关键词: DTD模型, TSEB模型, 下垫面类型, 地表蒸散发, 植被蒸腾, 土壤蒸发, 地表温度, 真实性检验

Abstract:

Operational application of an appropriate model to estimate evapotranspiration (ET) and the components evaporation (E), transpiration (T) at a range of space and time scales is very useful for managing water resources. The Two Source Energy Balance (TSEB) and Dual Temperature Difference (DTD) models have been applied to estimate land surface evapotranspiration under various landcover types and environment conditions. The DTD model requires twice radiometric temperature observations as inputs while the TSEB model only use single observation. This may reduce the uncertainty of DTD model which introduced from the observation or remotely sensed based radiometric temperatures. However, the two models may perform inconsistent under various land surface, which mainly associated with the different theoretical mechanisms in the models. In this study, the two models were evaluated using the long time ground observation data collected from three total different landcover types and environment conditions, including alpine grassland, semi-arid irrigated farmland and arid riparian forest in Heihe River Basin in Northwest China. The results showed that the latent heat flux estimated by the DTD model had a better agreement with half an hour ground measurements at the alpine grassland site, with the RMSE value of 62.00 W/m^2, while TSEB model showed a higher RMSE value of 75.49 W/m². But the performance of the two models was associated with the variation of the vegetation coverage. While, in the semi-arid farmland site, the performances of two models were more consistent where they produced a closer RMSE values, but in the arid riparian forest site, both of the models significantly underestimated the latent heat flux. The DTD model showed a worse agreement with the ground measurements in both sensible and latent heat fluxes. The DTD modeled latent heat flux had a higher RMSE values of 136.74 W/m² where the TSEB model had a RMSE value of 86.40 W/m². The better agreement of the TSEB model latent heat fluxes may associate with greater underestimation of modeled sensible heat flux which can partly compensate underestimation of net radiation. However, at the daily scale the performances of the DTD model and TSEB model were more similar. Additionally, the ratio of plant transpiration to evapotranspiration partitioned by the two models were in good agreement with results simulated from water use efficiency (uWUE) model with ground measurements, while the DTD model also performed better than the TSEB model. Finally, the TSEB model was more sensitive to the model input of land surface temperature. Therefore how to improve the accuracy of remote sense land surface temperature products is vital to the model application. Meanwhile, future researches can focus on optimizing model for extending applications over heterogeneous surface and different meteorological conditions.

Key words: DTD model, TSEB model, landcovers, evapotranspiration, transpiration, evaporation, land surface temperature, validation