Understanding the elevated PM2.5 pollution in the Middle East during May 2022: Insights from numerical simulations

Abstract 

During May 2022, the Middle East region (MER) experienced four prolonged and severe atmospheric pollution episodes (APEs), resulting in severe fine particulate matter (PM2.5) pollution in the region. In this study, the Weather Research and Forecasting (WRF) model was employed to simulate meteorological fields, while the Community Multiscale Air Quality (CMAQ) model was applied to simulate PM2.5 during the APEs. Using ground-based observations, the performance of the models was evaluated, and the spatiotemporal patterns of PM2.5 and meteorological influences during the APEs were elucidated. The WRF model adequately reproduced the observed meteorological variables, while the CMAQ model quantitatively captured the temporal trends of observed PM2.5 concentrations, and the models’ performance metrics met their suggested benchmarks. The results show that APE1 peaked on May 11 with its highest PM2.5 concentrations in Iran, the UAE, Qatar, Saudi Arabia, and Oman. On May 17, APE2 peaked as the pollution spread across the region with elevated PM2.5 concentrations (250 ≤ PM2.5 ≤ 400 μg/m3) in Iran, Saudi Arabia, Yemen, the UAE, and Oman. APE3 was the most severe episode, peaking during May 18–20 with clusters of elevated PM2.5 concentrations (150 ≤ PM2.5 ≤ 600 μg/m3), especially in Saudi Arabia, Iran, Yemen, Oman, and the UAE. APE4 was also severe but less compared to APE2 and APE3 in most areas. Furthermore, unfavorable meteorological conditions enhanced the formation of these episodes. The results demonstrate the CMAQ model’s capability in reproducing elevated PM2.5 concentrations during severe APEs and can be further used to elucidate source attributions and processes contributing to PM2.5 in the MER.

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