The climate of tropical southern Africa during the SAFARI 2000 campaign

WE DESCRIBE THE ATMOSPHERIC CIRCUlation over sub-equatorial Africa during August and September 2000, at the time of the Southern African Regional Science Initiative (SAFARI 2000). According to satellite imagery from the aerosol sensor of the Total Ozone Mapping Spectrometer (TOMS), most of the pyrogenic emissions recorded originated from the southern Congo (3-17degreesS, 17-33degreesE) and dispersed westward. Meteorological data from the National Center for Environmental Prediction were used to characterize the stability of the anticyclonic circulation. Tropical easterly winds were weak during August and pyrogenic emissions accumulated over Angola much of the time. Occasional bursts of easterly air flow swept pyrogenic plumes across the tropical Atlantic. Mid-latitude troughs formed during September 2000, causing substantial dilution of atmospheric pollutants and southeastward anticyclonic circulation. Composite fields of wind, vertical motion and stability identified the transport pathways and mixing of pyrogenic emissions from tropical southern Africa, and serve as a background for more detailed in situ observations.