Investigation of Summer Raindrop Size Distributions and Associated Relations in the Semi-arid Region over Inner Mongolian Plateau, China
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Graphical Abstract
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Abstract
The characteristics of summertime raindrop size distribution (DSD) and associated relations in the semi-arid region over the Inner Mongolian Plateau (IMP) were investigated, utilizing five-year continuous observations by a PARSIVEL2 disdrometer in East Ujimqin County (EUC), China. It is found that only 7.94% of the 15664 1-min precipitation samples meet classification criteria as convective rain (CR), but its contribution to the total rainfall amount is 63.87%. Notably, 40.72% of the rainfall comes from large-sized raindrops (D > 3 mm), despite the fact that large-sized raindrops account for only 1.73% of the CR total number concentration. Further results show that the mean value of mass-weighted mean diameters (Dm) is larger (2.43 mm) and generalized intercepts (lgNw) is lower (3.19) in CR, aligning with a “continental-like” cluster, which is mainly influenced by the joint impact of in-cloud ice-based processes and the below-cloud environmental background. Also, the empirical relationships of shape–slope (μ-Λ), radar reflectivity–rain rate (Z-R), and rainfall kinetic energy (KEtime-R and KEtime-Z) are localized. To quantitatively analyze the impact of DSD parameters on kinetic energy estimation, power-law KEtime-R and KEtime-Z relationships are derived based on the normalized gamma distribution. Nw takes precedence over μ in affecting variabilities of multiplicative coefficients, especially for KEtime-R relationship where the multiplicative coefficient is proportional to Nw −0.287. It should be noted that although the proportion of CR occurring throughout the summer is small, raindrops with lower Nw and larger Dm will generate higher KEtime, which will bring a higher potential risk of soil erosion in semi-arid regions over IMP.
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