资源环境科技发展态势分析平台

A hail observation dataset for 1972-2013 is analyzed to examine the temporal and spatial distributions of hail occurrence in South Korea. Furthermore, using radiosonde data, three thermodynamic factors which are 700500 hPa temperature lapse rate, water vapor mixing ratio in the lowest 100 hPa, and convective available potential energy (CAPE) and one dynamic factor which is 0-6 km bulk wind shear are calculated and their correlations with hail occurrence in South Korea are examined. Hail days per year in South Korea show a decreasing trend. The monthly variation of hail days exhibits double peaks in April and November. The minimum value of hail days appears in August, which is related to the high freezing-level height, the small midlevel temperature lapse rate, and the weak bulk wind shear. During a day, 44% of the whole hail events occur between 1200 and 1800 local standard time. Spatially, hail primarily occurs in the west coastal area and the east mountainous area of South Korea. Both the regions exhibit double peaks in the monthly variation of hail days, but the east mountainous area exhibits the later spring peak (May) and the lower hail frequency in late autumn compared to the west coastal area. The midlevel temperature lapse rate is strongly correlated with the monthly variation of hail occurrence. Hail is likely to occur when the low-level water vapor mixing ratio is in the range of -3-6 g kg(-1). CAPE is not strongly correlated with hail occurrence. The strong bulk wind shear is correlated with hail occurrence. The bulk wind shear is decreasing and the freezing-level height is increasing annually, which contributes to the annual decrease of hail occurrence. (C) 2017 Elsevier B.V. All rights reserved.