DERIVATION AND APPLICATIONS OF NEAR-INFRARED CLOUD REFLECTANCES FROM GOES-8 AND GOES-9

Recent deployments of the National Oceanic and Atmospheric Administrat ion (NOAA) Geostationary Operational Environmental Satellites (GOES-8 and -9) include full-time 3.9-mu m imaging capabilities. This shortwav e (near infrared) channel has been available at 3.7 mu m on the Advanc ed Very High Resolution Radiometer (AVHRR) instrument aboard the NOAA polar-orbiting satellite systems. In this spectral region, daytime sat ellite-observed radiances include contributions from both the reflecte d solar radiation and the emitted thermal emission. In particular, typ ical stratus and fog clouds posess near-infrared emissivities less tha n unity, which requires special processing to account for the angular dependence of the solar reflection. In this paper, a side-by-side comp arison of time-coincident GOES-and AVHRR-derived near-infrared cloud r eflectance is carried out in order to demonstrate the capability of GO ES-8 and -9 in both identifying and characterizing the microphysics of stratus and fog clouds during the daytime. The authors first present the mathematical formalism and then apply the technique to extract the near-infrared reflectances from GOES-8 and -9 data. The technique is applicable for operational usage and requires a lookup table to accoun t for the continuously changing sun-satellite viewing geometry. Near-i nfrared cloud reflectances are extracted from coincident GOES-9 and AV HRR data from both NOM-14 and -12 for different times of day and are v erified against theoretical reflectances derived from radiative transf er theory and previously published results. A retrieval of the cloud d rop size distribution effective radius is demonstrated on satellite da ta along coastal California during the summer of 1996.