SHI Jiqing, GAN Chenlong, Bianduo, Chuduo, DOU Yongli, Pubu Ciren, GUO Yinan
The observations from 39 meteorological observation stations in Tibet Autonomous Region from 1981 through 2015 were analyzed in relation to season changing. The analyses include the initial date and the duration of various seasons, the extreme date and the extreme duration of various seasons, season sooner or later, season getting longer and shorter, including rating of their trends, as well as their change trend and impact on agriculture, animal husbandry and tourism. The results indicate that the 35 a average initial dates of spring, summer, autumn and winter are February 25th, May 31st, September 15th and November 28th, respectively. The 35 a average durations of the four seasons were 99 d, 106 d, 73 d and 87 d, respectively, with an obvious regional difference. The initial date of spring had been -5.8, -1.2, -3.3, 2.5 and 2.3 d·(10a)-1 sooner in Bomi, Jiacha, Nimu, Shiquanhe and Shenzha, respectively. The initial date of autumn (winter) had been later 1.4 (1.5), 2.1 (4.2), 1.9 (4.4), 1.0 (2.5) and 1.2 (4.0) d·(10a)-1 in Bomi, Jiacha, Nimu, Shiquanhe and Shenzha, respectively. The duration in spring (summer, autumn) had extended 7.0 (1.3, 0.1), 0.04 (3.3, 2.1), 1.0 (4.6, 2.5), 0.1 (3.4, 1.6) and 1.7 (1.8, 2.8) d·(10a)-1, respectively, in the five stations. The duration in winter had shortened 8.5, 5.4, 7.8, 5.1 and 6.2 d·(10a)-1, respectively, in the five stations. The advancing of spring and the extension of spring duration make the planting time and the herbage turning-green early; the postponement of autumn and shortening the autumn duration make the opportunity of replanting crops great; at the same time, it has a certain impact on the planting structure, the mature distribution of crop varieties, as well as on the tourism.