hrvatski

Numerical simulations of desert dust episodes in the northern Adriatic; impact of Asian and African sources

Airborne mineral dust affects the climate by modifying radiation budget, formation of clouds and marine biogeochemical cycles. It's most abundant global source, the Saharan desert, has strong and frequent influence on the Mediterranean countries which is well documented in scientific papers. However, less attention from the scientific community is on the transport from Asian deserts towards European countries. Here, we present the simulations of one ‘typical’ Saharan dust outbreak and another one originating from deserts east to the Caspian Sea. In the first case, the increase of PM10 hourly values due to the Saharan dust outbreak was observed at the Italian and Croatian Adriatic coast in September 2015. The WRF-Chem model was applied to simulate the dust emission, transport and deposition, and two major sources of dust in Algeria and Tunisia were detected during the episode. The temporal evolution of spatially averaged dust emission at source locations shows strong morning peaks characteristic for NLLJ breakdowns. Although the chosen model's horizontal resolution is too coarse for grid-resolved simulation of convective processes detected by the NASCube method, the model exhibits a good agreement with AOD measured at 8 African and European AERONET stations and with PM10 measured at 10 Italian and Croatian air quality stations. In the second case, the untypically extreme dust outbreak was observed over the Balkan region from 27 to 30 March 2020. The anticyclone north of Croatia and cyclone over Anatolia formed a strong pressure gradient driving a transport from desert sources east to the Caspian Sea. The backward trajectories as well as satellite products indicated the Aral and surrounding deserts as major sources of dust. WRF-Chem based research is still in progress. At this stage the model shows high correlation with PM10 hourly values from regional air quality stations but it underestimates the observations. The peak hourly PM10 value was 612 μgm-3 measured in Belgrade. However the PM10 chemical (Pb, Cd, Cu, Zn, Fe, Mn, PAHs) and morphological (SEM analyses) composition at the site in the northern Adriatic indicate mainly the presence of the Saharan dust. Preceding the Asian dust advection, the presence of Saharan dust transport towards Balkan driven by Sharav cyclone was observed. Modeling results indicate the transport from Asia was below ~2 km, while the Saharan was up to ~8 km amsl. The mixing of the Asian and Saharan dust plume over Balkan was favored by subsidence due to anticyclonic high pressure conditions, and it is the most plausible explanation for the observed PMs chemical and morphological results. The authors acknowledge the financial support from the project “Marine Rogoznica Lake as a model for ecosystem functioning in the changing environment” (MARRES, IP-2018-01-1717).

Mineral Dust ; Saharan dust ; Aral lake ; WRF-Chem

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