Diurnal characterization of the atmospheric urban heat island over urban hot agglomerations

Abstract

Abstract The urban heat island ($\mathrm{UHI}$) is a physical climatic phenomenon; its effects in built-up areas can be observed in terms of air temperatures above the atmosphere, as well as in terms of thermal comfort under the urban canopy. This study aims to carry out a diurnal characterization of the atmospheric UHI over the agglomeration of $\mathrm{Guelma}$, Algeria during summertime. The characterization is organized into three main steps. First, quantifying the $\mathrm{UHI}$ intensity. Second, highlighting the factors contributing to affect the thermal environment in downtown $\mathrm{Guelma}$ and finally, defining an appropriate scale to measure it over $\mathrm{Guelma}$’s agglomeration of Guelma. The $\mathrm{UHI}$ quantification was done by calculating the positive differences of urban temperatures in daytime based on in situ and static approach. The results indicate that the maximum daily difference reached $4.8$ to $5.1{}^{\circ}\mathrm{C}$ with a positive difference of $6.1{}^{\circ}\mathrm{C}$ at $10:00$ a.m. and $6.4{}^{\circ}\mathrm{C}$ at noon, which means that $\mathrm{Guelma}$’s agglomeration is affected by the atmospheric UHI phenomenon. Depending on the difference of urban temperatures, we have defined appropriate scale to quantify the intensity of UHI phenomenon over Guelma’s agglomeration as follows: ${UHI}_{intensity}=0.3688\times \boldsymbol{\Delta }{T}_{\boldsymbol{urb}}+3.3157.$