资源环境科技发展态势分析平台

Knowledge of cloud cover, frequency, and duration is not only important to study cloud dynamics, but also critical in determiningwhenand where to take ocean measurements from geostationary orbits such as the Geostationary Coastal and Air Pollution Events (GEO-CAPE) mission due to the challenges in achieving complete hemispheric coverage of coastal oceans, estuaries, and inland waters at hourly frequency. Using GOES hourly measurements at 4 km nadir resolution between 2006 and 2011, the number of cloud-free hourly observations per day (N-cf) for solar zenith angle theta(o) < 80 degrees was estimated for each 0.1 degrees location of the Intra-Americas Sea. The number of Sun-glint-affected hourly observations per day (N-sg) was also calculated based on the planned GEO-CAPE observation geometry and realistic wind speed. High-latitude and equatorial oceans showed the lowest N-cf (< 2.4) in all climatological months, and highest N-cf was observed in the Gulf of Mexico (GoM) and Caribbean (> 4.5). Different regions showed differences in seasonality of cloud-free conditions and also showed differences in the hour of a day at which the satellite observations would have the maximal cloud-free and glint-free probability (T-max). Cloud cover from Moderate Resolution Imaging Spectroradiometer (MODIS) 1 km measurements are > 10% higher than those from the MODIS 250m measurements, supporting ocean color missions at subkilometer resolutions to enhance both spatial coverage and temporal frequency. These findings provide valuable information for GEO-CAPE mission planning to maximize its science value through minimizing the impacts of clouds and Sun glint.