The Improvement of Turbulent Heat Flux Parameterization for Use in the Tropical Regions Using Low Wind Speed Excess Resistance Parameter.

Reliable simulation of turbulent heat fluxes needed for modeling land-atmosphere interactions remains a challenge over the humid tropical region. This may be connected with inadequate parameterization of the roughness lengths for momentum (z_0m) and heat (z_0h) transfer usually expressed in term of excess resistance factor (). This paper assesses the performance of existing schemes developed for high wind speed conditions over the humid tropical region. Thereafter, a more appropriate suitable for low wind speed condition is developed for use in the aerodynamic resistance parameterization (ARP). Based on observed surface heat fluxes and profile measurements of wind speed and temperature from Nigeria Micrometeorological Experimental site (NIMEX), new was derived through application of the Monin–Obukhov similarity theory and Brutsaert theoretical model for heat transfer. The derived, where is the Reynolds number. Turbulent flux parameterization with this new formula provides better estimates of heat fluxes with reference to results from existing schemes. The R² increased while MBE and RMSE in the parameterized Q_H based on the derived reduced by about 85%, 63% and 66.7% respectively. Similarly, the R² increased while MBE and RMSE in the parameterized Q_E based on the derived reduced by about 38%, 47.8% and 52.6% respectively. The derived gave better estimates of Q_H than Q_E during daytime. The derived scheme corrects well documented large overestimation of turbulent heat fluxes and is therefore recommended for use in regions where low wind speed is prevalent.