ESRI grid showing the mean incident light for each quarter. This data is the surface solar irradiance data obtained for NASA/GISS to allow the prodction of photosynthetically active solar irradiance fields to allow the calculation of primary productio using satellite ocean colour products. The information comes from the Internation Satellite Cloud Climatology Project (ISCCP) using C1 data from multiple geostationary and polar orbiting meterological satellites to provide a global view of the occurrence and properties of clouds. Atmospheric, cloud and surface data from ICSSP are used as input along with a scheme for computing clear-sky irradiance from the solar zenith angle, air properties, and surface reflectance. The scheme then uses simple cloud properties (cloud fraction, cloud optical thickness, and diffuse albedo) to produce total and photosynthetically active solar irradiance fields (Bishop and Rossow 1991; ISCCP Documentation of Cloud Data; Frouin et al. 1989). Input and output data fields are given in a 2.5° latitude and longitude grid. These grids have been produced by CSIRO for the National Oceans Office, as part of an ongoing commitment to natural resource planning and management through the 'National Marine Bioregionalisation' project.