| The IPCC assessment report indicates that it is the the warmest period in the world during 1983 to 2012,the global climate warming tendency becomes more obviously.The temperature rises and the precipitation decreases on most regions in the northeast of China.Extreme events gradually increasing,for instance,the seriousness rainstorm occurs in the northeastern region in 1994,the catastrophic flood occurs in summer in the Nen River basin and the Songhua River basin in 1998 and the torrential rain weather occurs in Jilin province in 2013,and so on.They bring negative effects to the social economy and people’s property safety.In order to prevent the occurrence of floods,landslides and other natural disasters,to utilize water resources rationally.it is important to comprehend the tendency of precipitation and extreme precipitation.The article selects 31 hydrological observation sites’s daily precipitation dates during 1980 to 2014 in the upstream area of Songhua River. Through the methods such as trend analysis,concentration ratio,cumulati-ve anomaly analysis,spatial interpolation,and so on.To research the precipitation spatial change law and the characteristic of extreme precipitation,the results are as follows:(1)The precipitation and frequency which have a tendency to decrease in interannual variability in the upstream area of Songhua River;the interannual variability of extreme precipitation increases,the extreme precipitation frequency decreases;the annual precip-itation intensity and extreme intensity increase;the annual precipitation and extreme precipitation are mainly concentrated in June to September,there is significant correlation with flood season precipitation(P<0.01);the annual precipitation concentration is 0.62,the concentrated period appears in late July.There is a obvious precipitation mutation in the upstream area of Songhua River,the first mutation point is in 1987,the second in 2009;(2)The spring precipitation is plentiful and has a tendency to rise in the upstream area of Songhua River(P>0.05),the linear tendency slope is 4.5mm/10a;the precipitation in summer is more abundant than the other three seasons and has a tendency to decrease(P>0.05),the linear tendency slope is-10.4mm/10a;the autumn precipitation decreases as well(P>0.05)and the liner tendency slope is-0.7mm/10a,it has two obvious mutational sites in 1985 and in 1994;though there is short of winter precipitation,the interannual trends is rises(P>0.05) and the linear tendency slope is 3.0mm/10a;(3)Reasearch on the cycle of annual and extreme precipitation by the wavelet analysis in the upstream area of Songhua River and find out,there are two main cycle of annual precipitation,the first is 28a,the second is 5a;there are also four main cycle of extreme precipitation,they are 28a,13a,8a and 5a;the first main cycle of annual and extreme precipitation is 28a,it has the oscillation energy and periodic strongly;(4)The spatial distribution of annual precipitation is not uniform in the upstream of Songhua River.the annual precipitation,extreme precipitation and the change of frenquency is consistent but they are different in some parts,the distribution trend decreases in corrugated from southeast to northwest;the annual precipitation intensity shows the trend is degressive from the central region and southeast to northwest and southwest region; the center of extreme precipitation intensity is located in Dehui station nearby and declined towards the north;the maximum daily precipitation mainly focus on three regions,the center is located in Wudaogou station,Dehui station and Dayang station respectively and the scope extending constantly;the spatial distribution of seasonal precipitation shows that the southeast is high and the northwest is low;the spatial distribution of precipitation concentration shows that the northwest is high and decreces to southeast,the lowest value appears in.Manjiang station nearby. |
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