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SR-2002-005

Determination of Regional Scale Evapotranspiration of Texas from NOAA - AVHRR Satellite

Balaji Narasimhan, Dr. Raghavan Srinivasan

Evapotranspiration (ET) is defined as the combined loss of water by evaporation from soil and transpiration from plants. Depending on the geographic location, 60-80% of total annual precipitation is lost in the form of evapotranspiration. Since ET accounts for a major portion of water lost to the atmosphere, accurate estimation is essential for the success of hydrologic modeling studies. ET is estimated using climatic data like net radiation, air temperature, wind velocity, vapor pressure deficit and relative humidity obtained from the nearest weather stations. However, interpolating ET using data obtained from a point data source to derive regional ET could introduce errors of large magnitude. During the last two decades, GIS and Remote Sensing have evolved as an indispensable tool for monitoring natural resources. Due to the availability of spatially distributed data from satellites, and adopting GIS principles, accurate determination of ET is possible. The present study aims at deriving spatially distributed ET using NOAA-AVHRR satellite data.

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