Analysis on Dry Intrusion in Heavy Rain and Huang-Hai Cyclone

Using the water vapor(WV) image,isentropic flow,potential vorticity(isentropic potential vorticity,moisture potential vorticity) and θ_(se),a heavy rain process during Meiyu period is analyzed to reveal the effect of dry intrusion on heavy rainfall and Huang-Hai cyclone.The main results are as follows:(1) Dark zone in WV image is a good predictor for heavy rain and extratropical cyclone.(2) The development and change of vertical flow overlapped with relative humidity can clearly reflect the relationship between dry intrusion and heavy rain.It is a good predictor for very short-range forecasting.Dry intrusion triggers the heavy rain and the dry zone above middle-level corresponds well with dark zone in WV image.(3) The airflow on 340K and 330K isentropic surfaces indicates the characteristics of dry intrusion in the middle- and top- of troposphere and Huang-Hai cyclone,respectively.The jet sliding along the ridge on isentropic surface is consistent with the dark zone in WV image.The big value of IPV relates well with the initiation and development of cyclone.It′s distribution provides the features of dry intrusion.(4) The temporal and specialcross-section of MPV1 on isobaric surface can reflect the evolution of dry intrusion.Heavy rain occursin the southern 2-latitude when the area of MPV1 greater than 0.4 PVU extends downwards.(5) Dry intrusion can strengthen the rainfall near the cyclone.It is almost the same time for the happening of the heavy rain and the big value of MPV1.This indicates that the effect of dry intrusion on the heavy rain near and far from cyclone is different.Heavy rain often appear in the area of sharp and dense θ_(se).