Seasonal and interannual variability of Asian desert aerosols from Nimbus 7/TOMS data

Seasonal and interannual variability of Asian desert aerosols are observed using Nimbus 7/Total Ozone Mapping Spectrometer (TOMS) aerosol index for the years 1979-1993. It is assumed that dust aerosols can be observed if the TOMS aerosol index (AI) is greater than 1.0. According to the monthly mean from 1979 to 1993, dust aerosols originating from the arid deserts of Mongolia and China are observed frequently during springtime (March to May) throughout East Asia. The most frequent occurrence of dust aerosols over the source area is observed in May. On the other hand, the most frequent occurrence of Asian desert aerosol over Korea is observed in April. The frequency over Korea is consistent with in situ measurements. The discrepancy between source area and Korea may be due to meteorological variables such as wind. A time-longitude plot of the meridional mean of days (AI>1.0) between 75°E and 140°E shows year-to-year variability. During the 1982-83 and 1992-93 El Nin˜o, the most frequent occurrence of dust aerosols over the source area is observed.