Characteristics of precipitation in Jinan City from 1972 to 2016

In recent years,under the dual influence of global warming and intensified human social activities,the hydrological cycle process has been greatly affected,and even changed the spatial and temporal distribution characteristics of hydrological elements,directly affecting the regional water balance,and inducing natural disasters such as rainstorm,flood,heat wave,drought and so on.Therefore,the study of hydrological cycle process under changing environment has become one of the hot issues in the field of water science.Precipitation,as the most direct driving factor of urban waterlogging,is also the main component of hydrological cycle.The study on precipitation characteristics can reveal the characteristics of regional drought and waterlogging disasters more accurately. Moving average method is a relatively simple trend fitting method,which can be regarded as a kind of low pass filter.After moving average,the period shorter than the sliding length in the data series is greatly weakened,and the development trend of the data series can be more easily expressed.MannKendall nonparametric test method is a widely used trend analysis and test method for meteorological data series such as precipitation and temperature.Sen′s Slope estimation method:If there is a trend of change in a certain series of data,Sen′s Slope estimation method can be used to estimate the size of the trend to represent the average trend of change in the series of data,which is usually used in combination with MannKendall method.Morlet continuous complex wavelet transform analysis can reveal a variety of time series change period,so as to qualitatively evaluate the future trend. The results showed that :(1) Annual precipitation increased at a rate of 8.23 mm/(10 a),and showed an alternating period of abundance and drying,with a maximum main period of 10 a.(2) The precipitation was mainly concentrated in summer,accounting for 64.5% of the annual precipitation,and the proportion of winter precipitation was the smallest,accounting for 3.4% of the annual precipitation.The precipitation in spring,summer and winter showed no significant increase trend,and the precipitation in autumn showed no significant decrease trend.(3) The interannual,spring and summer variation of precipitation is mainly affected by the change of precipitation intensity;The variation in autumn and winter is mainly affected by the variation of precipitation frequency. (1) The annual precipitation in Jinan [JP2]showed an increasing trend from 1972 to 2016,increasing at a rate of 8.23 mm/(10 a),[JP]but the increasing trend was not significant,and it showed an alternating cycle of abundant and dry.The main period of interannual variation was 23 a,and it had three subcycles:5 a,10 a and 15 a.The maximum annual precipitation occurred in 1990 (939.9 mm),and the minimum annual precipitation occurred in 1989 (374.1 mm),with the maximum being 2.51 times of the minimum.(2) From 1972 to 2016,the precipitation in spring,summer and winter of Jinan showed no significant increase trend,and the precipitation in autumn showed no significant decrease trend.Moreover,the precipitation was mainly concentrated in summer,accounting for 645% of the annual precipitation,and the precipitation in winter was the least,accounting for less than 4% of the annual precipitation.The variation range of summer precipitation is the largest,followed by spring and autumn,and the variation range of winter precipitation is the least.(3) The interannual variability of precipitation in Jinan is mainly affected by precipitation intensity,and the increase of precipitation intensity is the main reason for the increase of precipitation;The increase of precipitation in spring and summer is also caused by the increase of precipitation intensity.On the other hand,the decrease of precipitation in autumn and the increase of precipitation in winter are mainly affected by the decrease and increase of precipitation frequency (i.e.,precipitation days).

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