Influence of Multiscale Orography on the Initiation and Maintenance of a Precipitating Convective System in North China: A Case Study

Abstract

Using convection‐resolving Weather Research and Forecasting simulation, this work studies a heavy rainfall event that occurred in the Shanxi Plateau, North China on 21–22 May 2017. Of particular interest is the influence of multiscale orography on the initiation and maintenance of the precipitating convective system. Results showed that the initial convection was triggered over the small‐scale Taiyue Mountain in the Shanxi Plateau. In the nighttime, with a stable boundary layer, orographic gravity waves were generated by the Taiyue Mountain. The gravity wave‐induced lifting cooled and saturated the lower troposphere adiabatically, thereby producing a moist absolutely unstable layer favorable for subsequent convection initiation. In the daytime, a mountain–plains solenoid (MPS) was established due to the differential solar heating between the Taiyue Mountain and Changzhi Basin. The MPS upslope wind increased the low‐level convergence above the mountain, which eventually promoted the convection. This convection moved eastward and grew into a quasi‐stationary, quasi‐linear convective system in the eastern Shanxi Plateau, which was significantly impacted by the daytime MPS caused by the Shanxi Plateau and North China Plain. The low‐level easterlies associated with the plateau‐scale MPS hindered the eastward propagation of the precipitating system and enhanced the low‐level vertical wind shear ahead of the quasi‐linear convective system, resulting in an overall balance with the system cold pool circulation. These findings provide some new insights into the development of a precipitating convective system under the influence of multiscale orography in a relatively pure environment of weak synoptic forcing and convective available potential energy.

Characteristics of Deep Convective Systems and Initiation during Warm Seasons over China and Its Vicinity

“…Several field campaigns were carried out worldwide to understand DCSI and evolutionary processes over complex terrain areas to (a) improve prediction of the location and timing of new convection and (b) improve quantitative precipitation forecasting (QPF) skills [23,[30][31][32][33][34]. Much work has been done to study the physical mechanisms of DCSI based on numerical weather models, and/or multi-platform measurements over the North China, South China and Eastern China, respectively [35][36][37][38]. Several statistical studies of DCSI have also been done in these regions in recent years using satellite and/or Doppler weather radar measurements [19,26,27,[39][40][41].…”

Development of a Clear‐Sky 3D Sub‐Grid Terrain Solar Radiative Effect Parameterization Scheme Based on the Mountain Radiation Theory

“…Effective representation of complex terrain and related effects has long been a difficult problem in numerical simulation studies (Davies & Brown, 2001; Jiménez & Dudhia, 2012; Phillips, 1957; Wallace et al., 1983; Xu et al., 2019). Adopting high‐resolution grid‐scale topography improves the model performance (Hua et al., 2020; Ji & Kang, 2013). However, the models perform worse when increasing the resolution to a certain degree without correspondingly improving the description of physical process (Carvalho et al., 2012; Falasca & Curci, 2018; Mass et al., 2002; Maurya et al., 2018), especially the sub‐grid terrain related processes (Elvidge et al., 2019; Lalande et al., 2021; Yu et al., 2019).…”

The Influence of a Cold Front and Topography on the Initiation and Maintenance of a Precipitation Convective System in North China: A Case Study

“…In the afternoon, the ascending branch of the MPS is located near the mountains and promotes the precipitation in the mountain areas, while in the evening, the ascending branch is located in plains or basins and facilitates the precipitation in plains or basins [ 4 , 23 , 24 ]. The topography of North China is complex, and the topographic forcing is closely related to the heavy rainfall in North China [ 10 , 25 ]. Past studies have shown that lifting of warm and wet low-level flow forced by mountains is beneficial to the heavy precipitation on the eastern slope of mountains near the plain [ 6 , 11 ].…”