Numerical analysis of urban heat island in the coastal tropical desert city Doha, Qatar

Abstract

Qatar has witnessed substantial urbanization in recent years; the Doha metropolitan area grew by approximately a factor of 8 between 1984 and 2020, while bare land was reduced by more than 50%. Recent Climate projections mark the Middle East as a climate change hotspot, making it an ideal region for studying urbanization and its implications. The distribution of the Urban heat island effect and its modification with urbanization over the tropical desert city of Doha, Qatar is investigated using high-resolution Weather Research and Forecasting (WRF-ARW) model simulations. Two fair weather cases corresponding to the winter and summer seasons during 2022 are considered for analysis. Four sets of simulations are conducted by modifying the land use land cover (LULC) data and urban parameterization schemes keeping all other physics options and configuration constant. The study includes the recent 100m hybrid CGLC-MODIS-LCZ dataset (Hybrid-LCZ data), which includes the global map of Local Climate Zones (LCZ), for the first time in the region. The simulations are (1) Comparatively older LULC data corresponding to the year 2001 (hereafter MODIS), (2) the current extensive urban area corresponding to 2018 coupled with a single-layer urban canopy model (UCM) (hereafter LCZ-UCM), (3) hybrid LCZ data coupled with multilayer Building Environment Parametrization (BEP) (hereafter LCZ-BEP), and (4) hybrid LCZ coupled with Building energy model (BEM) (hereafter LCZ-BEM). To the best of our knowledge, this is the first numerical analysis of the UHI effect over this region that includes simulations with the local climate zones (LCZ). The results indicate the presence of strong UHI intensity with a maximum of 4.5˚C (6.5˚C) during the winter (Summer) period. During late night and early morning hours, the urban heat island (UHI) effect is strong and during daytime, a strong urban cool island (UCI) effect dominates the region. During the winter period, the intensity of UHI and UCI are controlled by the prevailing synoptic wind systems. The amplitude of the UHI and UCI trend is reduced by the prevailing North Westerly winds, while the moisture-rich South Westerly winds enhance it. However, during summer the surface representation along with local weather patterns modulates the intensity of the UCI and UHI. A consistent improvement in the simulated meteorological parameters is noted from the simulation with MODIS, UCM, BEP, and BEM during the summer season. The LCZ-BEM model accurately simulates the urban heat island intensity, temperature, and relative humidity with minimal deviation from observations. However, in winter as the synoptic features play a crucial role in the surface conditions all model experiments show similar performance in comparison to the observations.