the second-order shear of the basic flow represents an instable factor for the symmetric disturbance, and drives the unstable mesoscale disturbance to travel in the meridional direction;
基流二次切变对于中尺度对称扰动来说是一个不稳定因子,并且驱动不稳定的中尺度对称扰动在南北方向传播;
using the analyses of weather process of an heavy rainfall system, it is found that there is a mesoscale disturbance in the lower troposphere over yangzi-hwai valley.