| The global warming will increase the evaporation of water vapor,strengthen the water holding increase the circulation of water vapor which would lead to an increasing of precipitation,which in turn will increase the frequency and intensity of extreme precipitation.The three provinces of northeastern China are the major food production areas and old industrial bases.Extreme precipitation will seriously affect these areas.In order to improve the capabilities of disaster prevention and reduction,based on the precipitation data from 84 stations of the three provinces in Northeast China from 1961 to 2015,the percentile threshold method was used to define extreme precipitation thresholds,and the trends of five indicators including extreme precipitation,extreme precipitation frequency,extreme precipitation intensity,extreme precipitation frequency ratio and extreme precipitation ratio were analyzed.EOF decomposition and wavelet analysis methods were used to analyze spatial distribution and periodic variation of extreme precipitation.The optimal probability distribution function was selected by comparing extreme precipitation and extreme precipitation sequence.The results were as follows:(1)The trend analysis results showed that the extreme rainfall,extreme precipitation intensity,and extreme precipitation frequency ratios showed a non-significant increase trends at most stations,and the regional average climate bias rate is 0.013mm/10 a,-0.0105d/10 a,and 0.0001.10 a.The frequency of extreme precipitation and extreme precipitation ratio showed a non-significant decreasing trends in most stations,and the regional average climate rate was 0.0001d/10 a,-0.00003/10 a.(2)The EOF decomposition results showed that the first modality except the extreme precipitation intensity exhibits the north-south inverse characteristics,and other indicators were all shown as spatially consistent.Extreme precipitation,the frequency of extreme precipitation shows an increasing trend from north to south,and the ratio of extreme precipitation and extreme precipitation decreases from north to south.In the second mode,the extreme precipitation,extreme precipitation frequency and extreme precipitation frequency ratio are both the characteristics of the South-North inverse,extreme precipitation ratio was the east-west inverse characteristic,and the extreme precipitation intensity showed a decreasing trend.In the third mode,the extreme precipitation,extreme precipitation frequency and extreme precipitation frequency ratio were the characteristics of the east-west reverse change,and the extreme precipitation ratio was the north-south inverse change characteristics.The Morlet wavelet analysis results of the three modal time coefficients showed that except for the time coefficient of the third mode of the extreme precipitation and extreme precipitation frequency ratios,the other time coefficients range from 3 to 5 years,indicating that most of the extreme precipitation indices were present3-5 year cycle.(3)The fitting results of extreme precipitation series in the three northeastern provinces showed that the generalized extreme distribution function,Johnson SB,generalized Pareto function,can better fit the probability distribution of extreme precipitation,and the K-S test statistic cumulative value was 6.29 respectively.6.47,7.41.According to the comparison of K-S test results and extreme fitting curves,it is found that the generalized extreme function and Johnson SB have better fitting results.(4)The return period results show that the effect of the generalized extreme distribution is better than the Johnson SB and Pearson-III functions for the extreme precipitation in 50 years,and the root mean square error between the theoretical and measured values is30.08 mm,38.88 mm,and 40.43 mm.The use of a generalized extreme value for the extreme precipitation predicted in the past 100 years ranges from 101 mm to 273 mm. |
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