The nonlinear variation of annual average temperature in the Yangtze Delta and its correlation with global oscillations

Climate change has been a major issue for scholars under the background of global warming. Yangtze Delta is one of major economic regions in China. How the temperature of the Yangtze Delta changes in the past decades and if this change has some relation to global climate change? To answer these questions, this paper tries to find the relationship between the temperature's change in the Yangtze Delta and five global oscillations from the point of multiple time scales, by using wavelet regression analysis method. The main findings are as follows: (1) at the larger time scale, like 32-year and 16-year scale, the annual average temperature in the Yangtze Delta presents an increasing trend. But at 8-year and 4-year scale, the temperature fluctuates obviously, and the 4-year scale is much more obviously. (2) The annual average temperature change in the Yangtze Delta associates closely with 5 global oscillations and the correlation becomes better while the time scale enlarged. Moreover, we could find that four oscillation indices (NAOI, PDOI, AOI and AAOI) have an active correlation with the annual average temperature in the Yangtze Delta. But for SOI, the correlation is negative. The reason for these is because of their different formations. Because latitude circulation is the main reason, the oscillations (NAO, AO and AAO) have closer association with the temperature in the Yangtze Delta.