A New Approach to Monitor Net Surface Solar Radiation from Geostationary Satellites

Net surface solar radiation forms a key component of the land surface energy balance and its accurate determination over large domains at high spatial and temporal resolution is vital in agriculture and water management applications. Simple techniques have been developed to derive instantaneous estimates of the net surface shortwave (SW) radiative flux from the narrow-band geostationary satellite (GEO) visible imagery under all sky conditions. The GEO visible imagery has been found to be very well correlated with the NASA-operated Clouds and Earth's Radiant Energy System's SW top of atmosphere (TOA) radiative flux and matching of the collocated imageries provides a calibration for the GEO narrowband imagery to yield a broadband SW TOA radiative flux. This is followed by implementation of the well-known parameterization (Li et al 1993; Masuda et al 1995) relating the TOA flux and solar flux absorbed at the surface. The scheme does not require knowledge of cloud structure or cloud optical properties, but needs additional ancillary input parameters such as the column water vapor amount and aerosol optical depth at 550 nm. Comparison of GEO imager-retrieved net surface SW flux with those obtained from combining ground-based pyranometer measurements at several ground sites covering different land cover types and seasons shows good agreements comparable to or in some cases even better than the more sophisticated approaches.