Structure Characteristics and Appearance Areas of a Spring Rainstorm Process in the Lower Reaches of the Yellow River

Using the results of HLAFS and really detected data this paper analyses a strong rainstorm process on April 17-18, 2003 in the Lower Reaches of the Yellow River. The obtained results show that this rainstorm process is mainly resulted from the joint effect of high-level cold air, low-level low pressure shear line and inverted trough around Huang-huai cyclone; the low-level southwest jet from the South China Sea to Shandong Province provides abundant water-vapor and heat energy; higher θse at 850 hPa, stronger updraft at 700 hPa, low-level convergence and high-level divergence are the main favorable and physical characters of this rainstorm process. The vertical distribution of physical characters in the rainstorm is higher positive vorticity at 500 hPa, stronger convergence and divergence over and below 600 hPa respectively, which provides dynamical mechanism for the rainstorm process.