Comparison study of environmental influences on the intensification of different deep Changjiang-Huaihe cyclones over the East China and Yellow Seas

Statistical classification of the intensification of different deep Changjiang-Huaihe Cyclones (CHCs) over the East China and Yellow Seas (ECYSs) during 2008 to 2012 is studied using the FNL reanalysis data. Based on the penetration depth and the season of occurrence, the CHCs are divided into four categories including warm-season-deep (WSD), warm-season-shallow (WSS), winter-shallow (WTS) and early-spring-bottom (ESB). Statistics show the CHCs take either an eastward or a northeastward path after entering ECYSs. After moving to the seas, the intensification of CHCs is more significant in cold season than that in warm season. They all have the reduction of the friction of the underlying surface and the increase of the near surface winds. The area of strong winds extends and migrates from the east to the southeast of the CHCs. A significant increase of precipitation during the warm seasons is consistent with the penetration depth of the cyclones. While a slight increase of precipitation in cold season cyclones and scattered precipitation is observed behind the ESB cyclones in the early stage of spring. Synthetic diagnosis analysis of the CHCs over ECYSs shows that the latent heat release plays an important role in the amplification of cyclones during the warm season. The ESB cyclones are sensitive to the dynamic and thermal effects from the underlying surface. The vertical stretching of the positive vorticity volume is much more significant in ESB cyclones than that in other cyclones. The height of maximum upper level divergence is proportional to the penetration depth of the cyclone for all the categories. Diabatic heating from the underlying surface is more prominent in cold season cyclones. Downward transport of the kinetic energy from upper level jet and the reduced friction both have positive contributions to intensification of the CHCs. Moist Potential Vorticity (MPV) has more contribution to the intensification of warm season cyclones, especially WSD cyclones. The combined effects from inertial stability and shear stability are beneficial to the amplification of the cyclones in cold season. The position and strength of the temperature and moisture front from MPV2 term at 1000 hPa coincides with the area and intensity of precipitation, which shows that the MPV2 is an effective reference for CHCs rainfall forecast.