Abstract
Evapotranspiration (ET) plays a key role in water resource management. It is important to understand the ET spatio-temporal pattern of South Asia for understanding and anticipating serious water resource shortages. In this study, daily ET in 2008 was estimated over South Asia by using MODerate Resolution Imaging Spectroradiometer (MODIS) products combined with field observations and Global Land Data Assimilation System (GLDAS) product through Surface Energy Balance System (SEBS) model. Monthly ET data were calculated based on daily ET and evaluated by the GLDAS ET data. Good agreements were found between two datasets for winter months (October to February) with R2 from 0.5 to 0.7. Spatio-temporal analysis of ET was conducted. Ten specific sites with different land cover types at typical climate regions were selected to analyze the ET temporal change pattern, and the result indicated that the semi-arid or arid areas in the northwest had the lowest average daily ET (around 0.3 mm) with a big fluctuation in the monsoon season, while the sites in the Indo-Gangetic Plain and in southern India has bigger daily ET (more than 3 mm) due to a large water supplement. It is suggested that the monsoon climate has a large impact on ET spatio-temporal variation in the whole region.
Highlights
Evapotranspiration (ET) is the sum of evaporation from the soil surface and plant transpiration to the atmosphere
Since South Asia is mainly composed of less-developed countries, few field surface energy flux observation sites are established over this region
The Surface Energy Balance System (SEBS) model is a single source model based on surface energy balance which was proposed to estimate atmospheric turbulent fluxes, the evaporative fraction, and actual ET using remote sensing data combined with land surface meteorological observation information [18]
Summary
Evapotranspiration (ET) is the sum of evaporation from the soil surface and plant transpiration to the atmosphere It is an essential part of water balance with a central role in energy and carbon balance, and plays a key part in the hydrological process. Because it is the biggest cause of loss of land water, the assessment of ET is of outstanding importance for water resource management, planning, and monitoring [1,2]. The extremes of rainfall and dry season cause severe drought and flood disasters which gravely threaten the agricultural production, economic development and social security of the countries in South Asia [5,6]. Former studies [7,8] were usually conducted using estimations based on meteorological stations using the Penman-Monteith method, which makes it difficult to attain the spatial information
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