METU, 2008. http://etd.lib.metu.edu.tr/upload/12609272/index.pdf.

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Impacts of climatic changes on in-land waters of Turkey is a topic that has not been sufficiently investigated yet. In this study, some exploratory work have been performed to form the core of further studies on the subject. EOF (Empirical Orthogonal Function) analysis has been applied to SLP (Sea Level Pressure) field with a wide coverage (20-70N, 50W-70E). The dominant sources of variability in this atmospheric system have been shown to be driven by 3 circulation indices, NAO (North Atlantic Oscillation), EAWR (East Atlantic - West Russia) and EA (East Atlantic) patterns. Linkages between this atmospheric system and the hydro-meteorological properties (data compiled from governmental organizations) of major Turkish lake ecosystems has been investigated with use of ordinary correlation analysis and CCA (Canonical Correlation Analysis). The results revealed the heavy forcing of large scale SLP field on regional temperature and E--P (evaporation minus precipitation) fields. The 15-year data set of Lake Mogan, as the longest available found, was used to exemplify the approaches and methodologies that can be employed for understanding the influence of climate variability on biological properties of lakes. It was suggested that temperature and salinity, being effective on phytoplankton and zooplankton groups, mediate the climatic impacts in Lake Mogan.

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Ganachaud, Alexandre Similien 1970. "Large scale oceanic circulation and fluxes of freshwater, heat, nutrients and oxygen." Thesis, Massachusetts Institute of Technology, 1999. http://hdl.handle.net/1721.1/58541.

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Thesis (Sc. D.)--Joint Program in Physical Oceanography (Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences; and the Woods Hole Oceanographic Institution), February 2000.
Includes bibliographical references (p. 250-266).
A new, global inversion is used to estimate the large scale oceanic circulation based on the World Ocean Circulation Experiment and Java Australia Dynamic Experiment hydrographic data. A linear inverse "box" model is used to combine consistently the transoceanic sections. The circulation is geostrophic with an Ekman layer at the surface and oceanic layers defined by neutral surfaces. Near-conservation of mass, salt and top-to-bottom silica is required and, in addition, heat and the phosphate-oxygen combination (170[PO 4]+[0 2]) are conserved in layers that are not in contact with the surface. A globally-consistent solution is obtained for a depth-independent adjustment to the thermal wind field, freshwater flux divergences, the Ekman transport, and the advective and diffusive dianeutral fluxes between layers. A detailed error budget permits calculation of statistical uncertainties, taking into account both the non-resolved part of the solution and the systematic errors due to the temporal oceanic variability. The estimated water mass transports during the WOCE period (1985-1996) are generally similar to previous published estimates. However, important differences are found. In particular, the inflow of bottom waters into the Pacific Ocean is smaller than in most previous estimates. Utilization of property anomaly conservation constraints allows the estimation of significant dianeutral diffusivities in deep layers, with a global average of 3 ± 1cm 2 s-1 north of 30'S. Dianeutral transfers indicate that about 20 Sv of bottom water is formed in the Southern Ocean. Significant oceanatmosphere heat fluxes are found, with a global heating of 2.3 ± 0.4 PW in the tropical band and a corresponding cooling at high latitudes. The signature of a large-scale average export production is found for nutrients in several temperate regions. Despite the large uncertainties, the production magnitudes are consistent with independent measurements from sediment traps and isotopic data. Net nutrient sources or sinks are found in several regions, suggesting either transport of dissolved organic matter or a seasonal alias. Oxygen indicates large exchanges with the atmosphere, with intake at high latitudes and outgassing/remineralization at low latitudes.
by Alexandre Similien Ganachaud.
Sc.D.

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10

Wetterhall, Fredrik. "Statistical Downscaling of Precipitation from Large-scale Atmospheric Circulation : Comparison of Methods and Climate Regions." Doctoral thesis, Uppsala University, Department of Earth Sciences, 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-5937.

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A global climate change may have large impacts on water resources on regional and global scales. General circulation models (GCMs) are the most used tools to evaluate climate-change scenarios on a global scale. They are, however, insufficiently describing the effects at the local scale. This thesis evaluates different approaches of statistical downscaling of precipitation from large-scale circulation variables, both concerning the method performance and the optimum choice of predictor variables.

The analogue downscaling method (AM) was found to work well as “benchmark” method in comparison to more complicated methods. AM was implemented using principal component analysis (PCA) and Teweles-Wobus Scores (TWS). Statistical properties of daily and monthly precipitation on a catchment in south-central Sweden, as well as daily precipitation in three catchments in China were acceptably downscaled.

A regression method conditioning a weather generator (SDSM) as well as a fuzzy-rule based circulation-pattern classification method conditioning a stochastical precipitation model (MOFRBC) gave good results when applied on Swedish and Chinese catchments. Statistical downscaling with MOFRBC from GMC (HADAM3P) output improved the statistical properties as well as the intra-annual variation of precipitation.

The studies show that temporal and areal settings of the predictor are important factors concerning the success of precipitation modelling. The MOFRCB and SDSM are generally performing better than the AM, and the best choice of method is depending on the purpose of the study. MOFRBC applied on output from a GCM future scenario indicates that the large-scale circulation will not be significantly affected. Adding humidity flux as predictor indicated an increased intensity both in extreme events and daily amounts in central and northern Sweden.

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11

Dambul, Ramzah. "The relationships between large-scale atmospheric circulation and surface climate : a case study for Borneo." Thesis, University of East Anglia, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.435307.

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12

Löfverström, Marcus. "On the interaction between ice sheets and the large-scale atmospheric circulation over the last glacial cycle." Doctoral thesis, Stockholms universitet, Meteorologiska institutionen (MISU), 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-107925.

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The last glacial cycle (c. 115-12 kyr BP) was the most recent in a series of recurring glaciations of the subpolar continents. Massive ice sheets evolved in Eurasia and North America, which, at their maximum, were of continental scale and together lowered the global sea-level by approximately 100 m. The paleo-modelling community has focused on the last glacial maximum (LGM, ~ 20 kyr BP), leaving the longer period when the ice sheets evolved to their LGM configurations largely unexplored. In this thesis we study the mutual interaction between the time-mean atmospheric circulation and the evolution of the Northern Hemisphere ice sheets over the build-up phase of the last glacial cycle. Experiments are conducted with coupled atmosphere-ice-sheet models and a circulation model forced by geologically consistent reconstructions of the ice-sheet topography at key stages of the glacial cycle. The main findings from these studies are that the ice evolution in North America may have been controlled by circulation anomalies induced by the background topography in conjunction with the ice sheets themselves. A geologically consistent pre-LGM ice sheet could only be obtained when including the North American Cordillera. However, the ice sheets' influence on the local climate conditions is also found to be paramount for this configuration. We further suggest that the incipient ice sheets may have had a limited influence on the large-scale winter circulation as a result of their location relative the westerly mean flow. The LGM Laurentide Ice Sheet (LIS) was, however, different because of its continent-wide extent, and it may therefore have had a large influence on the planetary-scale circulation, especially in the Atlantic sector. We find that the planetary waves forced by the LIS were considerably larger than at earlier times, and, as a result of a more frequent planetary wave reflection over the Atlantic Ocean basin, an altered stationary wave field and a zonalised winter jet.

At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 2: Manuscript. Paper 4: Manuscript.

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13

Yulaeva, Elena Valentinovna. "On the mechanism of the large-scale seasonally varying upwelling in the region of the tropical tropopause /." Thesis, Connect to this title online; UW restricted, 1997. http://hdl.handle.net/1773/10092.

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14

Lee, Cameron C. "The Relationship of Large-Scale Atmospheric Circulation Patterns to Tornadoes and the Impacts of Climate Change." Kent State University / OhioLINK, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=kent1274371690.

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15

Wang, Jinbo Ph D. Massachusetts Institute of Technology. "Instabilities of an eastern boundary current with and without Large-scale Flow Influence." Thesis, Massachusetts Institute of Technology, 2011. http://hdl.handle.net/1721.1/68890.

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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), 2011.
Cataloged from PDF version of thesis.
Includes bibliographical references (p. 221-227).
Eastern oceanic boundary currents are subject to hydrodynamic instability, generate small scale features that are visible in satellite images and may radiate westward into the interior, where they can be modified by the large-scale circulations. This thesis studies the stability of an eastern boundary current with and without the large-scale flow influence in an idealized framework represented by barotropic quasi-geostrophic dynamics. The linear stability analysis of a meridional current with a continuous velocity profile shows that meridional eastern and western boundary currents support a limited number of radiating modes with long meridional and zonal wavelengths and small growth rates. However, the linearly stable, long radiating modes of an eastern boundary current can become nonlinearly unstable by resonating with short trapped unstable modes. This phenomenon is clearly demonstrated in the weakly nonlinear simulations. Results suggest that linearly stable longwave modes deserve more attention when the radiating instability of a meridional boundary current is considered. A large-scale flow affects the short trapped unstable mode and long radiating mode through different mechanisms. The large-scale flow modifies the structure of the boundary current to stabilize or destabilize the unstable modes, leading to a meridionally localized maximum in the perturbation kinetic energy field. The shortwave mode is accelerated or decelerated by the meridional velocity adjustment of the large-scale flow to have an elongated or a squeezed meridional structure, which is confirmed both in a linear WKB analysis and in nonlinear simulations. The squeezed or elongated unstable mode detunes the nonlinear resonance with the longwave modes, which then become less energetic. These two modes show different meridional structures in kinetic energy field because of the different mechanisms. In spite of the model simplicity, these results can potentially explain the formation of the zonal jets observed in altimeter data, and indicate the influence of the large-scale wind-driven circulation on eastern boundary upwelling systems in the real ocean. Studies with more realistic configurations remain future challenges.
by Jinbo Wang.
Ph.D.

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16

Mauritzen, Cecilie. "A study of the large scale circulation and water mass formation in the Nordic seas and Arctic ocean." Thesis, Massachusetts Institute of Technology, 1993. http://hdl.handle.net/1721.1/59864.

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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, and the Woods Hole Oceanographic Institution, 1994.
Includes bibliographical references (leaves 205-212).
by Cecilie Mauritzen.
Ph.D.

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17

Valdés, Rodrigo. "Analysis of Long-Term Changes in Annual and Seasonal Precipitation in Chile and Related Large-Scale Atmospheric Circulation Patterns." Thesis, The University of Arizona, 2014. http://hdl.handle.net/10150/323414.

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The study of empirical teleconnections between annual and seasonal precipitation anomalies and different climate indices i.e. SOI, PDO, MEI, AAO, ONI, TWI, N3.4, TNI, and MJO, is an important approach to describe and analyze spatial and temporal precipitation variability. The objective of this study was to describe and analyze the main features of interannual and seasonal precipitation variability along Chile, and the influence of different ocean-atmospheric oscillations on secular long-term patterns. An exhaustive analysis through Empirical Orthogonal Functions (EOF) allowed determining the significant modes of annual and seasonal precipitation, and the main spatial patterns associated to them. Discrete Fourier Transform (DFT), the Singular Spectrum Analysis (SSA), and the Multichannel Singular Spectrum Analysis (M-SSA) were additionally used to determine the main frequencies and oscillatory components associated with leading climatic modes and precipitation patterns. The results agreed with those obtained by other authors and also when using different datasets. Despite advances on detailed annual and seasonal analysis that were carried out here, more detailed country-based studies are still required to develop a detailed understanding about climatic patterns along a country that is geographically very difficult to investigate.

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18

Wang, Liping. "The dynamic role of ridges in a β-plane channel : towards understanding the dynamics of large scale circulation in the Southern Ocean." Thesis, Massachusetts Institute of Technology, 1993. http://hdl.handle.net/1721.1/57741.

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19

Hristova, Hristina G. "Stability of large-scale oceanic flows and the importance of non-local effects." Thesis, Massachusetts Institute of Technology, 2009. http://hdl.handle.net/1721.1/52761.

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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), 2009.
This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Includes bibliographical references (p. 207-211).
My thesis covers two general circulation problems that involve the stability of largescale oceanic flows and the importance of non-local effects. The first problem examines the stability of meridional boundary currents, which are found on both sides of most ocean basins because of the presence of continents. A linear stability analysis of a meridional boundary current on the beta-plane is performed using a quasi-geostrophic model in order to determine the existence of radiating instabilities, a type of instability that propagates energy away from its origin region by exciting Rossby waves and can thus act as a source of eddy energy for the ocean interior. It is found that radiating instabilities are commonly found in both eastern and western boundary currents. However, there are some significant dierences that make eastern boundary currents more interesting from a radiation point of view. They possess a larger number of radiating modes, characterized by horizontal wavenumbers which would make them appear like zonal jets as they propagate into the ocean interior. The second problem examines the circulation in a nonlinear thermally-forced twolayer quasi-geostrophic ocean. The only driving force for the circulation in the model is a cross-isopycnal flux parameterized as interface relaxation. This forcing is similar to the radiative damping used commonly in atmospheric models, except that it is applied to the ocean circulation in a closed basin and is meant to represent the large-scale thermal forcing acting on the oceans.
(cont.) It is found that in the strongly nonlinear regime a substantial, not directly thermally-driven barotropic circulation is generated. Its variability in the limit of weak bottom drag is dominated by highfrequency barotropic basin modes. It is demonstrated that the excitation of basin normal modes has significant consequences for the mean state of the system and its variability, conclusions that are likely to apply for any other system whose variability is dominated by basin modes, no matter the forcing. A linear stability analysis performed on a wind- and a thermally-forced double-gyre circulation reveals that under certain conditions the basin modes can arise from local instabilities of the flow.
by Hristina G. Hristova.
Ph.D.

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20

Vieira, Agudelo Sara C. "Temporal variations of monsoon systems." Diss., Georgia Institute of Technology, 2010. http://hdl.handle.net/1853/37224.

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It has been proposed that the Asian-Australasian monsoon system is influenced by large-scale sea-surface temperature (SST) variability in the three tropical oceans although how this influence is manifested has remained a largely open question. Closure of this issue is important because it is needed to explain trends in monsoon precipitation and circulation that have occurred in the last 30 years. Using an atmospheric general circulation model, we run a series of experiments with different configurations of global SST relating to various epochs occurring during the last century to evaluate their influence on the monsoon. Comparisons of circulation fields show that a colder SST configuration generates a weaker large-scale monsoonal circulation. On the other hand, warmer SST states generate stronger large scale circulations with more vigorous centers of divergence and convergence. Warmer SST configurations are associated with positive anomalies of precipitation in the eastern Bay of Bengal, Eastern Indian Ocean and South East Asia. Cooler SST configurations are associated with negative anomalies of precipitation in the Arabian Sea and Indian peninsula, especially at the beginning of the summer. Since SST gradients determine, to a large degree, the low level flow, they are also going to influence the transport of atmospheric moisture. Comparison of vertically integrated moisture transport fields between the different experiments show that cold SST configuration favors an increased inter-hemispheric flow of moisture but decreases in the westerly moisture flow in to the Bay of Bengal and India. Warm SST configurations, on the other hand, strengthens westerly flow into the eastern Indian Ocean. An increasing availability of moisture in a region of stronger convergence constitutes a favorable environment for the production of monsoonal precipitation. African easterly waves (AEW) constitute an important component of the African and tropical Atlantic Ocean climate during the boreal summer. An understanding of this component is essential since AEW are closely related with tropical Atlantic storm activity. We adopt an idealized modeling approach using the WRF model initialized with ERA-40 reanalysis data to study the mechanisms that trigger the formation and maintenance of AEW. The model domain includes the African continent, central and eastern Atlantic Ocean and the western Indian Ocean. Experiments are designed to test the relative importance of the thermal effect of the eastern African topography and the influence of the cross-equatorial pressure gradient, induced by the sea surface temperature (SST) on the origins and maintenance of AEW. Topography and SST variation are selectively added and removed. The control experiment shows that the model reproduces many of the mean features observed during the boreal summer. Westward propagating disturbances of 3-8 day period that originate between 30 and 40E at the surface levels and in the mid troposphere are well depicted. In addition, the model provides a reasonable representation of the AEJ. When all topographic features are removed, there is a weakening of the AEJ over land and ocean, however, longitude-time sections of meridional velocity still exhibit westward propagating disturbances that reach the western African coast at the surface and at the jet level with the same 3-8 day period. Spectral analysis of meridional velocity show that the variability associated with AEWs is reduced over East Africa and West Africa at 850-hPa and is reduced west of 20E along the southern flank of the jet and over northern Africa at the jet level. Maximum amplitude of the disturbances occurs right at the coast. The spatial distribution of barotropic and baroclinic energy conversions explains the reduction in AEWs over land and the intensification of these features at the coast. When the zonal SST gradient is removed, a weaker AEJ displaces southward and a weaker monsoon flow ensues. Spectral analysis of meridional velocity displays a variance reduction in the 3-8 day band at the 850-hP a level in western and eastern Africa and at the coast. At the 650-hPa level significant changes are not observed at the latitude of the AEJ (15N), however, a decrease in the variance associated with AEW occurs at the southern flank of the jet. A southward displacement of the jet favors a weakening of the baroclinic energy conversions. Barotropic conversions also appear to be weaker when the SST gradient is removed. The present study suggests that orography plays an important role in determining the variability of meridional wind associated with AEW over Eastern Africa at the lower levels. Further, zonal SST gradients over the Atlantic favor intensification of waves when they reach the coast and the maintenance of disturbances across the Ocean. Also, results could suggest that SST gradients support genesis of AEW just off the coast of Africa.

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Burton, Kenneth R. "Influence of Antarctic oscillation on intraseasonal variability of large-scale circulations over the Western North Pacific /." Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2005. http://library.nps.navy.mil/uhtbin/hyperion/05Mar%5FBurton.pdf.

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22

Sotiropoulou, Georgia. "The Arctic Atmosphere : Interactions between clouds, boundary-layer turbulence and large-scale circulation." Doctoral thesis, Stockholms universitet, Meteorologiska institutionen (MISU), 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-134525.

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Arctic climate is changing fast, but weather forecast and climate models have serious deficiencies in representing the Arctic atmosphere, because of the special conditions that occur in this region. The cold ice surface and the advection of warm air aloft from the south result in a semi-continuous presence of a temperature inversion, known as the “Arctic inversion”, which is governed by interacting large-scale and local processes, such as surface fluxes and cloud formation. In this thesis these poorly understood interactions are investigated using observations from field campaigns on the Swedish icebreaker Oden: The Arctic Summer Cloud Ocean Study (ASCOS) in 2008 and the Arctic Clouds in Summer Experiment (ACSE) in 2014. Two numerical models are also used to explore these data: the IFS global weather forecast model from the European Center for Medium-range Weather Forecasts and the MIMICA LES from Stockholm University. Arctic clouds can persist for a long time, days to weeks, and are usually mixed-phase; a difficult to model mixture of super-cooled cloud droplets and ice crystals. Their persistence has been attributed to several mechanisms, such as large-scale advection, surface evaporation and microphysical processes. ASCOS observations indicate that these clouds are most frequently decoupled from the surface; hence, surface evaporation plays a minor role. The determining factor for cloud-surface decoupling is the altitude of the clouds. Turbulent mixing is generated in the cloud layer, forced by cloud-top radiative cooling, but with a high cloud this cannot penetrate down to the surface mixed layer, which is forced primarily by mechanical turbulence. A special category of clouds is also found: optically thin liquid-only clouds with stable stratification, hence insignificant in-cloud mixing, which occur in low-aerosol conditions. IFS model fails to reproduce the cloud-surface decoupling observed during ASCOS. A new prognostic cloud physics scheme in IFS improves simulation of mixed-phase clouds, but does not improve the warm bias in the model, mostly because IFS fails to disperse low surface-warming clouds when observations indicate cloud-free conditions. With increasing summer open-water areas in a warming Arctic, there is a growing interest in processes related to the ice marginal zones and the summer-to-autumn seasonal transition. ACSE included measurements over both open-water and sea-ice surfaces, during melt and early freeze. The seasonal transition was abrupt, not gradual as would have been expected if it was primarily driven by the gradual changes in net solar radiation. After the transition, the ocean surface remained warmer than the atmosphere, enhancing surface cooling and facilitating sea-ice formation. Observations in melt season showed distinct differences in atmospheric structure between the two surface types; during freeze-up these largely disappear. In summer, large-scale advection of warm and moist air over melting sea ice had large impacts on atmospheric stability and the surface. This is explored with an LES; results indicate that while vertical structure of the lowest atmosphere is primarily sensitive to heat advection, cloud formation, which is of great importance to the surface energy budget, is primarily sensitive to moisture advection.

At the time of the doctoral defense, the following paper was unpublished and had a status as follows: Paper 4: Manuscript.

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Selkirk, Henry Box. "An investigation of 40-50 day large scale divergent circulations in the tropical troposphere." Thesis, Massachusetts Institute of Technology, 1986. http://hdl.handle.net/1721.1/58331.

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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric and Planetary Sciences, 1986.
Microfiche copy available in Archives and Science.
Bibliography: leaves 273-281.
by Henry Box Selkirk.
Ph.D.

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Burton, Kenneth R. Jr. "Influence of Antarctic oscillation on intraseasonal variability of large-scale circulations over the Western North Pacific." Thesis, Monterey California. Naval Postgraduate School, 2005. http://hdl.handle.net/10945/2310.

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Approved for public release, distribution is unlimited
This study examines Southern Hemisphere mid-latitude wave variations connected to the Antarctic Oscillation (AAO) to establish connections with the 15- to 25-day wave activity in the western North Pacific monsoon trough region. The AAO index defined from the leading empirical orthogonal functions of 700 hPa height anomalies led to seven distinct circulation patterns that vary in conjunction with the 15- to 25-day monsoon trough mode. For nearly one half of the significant events the onset of 15- to 25-day monsoon trough convective activity coincided with a peak negative AAO index and the peak in monsoon trough convection coincided with a peak positive index. The remaining events either occur when the AAO is not significantly varying or when the AAO-related Southern Hemisphere mid-latitude circulations do not match 15- to 25-day transitions. When a significant connection occurs between the Southern Hemisphere mid-latitude circulations related to the AAO and the 15- to 25-day wave activity in the western North Pacific monsoon trough, the mechanism is via equatorward Rossby-wave dispersion. When wave energy flux in the Southern Hemisphere is directed zonally, no connection is established between the AAO and the alternating periods of enhanced and reduced convection in the western North Pacific monsoon trough.
Captain, United States Air Force

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Lücke, Karsten [Verfasser]. "On the Influence of Mixing on the Performance of Large-Scale Atmospheric Circulating Fluidized Bed Combustors / Karsten Lücke." Aachen : Shaker, 2003. http://d-nb.info/1179023390/34.

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Maity, Rajib. "Impact Of Large-Scale Coupled Atmospheric-Oceanic Circulation On Hydrologic Variability And Uncertainty Through Hydroclimatic Teleconnection." Thesis, 2007. http://hdl.handle.net/2005/721.

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In the recent scenario of climate change, the natural variability and uncertainty associated with the hydrologic variables is of great concern to the community. This thesis opens up a new area of multi-disciplinary research. It is a promising field of research in hydrology and water resources that uses the information from the field of atmospheric science. A new way to identify and capture the variability and uncertainty associated with the hydrologic variables is established through this thesis. Assessment of hydroclimatic teleconnection for Indian subcontinent and its use in basin-scale hydrologic time series analysis and forecasting is the broad aim of this PhD thesis. The initial part of the thesis is devoted to investigate and establish the dependence of Indian summer monsoon rainfall (ISMR) on large-scale Oceanic-atmospheric circulation phenomena from tropical Pacific Ocean and Indian Ocean regions. El Niño-Southern Oscillation (ENSO) is the well established coupled Ocean-atmosphere mode of tropical Pacific Ocean whereas Indian Ocean Dipole (IOD) mode is the recently identified coupled Ocean-atmosphere mode of tropical Indian Ocean. Equatorial Indian Ocean Oscillation (EQUINOO) is known as the atmospheric component of IOD mode. The potential of ENSO and EQUINOO for predicting ISMR is investigated by Bayesian dynamic linear model (BDLM). A major advantage of this method is that, it is able to capture the dynamic nature of the cause-effect relationship between large-scale circulation information and hydrologic variables, which is quite expected in the climate change scenario. Another new method, proposed to capture the dependence between the teleconnected hydroclimatic variables is based on the theory of copula, which itself is quite new to the field of hydrology. The dependence of ISMR on ENSO and EQUINOO is captured and investigated for its potential use to predict the monthly variation of ISMR using the proposed method. The association of monthly variation of ISMR with the combined information of ENSO and EQUINOO, denoted by monthly composite index (MCI), is also investigated and established. The spatial variability of such association is also investigated. It is observed that MCI is significantly associated with monthly rainfall variation all over India, except over North-East (NE) India, where it is poor. Having established the hydroclimatic teleconnection at a comparatively larger scale, the hydroclimatic teleconnection for basin-scale hydrologic variables is then investigated and established. The association of large-scale atmospheric circulation with inflow during monsoon season into Hirakud reservoir, located in the state of Orissa in India, has been investigated. The strong predictive potential of the composite index of ENSO and EQUINOO is established for extreme inflow conditions. So the methodology of inflow prediction using the information of hydroclimatic teleconnection would be very suitable even for ungauged or poorly gauged watersheds as this approach does not use any information about the rainfall in the catchment. Recognizing the basin-scale hydroclimatic association with both ENSO and EQUINOO at seasonal scale, the information of hydroclimatic teleconnection is used for streamflow forecasting for the Mahanadi River basin in the state of Orissa, India, both at seasonal and monthly scale. It is established that the basin-scale streamflow is influenced by the large-scale atmospheric circulation phenomena. Information of streamflow from previous month(s) alone, as used in most of the traditional modeling approaches, is shown to be inadequate. It is successfully established that incorporation of large-scale atmospheric circulation information significantly improves the performance of prediction at monthly scale. Again, the prevailing conditions/characteristics of watershed are also important. Thus, consideration of both the information of previous streamflow and large-scale atmospheric circulations are important for basin-scale streamflow prediction at monthly time-scale. Adopting the developed approach of using the information of hydroclimatic teleconnection, hydrologic variables can be predicted with better accuracy which will be a very useful input for better management of water resources.

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27

De, Silva Sirilath J. "Statistical relationships between the mesoscale organization of convection, precipitation and the large-scale wind fields during the GATE." Thesis, 1990. http://hdl.handle.net/1957/28794.

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Abstract:

Data from the GARP Atlantic Tropical Experiment (GATE) was analysed in an exploratory manner to discover the characteristics of mesoscale organization of convection and it's relationship to large-scale wind profiles. Automated methods were developed to identify the convective cells and their linear organization. These automated methods use a median high-pass filter to identify enhanced cells and a simple pattern recognition technique to ascertain the linear organization between them. Due to the simplified nature of the algorithm, the whole data set of the 21 day period from the phase 3 of GATE was processed in an economical manner obtaining a large data base which was used in the investigation of clusters and other associated phenomena. The mesoscale organization of convective cells and the widespread areas of lighter precipitation associated with them showed expected characteristics and compared satisfactorily with previous results. A large fraction of the rainfall (64%) fell from the widespread area. The total precipitation had a correlation of 0.94 with the fractional area of the widespread and a correlation of 0.89 with the fractional area of the clusters. The widespread precipitation had a correlation index of 0.97 with it's fractional area and the cluster precipitation had a strong linear relationship to it's area with a correlation of 0.99. These factors argue well for the parameterization of rainfall rate in tropical regions to a high accuracy by the area covered by organized convective cells and widespread areas. It was also seen that there was a good correlation with the number of clusters and number of cores with the total precipitation rate in a given area. These factors create a strong argument for identifying mesoscale systems consisting of convective cells and widespread precipitation as basic units of precipitation in tropical regions, having a characteristic life cycle of their own. The widespread and total precipitation showed very good correlation with upper-level vertical motion. Clusters tended to align parallel with the horizontal low-level wind shear and the degree of alignment appears to depend on the strength of the wind shear.
Graduation date: 1991

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28

Elston, Susan Anne. "The "flickering switch" of calcium concentration in the Greenland ice core as an indicator of changes in large scale atmospheric circulation patterns." 1995. http://catalog.hathitrust.org/api/volumes/oclc/35098416.html.

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Abstract:

Thesis (M.S.)--University of Wisconsin--Madison, 1995.
Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 105-164).

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Dissertations / Theses on the topic 'Large-scale atmospheric circulation'

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