ATMOSPHERIC BOUNDARY-LAYER FLUXES AND STRUCTURE ACROSS A LAND-SEA TRANSITION ZONE IN SOUTH-EASTERN AFRICA
Authors: JURY M.1; ROUAULT M.2; WEEKS S.2; SCHORMANN M.3
Source: Boundary-Layer Meteorology, Volume 83, Number 2, May 1997 , pp. 311-330(20)
Publisher: Springer
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Abstract:
The structure of the lower atmospheric boundary layer along the southeastern escarpment of Africa during November 1993 is investigated. The study region falls in a transition zone between dry desert to the west and sub-humid vegetated areas bordering the Agulhas Current to the east. The physical environment is described by in situ observations from aircraft and a coastal weather station; from satellite composites of sea surface temperature, vegetation reflectance and cloud temperatures; and synoptic weather data.
Example aircraft sections illustrate sharp spatial gradients and changes in surface heat fluxes of order 100 W m-2 (10 km)-1. Inland penetration of moisture depends on background zonal winds and depth of the marine layer. Aircraft turbulent covariance estimates are used to identify high surface heat fluxes over the inland Karoo desert. During easterly winds, moisture fluxes are greatest over vegetated coastal mountains in a plume 2 km deep. Surface moisture fluxes over the Agulhas Current and coastal mountains are double those over the cold inshore waters and inland desert. The injection of moist unstable air increases the convective potential during ridging anticyclone weather conditions.
Keywords: Boundary-layer fluxes; Land-sea transition; South-eastern Africa
Language: English
Document Type: Regular paper
Affiliations: 1: Current affiliation: Geography Department, University of Zululand, Kwa Dlangezwa, South Africa. 2: Oceanography Department, University of Cape Town, South Africa 3: CloudQuest, Nelspruit, South Africa
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