Assessing the effects of end-members determination on regional latent heat flux simulation in trapezoidal framework based model

Abstract Land surface temperature-fractional vegetation coverage (LST-fc) trapezoid framework based models have been widely developed, applied, and verified to estimate regional latent heat flux (LE) and its partitioning process. The basis of operating these models lies in the determination of end-members within the LST-fc trapezoid. However, the knowledge of how the end-members affect the LE and ratio of vegetation latent heat flux (LEv) to latent heat flux (LEv/LE) estimation is lacking in the literature. In this study, three widely used end-members determination methods, viz., determination of actual end-members within the scatter plot of LST-fc (AEM), determination of theoretical end-members through the Zhang's method (Zhang et al., 2005, TEM-Z), and determination of theoretical end-members through Long's method (Long and Singh. 2012b, TEM-L) were inter-compared. The outcome of this study was verified at the 11 Eddy Correlation (EC) observation stations for the 183 test days during 2015 using the Moderate-resolution Imaging Spectroradiometer (MODIS) products, revealing that different end-members combinations greatly alter the LE simulation. However, tuning of end-members do not shift the LEv/LE estimates, and spatial patterns of the LE and LEv/LE remained unchanged. Moreover, the performance of TEM-Z is better than the AEM, while the TEM-L provide relatively unstable performance during the 183 test days. Conclusively, this study endorses to adopt the TEM-Z method to determine the end-members. This study provides a clear understanding of the effect of different end-members to LE and LEv/LE simulation within the LST-fc trapezoid framework, and gives a clear insight for model selection, operation, and subsequent, guidelines for model improvement.