Observational Facts Regarding the Joint Activities of the Southwest Vortex and Plateau Vortex after Its Departure from the Tibetan Plateau

Using atmospheric observational data from 1998 to 2013,station rainfall data,TRMM（Tropical Rainfall Measuring Mission） data,as well as annual statistics for the plateau vortex and shear line,the joint activity features of sustained departure plateau vortexes（SDPVs） and southwest vortexes（SWVs） are analyzed.Some new and useful observational facts and understanding are obtained about the joint activities of the two types of vortex.The results show that：（1） The joint active period of the two vortexes is from May to August,and mostly in June and July.（2） The SDPVs of the partnership mainly originate near Zaduo,while the SWVs come from Jiulong.（3） Most of the two vortexes move in almost the same direction,moving eastward together with the low trough.The SDPVs mainly act in the area to the north of the Yangtze River,while the SWVs are situated across the Yangtze River valley.（4） The joint activity of the two vortexes often produces sustained regional heavy rainfall to the south of the Yellow River,influencing wide areas of China,and even as far as the Korean Peninsula,Japan and Vietnam.（5） Most of the two vortexes are baroclinic or cold vortexes,and they both become strengthened in terms of their joint activity.（6） When the two vortexes move over the sea,their central pressure descends and their rainfall increases,especially for SWVs.（7） The two vortexes might spin over the same area simultaneously when there are tropical cyclones in the eastern and southern seas of China,or move southward together if a tropical cyclone appears near Hainan Island.

Large-scale conditions of Tibet Plateau vortex departure

Based on the circumfluence situation of the out- and in-Tibet Plateau Vortex (TPV) from 1998–2004 and its weather-influencing system,multiple synthesized physical fields in the middle–upper troposphere of the out- and in-TPV are computationally analyzed by using re-analysis data from National Centers for Environmental Prediction and National Center for Atmospheric Research (NCEP/NCAR) of United States.Our research shows that the departure of TPV is caused by the mutual effects among the weather systems in Westerlies and in the subtropical area,within the middle and the upper troposphere.This paper describes the large-scale meteorological condition and the physics image of the departure of TPV,and the main differences among the large-scale conditions for all types of TPVs.This study could be used as the scientific basis for predicting the torrential rain and the floods caused by the TPV departure.