Global ETD Search
Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
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Showing 1 to 20 of 42 for “"Annular mode"”.
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Antarctic sea ice trends and its response to the Southern annular mode
… in the atmospheric circulation. The Southern Annular Mode (SAM) is the primary mode of variability in the atmospheric circulation of the Southern Hemisphere. Despite the overall warming of Antarctica, sea ice extent and sea ice area show a positive trend in the Southern Ocean and all its …
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Annular mode-like responses to external forcings in a simple atmospheric general circulation model
… of a simple atmospheric general circulation model to applied forcings to learn whether the annular mode patterns are a preferred model response to the forcings. The thesis is inspired by the appearance of annular mode patterns in Earth's atmosphere in response to a number of forcings. …
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Revisiting the links between the Southern Annular Mode and rainfall over the Western Cape region of South Africa
… this thesis is on the influence of the Southern Annular Mode (SAM) on rainfall over the region, the possible influence of El Niño Southern Oscillation (ENSO) is also considered. To achieve this, a correlation analysis was conducted using the Marshal (2003) SAM index and station rainfall anomalies …
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Exploring winter rainfall in western South Africa : connections, influences and the potential for statistical seasonal forecasting
… between SWC rainfall and the Southern Annular Mode (SAM), South Atlantic sea surface temperature (SST), Antarctic sea ice concentration (SIC), and the EI Nino-Southern Oscillation (ENSO) were explored using spatial and temporal correlations. Insight gained from the correlation analysis …
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Stratosphere - troposphere interaction during stratospheric sudden warming events
… understood. An idealized spectral core dynamical model is utilized in the present study in order to clarify the coupling timing, location and mechanisms. Since the coupling between the winter stratosphere and troposphere is strongly intensified during times of strong stratospheric variability such …
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Variability of zooplankton and sea surface temperature in the Southern Ocean
… behavior in an idealized biological-physical model. Second, I analyze observations of sea surface temperature variability in the region of the Antarctic circumpolar current. Results suggest that propagating anomalies can be explained as a linear response to local atmospheric forcing by the …
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Low frequency variabilty of the Agulhas Current region in a numerical model
… the current using output from a regional ocean model. Validation of the model with in situ and satellite observed values for the temperature and SSH showed the modelled SSH results to be only marginally different from the satellite observed, while the temperature validation showed the modelled …
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Response to stratospheric forcing and its dependence on the state of the troposphere
… show a surface response of about 0.5 - 1 m/s, modeling studies can show a signal two times and in a particular extreme, four to eight times larger. In this thesis, an investigation of this extreme result revealed the model's characteristic timescale associated with the leading mode of …
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Stratospheric ozone and Southern Hemisphere climate change : impacts and robustness in CMIP5 models
… depletion and the positive phase of the dominant mode of variability of the southern annular mode (SAM) have been found, which in turn are linked to changes in precipitation, atmospheric temperatures and winds. This dissertation investigates how well the models from the most recent Coupled Model …
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An analysis of anomalously wet summers in the South Western Cape of South Africa
… are found to be linked to a negative Southern Annular Mode pattern and in the late summer, also linked to ENSO and the zonal wave number 3 pattern. Overall, trends suggest decreases in rainfall days in the Greater Cape Town region and in the nearby mountain areas where most major dams are …
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On quasi-periodic Baroclinic variability in the extratropical circulation
… This phenomenon has been termed the Baroclinic Annular Mode (BAM), and is responsible for the modulation of eddy heat fluxes, eddy kinetic energy, and precipitation on large scales. However, the extent to which this periodic modulation is discernable or significant on smaller spatial scales had …
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Decadal rainfall variability over Southern Africa
… a combination of proxy, observed and climate model data to explore the nature, mechanisms and anthropogenic forcing of rainfall variability at decadal scales. The spatial nature of rainfall variability, demonstrated through EOF analysis and composite decadal events, is similar to that at …
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Reconstruction of the historical climate of the Southern Ocean from whaling ships’ logbooks
… (the 1930s and 1950s) is found to be lower than modern climatology (1981-2010). It is in contrast to the southern reaches (65°S latitudinal band) where MSLP is found to be decreasing over the same period. A historical Southern Annular Mode (SAM) index from 1930-1960 is generated from the whaling …
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Understanding the interannual variability of pCO2 in the sea-ice impacted Southern Ocean
… with remotely sensed data and reanalysis models during the austral summer months. The region of focus is divided into three sections: the Southern Ocean, three ocean basins, and the Goodhope line transect. Averaged over the Southern Ocean, the range of year-to-year variability of pCO2 …
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The role of the large-scale modes of climate variability in the Southern African wave climate
… coastal trends. The role of the Southern Annular Mode (SAM), El Nino Southern Oscillation (ENSO), and the semi-annual oscillation (SAO) on the interannual monthly wave energy flux and direction variations were assessed. Individually each mode showed significant anomalies for at least one …
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Eurasian Snow Cover and the Role of Linear Interference in Stratosphere-troposphere Interactions
… over Eurasia and the wintertime Northern Annular Mode (NAM). In general circulation model (GCM) simulations with prescribed autumn Siberian snow forcing, a vertically propagating Rossby wave train is generated, driving dynamical stratospheric warming and a negative NAM response that …
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Patterns of climate variability of the Northern Hemisphere wintertime circulation
… fields. The leading EOF corresponds to the NH annular mode (NAM) and the second EOF resembles the Pacific-North American (PNA) pattern. Together these two patterns account for roughly half the variance of SLP on interannual time scales and longer, and virtually all the planetary-scale SLP …
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High-Latitude Southern Hemisphere Climate Variability, Trends, and Tropical Forcing.
… using an Atmospheric General Circulation Model (AGCM). Three components are examined: Antarctic sea ice concentration (SIC) variability is investigated in relation to the leading modes of SH climate variability, the Southern Annular Mode (SAM) and the El Niño- Southern Oscillation (ENSO). …
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Environmental change recorded in physical and geochemical proxies over the Last Glacial Cycle from two Northland, New Zealand dune lakes: Lake Kanono and Lake Kai Iwi
… and storm belts associated with the Southern Annular Mode (SAM) and El Niño Southern Oscillation (ENSO). Here environmental conditions were reconstructed from lake sediment cores obtained from Lake Kanono and Lake Kai Iwi in Northland, New Zealand. Using a multi-proxy approach incorporating …
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Investigation of Wind Variability in the South Atlantic Sector of the Southern Ocean and the Influence on the Upper Ocean in a Numerical Ocean Model
… in the Southern Ocean (SO) with the Southern Annular Mode (SAM), which has seen an increase in the positive phase since the mid-1960s, due to the Antarctic ozone depletion and emissions of greenhouse gases. The SAM is recognized as the main mode of atmospheric variability in the SO. The SAM …
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