Estimation of land surface heat fluxes in the Beijing-Tianjin-Hebei region using a maximum entropy production model

Surface sensible and latent heat fluxes at the Xiaotangshan, Shunyi and Wuqing sites in the Beijing-Tianjin-Hebei region are calculated using a Maximum Entropy Production model (MEP) and observation data. The input data of the MEP model are net radiation, temperature and humidity. Among them, surface temperature and specific humidity are estimated respectively by surface upward and downward long wave radiation and relative humidity. The results of the MEP model are compared with Eddy Covariance (EC) observations to evaluate the model performance. In addition, daily averaged sensible and latent heat fluxes calculated by the MEP model at the three sites are also compared with the results from a simplified method (M20) and seven reanalysis datasets (NCEP1, NCEP2, MERRA2, ERA-5, ERA-Interim, JRA55, CRA) to analyze the accuracy of these methods for acquiring the surface sensible and latent heat fluxes in the Beijing-Tianjin-Hebei region. The results show that the fluxes calculated by the MEP model are generally consistent with observations and show similar diurnal, monthly and seasonal characteristics with those observed. Compared with results of the M20 method and reanalysis datasets, the results of the MEP model agree better with observations with smaller RMSEs (Root Mean Square Error) and average deviations. Therefore, the MEP model has high accuracy and reliability in calculating surface heat fluxes in the Beijing-Tianjin-Hebei region, and shows a good applicability in this region.