The Effect Of Urbanization To Nanchang Precipitation And Prediction

Recently，with the fast development of economy and the improvement of ourindustry level，more and more rural villages move to the urban in large scale，theindustry is expending fast, urban area also expanding quickly.With the Urbanizationdeveloping，the problem which was caused by the City of precipitation is nowbecoming more and more serious，the probability of urban waterlogging disasters areincreasing,Disaster losses also grow at an unprecedented speed。At the same time,wepay more attention to City hydrological effects caused by urbanization.This passagemaking use of the data of Nanchang urban and rural areas in total4sites and someRelevant statistical yearbooks to analyzes the Changes in precipitation characteristicsof Nanchang urban and rural areas in recent50years.through the analysis ofprecipitation characteristics of Nanchang urban and rural areas,studies the influencesof urbanization to Nanchang precipitation,and then,according to the more than50years’ rainfall time series of Nanchang city,the paper forecast the precipitation ofNanchang urban in future,and depending on it,get the recurrence interval’s size ofeach state. The article’s conclusion follows as this:(1)Nanchang urbanization in general can be divided into three stages: the firststage is from1949to1978(called Start wandering stage);the second is from1978to2000(called Stable development phase);the third is from new century to now on(called rapid development stage).(2)City in annual precipitation and precipitation days are increasing in somedegree Compared to the suburbs.Also the increasing rapid has a fast trend.Especiallyin recently30years,Urban annual precipitation days are usually much more than thesuburbs’. Per10years from more suburban precipitation and precipitation days, wecan find that,our urban shows a much more increasing extent than the suburbs or thereducing speed is far slower trend no matter in relation to city in annual precipitationor the precipitation days.In recently50years, the growth of average rainfall of Nanchang urban is59.96mm per10years,but the growth of average rainfall of Nanchang suburbs is41.21mm per10years. The contribution of urbanization to Nanchang urban rainfall increase is31.3%. the average precipitation days decrement of Nanchang city is-1.63days per10years,and the average precipitation days decrement of Nanchang suburbs is-5.38days per10years.the contribution of urbanization to Nanchang urban areaprecipitation days increase is69.70%.(3)According to Markoff chain, Combining with fuzzy set theory, we forecastthe annual precipitation of2013and2014in Nanchang urban respectively,concluding that Precipitation status value of2013is i=3（means a normal year）,Precipitation forecast value is1495.5mm, Precipitation status value of2014is i=5（means a rain waterlogging year）, Precipitation forecast value is1886.3mm.Recurrence interval of drought, partial drought, normal, partialwaterlogging and rain waterlogging condition in Nanchang urban respectively is5.49,6.56,2.41,17.69and5.15years,the possibility of having a normal year is the most,the possibility of having a partial state is the least.