Abstract
Abstract. Evapotranspiration (ET) was estimated from 1981–2005 over Wushen County located in the Mu Us Sandland, China, by applying the Advection-Aridity model, which is based on the complementary relationship hypothesis. We used National Oceanic and Atmospheric Administration (NOAA) Advanced Very High Resolution Radiometer (AVHRR), Moderate Resolution Imaging Spectroradiometer (MODIS), and meteorological data. Our results show that the estimated daily ET was about 4.5% higher than measurements using an Eddy Covariance (EC) system after forcing energy balance closure over an alfalfa field from 22 July 2004 to 23 August 2004. At a regional scale, the estimated monthly ET was about 8.7% lower than measurements using the EC system after forcing energy balance closure over an alfalfa field in August 2004. These results were about 3.0% higher than ET measurements by microlysimeter over sand dunes during June 1988. From 1981 to 2005, the average annual ET and precipitation levels were 287 mm and 336 mm, respectively, in Wushen County. The average annual ET varied from 230 mm in western parts of Wushen County to 350 mm in eastern parts of the county. Both inter-annual and seasonal variations in ET were substantial in Wushen County. The annual ET was 200–400 mm from 1981–2005, and the seasonal pattern of ET showed a single peak distribution. The cumulative ET during the June–September 2004 period was 250 mm, which was 87% of the total annual ET. The annual ET, precipitation, and the maximum Normalized Difference Vegetation Index (NDVImax) showed positive correlations temporally and spatially.
Highlights
Evapotranspiration (ET) is an indispensable component of surface energy and water balance
Most data concentrated around the 1:1 line, and the estimated ET was about 4.5% higher than ground measurements, providing evidence that the Advection-Aridity model is suitable for ET estimation in the Mu Us Sandland
The precision of the ET estimated by the AdvectionAridity model, with remote sensing data at regional scales, was validated by comparing Eddy Covariance (EC) measurements over the Research Centre alfalfa field from August 2004 and by examining microlysimeter measurements over sand dunes from June 1988
Summary
Evapotranspiration (ET) is an indispensable component of surface energy and water balance. The Mu Us Sandland is one of the four largest sand lands in China It is located at the transition zone of several ecological regions with greatly altered water and heat resources, little precipitation, and an arid climate (Yao et al, 1992). In this region, drought and water shortages can adversely impact this fragile ecosystem by causing grassland degradation and land desertification. Drought and water shortages can adversely impact this fragile ecosystem by causing grassland degradation and land desertification These climate variables are key limiting factors for local economic growth and social development. Estimations of regional ET are needed for the Mu Us Sandland, which can be used as a reference for other arid areas in China, such as the Ejina Basin located at the lower reaches of the Heihe River
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