Influence of Physical Features on Heavy Rain Region in the Middle Part of Henan Province

The heavy rain process in the middle part of Henan province during 4-6 July 2007 is diagnosed with routine meteorological observations and NCEP 1°×1° 6 h reanalysis data.The influence of physical features on the heavy rain is mainly analyzed.Results indicate that the steady Subtropical High over the West Pacific,the trough at middle level of the troposphere and the shear line at low level are the main influencing systems.The southwesterly jet at low level provides the abundant water vapor and the instability energy.The heavy rain region is located at the north side of the exit area of the jet axis.The southerly component of the wind speed has a greater impact on the precipitation intensity.The release of instability energy is rapidly triggered by the cyclonic convergence at the middle low level and the anticyclonic divergence at the upper level.The rainstorm region is exactly coincident with the thick ascending motions.