Evaluation of the WRF/Chem aerosol models - a dust episode case study

sented herein is an analysis of an intensive dust intrusion of 8-11 February, 2015. The intrusion has been associated with the development of an intense front over the Middle East. During the episode, dust concentrations in Ahvaz air quality monitoring station in south-western Iran (Khuzestan region) reached over 10000 μg/m3, which was beyond the capacity of air quality sensors to be recorded. In this paper the performance of WRF/Chem modelling system was evaluated for the west and southwestern Iran as well as the whole model domain. MADE and GOCART models as the main aerosol models implemented in WRF/Chem V3.6 were verified by ground observation data for specific points. We have taken into account the advantages and disadvantages of MADE and GOCART aerosol models over the study period, by comparing the simulations results for specific points with available dust concentration data. The time series of the area-average of modeled dust column mass density over the test area determined a coherent temporal variation with that of MERRA-2 model which shows the sensitivity of WRF/Chem modeling system for this area with the most frequent dust storm events in the Middle East. The validation of WRF/Chem V3.6 modeling system results for the overall model domain is implemented using Hovmoller diagrams. The modeled latitude-average of dust column mass density for the whole model domain showed some discrepancies of dust transport pattern with the results of MERRA-2 model. although there is a considerable difference between the modelled dust concentrations and the observations especially on the peak values, the temporal variations of the modelled dust concentration with MADE aerosol model is quite consistent with the observations. The results of MADE aerosol model for dust concentration were more close to observations for the points inside Khuzestan and surrounding low level plains with aeolian soils. The GOCART aerosol model had more reasonable simulation results for the points through the mountainous terrains of western Iran. It can be concluded that the structure of MADE and GOCART aerosol models can be revised with regard to their relative advantages in specific regions to minimize the error in modeling dust behavior. Scince this study has been employed on a dust episode, and considering that the gaseous air pollutants require the emissions data, the simulations of the gaseous aerosols has not been considered in this study. Howevr, the results of the WRF/Chem model for dust aerosols could be extended to the other aerosols, especially PM10 and PM2.5 particles.