Development of a trapezoidal framework-based model (PCALEP) for partition of land evapotranspiration

• Published in: Journal of hydrology (Amsterdam) Vol. 589; p. 124994
• Main Authors: Chen, Han, Jeanne Huang, Jinhui, Berg, Aaron, McBean, Edward
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.10.2020
• Subjects: Land surface temperature-fractional vegetation coverage (Tm-fc); PCALEP model; Soil evaporation; Trapezoidal boundary location algorithm (TBLA); Vegetation transpiration; Soil evaporation; Land surface temperature-fractional vegetation coverage (Tm-fc); Trapezoidal boundary location algorithm (TBLA); PCALEP model; Vegetation transpiration
• ISSN: 0022-1694; 1879-2707
• DOI: 10.1016/j.jhydrol.2020.124994

•Automatic boundary location methods for Tm-fc trapezoidal are proposed.•A newly-developed PCALEP model is constructed and verified in two EC sites.•PCALEP reduces the resistance parameters requirements of all pixel to four points. A trapezoidal boundary location algorithm (TBLA) for the dry/wet boundaries of the land surface temperature (Tm)-fractional vegetation coverage (fc) trapezoidal framework is derived. The new model, PCALEP, for Pixel Component Arranging Comparing and Layered Energy Partition, uses newly-developed TBLA and combines field-measured values of the extreme dry/wet points, to estimate the theoretical temperatures of the Tm-fc trapezoid and calculate surface energy fluxes. The automatic and high-precision location algorithm for dry/wet boundaries greatly reduces the uncertainty caused by the extreme pixels selection. The results show PCALEP simulates overall accuracy of root-mean-square-error (RMSE) and Bias for latent heat flux (LE) of 36.3 W/m2 and −21.3 W/m2, in Yueyang site and 39.7 W/m2 and −27.7 W/m2 in XiShuangBanNa (XSBN) site in three test days of 2015. PCALEP provides higher accuracy estimation of surface energy fluxes compared with several two-source models. The model simulation of T/ET (ratio of vegetation transpiration to evapotranspiration) in the study area was 0.69. Sensitivity analyses show that the greatest impacts on estimation of LE results are fc, Tm and solar radiation (So), followed by albedo-related parameters, with the least impact from meteorological parameters such as friction wind speed (u*). The TBLA proposed in the paper can be applied to all trapezoidal framework boundary location (such as Tm-fc, αm (Albdeo) - fc, etc.).