干旱区研究

Arid Zone Research ›› 2020, Vol. 37 ›› Issue (2): 275-281.doi: 10.13866/j.azr.2020.02.01

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The rate of warming is slowing and temperature is showing sharp changes in middle and high latitude regions

DAI Haiyan1,CHEN Gaowa2,WU Jianhua3,YANG Liping1,DU Wala1   

  1. (1. Inner Mongolia Ecology and Agricultural Meteorology Centre,Hohhot 010051,Inner Mongolia,China;  2. Hulun Buir Meteorological Bureau,Hulun Buir 021008,Inner Mongolia,China; 3. Chifeng Meteorological Bureau,Chifeng 024000,Inner Mongolia,China)
  • Received:2019-03-26 Revised:2019-07-05 Online:2020-03-26 Published:2020-04-21

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Abstract: This work used daily temperature data spanning 30 years from 13 national benchmark climate stations in the midlatitude regions of China to assess the freezing/thawing index and trends in the number of freezing/thawing days.The results show that the thawing index shows a significantly increasing trend and the freezing index shows a slightly increasing trend.An upward trend in thawing days and downward trend in freezing days were insignificant.The daily average thawing index significantly increased,whereas the daily average freezing index slightly increased.The characteristics of cold and warm polarizations were obvious.The more than 10 ℃ accumulated temperature and days in study area showed a significantly increasing trend,the less than -10 ℃ accumulated temperature showed a downtrend,and the less than -10 ℃ accumulated temperature days on the rise trend,the transition between two periods significantly decreased.The fluctuation in the thawing index was clearly less than that of the freezing index.Moreover,the thawing index was negatively correlated with latitude and altitude,whereas the freezing index was positively correlated with latitude and altitude.The influence of altitude on the thawing index was greater than that of the freezing index.As the latitude and altitude increased,the change in freezing index and freezing days were observed to be more stable,and the corresponding melting index showed larger fluctuations.On the whole,the rate of warming has slowed in China’s mid and high latitudes since the 1990s,and the polarization of average daily temperature and the sharp change in temperature are obvious in both the cold and warm seasons.

Key words: freezing index, thawing index, climatic anomaly, midlatitude, China