Evaluation of WRF-Chem Predictions for Dust Deposition in Southwestern Iran

The relationships between monthly recorded ground deposition rates (GDRs) and the ‎spatiotemporal characteristics of dust concentrations in southwest Iran were investigated. A simulation by the Weather Research and Forecasting Model coupled with the ‎Chemistry modeling system (WRF-Chem) was conducted for dust deposition during 2014–‎‎2015. The monthly dust deposition values observed at 10 different gauge sites (G01–G10) ‎were mapped to show the seasonal and spatial variations in dust episodes at each location. ‎An analysis of the dust deposition samples, however, confirmed that the region along the ‎deposition sites is exposed to the highest monthly dust load, which has a mean value of 2.4 ‎mg cm⁻2. In addition, the study area is subjected to seasonally varying deposition, which ‎follows the trend: spring > summer > winter > fall. The modeling results further demonstrate ‎that the increase in dust emissions is followed by a windward convergence over the region ‎‎(particularly in the spring and summer). Based on the maximum likelihood classification of ‎land use land cover, the modeling results are consistent with observation data at gauge sites ‎for three scenarios [S.I, S.II, and S.III]. ‎The WRF model, in contrast with the corresponding observation data, reveals that the rate ‎factor decreases from the southern [S.III—G08, G09, and G10] through [S.II—G04, G05, G06, ‎and G07] to the northern points [S.I—G01, G02, and G03]. A narrower gap between the modeling ‎results and GDRs is indicated‏ ‏if there is an increase in the number of dust particles moving ‎to lower altitudes or an increase in the dust resident time at high altitudes. The quality of the ‎model forecast is altered by the deposition rate and is sensitive to land surface properties ‎and interactions among land and climate patterns. ‎.