Impact of climate warming on temperature and heat resource in arid Northwest China

Climate change has changed agro-climatic resources, especially the degree of heat and the spatio-temporal distributions of resources. Against global warming, temperature has increased in arid Northwest China. Also arid Northwest China has been most influenced by climate change. Using daily meteorological data from 67 stations in arid Northwest China, this paper analyzed change patterns and trends of temperature, accumulated temperature, frost over the period for 1961-2011. The results showed that in the arid northwest region, temperature increased at 0.33 ℃·10a^-1, higher than the national average. The warming trend in Northern Xinjiang was larger than in other areas and winter season having the highest yearly variation in temperature. Accumulated temperature higher than 0 ℃ and 10 ℃ increased by 67.8 ℃·10a^-1 and 68.8 ℃·10a^-1. Accumulated temperature duration also increased over the 1961-2011 period. The increased days with ≥0 ℃ and ≥10 ℃ accumulated temperature were mainly caused by the delayed ending dates and the earlier initial dates, respectively. In the study area, there was delayed first frost, earlier last frost and lengthened frost free period. The rates of change in the first and last frost were 2 d·10a^-1 and 1.4 d·10a^-1, respectively. In the region, the longer frost-free period was mainly driven by delayed first frost. Inter-annual fluctuation in the first frost was less than that in the last frost in the arid Northwest China. The last frost date was more or less 10 days later than it used to be; even though climate warming caused no change in frost condition. Mostly, the last date of ≥10 ℃ accumulated temperature occurred earlier than the first frost date.