Spatial and temporal temperature variations in Xinjiang,China during 1961-2008

This study examines spatial and temporal changes in 16 extreme temperature indices at 37 weather stations in Xinjiang and their associations with changes in climate means during 1961-2008. Linear regression analyses reveal that significant increas- ing trends in temperature were observed over Xinjiang, with the rate of 0.13 ~C/decade, 0.24 ~C/decade, and 0.52 ~C/decade for annual mean temperature, annual maximum, and minimum temperature, respectively. Annual fi＇equency of cool nights （days） has decreased by -2.45 days/decade （-0.86 days/decade）, whereas the frequency of warm nights （days） has increased by 4.85 days/decade （1.62 days/decade）. Seasonally, the frequencies of summer warm nights and days are changing more rap- idly than the corresponding frequencies for cool nights and days. However, normalization of the extreme and mean series shows that the rate of changes in extreme temperature events are generally less than those of mean temperatures, except for winter cold nights which are changing as rapidly as the winter mean minimum temperatures. These results indicate that there have been seasonally and diurnally asymmetric changes in extreme temperature events relative to recent increases in tempera- ture means in Xinjiang.

Assessing changes in extreme precipitation over Xinjiang using regional climate model of PRECIS

In this paper, an analysis, with the simulation of PRECIS （Providing Regional Climate for Impact Studies）, was made for future precipitation extremes, under SRES （Special Report on Emission Scenarios） A2 and B2 in IPCC （Intergovernmental Panel on Climate Change） AR4. The precipitation extremes were calculated and analyzed by ETCCDI （Climate Change Detection and Indices）. The results show that： （1） In Present Scenario （1961 1900）, PRECIS could capture the spatial pattern of precipitation in Xinjiang. （2） The simulated annual precipitation and seasonal precipitation in Xinjiang had a significantly positive trend and its variability had been deeply impacted by terrain. There was a strong association between increasing trend and the extreme precipitation＇s increase in frequency and intensity during 1961-2008. Under SRES A2 and B2, extreme precipitation indicated an increasing tendency at the end of the 21st century. The extreme summer pre- cipitation increased prominently in a year. （3） PREC1S＇s simulation under SRES A2 and B2 indicated increased frequency of heavy precipitation events and also enhancement in their intensity towards the end of the 21 st century. Both A2 and B2 scenarios show similar patterns of projected changes in precipitation extremes towards the end of the 21st century. However, the magnitude of changes in B2 scenario was on the lower side. In case of extreme precipitation, variation between models can exceed both internal variability and variability of different SRES.

Identifying hot spots of long-duration extreme climate events in the northwest arid region of China and implications for glaciers and runoff

China’s Northwest Arid Region(NAR),with dry and cold climate conditions and glaciers widely developed in the high mountains,provides vital water resources for Asia.The consecutive cold,warm,dry and wet days have much higher impacts on the water cycle process in this region than extreme temperature and precipitation events with short durations but high intensities.Parametric and nonparametric trend analysis methods widely used in climatology and hydrology are employed to identify the temporal and spatial features of the changes in the consecutive cold,warm,dry and wet days in the NAR based on China’s 0.5°×0.5°meteorological grid datasets of daily temperature and precipitation from 1961 to 2018.This study found that(1)the consecutive cold days(Cold Spell Duration Indicator,CSDI),and the consecutive dry days(CDD)decreased,while the consecutive warm days(Warm Spell Duration Indicator,WSDI),and the consecutive wet days(CWD)increased from 1961 to 2018,(2)and the eastern Kunlun Mountains were the hot spots where all of these consecutive climate indices changed significantly,(3)and the changes in these consecutive climate indices were highly correlated with the rise in the Global Mean Land/Ocean Temperature Index.The results indicated that winters tended to warmer and dryer and summer became hotter and wetter during 1961–2018 in the NAR under the global warming,which can lead to the sustained glacier retreat and the increase in summer runoff in this region,and the eastern Kunlun Mountains are the area where could face high risks of water scarcity and floods if the changes in these climate indices continue in the future.Given the vulnerability of the socio-economic systems in the NAR to a water shortage and floods,it is most crucial to improve the strategies of water resources management,disaster prevention and risk management for this region under climate change.

塔克拉玛干沙漠南缘典型绿洲ET_(0)模型适用性评价及修正

ET_(0)模型在不同地区具有不同的适用性,而对极端干旱的塔克拉玛干沙漠南缘绿洲的ET_(0)模型的适用性研究较为稀缺。利用2006—2014年生长季(4—10月)策勒气象站逐日气象资料,以自动称重式蒸渗仪实测数据为标准,采用最大绝对误差(MAE)、均方根误差(RMSE)、模型效率(EF)和一致性指数(d)4个指标,在日、月时间尺度上评价了6种常用ET_(0)模型在策勒绿洲的适用性,并使用回归修正法和比例修正法分别修正了这6种模型。结果表明:(1)日、月时间尺度上,Hargreaves-Samani(H-S)模型高估程度较大,其余模型均不同程度低估,拟合度由高到低依次为FAO-56PM、Jensen-Haise(J-H)、Priestley-Taylor(P-T)、Makkink、Turc、H-S。(2)所有ET_(0)模型月值变化趋势与蒸渗仪实测值基本一致,除FAO-56PM和Turc模型计算的ET_(0)月值在6月达到峰值外,其余模型均在7月达到峰值,在生长季尺度所有模型ET_(0)月值与蒸渗仪实测值呈显著相关。(3)日、月时间尺度上,回归修正法和比例修正法修正后的ET_(0)模型计算结果与蒸渗仪实测值均呈极显著相关,回归修正法优于比例修正法。(4)相关性分析表明,对策勒绿洲ET_(0)影响由高到低的气象因子依次为Tmean>Tmin>P>Tmax>Rs>U2>RHmean。