The results show that the vorticity, divergence and vertical velocity are stronger in the flood season, but the cold wave and the low level jet are stronger in the non-flood season.

• 结果表明：二者在环流形势、动力条件和低空急流方面存在著明显差异，汛期暴雨涡度、散度、垂直运动场较强，而非汛期暴雨冷空气强度相对较强，低空急流也较强。