Surface and air temperature relationships: a microclimate, urban heat island study of the CSUN campus

Heat waves, on average, are responsible for more deaths annually than all other kinds of weather combined. In some instances, excessive heat is exacerbated by what is commonly known as the “urban heat island” effect, which arises from changes in the thermal properties of land surfaces which accompany urbanization. The instances of deadly heatwaves are expected to increase as a consequence of the climate changes that accompany the rising levels of carbon dioxide and other heat trapping gases in the atmosphere. In this study, the effect of surface type on temperature is assessed through a case study carried out at California State University, Northridge through the deployment of air temperature data loggers. The surfaces surrounding each sensor were classified by the percentage of impervious surface cover within ten meters of each sensor. Correlation analyses were performed to assess the relationships between warmer temperatures and increased percentages of impervious surface cover. The sensors were also grouped into four classes depending on the percentage of the impervious surface cover in their vicinities. A moderately strong correlation was observed between air temperatures and impervious surface cover. The grouped analysis displayed the same pattern but the most significant effect was the occurrence of significantly cooler temperatures over the least impervious surfaces. Areas with the most impervious surfaces were warmer much of the time, while areas of intermediate permeability showed no statistically significant trend.