Effects of Urban Geometry on Turbulent Fluxes: A Remote Sensing Perspective

Two different land surface temperatures (with considering geometry effect and without considering geometry effect) were derived to estimate sensible heat flux over urban areas using remotely sensed land surface temperature. Results showed that the surface temperatures with considering geometry effect could bring up to 18.0% difference in the estimated sensible heat flux over built-up areas. The sensible heat fluxes derived from surface temperature with considering geometry effect were lower than those without considering geometry effect, particularly over built-up areas (e.g., the mean value is 44.3 W · m-2). The sensible heat fluxes over built-up areas are higher than those over flat impervious surfaces. In addition to the anthropogenic heat emission over urban areas, dense buildings cause higher displacement heights and roughness lengths than flat surfaces; thus, aerodynamic resistances for heat are lower over built-up areas; this makes the sensible heat dissipation into atmosphere easier over built-up areas than over flat surfaces.

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