Analysis of Convection and Its Association with African Easterly WavesSource: Journal of Climate:;2006:;volume( 019 ):;issue: 020::page 5405DOI: 10.1175/JCLI3920.1Publisher: American Meteorological Society
Abstract: The association between convection and African easterly wave (AEW) activity over tropical Africa and the tropical Atlantic during the boreal summer is examined using satellite brightness temperature (TB) and ECMWF reanalysis datasets. Spectral analysis using 18 yr of TB data shows significant variance in the 2?6-day range across most of the region. Within the regions of deep convection, this time scale accounts for about 25%?35% of the total variance. The 2?6-day convective variance has similar amplitudes over western and eastern Africa, while dynamic measures of AEW activity show stronger amplitudes in the west. This study suggests that weak AEW activity in the east is consistent with initial wave development there and indicates that convection triggered on the western side of the mountains over central and eastern Africa, near Darfur (western Sudan) and Ethiopia, has a role in initiating AEWs westward. The subsequent development and growth of AEWs in West Africa is associated with stronger coherence with convection there. Results show large year-to-year variability in convection at the 2?6-day time scale, which tends to vary consistently with the mean convection and dynamical measures of AEW activity over West Africa and the Atlantic, but not over central and eastern Africa. The Darfur region is particularly important for providing convective precursors that propagate westward and trigger AEWs downstream. During wet years, convection over eastern Africa (western Ethiopian highlands) can be a significant source of AEW initiation. In addition to being important for precursors of AEWs, the Darfur region is also a source of convection that propagates eastward toward Ethiopia.
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contributor author | Mekonnen, Ademe | |
contributor author | Thorncroft, Chris D. | |
contributor author | Aiyyer, Anantha R. | |
date accessioned | 2017-06-09T17:02:29Z | |
date available | 2017-06-09T17:02:29Z | |
date copyright | 2006/10/01 | |
date issued | 2006 | |
identifier issn | 0894-8755 | |
identifier other | ams-78385.pdf | |
identifier uri | http://onlinelibrary.yabesh.ir/handle/yetl/4221048 | |
description abstract | The association between convection and African easterly wave (AEW) activity over tropical Africa and the tropical Atlantic during the boreal summer is examined using satellite brightness temperature (TB) and ECMWF reanalysis datasets. Spectral analysis using 18 yr of TB data shows significant variance in the 2?6-day range across most of the region. Within the regions of deep convection, this time scale accounts for about 25%?35% of the total variance. The 2?6-day convective variance has similar amplitudes over western and eastern Africa, while dynamic measures of AEW activity show stronger amplitudes in the west. This study suggests that weak AEW activity in the east is consistent with initial wave development there and indicates that convection triggered on the western side of the mountains over central and eastern Africa, near Darfur (western Sudan) and Ethiopia, has a role in initiating AEWs westward. The subsequent development and growth of AEWs in West Africa is associated with stronger coherence with convection there. Results show large year-to-year variability in convection at the 2?6-day time scale, which tends to vary consistently with the mean convection and dynamical measures of AEW activity over West Africa and the Atlantic, but not over central and eastern Africa. The Darfur region is particularly important for providing convective precursors that propagate westward and trigger AEWs downstream. During wet years, convection over eastern Africa (western Ethiopian highlands) can be a significant source of AEW initiation. In addition to being important for precursors of AEWs, the Darfur region is also a source of convection that propagates eastward toward Ethiopia. | |
publisher | American Meteorological Society | |
title | Analysis of Convection and Its Association with African Easterly Waves | |
type | Journal Paper | |
journal volume | 19 | |
journal issue | 20 | |
journal title | Journal of Climate | |
identifier doi | 10.1175/JCLI3920.1 | |
journal fristpage | 5405 | |
journal lastpage | 5421 | |
tree | Journal of Climate:;2006:;volume( 019 ):;issue: 020 | |
contenttype | Fulltext |