Numerical study of effects of mountains and lakes on a squall line in northern Jiangsu Province
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REVIEW ARTICLE
Numerical study of effects of mountains and lakes on a squall line in northern Jiangsu Province Bin Li1 · Liguang Wu2 Received: 7 March 2019 / Accepted: 17 December 2019 © The Author(s) 2020
Abstract Observational studies indicate that northern Jiangsu Province is the most active area for the occurrence of squall lines in east China. While the roles of the large-scale atmospheric environment have been investigated, the effects of the terrain and lakes on the squall line in northern Jiangsu Province have not been well understood. In this study, the squall line occurring on 14 June 2009 is simulated to investigate the influences of the terrain and lakes. The squall line occurred under the influence of a short westerly trough at 500 hPa, one of the typical synoptic-scale patterns favorable for the development of squall lines in east China. Using the grid spacings of 3 km, 1 km and 333 m, the Weather Research and Forecast model (WRF) reasonably well simulates the evolution of the squall line and the extreme rainfall. Sensitivity experiments are conducted to examine the effects of Mountain Meng, Hongze Lake and Gaoyou Lake. It is found that the valley wind associated with Mountain Meng plays an important role in the early development of the squall line by enhancing the vertical wind shear at the low levels. The presence of the lakes leads to a relatively cold area, resulting in a temperature gradient toward the southeast at the low levels. The horizontal temperature gradient enhances the low-level vertical wind shear and promotes the development of the squall line.
1 Introduction Squall lines are associated with strong surface winds, heavy rainfall, hail, and even tornadoes, usually causing significant property damage and loss of life (e.g., Fujita and Wakimoto 1981; Johns and Hirt 1987; Przybylinski 1995; Jorgensen and Weckwerth 2003; Atkins et al. 2004). Observational studies indicated that the middle and lower reaches of Yangtze River are the active region of squall lines, and the maximum frequency of occurrence is in the northern part of Jiangsu Province (Ding 1993; Bei et al. 2002; Sun et al. 2010; Meng et al. 2013). Numerical simulations have been conducted to understand the role of the large-scale Responsible Editor: E.-K. Jin. * Liguang Wu [email protected] 1
Pacific Typhoon Research Center (PTRC) and Key Laboratory of Meteorological Disaster of Ministry of Education, Nanjing University of Information Science and Technology, Nanjing, China
Department of Atmospheric and Oceanic Sciences and Institute of Atmospheric Sciences, Fudan University, Shanghai, China
2
environment in the occurrence of squall lines, but little attention has been paid to the effects of mountains and lakes in the area. The observational analysis shows that the squall line occurs in the middle and lower reaches of Yangtze River from March to October, with a peak in July (Meng et al. 2013). The diurnal variation shows a major peak in the early evening and two minor peaks in the early morning and early afterno
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