Climatological Features of the Northeast Cold Vortex and Its Impact on Precipitation in Intraseasonal Timescale of China
|School||Nanjing University of Information Engineering|
|Keywords||Northeast Cold Vortex intraseasonal oscillation precipitation overeastern China|
The Northeast Cold Vortex (NECV) is a major synoptic system that causes chilling damage, sustained rainfall and sudden severe convective storms over Northeast China. By using the National Centers of Environmental Prediction-National Center for Atmospheric Research (NCEP/NCAR) reanalysis data and high resolution gridded precipitation data over China provided by Chinese Academy of Meteorological Sciences, at first based on former research, the basic characteristics of NECV is studied, then an objective index of the NECV (NECVI) is defined, and then the characteristics of the Northeast Cold Vortex activities in intraseasonal timescale and its relationship with the circulation and rainfall are investigated, at last, by analyzing the feature of a kind of typical wave trains associated with Northeast Cold Vortex, the understand of the characteristics of the NECV activities is reinforced.Results show that the time scale of NECV generally is3-5days and its spatial scale is about1000kilometers in summer; the centers of the NECV are mainly distribute in (40°N-50°N,120°E-130°E). In accordance with the different of main influence area, the activities of NECV path can be classified as northerly path, middle path and southerly path, each vortex path can exert different and significant impact on local and non-local precipitation and circulation.The activities of the NECV exhibit remarkable10-30-day oscillation. The10-30-day oscillation of atmosphere circulation associated with the NECV activities obviously locks with the precipitation anomalies over eastern China, and modulates the locations of anomalous rain belts. The anomalous rain belts over eastern China shift from north to south along with the northwest-southeast movements of the NECV and associated low frequency circulation.Moreover, the relationship between the10-30-day activities of the NECV and the atmospheric teleconnection patterns in mid-high latitude is discussed. The low frequency circulation associated with the NECV is one part of the Eurasian (EU) pattern teleconection-like wave train in summer. The EU wave train converges with the East Asian-Pacific (EAP) pattern teleconnetion-like wave train at eastern Asia. The interaction between them affects the velocity and direction of low frequency system related with the NEC V, and further determines the location and duration of precipitation over eastern China. Therefore, the preceding development of the low frequency wave trains of EU pattern and EAP pattern might indicate the following stage of rainfall over eastern China. This study will provide a reference for the10-30-day extended-range weather forecast of severe precipitation over eastern China.