Helicity Analysis on the Torrential Rain in Henan in July 16,2004

By using of the helicity theory, the torrential rain in Henan province during July 16-17,2004 was diagnosed. The analysis results show that the rainstorm is produced in higher temperature, higher humidity and unstable atmosphere. There is a higher relative vertical helicity(HR) in rainstorm area; The trend of the low-level vertical helicity is consistent with that of the precipitation. The variation of helicity indicates weather systems moving developing and falling area and intensity of torrential rain.Helicity also reflects the distribution of vertical moving and rotation status of atmosphere.