Abstract:

Based on observation data of daily precipitation in Jinzhou area, we analyzed the probability distribution of daily precipitation in this region, and determined the shape parameter and scale parameter of the Gamma function distribution using the maximum likelihood estimation method.We used the Gamma distribution to simulate the probability distribution of daily precipitation.The results showed that the occurrence frequency of daily precipitation has a trend that increases first and then decreases, and exhibits a symmetrical distribution.Precipitation probability has some oscillation, with the precipitation frequency on some specific days much higher than that on the adjacent days at times.The highest precipitation frequency occurs on July 21, and the lowest value is zero on several days when ignoring small precipitation.Low precipitation probability during all seasons is one of the reasons responsible for the drought in the Yixian area.Beizhen area has the lowest precipitation frequency and the highest precipitation amount during summer, which means that heavy and extremely heavy precipitation events are likely to occur in Beizhen.The precipitation probability is higher than 50% during the Qingming Festival and higher than 80% during the national college entrance examination, which is consistent with the public knowledge on the precipitation on these special days.Daily precipitation probability can provide a new way for public meteorological services.Extreme precipitation events are prone to occur in Linghai and Beizhen.Small rainfall events have the highest occurrence probability in Jinzhou, heavy precipitation and above have a low probability, and extremely heavy precipitation hardly occurs at stations in Jinzhou area.It has some meaningful guidance for the precipitation level forecast, especially for the heavy precipitation or extremely heavy precipitation and the level above.

Key words: Daily precipitation, Gamma function, Probability distribution