Analysis of Changes in Starting Dates of the Four Seasons and the Length of the Growing Season in China during 1971 to 2013

Linear trend estimation and empirical mode decomposition (EMD) etc. were applied to analyze daily temperature data during 1971-2013 collected at 584 standard meteorological stations and provided by the National Meteorological Information Center, China Meteorological Administration. Based on the geographic information system data processing platform, the variation trends of starting dates of the four seasons and the length of the growing season in the recent 43 years were analyzed. The results show that changes in starting dates of seasons in Xinjiang, Yunnan, and Sichuan showed significant differences between the north and south. The starting dates of spring and summer advanced in most regions of China, particularly for the spring. In Jiangsu, Anhui, Hubei, and northern Yunnan, the staring date of spring advanced by 4.1-7.2 d/10 a. The area with advanced starting date of summer was wider than that with advanced spring. Eastern Xinjiang, western Gansu, southern Yunnan, and South China experienced the most significant advancement of summer, which could reach 2.9-4.6 d/10 a. The starting dates of autumn and winter delayed in most areas of China. The autumn season started late by 4.4-8.6 d/10 a in southern Xinjiang and western Sichuan fall, while later starting of the winter was even more significant, particularly in southeastern Xinjiang and Qinghai, where the winter started late by 4.7-13.8 d/10 a. The length of growing season became longer in various regions, with the largest increase of 9.7-20.1 d/10 a occurring at the border of Sichuan and Yunnan and southeastern Xinjiang. EMD and linear tendency estimate results basically were identical, but the area of late spring starting was bigger in EMD result than in linear tendency estimate results. Changes in the starting dates of summer, autumn, winter were more prominent than that in the length of growing season.