Temperature Change In The Yangtze River Delta Of China And Its Response To Atmospheric Circulation Factors

Temperature change is influenced by natural factors and human activities. Fluctuation in atmospheric circulation is one of the important driving factors of regional temperature change. Atmospheric circulation not only has decadal and inter-annual changes, but also it has seasonal change. There are seasonal differences existing in atmospheric circulation. The position and intensity of semi-permanent atmospheric activity center are changed in different seasons, which affectes the regional temperature, the climate system and the ecological environment. The temperature data in 29 meteorological stations of Yangtze River Delta (YRD) and time series data of five atmospheric circulation factors from 1960 to 2010 are used in this paper. Five atmospheric circulation factors are North Atlantic Oscillation (NAO), North Pacific Oscillation (NPO), Arctic Oscillation (AO), Antarctic Oscillation (AAO) and Siberian high (SH). From the annual and seasonnal scales, the temporal variation characteristics of the temperature and the change trend features of atmospheric circulation factors are analyzed. And the correlation between them is studied further. The main conclusions are as follows:The interdecadal variation of annual, spring, summer and autumn mean temperature in YRD show the downward trends before 1980s. And it becomes fairly warming after 1980s. While the winter mean temperature shows the fluctuations in the warming trend. The change trends of annual and seasonal temperature are becoming warming significantly for nearly 50 years. The contribution rate of annual temperature change is the maximum in winter, then in spring and autumn, and the minimum in summer. The abrupt changes in the annual and seasonal temperature appear basically in 1990s. In study area, the annual mean temperature is higher in southern and lower in northern. The spring and summer mean temperature show the different spatial distribution with higher in southwest and lower in northeast. The spatial distribution of autumn and winter mean temperature is higher in southeast and lower in northwest. Influencing by ocean, human activity and urbanization, spatial distribution patterns of the annual and seasonal warming trend show the higher warming extent in northern and lower warming extent in southern.For five atmospheric circulation factors, the annual index of NAO, NPO, AO and AAO display the significant rising trend, while the annual index change of SH isn’t obvious. In spring, NPO, AO and AAO indicate the uptrend evidently. The summer atmospheric circulateon indexes have a stronger trend except NAO. Only AO and AAO in automn have obvious increase. And NAO, NPO, AO and AAO winter index show the uptrend significantly. For nearly 50 years, the abrupt change of SH isn’t obvious. The abrupt change points of NAO, NPO and AO are detected in 1960s and 1970s basically. And AAO is in 1980s and 1990s. The abrupt change of temperature in YRD is later than the atmospheric circulation factors.Controling the other four atmospheric circulation factors, this paper analyze the correlation between an atmospheric circulation factor and temperature change. The correlation between mean temperature in summer and atmospheric circulation are weak. The summer mean temperature has close relation with NPO. The annual mean temperature has significant relation with AAO. The correlation between spring mean temperature and AAO, SH are obvious. The automn mean temperature has close relationship with NPO and AAO. The winter mean temperature has significant correlation with SH and AAO. From annual and seasonal scale, AAO and SH have close relationship with the temperature of YRD. The influence of NAO and AO are not obvious.