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Journal Article: BibTeX citation key:  Kalapureddy2010a
Kalapureddy, M. C. R., Lothon, M., Campistron, B., Lohou, F. & Saïd, F. (2010) Wind profiler analysis of the African Easterly Jet in relation with the Boundary-layer and the Saharan Heat Low. IN Quarterly Journal of the Royal Meteorological Society, 136. 77–91.
Added by: Madhu Chandra R KALAPUREDDY 2008-12-16 09:43:01    Last Edited by: Fanny Lefebvre 2010-11-17 16:36:51
 B  
Categories: Monsoon system and its variability
Keywords: Atmospheric Boundary Layer, Diurnal cycle, Dynamics, Intraseasonal variability, Seasonal cycle
Creators: Campistron, Kalapureddy, Lohou, Lothon, Saïd
Collection: Quarterly Journal of the Royal Meteorological Society
Bibliographies: Prior150410

Peer reviewed
Number of views:  1241
Popularity index:  65.66%

 
Abstract
The measurements of UHF and VHF wind profilers in Niger and Benin during the African Monsoon Multidisciplinary project are used to study the intra-seasonal variability of the low- and mid-troposphere at several timescales. We especially focus on the African Easterly Jet (AEJ) and its interaction with the Saharan Heat Low (HL) and the Planetary Boundary Layer (PBL).
We find a pronounced diurnal cycle of the AEJ, which is signed by a decrease of wind speed during the afternoon, reaching a minimum at 1800 UTC of about 15 to 20% of the daily average during the pre-onset period. This decrease is out of phase with the HL intensity, but in phase with the daytime turbulent mixing associated with the PBL. The interaction between the PBL and mid troposphere is likely responsible for this daily decrease of AEJ.
During the transition periods, the HL seems to govern the AEJ, but slightly before the monsoon onset, it has no direct influence on the jet. During that time, we find smaller AEJ wind speed for deeper PBL, as found at the diurnal timescale. This is consistent with the still large surface heating at that time, which favours deep PBL growth, with a summit inversion often higher than the shear layer between monsoon and easterlies. After the monsoon onset, deep convection, AEWs, and dry intrusions make the synoptic environment complex and blur the interaction between AEJ and PBL. We still find weaker AEJ for deeper PBL, but likely without a direct connection between them.
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Added by: Madhu Chandra R KALAPUREDDY    Last Edited by: Fanny Lefebvre