Abstract: Based on the 1961-2013 daily maximum/mean/minimum temperature at 25 meteorological observation stations across Dongting Lake ecological economic zone, the change characteristics for heat resources were systematically analyzed by using the relevant statistical methods. Moreover, the impacts of maximum/minimum temperature on the variations of mean temperature were also analyzed by caculating the contribution ratio. Results show that different temperature elements show different spatial distribution patterns. The spatial distribution of steady temperature above 0/5/10/15/20℃ accumulated temperature are consistent, which are high in west and low in east. The largest difference between the beginning and ending dates of steady temperature above 0/5/10/15/20℃ is 10 days at different stations. But most of the difference is within 5 days. Significant increasing or extremely significant increasing trends are identified in the maximum/mean/minimum temperature. But in terms of the warming, there is inhomogeneity in different meteorological elements and seasons. The main feature of climate warming is the increase of minimum temperature. The maximum temperature increasing plays a role in acceleration of warming in spring, which leads to the biggest seasonal temperature rising rate. Extremely significant increasing trends are identified in steady temperature above 0/5/10/15/20℃ accumulated temperature for the climate warming. The variations of beginning and ending dates of steady temperature, abrupt change time are directly affected by inhomogeneous temperature increase. The beginning date of steady above 5/15℃ is earlier than before significantly. The abrupt change time of the steady above 0/5/10℃ accumulated temperature is similar to that of minimum temperature, and the abrupt change time of the steady above 15/20℃ accumulated temperature is similar to that of maximum temperature. Spring cold damage will happen more likely under the background of climate warming.

Key words: heat resources, climate change, agriculture, Dongting Lake ecological economic zone