Tuesday, 4 June 2002: 10:30 AM
Seasonal and Diurnal Variations of Cloud Properties Derived for CERES from VIRS and MODIS Data
Cloud optical and physical properties are essential for linking the hydrological cycle with the Earth’s radiation budget. Simultaneous measurements of cloud properties and broadband radiative fluxes provide the empirical basis for accurate modeling of both processes in climate models. The Clouds and Earth’s Radiant Energy System (CERES) project is designed to provide such measurements by matching very consistent cloud properties with radiation budget data. Multispectral imagers, the Visible Infrared Scanner (VIRS) on the Tropical Rainfall Measuring Mission (TRMM) satellite and the Moderate Resolution Imaging Spectroradiometer (MODIS) on Terra, are used to remotely sense a wide range of cloud properties on a global basis at different times of day from very similar instruments coincident with the CERES brodaband flux data. The TRMM, launched during late 1997, continues to provide coverage at all local hours between 37°N and 37°S over a period of 46 days, while the MODIS, operating since Spring 2000, has a 1030 LT Equatorial crossing time providing twice-per-day coverage in the Tropics and midlatitudes and higher temporal sampling in polar regions. Cloud amount, temperature, height, phase, effective particle size, optical depth, and water path are derived from the 2-km VIRS and 1-km MODIS radiances taken at 0.64, 1.6, 3.7, 11, and 12 µm. The VIRS data have been analyzed for data taken since January 1998. Provisional MODIS data have been analyzed for spring and summer 2001. Analysis is proceeding on both datasets to provide a continuous long-term record. These pixel-level data are convolved into the footprint (10-20 km) of each CERES radiance to provide the link between clouds and the radiation budget. The results of these analyses are also valuable for studying the variation of cloud properties at many different spatial and temporal scales over the globe. This paper will focus on the seasonal and diurnal variations of each parameter over different regions and surface types. The data are available for studies of cloud processes, climatology, and aerosol-cloud interactions.