Abstract
The urban heat island (UHI) phenomenon is a harmful environmental problem in urban areas affecting both climatic and ecological processes. This paper aims to highlight and monitor the spatial distribution of Surface UHI (SUHI) in the Casablanca region, Morocco, using remote sensing data. To achieve this goal, a time series of Landsat TM/ETM+/OLI-TIRS images was acquired from 1984 to 2016 and analyzed. In addition, nocturnal MODIS images acquired from 2005 to 2015 were used to evaluate the nighttime SUHI. In order to better analyze intense heat produced by urban core, SUHI intensity (SUHII) was computed by quantifying the difference of land surface temperature (LST) between urban and rural areas. The urban core SUHII appears more significant in winter seasons than during summer, while the pattern of SUHII becomes moderate during intermediate seasons. During winter, the average daytime SUHII gradually increased in the residential area of Casablanca and in some small peri-urban cities by more than 1 °C from 1984 to 2015. The industrial areas of the Casablanca region were affected by a significant rise in SUHII exceeding 15 °C in certain industrial localities. In contrast, daytime SUHII shows a reciprocal effect during summer with emergence of a heat island in rural areas and development of cool islands in urban and peri-urban areas. During nighttime, the SUHII remains positive in urban areas year-round with higher values in winter as compared to summer. The results point out that the seasonal cycle of daytime SUHII as observed in the Casablanca region is different from other mid-latitude cities, where the highest values are often observed in summer during the day.
Highlights
Since 1950, world urban population and urban infrastructure has grown rapidly [1]
This study focuses on assessing and monitoring the spatial distribution of the surface urban heat island intensity from 1984 to 2015, in Casablanca region, in order to study the influence of season cycles and urbanization on SUHI intensity (SUHII) patterns in Casablanca municipality and the cities at its outskirts and close by region
Results show that spatial distribution of SUHII varies considerably during the year and18isofmore pronounced in winter than summer and intermediate seasons
Summary
Much research documented that this urban concentration leads to substantial climatological and meteorological problems [2], posing a heavy burden on the environmental sanitation and water quality, accompanied by a significant increase of air temperature [3,4,5,6]. The most important problem affecting urban microclimate is the urban heat island (UHI) that is considered as a difference of temperature between the urban and rural area [7]. The UHI results from several factors such as built-up intensity [8], city size [9], low albedo [4] and greenhouse gases emissions [10]. Its worsening is based on specific synoptic conditions which are summarized in anticyclonic weather, nebulosity and a low wind [11].
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