THE ANALYSIS OF DRY INTRUSION FEATURE OF A HUANGHUAI CYCLONE DEVELOPMENT IN MEIYU PERIOD

In this paper,by using water vapor imagery,the physical quantity of isentropic airflow and θse etc.,a process of a Huanghuai cyclone development in the Meiyu period of 2003 is analyzed to reveal the effect of dry intrusion on the development of Huanghuai cyclone.The result of the analysis indicates that the change of the movement and development of the ‘dark zone’ associated with dry intrusion in water-vapor imagery correspond well to the development,enhancement and weakening of Huanghuai cyclones.The leading edge of ‘dark zone’ in water vapor imagery appeared at the west,south and east of Huanghuai cyclone in the three stages of developing enhancing and weakening of the cyclone.The flows in vertical showed that dry intrusion moved downward from the middle or high levels.They relate well with dry intrusion coming down from the middle or high levels and ‘dark zone’ in water-vapor imagery.The downdraft zone of the dry intrusion moves northward d eastward during the development of the cyclone.The air momentum down from high levels developed the cyclone and cooled the air in middle and low troposphere.The flows and steep terrain on θse =335 K isentropic surface correspond well to the ‘dark zone’ in water vapor imagery.The vertical profile of θse in any direction can show the feature of dry intrusion.The folding of isentropic surface in the vertical can generate potential convective instability in the middle or low levels.The tongue of θse =335 K can reflect 3D structure of synoptic systems and the feature of dry intrusion.High PV moves down from high levels to low levels and enhanced high PV can show dynamical features of dry intrusion.