Research Of Climate Change In The Arid Regions Of Northwest China And Its Impacts And Adaptation On Typical Basins

Global warming has generated obvious impacts on natural ecosystems and human society.In the future arid regions will face higher climate change risks than humid regions.The water resource and ecological environment in the arid regions of Northwest China are fragile and such regions have sensitive responses to global climate change.As a result,it is of great scientific and practical significance to study regional climate change and its impacts as well as adaptation in the arid regions of Northwest China of such changes.In the paper,based on the observational data and the CMIP5 simulation data,facts,attribution and projection of climate change in the arid regions of Northwest China were addressed.The impacts of regional climate change on water resources in Hexi Corridor and climate change adaptive strategy in Shiyang River basin are also studied.The main results are as follows:1.The climate is getting warmer and drier since the 1960s in the arid regions of Northwest China.The regional averaged annual temperature increasing rate was 0.31 ?/10a during 1961-2012 with the remarkable rise of annual minimum temperature(0.46 ?/10a)as a main contributor for it.The seasonal temperature ascending rates in winter(0.41 ?/10a)and autumn(0.34?/10a)are relatively larger than in spring(0.25 ?/10a)and summer(0.26 ?/10a).The annual precipitation averaged in the arid regions of Northwest China remarkably increased at the rate of 5.4 mm/10a,and the largest increase occured in summer(2.4 mm/10a),then in spring(1.1 mm/10a),autumn(0.9 mm/10a)and winter(0.9 mm/10a).The fastest warming regions are located in western Qinghai,northern Xinjiang,the Alashan Plateau of Inner Mongolia and the northwestern Ningxia and the largest precipitation increase regions are located in Qinghai and Tianshan Mountain while precipitation decrease trend in northwest of Inner Mongolia and northwest of Ningxia.During 1961-2016,the extents of climate warming of the three inland river basins in Hexi Corridor from east to west decreased gradually,with the warming of Shiyang River Basin was the fastest(0.45?/10a)and that of Shule River Basin was the slowest(0.19?/10a).However,the annual precipitation gradually increased from east to west,with the precipitation increase of Shule River Basin was the most(8.1 mm/10a)and that of Shiyang River Basin was not apparent(1.6 mm/10a).2.Increase in warm extremes and decrease in cold extremes as well as an intensification of precipitation extremes have been observed since the 1960s in the arid regions of Northwest China.For the minimum of daily minimum temperature(TNn)and the maximum of daily maximum temperature(TXx),a significantly increasing trend is clearly observed during 1961-2012.The respective warming rates for TNn and TXx were 0.43 ? and 0.17? per decade.Frost days(FD)and ice days(ID)decreased at a rate of 3.9 days and 2.0 days per decade,respectively.Increases in warm days(TX90p)and nights(TN90p)concurrent with decreases in cold days(TX10p)and nights(TN10p)were very pronounced.The trends were 1.1%and 2.3%per decade for TX90p and TN90p respectively,and-0.6%and-1.3%per decade for TX10p and TN10p respectively.During the same period,the total extremely wet days'total amount(R95p)and the number of wet days(Rlmm)had a tendency toward increases,with the rates of 2.4 mm and 1.2 days per decade respectively,while the maximum number of consecutive dry days(CDD)showed a downward trend with a value of 5.4 days per decade.3.The quantified analyses based on an optimal fingerprinting method show that all forcing(ALL)and anthropogenic forcing(ANT)signals can be robustly detected in the mean temperature change in the arid regions of Northwest China during the period of 1958-2012.By using one-signal detection,the optimal estimation of ALL and ANT scaling factors were 1.22 and 1.40 respectively.As for two-signal detection,ANT and natural forcing(NAT)signals could also be detected and separated from wach other.The contributions of ALL,ANT and NAT to warming were 1.45?,1.37? and 0.13? respectively.4.Compared with the 1980s,the glacier areas in the east,middle and west sections of the Qilian Mountain reduced by 71.3%,75.6%,and 23.4%,respectively,due to the impacts of climate change.The annual average runoff volumes of the Haihe River and the Shule River in Hexi Corridor increased in 1961-2015.The increase inthe Shule River Basin was the most remarkable one at the rate of 3.3 m/s/10a,while the runoff in the Shiyang River Basin showed no apparent trend.The runoff volume in the Shiyang River is positively related to annual precipitation of its upstream and negatively related to air temperature.The runoff volume in the Heihe River and the Shule River are positively related to annual precipitation of their upstream areas and annual average temperature.5.Under the background of future climate change,continuous warming in temperature concomitant with decreases in cold extremes and increases in warm extremes is projected across the arid regions of Northwest China,with greater change in RCP8.5 than in RCP4.5.Under the RCP8.5 scenario and by the end of the 21st century,the annual mean temperature,TNn and TXx are projected to increase by 5.5?,6.6? and 5.6?,respectively;FD and ID are projected to decrease by 58 days and 47 days,respectively;TX90p and TN90p are projected to increase by 47.2%and 55.7%,respectively;and TX10p and TN10p are projected to decrease by 7.7%and 7.6%,respectively,compared with 1986-2005.A general intensification of precipitation is projected over the arid region.Relative to 1986-2005,the percentage changes in annual precipitation and R95 are projected to increase by 13.6%and 36.7%under the RCP4.5 scenario and by 20.8%and 71.5%under the RCP8.5 scenario,respectively,by the end of this century.6.In the future,if the global temperature rise threshold value is 1.5 ?,the annual mean temperature of the Shule River,Heihe River and Shiyang River Basins are projected to increase 2.11 ?,2.07?,2.03 ? respectively compared to that before the industrialization.Relative to 1976-2005,average annual precipitation will increase by 15%,10%and 8%respectively.Average annual runoff in the Shule River Basin will increase by 10%,and that in the Heihe River and Shiyang River Basins will decrease by 3%and 8%,respectively.7.The most outstanding features in the Shiyang River Basin during the recent 55 years were rapid temperature rise,relatively stable precipitation and nearly exhausted glaciers.With the future continuous warming,the runoff will decrease and the river basin will face a higher climate risk.At present,the adaptive policy only contained the ecological environment deterioration.The shortage of water resource is still the bottleneck which affects the development of social-economy.Considering the impacts of future climate change on water resource restrictions,the measures such as increasing water resources,developing agricultural water saving technology,and performing structural adjustment and climate migration are suggested to cope with climate changes.The Wuwei and Mingqin oases can not only maintain their own survival,but also can have 2.0×108 m3 to improve the natural ecosystem and 3.0×108 m3 to supply groundwater.This adaptation strategy can maintain the sustainable development of the oases.