Evapotranspiration (ET) is an important component of surface energy balance and a key process of hydrological cycle. Continuous and accurate estimation of regional ET is meaningful for water management, agricultural production, and climate change adaptation. Remote Sensing (RS) technique is of important meaning for estimating ET on regional scale. However, there are some problems in the ET estimation model based on RS such as: (1) Surface resistance and aerodynamic resistance which are necessary in energy balance method are not easy to be estimated accurately, (2) Advective energy, which is an important driver of ET in heterogeneous regions, is not accounted for. In this study, a new method is developed to integrate the RS information and meteorological data based on the decouple model which is deduced from Penman-Monteith (PM) model. Firstly, a parameterization method for decoupling factor (Ω) which is key parameter in the decouple model and could reflect the coupling relationship between the land surface and atmosphere systems is introduced.

Subsequently, the decouple model is applied to inverse regional ET in Beijing City and nearby region, from 1st, May, 2013 to 31th, October, 2020. Thirdly, the inversed daily ET values are evaluated based on the measured data at Huailai station and in Badaling 2 Forest Farm. The results show that the changing trend of estimated ET and measured ET are basically the similar.The mean value of the daily estimated ET is 1. 40 mm d -1 and the mean value of the daily measured ET is 1.52 mm d -1 . The bias value is -0.12 mm d -1 , the RSME value is 0.66 mm d -1 , and the correlation coefficient is 0.52 . Finally, the spatiotemporal trend of water consumption in study area is analyzed based on the ET estimation results. The month with the largest water consumption in 2013 is July with the quantity of 0.92 billion m 3 , accounting for about 22% of the regional total water consumption in growing season. The regions with high ET values agree well with the regions of high soil moisture and high air humidity as well as high biomass. These results suggest that the decouple model is with great potential to generate regional daily ET products and to support irrigation management.