Snow is a major component of the Water and Energy Cycles, covering a large portion of the Nortern Hemisphere in winter time. Knowledge of the water stored in snowpacks (e.g., snow water equivalent, SWE) is fundamental in many areas such as global energy balance, regional or global climate change, fresh water budget estimation and weather prediction. Improved estimates of snow storage can benefit regional-scale hydrological models, general circulation models (GCMs), forecast of drought and floods and estimation of drinkable water. Estimates of SWE can be obtained from the Advanced Microwave Scanning Radiometer for EOS (AMSR-E), launched on NASA�s EOS Aqua spacecraft on May 4, 2002. The AMSR-E SWE product is one of the five key cryosphere science products, being the latest in a lineage of measurements dating back to 1979 (SMMR and SSM/I radiometers). In this project, we propose to maintain and refine a recently delivered AMSR-E SWE algorithm, which, differently from the previous ones, makes use of a dynamic approach for accounting for the evolution of snow along the season. We will maintain the current NASA AMSR-E algorithm for high quality retrievals of global SWE on a daily, pentad and monthly basis through periodic maintenance operations on the software, its modification and testing due to refinement and the compilation of release notes for colleagues and the scientific community. We will refine the current algorithm by improving its capability of accounting for dynamic evolution of snow; by reducing the uncertainty on the retrieval by accounting for factors such as snow wetness, atmospheric effects (precipitating and non-precipitating water), water bodies and vegetation; by producing error maps based on per-pixel standard deviations of SWE and uncertainty maps derived from an analytical estimation of uncertainty of the retrieved SWE; by validating the current algorithm; by extending and applying the current algorithm for implementation to SSM/I and SMMR data . We expect to refine the product such that it will reach a level of validation that is consistent with other validated AMSR-E science data products. This project is an EOS Instrument-specific Algorithm Refinement and Cal/Val Activities Proposal. We will support the stated objective of the EOS science missions �to develop a comprehensive set of long-term, consistent, and validated data products from the EOS spacecraft�; the NASA Water and Energy Cycle scientific objectives through the �exploration of the responses of hydrologic regimes to changes in climate and the influence of surface hydrology (soil moisture, snow accumulation and soil freezing) on climate�; the goal of the NASA Terrestrial Hydrology Program to �remotely sense water at land surface and understand the interfaces of these water stores with the atmosphere, cryosphere, and oceans�; the more general NASA mission statement �to advance and communicate scientific knowledge and understanding of the earth�.
