Abstract
The partitioning of available energy between sensible heat and latent heat is important for precise water resources planning and management in the context of global climate change. Land surface temperature (LST) is a key variable in energy balance process and remotely sensed LST is widely used for estimating surface heat fluxes at regional scale. However, the inequality between LST and aerodynamic surface temperature (Taero) poses a great challenge for regional heat fluxes estimation in one-source energy balance models. To address this issue, we proposed a One-Source Model for Land (OSML) to estimate regional surface heat fluxes without requirements for empirical extra resistance, roughness parameterization and wind velocity. The proposed OSML employs both conceptual VFC/LST trapezoid model and the electrical analog formula of sensible heat flux (H) to analytically estimate the radiometric-convective resistance (rae) via a quartic equation. To evaluate the performance of OSML, the model was applied to the Soil Moisture-Atmosphere Coupling Experiment (SMACEX) in United States and the Multi-Scale Observation Experiment on Evapotranspiration (MUSOEXE) in China, using remotely sensed retrievals as auxiliary data sets at regional scale. Validated against tower-based surface fluxes observations, the root mean square deviation (RMSD) of H and latent heat flux (LE) from OSML are 34.5 W/m2 and 46.5 W/m2 at SMACEX site and 50.1 W/m2 and 67.0 W/m2 at MUSOEXE site. The performance of OSML is very comparable to other published studies. In addition, the proposed OSML model demonstrates similar skills of predicting surface heat fluxes in comparison to SEBS (Surface Energy Balance System). Since OSML does not require specification of aerodynamic surface characteristics, roughness parameterization and meteorological conditions with high spatial variation such as wind speed, this proposed method shows high potential for routinely acquisition of latent heat flux estimation over heterogeneous areas.
Highlights
Land surface heat fluxes are essential components of water and energy cycles interactions in the hydrosphere, atmosphere and biosphere [1,2,3,4,5,6]
Much effort has been made to compensate for the difference between land surface temperature (LST) and Taero in one-source models, most of which was concentrated on making corrections by: (1) adjusting temperature based on empirical relationship between LST and Taero [19,21,23]; and (2) adjusting the aerodynamic resistance roughness length for heat or the kB−1 parameter, or by including empirical “extra resistance” factors [24,25]
Validation of energy balance components of Rn and G are shown in Figure 5a,b, while the One-Source Model for Land (OSML)- and Surface Energy Balance System (SEBS)-derived latent heat flux (LE) and H estimations are plotted against corresponding eddy covariance (EC) measurements in Figure 5c,d respectively
Summary
Land surface heat fluxes are essential components of water and energy cycles interactions in the hydrosphere, atmosphere and biosphere [1,2,3,4,5,6]. The energy balance and its partitioning between sensible heat flux (H) and latent heat flux (LE) are extremely important for understanding global climate change and land-atmosphere interaction [7]. Because of the inequality between LST and aerodynamic surface temperature (Taero ), one-source and two-source surface energy balance models have been proposed with various expressions for aerodynamic resistance, in order to estimate the sensible heat loss based on difference between surface and air temperature [19,20,21,22,23]. Much effort has been made to compensate for the difference between LST and Taero in one-source models, most of which was concentrated on making corrections by: (1) adjusting temperature based on empirical relationship between LST and Taero [19,21,23]; and (2) adjusting the aerodynamic resistance roughness length for heat or the kB−1 parameter, or by including empirical “extra resistance” (rex ) factors [24,25]
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