Dynamic changes in the thermal growing season and their association with atmospheric circulation in China.

Vegetation phenology is one of the key agroclimatic indices that is sensitive to climate change. Analyzing the variation in plant phenology under a changing environment can provide reference information to assess the impact of climate change on ecosystems and agricultural management. In this study, we focused on the thermal growth season, an important phenology index. We defined four growing season indices based on the surface temperature to quantify the changes in thermal growth season and analyze their association with atmospheric circulation in China. The results showed that the start date of the growing season exhibited a significant advanced trend (P < 0.001), while the end date exhibited a significant delayed trend (P < 0.001). The length of growing season and the number of ≥ 10℃ days increased significantly in China (P < 0.001) from 1960 to 2018. The variation in thermal growth season differed in different regions. The Qinghai-Tibet Plateau and the Loess Plateau were the regions in which thermal growing season was the most sensitive to climate changes. Atmospheric circulation was one of the main factors affected the change in thermal growing season indices. The West Pacific Subtropical High Intensity Index and the Arctic Oscillation Index significantly negatively correlated with the start date of the growing season (P < 0.05), and significantly positively correlated with the length of growing season and the number of ≥ 10℃ days (P < 0.01). Atmospheric circulation affected the change in temperature and subsequently affected the thermal growth season. These findings will provide useful information to assess the risk assessment of climate change and take action to reduce in the impact of climate change on ecosystems and agricultural management.