VALIDATION OF STRATOSPHERIC AEROSOL AND GAS EXPERIMENT-I AND EXPERIMENT-II SATELLITE AEROSOL OPTICAL DEPTH MEASUREMENTS USING SURFACE RADIOMETER DATA

The stratospheric aerosol measurement II, stratospheric aerosol and ga s experiment (SAGE) I, and SAGE II series of solar occultation satelli te instruments were designed for the study of stratospheric aerosols a nd gases and have been extensively validated in the stratosphere. They are also capable, under cloud-free conditions, of measuring the extin ction due to aerosols in the troposphere. Such tropospheric extinction measurements have yet to be validated by appropriate lidar and in sit u techniques. In this paper published atmospheric aerosol optical dept h measurements, made from high-altitude observatories during volcanica lly quiet periods, have been compared with optical depths calculated f rom local SAGE I and SAGE II extinction profiles. Surface measurements from three such observatories have been used, one located in Hawaii a nd two within the continental United States. Data have been intercompa red on a seasonal basis at wave-lengths between 0.5 and 1.0 mum and fo und to agree within the range of measurement errors and expected atmos pheric variation. The mean rms difference between the optical depths f or corresponding satellite and surface measured data sets is 29%, and the mean ratio of the optical depths is 1.09.