Abrupt change of winter temperature over the Mongolian Plateau during 1961-2017

Studying the abrupt change of winter temperature(ACWT)over the Mongolian Plateau(MP,including Inner Mongolia Autonomous Region and State of Mongolia)is of great significance for understanding the spatiotemporal distribution of temperature and the mechanism of global climate change.Monthly temperature data during 1961–2017was collected,and the abrupt change point was determined by the Mann–Kendall test and sliding ttest,to analyze the characteristics and causes of ACWT.The results showed that(a)The winter temperature has rapidly increased with a trend of 0.41℃/10a,which was significantly higher than that of the rest area of Chinese mainland,indicating that climate change in the MP was more sensitive to global warming.(b)The abrupt change point occurred in 1988,with temperature of-15.5℃and-14.1℃before and after abrupt change,respectively.The ACWT in 50°N was 1–3 years later than that in 40°N,and the isotherms of different temperatures moved northward by 10–200 km,especially-16℃isotherms moved approximately 200 km northward after 1988.(c)The Arctic Oscillation(AO)and Mongolian High(MH)anomaly affects winter temperature over the MP.When the AO is unusually strong,the MH and East Asian winter monsoon are weak,and southerly winds prevail in most regions,which is not conducive to the cold air developing southward,leading to higher winter temperature in the MP.Overwise,abnormally northerly winds prevail and temperature is low.Meanwhile,the abrupt change time of AO occurred in 1987 before winter temperature.It shows that the AO indirectly causes winter temperatures to rise by influencing the MH and is also the main driving factor of ACWT.

Spatial-temporal Variation of Air Temperature for the Recent 40 Years in Lhasa

It was all known that Lhasa went through a high temperature of 30.8℃in late June 2019,which hit record highs.To better understand the reasons,based on observations recorded at automatic weather stations in Lhasa,the characteristics of temperature variation at multiple time scales were studied using the linear trend method,Mann-Kendall mutation test,Morlet wavelet analysis,R/S analysis and so on.The results showed that:(a)the annual mean temperature(AMT)is rising at a rate of 0.5℃/10 a,and the average temperature for different seasons also increased significantly,especially in winter.(b)Although there was an intersection in 1995,it was found that AMT,did not pass the reliability test of significance levelα=0.05,this means there are no abrupt changes for AMT,the values are 7.97 and 9.15℃respectively before and after the intersection point.(c)AMT has a periodic oscillation for 18-25 and 25-32 a based on a mass of data and the wavelet variance diagrams in Lhasa.AMT has a main cycle of 28 a,cyclic patterns of temperature changes in spring,summer and autumn is similar to AMT,but it is relatively complex in winter.(d)The Hurst index of AMT and different seasons demonstrates that the temperature is likely to continue to rise in the future in Lhasa.