Variation Characteristics of Thermal Resources in Northeast China in Recent 50 Years

Using the daily average air temperature data from 100 meteorological stations in Northeast China from 1951 to 2005, the variation of accumulated temperature steadily above 10 ℃ and 0 ℃, their lasting days, the beginning and ending date is summarized, and then the variation characteristics of thermal resources under the background of climate warming are analyzed. The air temperature increases continuously in Northeast China, and the climatic trend rate of the annual average air temperature is 0.4 ℃/10 a, more significant than any other region in China. And it is well correlated with the thermal resource indexes such as the accumulated temperature steadily above 10 ℃ and 0 ℃, and their lasting days, and the beginning and ending date. Climate warming has made the accumulated temperature steadily above 10 ℃ and 0 ℃ increase significantly in Northeast China widespread. The accumulated temperature steadily above 10 ℃ has also increased significantly by more than 40 ℃·d/10 a. The lasting days of accumulated temperature steadily above 10 ℃ and 0 ℃ increase significantly too. The increasing amplitudes are more than 2 d/10 a on average and reach up to more than 4 d/10 a in the north region of Northeast China. For some regions of Inner Mongolia close to Mongolia, southern Liaoning Province, southern Heilongjiang Province, Changbai Mountains and the west part of Jilin Province, the lasting days increase by 2-4 d/10 a. The contours of accumulated temperature steadily above 10 ℃ and 0 ℃ and their lasting days move greatly northward in Northeast China Plain and relatively flat Inner Mongolia Plateau, and an uplift trend from mountain areas to high altitude areas is found on the contours. The beginning dates of accumulated temperatures steadily above 10 ℃ has advanced by 0.1-2.9 d/10 a, and at some stations of Northeast China Plain, the advancing trends are more than 1.0 d/10 a. On the other hand, the ending dates has delayed to a less obvious extent by 0.0-2.1 d/10 a, and the stations with the delaying trends more than 0.8 d/10 a centralize in Liaoning Province and Changbai Mountains in Jilin Province. The beginning dates of accumulated temperatures steadily above 0 ℃ have advanced by 0.8-4.3 d/10 a, while the ending dates have delayed by 0.0-2.1 d/10 a, and the stations of the significant delayed ending dates centralize in the north region of Northeast China with the trend more than 1.0 d/10 a. These changes in thermal resources are conductive to increase food production and maintain the stability of food production in Northeast China.