VALIDATION OF NOAA/AVHRR AEROSOL RETRIEVALS USING SUN-PHOTOMETER MEASUREMENTS FROM R/V AKADEMIK-VERNADSKY IN 1991

NOAA has produced aerosol optical thickness tau(SAT)(A) retrievals from NOAA-11 over oceans operationally since 1990/1/. The upward radiances L (W . m(-2).mu m(-1). sr(-1)) in AVHRR/Channel 1 (Chi; lambda=0.63 mu m) are converted to tau(SAT)(A) using a look-up-table (LUT), pre-calculated for various combinations of illumination-observation geometries assuming all oceanic and aerosol optical parameters constant but the total aerosol amount /2/. An earlier paper /3/ described the results of tau(SAT)(A) validation using a set of sun-photometer (SP) measurements tau(SP)(A) from the R/V Akademik Vernadsky during its Cruise in the Atlantic ocean and Mediterranean Sea in Sept-Dec 1989 (AV-89) /4/. That analysis revealed errors in tau(SAT)(A). This paper provides an independent check of that conclusion using the SP measurements taken during another Cruise of the RN Akademik Vernadsky in Jul-Sept 1991 (AV-91), using the same validation methodology as described in /3/. The results of the two experiments are in agreement.