Abstract: Based on the daily maximum temperature data from the National Meteorological Information Center,the characteristics of extremely high temperature in Northwest China were analyzed in order to reveal some new features in extreme temperature in recent 20 (from 1996 to 2015) and 55 years (from 1961 to 2015).The results show that except the southern parts of Xinjiang Uygur Autonomous region and Shaanxi province,the frequency of extremely high-temperature events in Northwest China generally increases from 1961 to 2015.The high number of extreme event is mainly located in the southeastern Xinjiang Uygur Autonomous region,northern Qinghai province,western GanSu province,and central Ningxia province,with a linearly increasing number of extreme event more than 3.00 per decade.Most of them pass 99.5% or more significant tests.This is consistent with the characteristics of global warming.For the last 20 years (from 1996 to 2015),the frequency of extremely high-temperature events increases in the west and south parts,and reduces in the east and north parts.This is consistent with that in the previous 20 years (1961-1980),but opposite to that in nearly 30 years (from 1981 to 2010).In the past 55 years,the average number of extremely high-temperature events in Northwest China is on the rise with 1.73 per decade,and that in the previous 20,nearly 30,and the last 20 years rises 0.06,3.90 and-0.46 per decade,respectively.The decreasing trend in the number of extremely high-temperature events in the last 20 years is consistent with the stagnation status of global warming occurring after 1998.It suggests that this decreasing trend is a kind of responses to the stagnation of global warming.Based on the typical temperature field analysis,it indicates that the abnormal variation in high temperature in Northwest China has a significant response to the change in sea surface temperature in the Indian Ocean and the Pacific Ocean.The distributions of temperature intensity both in extreme maximum temperature and in extremely high-temperature events in Northwest China are mainly related to the elevation above sea level,local topography,and the underlying surface properties.

Key words: Northwest China, Extremely high temperature, Climate warming, Stagnation, Elevation above sea level