Short communicationMeteorological constraints on characteristics of daily dustfall in Xi'an

Dust deposition is a crucial link of dust cycle that is less constrained in model studies. This study acquired profiles of flux and size distribution of daily dustfall from 2012 to 2013 in Xi'an on the southern Chinese Loess Plateau. On this basis, we made quantitative estimates of dust contribution from particular sources and processes, which provides important boundary conditions for model studies. Regrouping the data into transport- and source-limited deposition scenarios, we revealed that besides precipitation extreme wind speed and average relative humidity are the primary meteorological constraints in the transport- and source-limited scenarios, respectively. Stronger extreme wind speed promotes higher flux and deposition of dust >16 μm, corroborating previous interpretations of variation of flux and grain size of aeolian deposits. However, higher average relative humidity favors lower flux and deposition of dust <16 μm, which is a deposition process not recognized before, and is possibly due to hygroscopicity of mineral dust or the influence of water vapor on air convection. Elucidating this process in future studies might substantially improve model performance on dust deposition.