The climate of desiccation in the SW Cape

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Abstract. Hydro-meteorology conditions in the Southwest Cape of South Africa are analyzed for historical trends in satellite and station measurements. Results show an increase of coastal upwelling, low-level subsidence and shorter winters. The shearing by offshore easterly winds causes a circulation over the SW Cape which entrains dry air from the south coast upwelling zone. Potential evaporation exceeds precipitation and streamflow discharge has declined particularly northwest of the Hottentots Holland mountains. Many of Cape Town's water reservoirs are drying up, and show steep in-creases in surface temperature (+.2 C/yr) and browning of perimeter vegetation. The unfavorable wind shear is compounded by negative sensible heat flux and a capping inversion, so alongshore winds and mountain-top clouds divert seaward, desiccating the upper Berg River catchment.

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