Effects of Precipitation Latent Heating on Structure and Evolution of Northeast China Cold Vortex: A PV Perspective

Based on potential vorticity (PV) thinking, northeast China cold vortex (NCCV) corresponds to an upper-level high PV anomaly from stratospheric PV downward intrusion. Within a vortex, latent heating from precipitation would produce a vertical dipole of PV anomalies that would affect structures and evolution of the vortex. In this paper, three-dimensional structures and evolution of NCCV and, effects of latent heating from precipitation along bent-back, cold and warm fronts on them are investigated based on convection-allowing simulations for an intense NCCV case during 8-17 June 2012. Trajectory analysis shows that the negative upper-level diabatic PV anomaly from bent-back frontal precipitation, near the vortex center, is the dominant contributor to erosion of high PV in the vortex core region as it is advected in, leading to the weakening of the vortex. The negative PV anomalies along the cold and warm fronts, at the east-to-southeast side of the vortex, are mostly advected downstream away from the NCCV. In the middle troposphere, positive PV anomalies are primarily generated along fronts and the accumulated positive PV anomalies filling the vortex region help to reinforce the low-level cyclonic circulation. The lower-level PV is affected by surface heating and cooling through their effects on static stability, but such effects are periodic and create mainly diurnal variations. The NCCV eventually decays as the upper-level vortex weakens due to significant PV erosion.