Abstract: Based on the hourly precipitation data in May-September 1994-2008 from 52 meteorological stations in Liaoning Province, and by using four precipitation indices (hourly precipitation, hourly precipitation frequency, hourly precipitation intensity, and different duration precipitation), this paper analyzed the diurnal variation characteristics of precipitation in the Province from May to September. Both the precipitation and the precipitation frequency in the Province in May-September presented a diurnal pattern of bimodal distribution, with the peak periods at 14:00-17:00 and 2:00-8:00, and the precipitation intensity presented unimodal pattern, with the peak period at 14:00-17:00. The average correlation coefficient of precipitation and precipitation intensity was 0.8, while that of precipitation and precipitation frequency was 0.5, suggesting that the precipitation was closely related to precipitation intensity, and less affected by precipitation frequency. The precipitation and precipitation frequency of short-time precipitation events had greater contribution to the total precipitation and total precipitation frequency, compared with those of long-duration precipitation events, and the short-time precipitation events mainly took place at 14:00-19:00, while the long-duration precipitation events mainly appeared at 2:00-9:00.

Key words: Heavy metal, Phytochelatin, Molecular biology, Tolerance