An Updated Analysis Of The Climate Change In China In Recent 50 Years And The Climatology Of Summer Rainfall In China

Some new features of the climate change in China in recent 50 years is shown by investigating the characteristics of the change of temperature, precipitation, relative humidity, wind speed and sea level pressure based on the 740 stations daily data in China, which is the most complete station data set in China processed by National Meteorological Center recently. On the basis of long-term mean summer rainfall in China, the onset, progression and withdraw of rainy season in China are analyzed, as well as the LFO climatology of summer rainfall over China is discussed. The major conclusions of this study are as follows:(1) The average temperature in the whole country has been increasing most obviously since 1980's in recent 50 years. Also, the temperature in Southwestern China has been increasing since 1990's after a long-term low temperature period. However, the temperature in Upper-middle Yangtze basins shows the decreasing trend evidently in summer.(2) Rainfall in China oscillates on a ten-year scale. There is an apparent rainfall distribution of "floods in the south and droughts in the north" in 1990's, Total amount of rainfall in China has the slight decreasing trend. However, the precipitation in summer has increased since 1990's, particularly in the south of Yangtze River and the Western Northwest China. At the same time, precipitation in North China has decreased greatly.(3) The change of relative humidity in the whole country is similar with that of precipitation. Taking account of the change in temperature and precipitation, it can be found that West China is becoming wanner and wetter, especially in Northwest China, while Northeast China and North China warmer and drier.(4) Wind speed has decreased evidently in the whole China, especially in winter and Western Northwest China, where average wind speed decreased by 29% or so, comparing the wind speed in 1990's and in 1950's.(5) Average sea level pressure has been getting higher in China, particularly in North China in winter. This kind of change is probably relative to wind speed's great decrease.(6) ENSO influences significantly China's climate. Each meteorological factor has different features in years when El Nino or La Nina happens.(7) Onsets of rainy seasons in the east part of China propagate from south to north, but things reverse in the west. Some 4 pentads after onsets, rainy seasons in China reach crest. Rainy seasons may last 1 to 3 months. Rain bands shaped by rainy seasons are different between in the east and in the west part of China, in which the former is continuous from south to north, while the later are two relativelyindependent rain bands.(8) Climatologically, 30-60 LFO is more apparent in South China while 10-20 LFO is dominant in North China. There is no LFO in the west part of China. But in the east, 30~60-day low frequency propagates toward north and west and 10~20-day low frequency spreads to south from mid-latitude as well as to east from 90" E. 10-20-day and 30-60-day low frequent rain band centers, located in South China, Upper-middle Yangtze basins, Northeast China, North China and the west part of China, are all important parts of Asian summer monsoon rainfall.