Analysis of Extreme Rain and Snow Weather Dynamic and Water Vapor Conditions in Northeast China from 17 to 19 November 2020
3
Citation
3
Reference
10
Related Paper
Citation Trend
Abstract:
Based on hourly precipitation data from 2413 national ground observation stations in China and ERA5 (0.25° × 0.25°), this study analyzes the characteristics and causes of extreme rainfall and snow in northeast China from 17–19 November 2020. The results show that extreme precipitation is mainly attributed to the abnormally strong large-scale low vortex and ground cyclone. The significant high-level and low-level coupling in areas with strong rain and snow is conducive to the continuous upward motion, which provides favorable dynamic conditions for the generation and development of extreme precipitation. The frontogenesis effect below the 850 hPa level is obvious, and the extreme precipitation period corresponds to the meeting of the north and south front areas. The symmetrical unstable atmosphere of 925 hPa~700 hPa is forced by the frontogenesis, which strengthens the oblique rising of the low layer and increases the instability, leading to the strengthened development of precipitation. For heavy rainfall and snow in early winter in China, water vapor transport is crucial. The extremely strong low-level jet also provides extremely strong water vapor conditions for the occurrence of heavy rain and snow. The analysis of the extreme rain and snow characteristics and formation mechanism of this weather process can deepen the understanding of extreme weather processes, and provide a useful reference for the research and prediction of extreme precipitation processes.Keywords:
Frontogenesis
Extreme Weather
Upper-tropospheric fronts and frontogenesis are viewed from a potental vorticity (PV) perspective. The rudiments of this approach are to regard such a front as a zone of strong PV gradient on isentropic surfaces, and to treat the accompanying frontogenesis as the process whereby this gradient is enhanced on tropopause-transcending isentropic surfaces. A case study suggests that this concept of PV frontogenesis provides a concise dynamically based definition of upper-level frontal zones, and a compact and transparent approach for diagnosing the frontogenesis. The concept provides fresh insight on the dynamics of the upper-level fronts, and has the potential to shed light on related phenomena and processes.
Frontogenesis
Tropopause
Cite
Citations (72)
Frontogenesis
Balanced flow
Cold front
Cite
Citations (14)
Frontogenesis
Confluence
Diabatic
Cite
Citations (52)
Various differences and similarities between warm and cold frontogenesis are numerically modeled. The hydrostatic adiabatic Boussinesq primitive equations are integrated on a two‐dimensional grid. The frontogenesis is forced by an along‐front gradient of potential temperature and by a vertically sheared cross‐front wind field. The model develops fronts with the proper vertical circulations, strengths, and slopes; more positive relative vorticity than negative relative vorticity is produced, and the frontal zone at the surface develops in a zone of convergence. Model results indicate that cold fronts will propagate faster than warm fronts and that the fronts will develop on the time scale of 1–3 days. Nonlinear advections brake the frontogenesis for cold fronts in the model and are almost entirely responsible for realistic frontogenesis of warm fronts in the model. Conceptual models of both warm and cold frontogenesis are developed which clarify the origin of the vertical circulation and some of the frontogenesis processes.
Frontogenesis
Cold front
Warm front
Hydrostatic equilibrium
Cite
Citations (17)
Abstract Two major mechanisms of frontogenesis‐deformation and shear‐are important in frontal wave cyclone development. Horizontal deformation can suppress the nonlinear wave development. Using an analytic model, Bishop and Thorpe have shown that large strain rates inhibit any wave‐slope amplification. For real cases, this ambient strain can be measured using the vorticity‐divergence attribution method developed by Bishop. This technique permits us to confirm the crucial role of such strain on the evolution of cases of wave development during the Fronts and Atlantic Storm Track Experiment (FASTEX). Horizontal shear in the presence of an along‐front thermal gradient is also an important mechanism of frontogenesis. Using an Eady model, Joly and Thorpe have shown that, in cases of large along‐front thermal gradient, frontal waves have growth rates smaller than the front itself, and thus would not develop. the domain‐independent attribution method developed by Bishop is here extended to a geopotential‐field partition. This leads, via a nonlinear balance condition, to the estimation of the ambient along‐front potential‐temperature gradient. the role of such an along‐front potential‐temperature gradient is discussed. as well as the relative contributions of the two frontogenesis mechanisms for the FASTEX cases.
Frontogenesis
Temperature Gradient
Cyclogenesis
Extratropical cyclone
Cold front
Cite
Citations (34)