Study On Summer Precipitation And The Temporal And Spatial Characteristics Of Rainstorms In The West Of Jilin Province

As an important component of the nature environment, climate is vital to human survival.Every change of the climate can make an effect on nature eco-system and social economy.The effect will be multi-scale and multi-level. As an important nature resource, also climate isthe main component of nature environment. Therefore the effect on social economy systemwill be from two aspects. At different degrees, climate-change has an effect on every aspect ofglobal and regional social economy. Varying with the location, time, society developmentlevels and the environment condition, the social system is sensitive and vulnerable toclimate-change. Thus the study on regional climate change and its character should bereinforced. It is vital to the making of region development policy and the eco-construction.Taking five stations in the west of Jilin province as study area, they are Baicheng,Tongyu,Qianguo,Qian'an and Changling. Making use of their daily precipitation databetween 1951-2003, combining the knowledge of aerography and hydrology, using thewavelets function of MATLAB6.5,Visual FoxPro6 data-base,SPSS,EXCEL and thestatistics theory to do some significative discussion on the long time average status of summerprecipitation and the Temporal and spatial distribution rule, then pointing out interrelatedmeasures of controlling flood based on the results of Temporal and spatial distribution rule.This study area is semi-drought eco-frailty area, the research of summer precipitationcharacteristic is much helpful to industry and agriculture production. The evidentcharacteristic of climate in this area is inadequate precipitation, odds temporal and spatialdistribution, and rainy summer, but usually falling as rainstorm or shower, and then flowing asflood, drought usually happen after rainstorms. Just because of the odds temporal and spatialdistribution, drought and flood happen usually, but drought is much heavier flood, almost 9times in 10 years, just because of this, in a long period the consciousness of control flood is soweak and there is a lack of flood control measures that the loss is heavily when the flood iscoming. So finding out the variation rule of precipitation and making theory base for flood isvery necessary. At present, the research fruit of this area is almost about drought father, butthe research about the average status and extreme status such as rainstorm of precipitation isstill infrequent.The research and statistic results of this paper reveals: in the latest century, the averageprecipitation of summer is 301mm and the trend is decreasing steadily, the precipitation inJuly is the most, as to space Changling is the most which is southmost, Baicheng is the leastwhich is westmost. 1950s,1960s and 1980s are relatively rainy time, 1970s and 1990s arerainless time, in the future years drought is still the archenemy, but flood also can't beneglected.We can see from the wavelets maps of the five stations and the whole west: summerprecipitation has obvious 22year rainy-rainless long cycle surge and 11-12year less longercycle surge, it is just coincident with the double cycle and single cycle of macula activity, italso validates the fact that natural disaster is much more in macula double cycle. During thelong cycle, there is low frequency wave of 3year and every cycle has the trend of shorten.From the 22 cycle, we can see the two rainy time are 1960-1973 and 1987-2000,before 1959,1974-1986 and after 2001 are the three drought time, and now we are on rainless time of longcycle, the four break dot of change from dry to wet are 1959,1973,1986 and 2000. From the11-12year cycle we can see nowadays is also on rainless time, so in the coming 11-12 yearswe still should pay attention to drought control in this area.According to the factual status of the study area, we establish the precipitation whichover 45mm per day as the rainstorm standard and over 100mm per day as severe rainstormstandard. The knowledge of probability theory reveals: in the half latest century, both thenumber and the quantity of rainstorm is decreasing, however, the quantity of severe rainstormhas biggish increase, in the five stations Changling has the most rainstorm and Qianguo hasthe least, the distribution of rainstorm in a year is completely consistent with precipitation. Inthe whole west area the frequency of rainstorm is 4.69time per year, the probability ofhappened rainstorm in a year reaches 96%, in the 53 statistical years only 1952 and 2002 hasno rainstorm. The probability of happened severe rainstorm in a year is 19%. In the sevengrades of rainstorms the one of 50-60mm is the most frequent, about 1.52time per year. Thereare many rainstorms in this study area, that is about 225 times, but not every rainstorm canbring flood, it is also according to the former base water level and the concrete status, so if wedo the control flood measure well, even the flood is coming, the situation of a disaster alsocan be artificial knocked-down.