Dynamics Governing a Simulated Bow-and-Arrow-Type Mesoscale Convective System

作者：Shushi Zhang, David B. Parsons, Xin Xu, Jisong Sun, Tianjie Wu, Abuduwaili Abulikemu, Fen Xu, Gang Chen, Wenqiang Shen, Lihang Liu, Xidi Zhang, Kun Zhang, Wei Zhang · 发表于：Monthly Weather Review · 年份：2023 · DOI：10.1175/mwr-d-22-0091.1 · 被引用次数：7 · 研究领域：Meteorological Phenomena and Simulations、Flood Risk Assessment and Management、Tropical and Extratropical Cyclones Research

Abstract The bow-and-arrow Mesoscale Convective System (MCS) has a unique structure with two convective lines resembling the shape of an archer’s bow and arrow. These MCSs and their arrow convection (located behind the MCS leading line) can produce hazardous winds and flooding extending over hundreds of kilometers, which are often poorly predicted in operational forecasts. This study examines the dynamics of a bow-and-arrow MCS observed over the Yangtze–Huai Plains of China, with a focus on the arrow convection provided. The analysis utilized backward trajectories and Lagrangian vertical momentum budgets to simulations employing the WRF‐ARW and CM1 models. Cells within the arrow in the WRF-ARW simulations of the MCS were elevated, initially forming as convectively unstable air within the low-level jet (LLJ), which gently ascended over the cold pool and converged with the MCS’s mesoscale convective vortex (MCV) at higher altitudes. The subsequent ascent in these cells was enhanced by dynamic pressure forcing due to the updraft being within a layer where the vertical shear changed with height due to the superposition of the LLJ and the MCV. These dynamic forcings initially played a larger role in the ascent than the parcel’s buoyancy. These findings were bolstered by idealized simulations employing the CM1 model. These results illustrate a challenge for accurately forecasting bow-and-arrow MCSs as the updraft magnitude depends on dynamical forcing associated with the interactio...