Abstract:
Thermal comfort is defined as that condition of mind which expresses satisfaction with the thermal environment (Brager & De Dear, 2000, Fanger, 1973, Parson`s 2003) and no preference to be warmer or cooler. With the Remote Sensing and GIS, Temperature Humidity Index (THI) as human comfort indicator was derived and was related with Land Use Land Cover Change (LULC) of Laikipia county using a time series of Landsat images from 1989 to 2019 (4 epochs). The primary aim of the study was to assess the impact of Land Use Land Cover on temperature Humidity index as a measure of thermal human discomfort. To achieve this Landsat images of years 1989, 1999, 2009 and 2019 was classified to 5 classes (built up, vegetation, forest, waterbodies, and bare ground) to produce the LULC maps of Laikipia county over time. The (Land surface Temperature) LST values were retrieved using the mono window algorithm from the Landsat images which helped in estimating Air Temperature (Ta) using a univariate regression equation. Landsat images were used to estimate the Relative Humidity of the study area by combining factors such as NDVI, LST, albedo, saturate water vapor pressure and actual water vapour pressure. Relative Humidity was used to relate the thermal state that is actually felt by human body in the area with reference to the air temperature. With the estimated Ta and RH, THI maps were generated. Using the THI maps the human Discomfort Index (DI) maps were generated by classifying THI values as follows; <21 no discomfort, 21-24: under 50% feels discomfort, 25- 27: Over 50% of population feels discomfort, 28-29: Most of population suffers discomfort, 30-32: Everyone feels stress, >32: State of medical emergency. THI was then related with LULC, which showed that discomfort relies on the type of land use where the analysis showed that discomfort was high on bare land and built up areas as opposed to vegetated and forested areas. The study results increased knowledge on the extent and patterns of thermal comfort variations under different land cover/ land use change episodes in Laikipia. In turn the governing authority can make proper mitigation measures to lessen the severity of the type of outcome shown in this study