,a process of a Huanghuai cyclone development in the Meiyu period of 2003 is analyzed to reveal the effect of dry intrusion on the development of Huanghuai cyclone.

The heavy rain in the earlier stage was caused by the βmesoscale system which was developed under the background of Huanghuai cyclone.

It is analyzed the perpendicular structure of a Huanghuai cyclone.

The heavy rain in the earlier stage is caused by the β mesoscale system which is developed under the Huanghuai cyclone.

The forecast points for the sandstorm obtained by the investigation are as follows: The positive three-hour allobar is mainly decided by the cold temperature advection in lower troposphere,and the Mongolian cyclone′s development makes the positive three-hour allobar obviously produced by the supplementary cold air from the Lake Baikal.

Case study on the impact of atmospheric baroclinicity to the initial development of Jianghuai cyclones;

Results show that the east and south airflow of the Jianghuai cyclone provided abundant water vapor for the heavy rain-snow storm,meanwhile,cold-dry air played different roles at different heights and paths:1)in the lower troposphere,cold-dry air acted as a cold cushion that wedged into the bottom of warm wet air flow,resulting in frontogenesis,elevation of warm-wet air and condensation.

On the Huang-Huai River Flood Prevention Measures in Ming and Qing Dynasties