Basic Evaluation of Bioclimatic Conditions over Southwest Nigeria

Abstract

This study examined the magnitude and spatio-temporal variation of outdoor bioclimatic conditions using observed mean monthly values of air temperature (°C), relative humidity (%), wind speed (m/s), vapor pressure (hpa) and cloud cover (octas) for the period of 1983  to 2012. The data were obtained from the Nigerian Meteorological Agency (NIMET) for five southwest-Nigerian stations. The bioclimatic indices adopted to evaluate the outdoor thermal comfort based on the thermal physiological balance of the human body in this study, are the Temperature-Humidity Index (THI) and Physiological Equivalent Temperature (PET). Radiation and Human Bioclimate (RayMan) model was used to simulate PET and Mean Radiant Temperature (MRT) in just one run based on the human energy balance model such as the Munich Energy Balance Model for Individual (MEMI). The estimated THI and PET were classified into different categories of thermal perceptions based on the established classes for Nigeria. The monthly, seasonal, and spatial variations of meteorological variables and thermal indices were also analysed. Results indicated air temperature to be the highest contributing meteorological parameter to thermal conditions. The discomfort level deteriorated over the years, most noticeable is the last decade between 2003 to 2012 of the study period. The years 1987 and 1998 were marked as period of peak discomfort in the entire region. The result also showed  three different grades of thermal discomfort conditions namely; slightly warm, warm and hot over the tropical wet, and tropical wet and dry zones. In conclusion, thermal discomfort was observed to decrease from the northern part of the region towards the southern part of the region in the examined period. This work could be of great interest for the stakeholders involved in public health and tourism industry sectors in decision making process.

Keywords: Bioclimatic condition, PET, THI, Thermal discomfort.