关键词: 长江下游, 越冬季节, 冷暖, 长期变化, 大型环流, 低频振动

Abstract: This paper analyzes, by means of records of monthly mean temperature in the last 112 years (1873-1984) and the monthly mean sea level pressure fields in the last 110 years (1871-1980), the long-term change in temperature from colder to warmer during overwintering season in Chang Jiang (Yangtze River) Lower Reach, represented by Shanghai data, and the low-frequency fluctuations of large-scale pressure circulation system, associated with the former. It is discovered that in the last 100 years or so, there are similar long-term variation trend in cold warm between early winter (November and December) and late winter (February). The general feature of it is that the temperature in the three months presents itself an increase in tendency: in early 50 years or so there is colder period, namely, the temperature in average of this period is lower than the average temperature of last 100 years, and in late 50 years or so there is warmer period, namely, the temperature in average of this period is higher than it. The transition from colder period to warmer occurred in year 1930 or so.The cold valley──a phase of extreme low temperature in colder period and the warm peak──a phase of extreme high temperature in warmer period are all counted up. The advantages and disadvantages of cold valley or warm peak are also analysed in agriculture production.The change of large-scale circulations in October, which is corresponding to the change from colder to warmer period as above, is presented that the strength and position of Asia Continental cold high show a low-frequency fluctuation, and so does the strength of Northern Pacific. It can be considered that the changes of the both large-scale circulations occur in October and it impacts on East Asian climate in overwintering season as that, a notable trend variation exists just in the starting of the winter monsoon moving forward during autumn-winter in East Asia. The feature of these trend variations can be described that it is prevailing in early 50 years or so, the colder period, that Asia Continental cold high is stronger and eastward; Northern Pacific high is weaker, namely, the early winter monsoon in East Asia is stronger. However, there is an inversely prevailing in late 50 years or so, the warmer period, namely, Asia Continental cold high is weaker and westward; Northern Pacific highis stronger; the early East Asian winter monsoon is weaker correspondingly.In addition, the long-term change of temperature in January is different from that in above three months, November, December and February. The large-scale circulation, associated with the temperature in January, is correcpondingly different too.The representation and application of Shanghai temperature for Chang Jiang Lower Reach are discussed. It is indicated that the extreme temperature in the west region of Shanghai is lower than that in Shanghai

Key words: Chang Jiang (Yangtze) Lower Reach, overwintering season, cold/warm, long-term change, large-scale circular/on, low-frequency fluctuation