Parameterization of Convective Heat Fluxes over Ile-Ife Using Bowen Ratio, Aerodynamic Gradient and Aerodynamic with Resistance Techniques

B Adeyemi,M P Ajakaiye,E O Ogolo

doi:10.21767/2394-9988.100061

Abstract

This research parameterized sensible and latent heat fluxes using Bowen Ratio (BR) also known as (Bowen Ratio Energy Balance), Aerodynamic Gradient (AG) and Aerodynamic Resistance (AR) techniques. Energy Residuum as well as Closure fractions were obtained and were used to assess closures for both direct and indirect fluxes. The data used were sourced from the Nigeria Micrometeorological Experiment (NIMEX-1) conducted within the transition period, 2004. The research site is located at the agricultural farm of Obafemi Awolowo University, Ile-Ife, (lat. 7.55o N, Long. 4.56o E), Nigeria. The results from each of the techniques were correlated with the measured heat fluxes in order to decide the best theoretical approach for the estimation of fluxes over the region of study. BR and AG compared moderately with the measured fluxes. BR scheme overestimated latent heat flux but underestimated sensible heat flux; AG technique slightly underestimated sensible heat flux but strongly underestimated latent heat fluxes with only few days of overestimation of sensible heat flux. AR, on the other hand, underestimated both latent and sensible heat fluxes. The obtained closure for AG proved much closer to the closure obtained from the direct measurement, BR has a better theoretical closure while AR failed as a whole. The trends as well as statistical analysis proved that AG performed best for sensible heat flux while BR presented good results for both latent heat flux and energy closure.

Highlights

The role of convective heat fluxes in the tropospheric processes cannot be overemphasized
In 2012, Omokugbe et al investigated the portioning of the net radiation flux and the surface energy fluxes using the Eddy Covariance method and presented that the midnight and the early morning hours of the days recorded negative values for the net radiation but increased at 7:30 h to peak values ranging from 317 W/m2 to 586 W/m2 [8]
Other needed parameters required for estimation of sensible and latent heat fluxes were parameterized from these meteorological variables

Summary

Introduction

The role of convective heat fluxes in the tropospheric processes cannot be overemphasized. Land surface heat fluxes are essential components of the water and energy cycles and govern the interactions between the Earth surface and the atmosphere. Katavoutas et al investigated thermal comfort in the hot outdoor environment under unsteady conditions [3]. Their results indicate that human heat flux fluctuates due to fluctuations in air temperature and other atmospheric variables such as humidity. There is a dependent of human comfort on surface convective heat fluxes. In 2012, Omokugbe et al investigated the portioning of the net radiation flux and the surface energy fluxes using the Eddy Covariance method and presented that the midnight and the early morning hours of the days recorded negative values for the net radiation but increased at 7:30 h to peak values ranging from 317 W/m2 to 586 W/m2 [8]. As good as direct measurement of heat fluxes has been, it is important to stress that the cost of acquiring, installing and maintaining stations for direct measurement (using eddy covariance method) is beyond

Objectives

Methods

Results

Conclusion