Evaluation of the harmonic-analysis method for surface soil heat flux estimation: a case study in Heihe River Basin

摘要

Surface soil heat flux (G_0) is an important component of surface energy balance, and it causes large uncertainty in evapotranspiration estimation. In present study, soil heat flux was calculated at different depths based on the harmonic analysis method (HM) using field data in Heihe River Basin, northwestern China. The soil heat fluxes at a certain depth and at the surface were validated by heat-plate measurements and G_0 derived from thermal diffusion equation, respectively. Results showed that HM method obtained good result during the daytime, yet the errors were relatively large at nighttime mostly due to the assumption of symmetry of G_0 during daytime and nighttime. Moreover, a regional G_0 map was provided based on remote sensing data. This study highlighted the simplicity of HM method and its potential application in large spatial scale mapping. Its internal limit was also discussed here.