Dry deposition of dust particles during medium- and high-level dust storms to a forest canopy in a semi-arid region

In the present study the impact of forest canopy on the spatial distribution of PM₁₀ concentration during dust events in a region, which is subjected to frequent occurrences such as dust storms is investigated. The developed two-dimensional model is based on the application of theory of turbulent diffusion in the forest canopy in conjunction with model of dust particles deposition to vegetation elements. The leaf area density (LAD) distribution with height as well as dust particle size distribution are taken into account. The initial wind velocity profiles on the windward side of the forest were fitted from data obtained in field measurements in the studied region. The resulted dust transport in the forest canopy was validated by comparison of theoretical results with the empirical data in the studied region. Using the suggested model, we analyzed the evolution of wind velocity profiles in and above the forest canopy as well as the process of dry deposition of PM to vegetation elements. Numerical calculations performed using the developed model showed that in dust storms, PM₁₀ concentrations at the leeward side of the forest are reduced by ≈ 16–18% depending on dust storm level. We also found that inside the canopy the ratio of PM₁₀ concentrations between the points along the studied transect and windward side (not affected by the forest) is higher, the higher the level of the dust storm. Our model results of the atmospheric PM distribution show fairly good agreement with the data of the field measurements.