Application of GCOM-C SGLI for agricultural water management via field evapotranspiration

摘要

Evapotranspiration is a key parameter in agricultural water planning and management strategies because it determines the crop and irrigation water requirements. With the recent advance in satellite-based field observations and meteorological modeling, several techniques have been developed and applied to estimate actual evapotranspiration. This paper presents the first results of the application to field evapotranspiration monitoring of land surface temperatures observed by Japan's new Global Change Observation Mission-Climate (GCOM-C) satellite. Through a test application conducted in an irrigation region in the western USA, specifications of the GCOM-C surface temperature observation and the derived field evapotranspiration were evaluated. The specifications of the surface temperature observation were that the satellite observed the study fields with a spatial resolution of about 300m at a frequency of 4-5days per week. Clouds further degraded observation frequency. However, at least one constant successful observation of land surface temperature was available each week during the study period from June 17 to July 21, 2018. With the unique spatial and temporal resolution of GCOM-C, the surface temperature data allowed weekly monitoring of individual field evapotranspiration for large-size fields. Estimation results of field evapotranspiration by the GCOM-C ETindex estimation algorithm were evaluated for fields of wheat, pea, alfalfa, bean, and corn/potato/beet, as well as for rangeland. The result reasonably explained the relative differences of evapotranspiration among the different crop types and among individual fields having the same crop type. Quantitatively, some indications of underestimation of evapotranspiration were found during the application.