To what extent can explicit consideration of dust aerosols in the atmosphere improve urban climate modelling?

Dust aerosol affects the radiation balance of the atmosphere and the resulting air temperature near the ground. However, the profile of dust aerosol content in the atmosphere is usually taken from climatological data in urban climate simulations without considering daily and event-related variations. This limitation may affect the accuracy of the simulations in specific situations. This study investigates whether taking explicitly into account the dust aerosol could increase the model performance, more specifically its ability to estimate the 2 m air temperature and thermal comfort indices.

 

The research question is investigated in the context of a heat wave that occurred in the Paris region from 16 to 19 June 2022. During this event, a hot air mass was advected from the Sahara region, transporting a high content of dust aerosol. A simulation of this event using the Meso-NH atmospheric model coupled with the SURFEX land surface model shows low agreement with 2 meter air temperature observations when climatological aerosol were used.

 

To evaluate the effect of the aerosol amount on the simulation results, three simulations were performed using different assumptions about the dust aerosol content of the atmosphere, based on data from Copernicus Atmospheric Monitoring Service (CAMS) analyses:

• a reference simulation without dust aerosol,

• a simulation using the CAMS data as input of the simulation,

• a simulation using the CAMS data but its value was multiplied by 2.

The results show that compared to the reference simulation, taking into account the aerosol improves the accuracy of the simulations, especially by reducing the warm bias in near-surface air temperature (even thought it might not be the main explanation of the warm bias of the model).