Multichannel sea surface tempratures (MCSSTs) have been produced operationally on a global basis from AVHRR data since November 1981. Although the basic technique has been unchanged for over S years, refinements and modifications to handle special situations (e.g. volcanic and sandstorm aerosols) are under development and a cross-product (nonlinear) procedure for atmospheric corrections has been tested. The aerosol optical depth estimates have been made experimentally for about a year using AVHRR data from channel-1, and special cloud screening techniques have been developed to differentiate between clouds and aerosols.