Search results for "Tropical Easterly Jet"

Recent changes in precipitation, ITCZ convection and northern tropical circulation over North Africa (1979-2007)

2011

This article focuses on some recent changes observed in the Tropics with special emphasis on the African monsoon region using high-resolution gridded precipitation from the Climatic Research Unit (period 1979–2002), outgoing longwave radiation at the top of the atmosphere from the National Oceanic and Atmospheric Administration and atmospheric reanalyses from the Climate Prediction Center (NCEP-DOE2, period 1979–2007). The results show a rainfall increase in North Africa since the mid-90s with significant northward migrations of rainfall amounts, i.e. + 1.5° for the 400 mm July to September isohyets, whereas deep convection has significantly increased and shifted northward. The subsidence b…

2010

Abstract. Southern Asia, extending from Pakistan and Afghanistan to Indonesia and Papua New Guinea, is one of the most heavily populated regions of the world. Biofuel and biomass burning play a disproportionately large role in the emissions of most key pollutant gases and aerosols there, in contrast to much of the rest of the Northern Hemisphere, where fossil fuel burning and industrial processes tend to dominate. This results in polluted air masses which are enriched in carbon-containing aerosols, carbon monoxide, and hydrocarbons. The outflow and long-distance transport of these polluted air masses is characterized by three distinct seasonal circulation patterns: the winter monsoon, the s…

Intercomparison and analyses of the climatology of the West African Monsoon in the West African Monsoon Modeling and Evaluation project (WAMME) first…

2010

International audience; This paper briefly presents the West African Monsoon (WAM) Modeling and Evaluation Project (WAMME) and evaluates WAMME general circulation models' (GCM) performances in simulating variability of WAM precipitation, surface temperature, and major circulation features at seasonal and intraseasonal scales in the first WAMME experiment. The analyses indicate that models with specified sea surface temperature generally have reasonable simulations of the pattern of spatial distribution of WAM seasonal mean precipitation and surface temperature as well as the averaged zonal wind in latitude-height cross-section and low level circulation. But there are large differences among mo…

On the occurrence of strong vertical wind shear in the tropopause region: a 10-year ERA5 northern hemispheric study

2021

A climatology of the occurrence of strong wind shear in the upper troposphere–lower stratosphere (UTLS) is presented, which gives rise to defining a tropopause shear layer (TSL). Strong wind shear in the tropopause region is of interest because it can generate turbulence, which can lead to cross-tropopause mixing. The analysis is based on 10 years of daily northern hemispheric ECMWF ERA5 reanalysis data. The vertical extent of the region analyzed is limited to the altitudes from 1.5 km above the surface up to 25 km, to exclude the planetary boundary layer as well as strong wind shear in higher atmospheric layers like the mesosphere–lower thermosphere. A threshold value of St2=4×10-4s-2 of t…

Time evolution of observed July–September sea surface temperature-Sahel climate teleconnection with removed quasi-global effect (1900–2008)

2011

[1] Using sea surface temperature (SST), precipitation, and atmospheric information, this statistical study revisits the questions of the July–September SST-Sahel teleconnection variability after removing impact of quasi-global SSTs over the period 1900–2008. The eastern Mediterranean and the Indian Ocean dominate the relationship, both in terms of intensity and time stability, with significant values in 52% and 47% of years, respectively. More than two thirds of the rainy seasons classified as dry (wet) and 16 out of 18 (12 out of 15) of those classified as very dry (very wet) are concomitant of negative (positive) differences between the Mediterranean and the Indian Ocean. Correlations wi…