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Hydrology Overview

Nowcasts of evapotranspiration, soil moisture, and outflow are produced daily and weekly by TOPS and the Ecocast architecture at continenal and regional scales. Taken together, these nowcasts provide a comprehensive overview of the hydrologic state of watersheds, and can be used to estimate available water resources and predict floods, droughts, and fire. They can also be used as inputs to other models, and used to generate nowcasts for other ecosystem parameters including phenology and GPP.

Our hydrology models are currently being updated and our nowcasts are temporarily offline. Check back soon for access to regional and continental nowcasts of the hydrologic parameters described below.

Sample outflow nowcast.
Evapotranspiration
 
Soil Moisture
 Evapotranspiration is calculated daily for the continental U.S. at a 8 km resolution. This product is calculated as a fractional value known as "evaporation fraction (EF)," which is the fraction of latent heat energy to available energy. This value represents not only the "dryness" of the land surface but also the characteristics of the land surface in terms of energy partitioning, which has a large influence on the local and regional climate and environment. Evapotranspiration nowcasts for the continental U.S. will be available here soon.
 
Soil moisture, or soil water content, is a measure of the volume of water per unit of soil. For example, it may be expressed as liters of H2O per cubic meter of soil. TOPS produces daily nowcasts of soil moisture for the continetnal U.S. at an 8 km resolution. This nowcasts are currently offline but will be available soon.
   
Outflow
   
Outflow is a measure surface water leaving an area, and is calculated by substracting evapotranspiration and infiltration from precipitation. Outflow can be used to estimate available water reserves for human use, and to floods and droughts. Check back soon for access to outflow forecasts for the continental U.S.
   
   
 
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Questions & Comments
updated 09/18/04

NASA Official: Rama Nemani
Curator: Forrest Melton