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2021 ◽  
Author(s):  
Dipanjan Dey ◽  
Aitor Aldama Campino ◽  
Kristofer Döös

Abstract. The global atmospheric water transport from the evaporation to the precipitation regions has been traced using Lagrangian trajectories. A matrix has been constructed by selecting various group of trajectories based on their surface starting(evaporation) and ending (precipitation) positions to show the connectivity of the atmospheric water transport within and between the three major ocean basins and the global landmass. The analysis reveals that a major portion of the evaporated water precipitates back into the same region, namely 67 % for the Indian, 64 % for the Atlantic, 85 % for the Pacific Ocean and 72 % for the global landmass. The evaporation from the subtropical regions of the Indian, Atlantic and Pacific Oceans is found to be the primary source of atmospheric water for precipitation over the Intertropical Convergence Zone (ITCZ) in the corresponding basins. The evaporated waters from the subtropical and western Indian Ocean were traced as the source for precipitation over the South Asian and Eastern African landmass, while Atlantic Ocean waters are responsible for rainfall over North Asia and Western Africa. Atlantic storm tracks were identified as the carrier of atmospheric water that precipitates over Europe, while the Pacific storm tracks were responsible for North American, eastern Asian and Australian precipitation. The bulk of South and Central American precipitation is found to have its source in the tropical Atlantic Ocean. The recycling of evapotranspirated water from land is pronounced over the western coast of South America, Northeastern Asia, Canada and Greenland. The ocean-to-land and land-to-ocean water transport through the atmosphere was computed to be 2 × 109 kg/s and 1 × 109 kg/s, respectively. The difference between them (net ocean-to-land transport), i.e. 1 × 109 kg/s, is transported to land. This net transport is approximately the same as found in previous Eulerian estimates.


Conjecturas ◽  
2021 ◽  
Vol 21 (6) ◽  
pp. 157-170
Author(s):  
Rose Ane Pereira de Freitas ◽  
Fernanda Casagrande ◽  
Douglas da Silva Lindemann ◽  
Jéferson Prietsch Machado ◽  
Jackson Martins Rodrigues ◽  
...  
Keyword(s):  

Nesse estudo utiliza-se simulações numéricas do modelo ECHAM5/MPI-OM  para identificar os padrões dominantes de energia cinética  com o objetivo de explicar a gênese e manutenção das trajetórias preferenciais dos ciclones extratropicais (Storm Tracks, ST) no Hemisfério Sul, localizando suas origens e apresentando suas trajetórias preferenciais através do vetor E ⃗. Os resultados mostraram que para um cenário futuro, os ST parecem estar ligados diretamente ao fluxo de oeste, podendo-se afirmar que em um cenário futuro haverá uma intensificação desse transporte e os mesmos poderão deslocar-se mais para Sul. Dessa forma, espera-se que haja implicações nos abastecimentos de água de algumas regiões como o Sul da África, onde maior parte da população é dependente da precipitação na região. No Sul do Brasil, os resultados indicam aumentos nas chuvas durante os meses de verão, contrastando com uma diminuição na frequência dos ST e aumento na intensidade no inverno. Sugerimos que essas mudanças podem impactar a dinâmica climática do litoral sul brasileiro, com magnitude ainda desconhecida.


2021 ◽  
Author(s):  
Matthew D. K. Priestley ◽  
Jennifer L. Catto

Abstract. Future changes in extratropical cyclones and the associated storm tracks are uncertain. Using the new CMIP6 models, we investigate changes to seasonal mean storm tracks and composite wind speeds at different levels of the troposphere for the winter and summer seasons in both the Northern (NH) and Southern Hemispheres (SH). Changes are assessed across four different climate scenarios. The seasonal mean storm tracks are predicted to shift polewards in the SH and also in the North Pacific, with an extension into Europe for the North Atlantic storm track. Overall, the number of cyclones will decrease by ~5 % by the end of the 21st century, although the number of extreme cyclones will increase by 4 % in NH winter. Cyclone wind speeds are projected to strengthen throughout the troposphere in the winter seasons and also summer in the SH, with a weakening projected in NH summer, although there are minimal changes in the maximum wind speed in the lower troposphere. Large amounts of this change can be associated with changes in the speed of cyclones in the future. Changes in wind speeds are concentrated in the warm sector of cyclones and the area of extreme winds may be up to 40 % larger by the end of the century. The largest changes are seen for the SSP5-85 scenario, although large amount of change can be mitigated by restricting warming to that seen in the SSP1-26 and 2-45 scenarios. Extreme cyclones show larger increases in wind speed and peak vorticity than the average strength cyclones, with the extreme cyclones showing a larger increase in wind speed in the warm sector.


Atmosphere ◽  
2021 ◽  
Vol 12 (10) ◽  
pp. 1362
Author(s):  
Mihaela Caian ◽  
Florinela Georgescu ◽  
Mirela Pietrisi ◽  
Oana Catrina

Recent changes in cyclone tracks crossing Southeast Europe are investigated for the last few decades (1980–1999 compared with 2000–2019) using a developed objective method. The response in number, severity, and persistence of the tracks are analyzed based on the source of origin (the Mediterranean Sea sub-domains) and the target area (Romania-centered domain). In winter, extreme cyclones became more frequent in the south and were also more persistent in the northeast of Romania. In summer, these became more intense and frequent, mainly over the south and southeast of Romania, where they also showed a significant increase in persistence. The regional extreme changes are related to polar jet displacements and further enhanced by the coupling of the sub-tropical jet in the Euro-Atlantic area, such as southwestwards shift in winter jets and a split-type configuration that shifts northeastwards and southeastwards in the summer. These provide a mechanism for regional variability of extreme cyclones through two paths, respectively, by shifting the origins of the tracks and by shifting the interaction between the anomaly jet streaks and the climatological storm tracks. Large-scale drivers of these changes are analyzed in relation to the main modes of atmospheric variability. The tracks number over the target domain is mainly driven during the cold season through a combined action of AO and Polar–European modes, and in summer by the AMO and East-Asian modes. These links and the circulation mode’s recent variability are consistent with changes found in the jet and storm tracks.


2021 ◽  
pp. 1-48
Author(s):  
Olivia Martius ◽  
Kathrin Wehrli ◽  
Marco Rohrer

AbstractThree sets of model experiments are performed with the Community Earth System Model to study the role of soil moisture anomalies as a boundary forcing for the formation of upper-level Rossby wave patterns during Southern Hemisphere summer. In the experiments, soil moisture over Australia is set to ±1STD of an ERA-Interim reanalysis derived soil moisture reconstruction for the years 2009 to 2016 and 50 ensemble members are run. The local response is a positive heating anomaly in the dry simulations that results in a thermal low-like circulation anomaly with an anomalous surface low and upper-level anticyclone. Significant differences in convective rainfall over Australia are related to differences in convective instability and associated with changes in near surface moisture and moisture advection patterns. A circum-hemispheric flow response is identified both in the upper-level flow and in the surface storm tracks that overall resembles a positive Southern Annular Mode-like flow anomaly in the dry simulations. The structure of this atmospheric response strongly depends on the background flow. The results point to a modulation of the hemispheric flow response to the forcing over Australia by the El Niño Southern Oscillation. Significant changes of precipitation over the Maritime continent and South Africa are found and significant differences in the frequency of surface cyclones are present all along the storm tracks.


2021 ◽  
Vol 4 (1) ◽  
pp. 103-110
Author(s):  
Viacheslav S. Gradov ◽  
Irina V. Borovko ◽  
Vladimir N. Krupchatnikov

This paper focuses on the effect of sea ice melting under the effect of the mechanism of decreasing albedo of dry and wet ice and snow on the structure of atmospheric circulation. In particular, the Impact on storm tracks in the Pacific and Atlantic Oceans is analyzed. Extreme weather events are usually associated with atmospheric blocking conditions. Blocking is such meteorological conditions in which a large anticyclonic atmospheric vortex is observed over an area for several days. The Molteni-Tibaldi blocking criterion and the magnitude of the local anticyclonic wave activity (LAWA) are used to estimate the number of blockings. Extreme values of LAWA may indicate the presence of atmospheric blockings. As a result, there is a weakening and eastward shift of Atlantic storm trajectories. There is almost no influence on the Pacific storm tracks.


2021 ◽  
Vol 9 (4) ◽  
pp. 377
Author(s):  
Dong Eun Lee ◽  
Jaehee Kim ◽  
Yujin Heo ◽  
Hyunjin Kang ◽  
Eun Young Lee

The impact of climatic variability in atmospheric conditions on coastal environments accompanies adjustments in both the frequency and intensity of coastal storm surge events. The top winter season daily maximum sea level height events at 20 tidal stations around South Korea were examined to assess such impact of winter extratropical cyclone variability. As the investigation focusses on the most extreme sea level events, the impact of climate change is found to be invisible. It is revealed that the measures of extreme sea level events—frequency and intensity—do not correlate with the local sea surface temperature anomalies. Meanwhile, the frequency of winter extreme events exhibits a clear association with the concurrent climatic indices. It was determined that the annual frequency of the all-time top 5% winter daily maximum sea level events significantly and positively correlates with the NINO3.4 and Pacific Decadal Oscillation (PDO) indices at the majority of the 20 tidal stations. Hence, this indicates an increase in extreme event frequency and intensity, despite localized temperature cooling. This contradicts the expectation of increases in local extreme sea level events due to thermal expansion and global climate change. During El Nino, it is suggested that northward shifts of winter storm tracks associated with El Nino occur, disturbing the sea level around Korea more often. The current dominance of interannual storm track shifts, due to climate variability, over the impact of slow rise on the winter extreme sea level events, implies that coastal extreme sea level events will change through changes in the mechanical drivers rather than thermal expansion. The major storm tracks are predicted to continue shifting northward. The winter extreme sea level events in the midlatitude coastal region might not go through a monotonic change. They are expected to occur more often and more intensively in the near future, but might not continue doing so when northward shifting storm tracks move away from the marginal seas around Korea, as is predicted by the end of the century.


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