Exploiting Surface Albedo Products: Examples of Anticipated Downstream Applications from the GlobAlbedo Project
Abstract
ESA has recently initiated the GlobAlbedo project aiming at the production of surface albedo products at global scale generated from a synergistic approach involving long time series of data acquired by sensors on board ENVISAT as well as some predecessors such as Along Track Scanning Radiometer (ATSR) launched in the context of the Earth Observation Program. When available in a couple of years, these time-series of surface albedo products might be exploited further to retrieve a consistent ensemble of land surface variables characterizing the terrestrial surfaces (such as the effective LAI and the albedo of the vegetation background) as well as to assess a meaningful partitioning of the solar fluxes between the soil, vegetation and atmosphere layers, along multiple years and over large geographical regions. We present and discuss results from the application of an inversion package designed to assimilate surface albedo products into a state of the art radiation transfer scheme. This method implements the adjoint and Hessian codes, generated using automatic differentiation techniques, of a cost function accounting for 1) the deviation from the prior knowledge on the model parameter values and, 2) the misfit between the remote sensing products and the model calculations. Uncertainties associated with the products, models and priors are specified via relevant prior covariance matrices. The inversion method provides an estimate of the posterior covariance matrix on the model parameters which is further exploited to evaluate, in turn, the posterior probability density functions of the radiant fluxes simulated by the radiation transfer model, including those that are not measured, e.g., the fraction of solar radiation absorbed in the ground. Global scale applications presented here are performed using the MODIS broadband surface albedo products. Our results illustrate the capability of this inversion package to retrieve efficiently a panoply of land surface variables, including some Essential Climate Variables, in a consistent manner and with documented accuracy.
- Publication:
-
ESA Living Planet Symposium
- Pub Date:
- December 2010
- Bibcode:
- 2010ESASP.686E.181P