Innovative trend analysis of annual and seasonal air temperature and rainfall in the Yangtze River Basin, China during 1960-2015

The variation characteristics of air temperature and precipitation in the Yangtze River Basin (YRB), China during 1960-2015 were analysed using a linear regression (LR) analysis, a Mann-Kendall (MK) test with Sen's slope estimator and Sen's innovative trend analysis (ITA). The results showed that the annual maximum, minimum and mean temperature significantly increased at the rate of 0.15°C/10yr, 0.23°C/10yr and 0.19°C/10yr, respectively, over the whole study area during 1960-2015. The warming magnitudes for the above variables during 1980-2015 were much higher than those during 1960-2015:0.38°C/10yr, 0.35°C/10yr and 0.36°C/10yr, respectively. The seasonal maximum, minimum and mean temperature significantly increased in the spring, autumn and winter seasons during 1960-2015. Although the summer temperatures also increased at some extent, only the minimum temperature showed a significant increasing trend. Meanwhile, the highest rate of increase of seasonal mean temperature occurred in winter (0.24°C/10yr) during 1960-2015 and spring (0.50°C/10yr) during 1980-2015, which indicated that the significant warming trend for the whole YRB could be attributed to the remarkable temperature increases in winter and spring months. However, both the annual and seasonal warming magnitudes showed large regional differences, and a higher warming rate was detected in the eastern YRB and the western source region of the Yangtze River on the Qinghai-Tibetan Plateau (QTP). Additionally, annual precipitation increased by approximately 12.02 mm/10yr during 1960-2015 but decreased at the rate of 19.63 mm/10yr during 1980-2015. There were decreasing trends for precipitation in all four seasons since 1980 in the YRB, and a significant increasing trend was only detected in summer since 1960 (12.37 mm/10yr). Overall, a warming-wetting trend was detected in the south-eastern and north-western YRB, while there was a warming-drying trend in middle regions.