Closure in Surface Flux Estimation by Energy Balance Model: Comparison of Priestly-Taylor and Penman-Monteith Computations for a Tropical Site in Ibadan

Increasing demand to further understand complexity in surface energy flux partitioning necessitates the adaptation of numerous estimation methods to fit the site of observation. This is useful for reducing the uncertainty in physically measurable parameters especially those in tropical regions with high human interference in the atmospheric boundary layer. In this study, we used computations from two methods - the Priestley-Taylor (PT) and the Penman-Monteith (PM), based on the Energy Balance model to ascertain closure performance in the surface flux estimations. The study was carried out at the Nigerian Meteorological Experiment III site (7.38oN and 3.93oE, 224.2m) located in Ibadan, Southwest Nigeria. Thirty days of a year (2006) dataset were examined using the Bowen ratio (BR) energy balance model to validate the PT and PM methods. The systems were examined across daily and diurnal cycles to better understand the differences in energy partitioning. Results showed that both systems generally favored latent heat flux compared to sensible heat flux perhaps due to above-normal rainfall during the period. The PM method performed better than the PT method with a period average for the sensible heat and latent heat fluxes as 32.05 Wm-2 and 67.66 Wm-2 respectively, accounting for 29.22% and 61.39% of the total net radiation. The PT method underestimates the sensible heat flux by as much as 19.70 Wm-2 compared to the PM method, with a period average of 12.36 Wm-2 representing 11.26% of total net radiation. The PM method also gives a period average Bowen ratio estimate of 0.55, consistent with the standard range for grasslands. The study suggests that the performance of the PM method is related to its response to heat and water vapor transfer over humid regions and would contribute to further research on land-surface interactions over the tropics. Finally, we propose that the measurement of available energy, net radiation, and ground heat flux should be separated for different collocated systems in order to reduce the forcing of closure and aid in proper partitioning of the fluxes. Keywords: surface energy flux, energy balance model, Priestly-Taylor, Penman-Monteith, West Africa, latent heat, sensible heat, NIMEX_3 DOI: 10.7176/JEES/11-5-05 Publication date:May 31st 202

Correction to: Emergence of robust anthropogenic increase of heat stress-related variables projected from CORDEX-CORE climate simulations

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Determination of Heat Stress in the Tropical Urban Area of Ibadan, Southwest Nigeria

Diurnal Temperature Humidity Index (THI) and Wind Chill Index (WCI) in Ibadan (7.380N, 3.930E), an urban tropical station are presented. Diurnal variation of THI was shown to be a mirror image of WCI. Morning and evening THI mostly bring about comfortable sensation, with the exception of months with high temperature. People are mostly uncomfortable during the afternoon due to the afternoon THI values, except during July-August- September (middle of the wet season) when people feel partly comfortable in the afternoon. A series of the average afternoon values of THI for the period January to December 1998 and 2000 were also shown. The following annual cycles were found significant in the average afternoon THI variations: 360 days, 182, 120, 60-90 days, 25-40 and 11-13 days, using Fourier analysis. The year 1997 had the highest THI values, the other years in order of decreasing THI values were 1998, 2001, 1999 and 2000. No cold episode was recorded throughout the period of investigation. Keywords: Temperature, humidity, wind chill index, comfortable, Fourier analysis, cold episode International Journal of Natural and Applied Sciences, 5(3): 235-243, 200