Using MODIS land products to estimate regional evapotranspiration

Evapotranspiration (ET) is one of the most important land surface processes for terrestrial ecosystems because it strongly relates to both the energy balance and the mass balance of these ecosystems. Though there are many ground based approaches to estimate ET, it is still a challenge to estimate ET by remote sensing for most applications. A methodology was proposed to calculate regional actual ET by using the energy balance equation and MODIS products, i.e., MOD11A2, MOD13A2 and MCD43B3. The key point in the proposed method is that a cloud coefficient was introduced to adjust the clear days in a given period, because the MODIS products represent a mean and most cloudless condition in that time interval. A case study was carried out in Jinghe River Basin, located in the southern part of the Loess Plateau, China. The results showed that the proposed method had reasonable accuracy, with an absolute error of 47 mm/a when compared with the ET calculated by using water balance equation. This accuracy is acceptable for most application purposes.