Estimation of Evapotranspiration in Sparse Vegetation Areas by Applying an Optimized Two-Source Model

Evapotranspiration (ET) is an important part of the water, carbon, and energy cycles in ecosystems, especially drylands. However, due to particularity sparse vegetation, estimation accuracy ET has been relatively low Therefore, based on dry climate vegetation distribution characteristics drylands, this study optimized core algorithms (canopy boundary resistance, aerodynamic coverage) explored method Shuttleworth–Wallace two-layer model (SW model). Then, Beijing–Tianjin sandstorm source region (BTSSR) was used as area evaluate applicability improved Results show that: (1) The R2 value results increased by 1.4 RMSE reduced 1.9 mm, extreme regions (maximum or minimum). (2) Regardless spatial seasonal changes (63–790 mm), could accurately capture differences. Furtherly, different stand for a certain extent. higher semi-arid (R2 = 0.92 0.93), while had best improvement effect arid region, with increasing 0.12. (3) Precipitation decisive factor affecting transpiration ET, both exceeding 0.9. coverage (VC) less. This expected provide more accurate adaptable