The effect of soil sealing on the urban heat island phenomenon

Indisputably, urban design and soil sealing are parameters that can either aggravate or mitigate the urban heat island phenomenon, observed in dense urban environments around the world. Large sealed surfaces have been extensively reported to induce higher surface temperatures. The aim of this work is to answer a critical scientific question: on what extent do actually sealed soils contribute to the urban heat island. As an example, a case study was developed for the case of Nicosia - a city that experiences high urban heat island intensities due to its geographical location and its continuous urban growth. Three scenarios were developed with ranging percentages of unsealed surfaces - 0%, 20% and 40% of vegetation coverage and were simulated in an established microclimate modelling tool ENVI-met. The effect of the urban design and soil sealing in the investigated scenarios was analysed by presenting the results for a range of parameters, including ground- and canopy-level temperatures, diffused and reflected radiations, relative humidity, wind speed and sky view factor. The results indicated that the most effective scenario is the case where 40% of the ground is unsealed, primarily due to the impact on the canopy-level temperature and the wind speed. The authors believe that more attention should be drawn to this alarming topic by both policy-makers and researchers.