Intra- and inter-hemispheric teleconnections using seasonal southern hemisphere sea level pressure

1985 ◽  
Vol 5 (3) ◽  
pp. 283-296 ◽  
Author(s):  
Robert P. Harnack ◽  
Jeremi Harnack
Keyword(s):  
Sea Level ◽  
Southern Hemisphere ◽  
Sea Level Pressure ◽  
Level Pressure

scholarly journals Projected Significant Increase in the Number of Extreme Extratropical Cyclones in the Southern Hemisphere

2017 ◽  
Vol 30 (13) ◽  
pp. 4915-4935 ◽  
Author(s):  
Edmund K. M. Chang
Keyword(s):  
Sea Level ◽  
Southern Hemisphere ◽  
Cmip5 Models ◽  
General Interest ◽  
Extratropical Cyclones ◽  
The South ◽  
Sea Level Pressure ◽  
Near Surface ◽  
Level Pressure ◽  
South Indian

Extratropical cyclones are responsible for much of the extreme weather in the midlatitudes; thus, how these cyclones may change under increasing greenhouse gas forcing is of much general interest. Previous studies have suggested a poleward shift in the location of these cyclones, but how the intensity may change remains uncertain, especially in terms of maximum wind speed. In this study, projected changes in extreme cyclones in the Southern Hemisphere, based on 26 models participating in phase 5 of the Coupled Model Intercomparison Project (CMIP5), are presented. Multiple definitions of extreme cyclones have been examined, including intensity exceeding constant thresholds of sea level pressure perturbations, 850-hPa vorticity, and 850-hPa winds, as well as variable thresholds corresponding to a top-5 or top-1 cyclone per winter month in these three parameters and the near-surface winds. Results presented show that CMIP5 models project a significant increase in the frequency of extreme cyclones in all four seasons regardless of the definition, with over 88% of the models projecting an increase. Spatial patterns of increase are also consistent, with the largest increase projected between 45° and 60°S, extending from the South Atlantic across the south Indian Ocean into the Pacific. The projected increases in cyclone statistics are consistent with those in Eulerian statistics, such as sea level pressure (SLP) variance. However, while the projected increase in SLP variance can be linked to increase in the mean available potential energy (MAPE), the increases in cyclone statistics are not well correlated with those in MAPE.

scholarly journals Caracterização de Mudanças Climáticas na Antártica a partir da Segunda Metade do Século XX

2019 ◽  
Vol 12 (6) ◽  
pp. 2091
Author(s):  
Natália Silva ◽  
Ilana Elazari Klein Coaracy Wainer ◽  
Marcos Henrique Maruch Tonelli
Keyword(s):  
Climate Change ◽  
Wind Speed ◽  
Sea Level ◽  
Southern Hemisphere ◽  
Sea Level Pressure ◽  
Annular Mode ◽  
Level Pressure ◽  
British Antarctic Survey ◽  
Southern Hemisphere Annular Mode ◽  
San Martín

A Antártica é uma região do planeta extremamente sensível às mudanças globais do clima. Para quantificar essas mudanças, é possível estudar a variação de algumas propriedades atmosféricas como temperatura (T), pressão no nível do mar (PNM) e velocidade de ventos (v). Dados de estações meteorológicas espalhadas pela Antártica distribuídos pelo British Antarctic Survey são analisados. Os resultados mostram que as tendências de temperatura apresentam uma distribuição peculiar, visto que na porção oeste do continente há um intenso aquecimento (e.g.,0.55°C/década em San Martin), enquanto que o lado leste observa um resfriamento (-0.06°C/década em Zhongshan). O índice Intervalo de Temperatura Diária (ITD) também é utilizado para caracterizar mudanças climáticas e é consistente com as variações obtidas para a temperatura, caracterizando, portanto, o chamado Padrão de Dipolo na temperatura. Com relação à PNM, 19 estações meteorológicas das 20 estudadas, apresentam tendências negativas e na grande maioria dessas observa-se também intensificação da velocidade dos ventos. Essas mudanças estão associadas principalmente aos modos de variabilidade natural do planeta, sendo que o maior determinante das características climáticas nas regiões extratropicais do Hemisfério Sul é o Modo Anular do Hemisfério Sul (SAM). Characterization of climate change in Antarctica from the second half of 20th CenturyA B S T R A C TAntarctica is a region of the planet extremely sensitive to global climate change. To quantify these changes, it is possible to study the variation of some atmospheric properties such as Temperature, Sea Level Pressure and Wind Speed. Data from meteorological stations in Antarctica provided by the British Antarctic Survey are analyzed. The results show that Temperature trends have a peculiar distribution, since on the western side of the continent there is intense heating (e.g., 0.55°C/decade in San Martin), while the east side observes cooling trends (-0.06°C/decade  in Zhongshan). The Daily Temperature Range index is also used to characterize climatic changes and agrees with the variations obtained for the Temperature, thus characterizing the so-called Dipole Pattern in temperature. About the Sea Level Pressure, 19 meteorological stations of the 20 studied, present negative trends and in the great majority of these it is also observed intensification on the wind speed. These changes are mainly associated with the natural modes of variability of the planet, and the Southern Hemisphere Annular Mode (SAM) is the major determinant of the climatic characteristics in the extratropical regions of the Southern Hemisphere.Keywords: Antarctica, Climate Change, Temperature Dipole, Southern Hemisphere Annular Mode.

scholarly journals Historical SAM Variability. Part I: Century-Length Seasonal Reconstructions*

2009 ◽  
Vol 22 (20) ◽  
pp. 5319-5345 ◽  
Author(s):  
Julie M. Jones ◽  
Ryan L. Fogt ◽  
Martin Widmann ◽  
Gareth J. Marshall ◽  
Phil D. Jones ◽  
...  
Keyword(s):  
Sea Level ◽  
Southern Hemisphere ◽  
Austral Summer ◽  
Principal Component ◽  
Reanalysis Data ◽  
The Other ◽  
Considerable Variability ◽  
Sea Level Pressure ◽  
Level Pressure ◽  
The Individual

Abstract Seasonal reconstructions of the Southern Hemisphere annular mode (SAM) index are derived to extend the record before the reanalysis period, using station sea level pressure (SLP) data as predictors. Two reconstructions using different predictands are obtained: one [Jones and Widmann (JW)] based on the first principal component (PC) of extratropical SLP and the other (Fogt) on the index of Marshall. A regional-based SAM index (Visbeck) is also considered. These predictands agree well post-1979; correlations decline in all seasons except austral summer for the full series starting in 1958. Predictand agreement is strongest in spring and summer; hence agreement between the reconstructions is highest in these seasons. The less zonally symmetric SAM structure in winter and spring influences the strength of the SAM signal over land areas, hence the number of stations included in the reconstructions. Reconstructions from 1865 were, therefore, derived in summer and autumn and from 1905 in winter and spring. This paper examines the skill of each reconstruction by comparison with observations and reanalysis data. Some of the individual peaks in the reconstructions, such as the most recent in austral summer, represent a full hemispheric SAM pattern, while others are caused by regional SLP anomalies over the locations of the predictors. The JW and Fogt reconstructions are of similar quality in summer and autumn, while in winter and spring the Marshall index is better reconstructed by Fogt than the PC index is by JW. In spring and autumn the SAM shows considerable variability prior to recent decades.

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