Circulation and Eddy Kinetic Energy Budget Analyses on the Evolution of a Northeast China Cold Vortex (NCCV) in May 2010

This study examines the vorticity budgets, turbulent extended exergy and kinetic energy evolution equations to investigate the major dynamical and energy conversion processes contributing to the initiation and intensification of the cold vortex over Northeast China that occurred during June 19–22, 2009. The results show that the cyclonic vorticity was initiated in the lower troposphere due to the intense convergence of horizontal winds. The growth of cyclonic vorticity in the middle troposphere is mainly due to the vertical transportation of the vorticity, yet the increase of cyclonic vorticity in the upper troposphere primarily results from the horizontal advection of vorticity. Of special interest in this study is the evaluation of the role of thermal advections in the baroclinic development of the cold vortex. The results indicate that the rising of the air over relatively warm areas and the sinking of the air in relatively cold regions are favorable for releasing turbulent extended exergy $$ \left( {e_{\text{t}} } \right) $$
 , which is later converted to turbulent kinetic energy $$ \left( {k_{\text{t}} } \right) $$
 , and this process occurs during the initiation and intensification of the cold vortex. In addition, barotropic energy conversion is another important process that contributes to the growth of k
 t, and it strengthens gradually after the initiation of the cold vortex. Other than frictional consumption, the flux of k
 t in the vertical direction also depletes some of k
 t. The fluxes of e
 t, baroclinic energy conversions and diabatic generations are favorable factors for the growth of e
 t, whereas it decreases with time as a result of a large amount of e
 t that is released. Most of the energy conversion processes, including the baroclinic and the barotropic energy transformations and the energy conversions from e
 t to k
 t, as well as the fluxes of e
 t, are stronger in the lower troposphere than the other areas during the formation of the cold vortex. This accounts for the initiation of the cyclonic vorticity in the lower troposphere. Finally, the fact that the turbulent extended exergy releases primarily in the middle troposphere through the vertical thermal circulation is consistent with our understanding based on the vorticity budget analyses.

https://link.springer.com/content/pdf/10.1007%2Fs00703-012-0203-y.pdf

On the vorticity and energy budgets of the cold vortex in Northeast China: a case study

The Northeast China cold vortex (NCCV) is an important type of synoptic scale system, which often induces local torrential rainfall events, strong winds, and lightning during warm seasons (May–September). By using an automatic identification method that involves a three‐step algorithm, NCCVs during warm seasons of 1980–2018 were identified based on ERA5 and MERRA‐2, the latest generation of reanalysis. Employing this recognition result and intensive surface observations, climatology of the NCCV was analysed. With respect to average climatic characteristics, the results indicate that the NCCV is most frequently located from the east of the Yablonov Mountains to the west of the Xiao Hinggan Mountains. The average rain belt and cold tongues resulting from NCCVs both mainly fall within Northeast China, Japan, Southeast Russia, and the Korean Peninsula, causing precipitation and temperature anomalies there, especially in Northeast China. Regarding interannual variation, the number of NCCV‐occurrence hours varies at a cycle of about 3 years, and has increased in the last 10 years compared to 1999–2008. The intensity of the NCCV also fluctuates in a cycle of approximately 3 years and shows a weakening trend, particularly from July to September. As for life characteristics, NCCVs usually form at the border area between China, Mongolia, and Russia, then develop and move eastwards, and finally disappear in areas of Heilongjiang in China, southeastern Russia, and the Okhotsk Sea. The NCCV moves in complex paths; among all 55 types of routes that occurred in warm seasons of 1980–2018, the most favoured paths are east, southeast, northeast, southeast‐to‐northeast, and circular. The above results based on the up‐to‐date reanalysis datasets with high resolutions are updates and supplements to previous studies, further improving our understanding of the NCCV in aspects of its cooling effects, weakening trends, and crucially, paths of movement and their occurrence frequency.

Climatology of Northeast China cold vortices during the warm season: A comparison of ERA5 and MERRA‐2 reanalyses

The northeastern China cold vortex (NCCV) is the main weather system affecting Northeast China. Based on the precipitation products from the dual-frequency precipitation radar (DPR) onboard the Global Precipitation Measurement core observatory (GPM) satellite, the precipitation structures and microphysical properties for different rain types in 6432 NCCVs from 2014 to 2019 were studied using dynamic composite analysis. Our results show that the precipitation in NCCVs is dominated by stratiform precipitation. Regions with high stratiform and convective precipitation frequency have a comma shape. The growth mechanism of precipitation particles changes at ~4 km in altitude, the lower particles grow through collision (more pronounced in convective precipitation), and the upper hydrometeors grow through the Bergeron process. Additionally, the precipitation structures and microphysical properties exhibit great regional variations in NCCVs. The rainfall for all rain types is the strongest in the southeast region within an NCCV, mainly characterized by higher near-surface droplet concentration, while precipitation events occur more frequently in the southeast region for all rain types. There are active rimming growth processes above the melting layer for convective precipitation in the western region of an NCCV. In the southeast region of an NCCV, the collision growth of droplets in both types of precipitation is the most obvious.

/pdf/a-preliminary-analysis-of-typical-structures-and-1ecxt347.pdf

A Preliminary Analysis of Typical Structures and Microphysical Characteristics of Precipitation in Northeastern China Cold Vortexes

Study on the Evolution of a Northeast China Cold Vortex During the Spring of 2010

The rainstorm usually occurs in the developing stage of northeast cold vortex,not in the declining phaseSo people are apt to miss the rainstorm that appears during the declining phase of cold vortexBased on the observed data and the numerical simulation results,the process of the rainstorm which occurs during the declining phase of one northeast cold vortex is analyzed in middle and eastern Jilin Province on 21 Jun 2005The results show that there is one instable layer at the center of the rainstorm,with a little convective available potential energy(CAPE)The coupling and fluctuation of low levels jet in different layers present the "relay shape" in time and space,which leads to the especial water-vapor configuration and the right instability condition,which further lead to the intense development of moist potential vorticity in the heavy rain areaUnder the condition of convective instability(CI) and conditional symmetric instability(CSI),the mesoscale convective system(MCS) forms and the convection develops in the stratiformis cloud,which directly bring the precipitationGravity wave is the possible trigger mechanism of rainstorm

Qian Zhen

Papers

Analyses of Formation Mechanisms of a Rainstorm during the Declining Phase of a Northeast Cold Vortex