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

A typical Northeast China cold vortex (NCCV) that lasted for approximately 51 hours (from 0000 UTC 18 May to 0300 UTC 20 May, 2010) and produced several heavy rainfall events over Northeast China was successfully simulated using the Weather Research and Forecasting Model (WRF). Based on this successful simulation, the NCCV was analyzed in detail. Synoptic analyses revealed that the NCCV developed downward from the top and finally stretched to a maximum vertical extension of 900-200 hPa. The NCCV was colder than its surroundings in the middle-lower troposphere, whereas in the upper troposphere, it was warmer than its surroundings. There were significant warm and cold advections for the duration of the NCCV, favoring the enhancement of available potential energy (APE) and conducive to sustaining the vortex. The results of the quasi-Lagrange-form eddy flux circulation (EFC) and eddy kinetic energy (EKE) budget analyses indicate that different factors dominated the NCCV in various stages of its evolution. As for the EFC budget, the interactions between the NCCV and background circulations were more important than the interactions between the vortex and other synoptic systems; in contrast, for the EKE budget, the interactions between the NCCV and other synoptic perturbations were more important. The pattern of environmental circulations was very important to the NCCV because the vortex intensified as it moved from areas of low vorticity or EKE to areas with higher values. The baroclinic energy conversion was much greater than the barotropic energy conversion during the life cycle of the NCCV, implying that the NCCV was a typical baroclinic cyclone. Moreover, during the decaying stage, the attenuation of the NCCV appeared to be closely related to the frequency dispersion processes of the baroclinic Rossby wave.