Urban Surface Energy Flux Estimations Utilizing a Thermodynamic Analytical Framework

At the local scale, energy exchange shapes microclimates and ecosystems crucial for human health and well-being. For urban areas, the effect, such as Urban Heat Island, is directly manifested in these surface energy fluxes with contrasting responses in values between urban and rural areas. Although progress has been achieved in modeling the land surface energy balance, challenges arise from complex, variable parameterizations linked to surface and climate characteristics, introducing uncertainties. In this work, we utilized the thermodynamic theory that considers the land-atmosphere as a radiative-convective system to analytically estimate total turbulent heat flux and land surface heat storage flux for 20 Urban sites and compared them with Eddy covariance observations. The heat fluxes are determined only from four primary parameters: incoming and outgoing longwave and shortwave radiations at the terrestrial surface. Using the monthly averages derived from the total turbulent flux estimates at the eddy covariance sites, we observed root-mean-square error (RMSE) of 29.16 ± 11.3 Wm⁻², a mean bias error (MBE) of -7.09 ± 19.6 Wm⁻² and R² value of 0.82 ± 0.16. We further tested the analytical estimates with land use land cover of Urban sites. Our findings illustrate the distribution of land surface heat storage flux estimates following land use land cover characteristics. The analytical estimates of heat fluxes for urban areas offer several advantages, such as ease of implementation and inexpensive computation, facilitating the evaluation of urban land use feedback for informed urban planning.