The surface energy budget (SEB) is the core of all land surface process models. It is the resultant of surface radiation and non-radiative components (e.g., sensible and latent heating). Land surface models usually rely on incoming radiation of the general circulation model (GCM) outputs as the atmospheric forcing, and calculate some key SEB variables (e.g., albedo and surface temperature) and the heating components. The NASA EOS program is routinely generating high-resolution albedo and temperature as the standard products that are used to validate the corresponding modeling components. There are currently several global radiative flux data sets derived from either satellite observations or GCM reanalysis, but the spatial resolution (usually >1 ) and accuracy of these products are not satisfactory for high-resolution modeling and applications. The MODIS team has to disaggregate NASA�s 1 *1.5 reanalysis incident solar radiation to produce the 1km net primary productivity (NPP) product. There are also other compelling reasons that we urgently need to produce high-resolution radiative fluxes. For example, since it has been widely recognized that it is so difficult to separate emissivity and temperature from satellite observations, why do we not just produce upwelling longwave radiation instead?
Our overall objective is to develop the algorithms for routinely producing high-resolution land radiative fluxes from MODIS, including incident shortwave solar radiation (insolation) and photosynthetically active radiation (PAR), shortwave net radiation, longwave downward, upwelling and net radiation, and all-wave net radiation. All sky conditions for shortwave radiation and all-wave net radiation but only clear-sky conditions for longwave radiation products will be considered. Because of two MODIS sensors and the orbit convergence, both instantaneous and daily integrated products can be generated. The strategies for integrating multiple satellites (both geostationary and polar-orbiting) will also be explored.
Since some algorithms have already been developed and extensively validated with NASA funding support, our strategy is to make the codes available to NASA and the public at different times. Except insolation and incident PAR, we have explored two types of algorithms for each product, one using other MODIS land or atmospheric products and another using MODIS TOA radiance of several bands directly. Integration of these products and algorithms will be investigated. Extensive validation activities will be carried out through the whole course of this study.
This proposal is built on our existing projects and is a direct response to NASA�s call for Integrated Science Data Analysis proposals �with innovative approaches to analyze EOS data or develop significantly different and/or new products required to answer science questions�. It will help bridge the gaps between the EOS high-level products and various SEB related applications.
