COMPARISON OF AN EXPERIMENTAL NOAA AVHRR CLOUD DATASET WITH OTHER OBSERVED AND FORECAST CLOUD DATASETS

CLAVR [cloud from AVHRR (Advanced Very High Resolution Radiometer)] is a global cloud dataset under development at NOAA/NESDIS (National Env ironmental Satellite, Data, and Information Service). Total cloud amou nt from two experimental cases, 9 July 1986 and 9 February 1990, are i ntercompared with two independent products, the Air Force Real-Time Ne phanalysis (RTNEPH), and the International Satellite Cloud Climatology Project (ISCCP). The ISCCP cloud database is a climate product proces sed retrospectively some years after the data are collected. Thus, onl y CLAVR and RTNEPH can satisfy the real-time requirements for numerica l weather prediction (NWP) models. Compared with RTNEPH and ISCCP, whi ch only use two channels in daytime retrievals and one at night, CLAVR utilizes all five channels in daytime and three at night from AVHRR d ata. That gives CLAVR a greater ability to detect certain cloud types, such as thin cirrus and low stratus. Designed to be an operational pr oduct, CLAVR is also compared with total cloud forecasts from the Nati onal Meteorological Center (NMC) Medium Range Forecast (MRF) Model. Th e datasets are mapped to the orbits of NOAA polar satellites, such tha t errors from temporal sampling are minimized. A set of statistical sc ores, histograms, and maps are used to display the characteristics of the datasets. The results show that the CLAVR data can realistically r esolve global cloud distributions. The spatial variation is, however, less than that of RTNEPH and ISCCP, due to current constraints in the CLAVR treatment of partial cloudiness. Results suggest that if the sat ellite cloud data is available in real time, it can be used to improve the cloud parameterization in numerical forecast models and data assi milation systems.