Numerical study of dust plume impact on urban thermal comfort

Abstract. In Europe, heatwave conditions associated with southern synoptic flows can sometimes be combined with dust plume events coming from the Saharian desert. The aerosol plume modifies the radiation observed near the ground and consequently other variables such as air temperature. This study focuses on a heatwave and its corresponding plume of Saharian dusts that have reached the Paris region from 15 to 19 June 2022. To investigate the aerosols impact on the thermal comfort, three numerical simulations based on the Meso-NH model are used: one without dust aerosol (C0), one with CAMS dust data (C1) and one with twice the concentration of CAMS dust data (C2). Simulation C1 is validated against observations from the PANAME-Urban experimental campaign. The impact of aerosols on Aerosol Optical Depth and incoming solar radiation at the surface are well reproduced, and the air temperature and boundary layer heights are improved when taking into consideration the aerosols. The presence of a dust plume during the heat wave contributes to reduce solar radiation and air temperature to up to 75 W/m² and 1 K, respectively. At 16:00 UTC in sunny places of urban and suburban areas, it results in a thermal comfort improvement of up to 1 °C. However, in the shade of suburban areas, the increase of diffuse radiation and relative air humidity as well as the decrease of wind speed induced by the dust aerosols counterbalance the air temperature decrease, thus leading to no improvement of the thermal comfort.