Effects of land-use mitigation scenarios on urban heat island intensity in Istanbul

This is the first comprehensive study to examine how urbanization affects the microclimate of Istanbul using the urban climate model MUKLIMO_3 with a 200 m horizontal resolution. In this study, the parameters in the land use table were estimated for Istanbul by combining different land use data sets and creating a high-resolution land use distribution. A specified heat wave episode was simulated via MUKLIMO_3 by using defined land use, meteorological sounding, and surface measurements. The findings suggest that MUKLIMO_3 can reasonably capture the 24-h daily temperature variation in both rural and urban locations, but it has a negative bias compared to station observations. We also employ eight mitigation scenarios by changing the albedo of roofs and implementing green-roofs and walls. All scenarios reduced air temperatures to varying degrees in urbanized areas along the northern Marmara coastline on both sides of Istanbul during daylight hours. The white and hybrid scenarios resulted in a temperature drop of up to 2 K at 12:00 UTC, with the most significant cooling effect observed in hybrid 4. Increasing the albedo of roofs from 0.5 to 0.7 resulted in the spatial expansion of cooled areas towards the north of the city along the Bosphorus. However, green roof scenarios are not found to be as effective as high-albedo scenarios.