Analyses Of Climate Change On Dengkou Oasis In The Northeastern Of Wulanbuhe Desert

Climate resources are the basic and most important regenerated resources for the existence and sustainable development of oasis.Dengkou country situated on the joint area between North China and northwest in the northeastern Wulanbuhe Desert,there is a dividing line between desert and grass land in Asia center.It belongs to transitional zone from grassland-desert to desert-grassland.It is the very most geography dividing line.We are establishe a climate date about climate resources of Dengkou County.The study maily analyses the climate factors in order to find a change rule of special characteristics.The main research results are:1.The annual mean temperature is increasing.The cool years are between l950s to 1970s, the annual mean temperature have been increased since 1980s.The feature of temperature from low to high is showed.The annual mean and the four season temperature shows obvious increasing tendency.The ascending trend from much little is winter,summer and spring.The ascending trend of winter is more than that of annual mean temperature.2.The decadal variation of annual precipitation shows obviously.The precipitation has an evident increasing trend between 1960s and 1990s.It is found that the abrupt change of precipitation occurred in 1970s and the precipitation become lower.The variation trend of annual precipitation is not distinctness.The variation trend of decadal precipitation from much little is summer,autumn and winter.Precipitation in summer is the most.The trend of annual precipitation is same as that of summer.3.Evaporation increased obviously,especially in summer,followed in spring.But the increase trend became slight in winter.The variety of annual evaporation appeared single peak curve.The peak values of evaporation occurred in May,while the lower value was in January.The decadal variations of the seasonal and annual evaporation show no regularity, but the seasonal and annual evaporation show increased quickly during recent 5 years.While decreasing trend happens in 1950s and 1970s.The decadal variation of summer evaporation is largest and trend is closely similar to the annual evaporation.4.Relative humidity of summer is close to that of autumn.The spring is the lowest. The least annual relative humidity is in April,while the largest annual relative humidity is in August.The 1990s has the longest time for relative humidity except autumn and winter.5.The climate is mainly drought,keeping long time and the longest one remain 14 years. Heavy drought is dominant in winter and spring moderate drought occurs in summer,the frequency of heavy drought is same as moderate drought in autumn,variations trend of season drought index is corresponding with that of percentage of precipitation anomaly.This shows there is a very good accordance between the drought index rates and percentage of precipitation anomaly to division and assessment Dengkou County's climate.6.Most sunshine hours occurred in summer and spring,while the least sunshine hours occurred in winter.The variety of annual sunshine hour appeared single peak curve.The peak values of sunshine hour occurred in May,followed in June,while the lower value was in December.The yearly and seasonal sunshine hours have decreased fastest in the 1980s and that has decreased slowest in recent 5 years.It showed that annual variation is same as inter decadal variability of autumn and winter from quadratic fit curve.The sunshine hours is reduced at first,and increased afterwards,while the variation of spring and summer is same and the sunshine hours increases and then decreases.7.Sand-blowing weather occurs mainly in spring,the peak happens in April.The number of sand-blowing days is the least in August and September.The annual and other seasons of sand-blowing days decreased with inter annual time.The maximum of the number of the sand-blowing days emerged in 1950s,and the minimum of that is in the recent 5years. In autumn,the most sand-blowing days is the 1960s,followed 1950s.Before the 1980s.the annual and season of sand-blowing days shows a linear decline.The significance inspection for equation shows the confidence degree of equation is 0.01;The orders of decline rate:year＞spring＞winter＞summer＞autumn.Most of the number of sand-blowing days is positive anomaly and the variation frequency is larger,while negative one appeared in the years after the 1980s,and the variation frequency is steady.The 1980s is a jump point of sand-blowing day discontinuity.The trend shows increases at the beginning and then decreases.The annual number of sand-blowing days has a close accordance with that of spring.8.The dust storm annual occurring day is simultaneous observation with gale day in the region.Dust storms are most frequent in spring;much less frequent is in autumn.The annual and seasonal dust storm and gale day decrease steadily.In the 1970s,dust-storm occurs frequently and decreases in recent 5 years.It dropped to the lowest value in 1980s and 1990s.in recent 5 years,the dust storm frequency decrease little.The annual and seasonal dust storm and gale day shows a linear decline.The significance inspection for equation shows the confidence degree of equation is 0.01;The orders of decline rate:year＞spring＞summer＞ winter＞autumn.Before the 1990s,most of the number of dust storm and heavy wind day is positive anomaly and the decrease variation frequency is obvious larger,while negative one appeared in the years after the 1990.the decrease variation frequency is steady the 1990s is a jump point of dust storm day discontinuity.The trend shows increases at the beginning and then decreases.The annual number of dust storm days is a close accord with that of spring.