Extended Abstract (924K)1B.4
The Significance of African Easterly Waves on Convection
Ademe Mekonnen, SUNY, Albany, NY
Studies using composite analysis suggest that there is a coherent relationship between AEWs and convection and associated rainfall during the summer season in tropical North Africa. However, we still lack a quantitative description of the significance of waves on convection. The present study aims to investigate the significance of AEWs on convection and how this varies in space and time (seasonally and interannually). Analysis of variance including spectral analysis has been carried out on a high resolution (3-hourly, 0.50 lat.-long grid) brightness temperature, TB, of CLAUS (Cloud Archive User Service of the European union project) data set and ECMWF analysis.
Application of spectral analysis shows a significant power in the period ranging from 2 to 5days. Maximum 2-5 days filtered variances centers are collocated with the ITCZ over the land and tropical Atlantic. Another maximum variance center is located over equatorial region. Very weak variances at this timescale are found over the highlands where the intradiurnal variance dominates, and over dry and dominantly cloud-free regions of the Sahara and northern and southern parts of the Atlantic. Percentage ratio of 2-5 days filtered variance to the total variance shows 20% to 30% over most regions of summer time convection, exceeding 25% in places, over land, and peak values of more than 30% are seen over the Atlantic. Indices of 2-5days filtered variance, unfiltered TB, rainfall and SST show large interannual variability. The relative roles of AEWs on Mesoscale Convective Systems (MCSs) will be presented.
Uploaded Presentation File(s):
Presentation4.ppt
Supplementary URL: http://www.atmos.albany.edu/student/ademe/AEW.html
Session 1B, CONVECTION, waves, and precipitation I
Monday, 3 May 2004, 8:30 AM-10:15 AM, Napoleon I Room
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