Primary Character Of Climate Change And The Research On Extreme Weather-climate Events In Chongqing

Based on the daily precipitation and air temperature records of 34 stations over 1961-2008 period, the climatic variations tendencies of yearly and seasonal air temperature, precipitation, snow fall, hail, thunder and fog during last 48 years are investigated.Also, the cause of summer flood/drought and high-temperature extremes in Chongqing are analyzed by using NCEP/NCAR reanalysis data and the characteristics of circulation over China.During last 48 years in Chongqing, the precipitation amount and precipitation days tended to decrease. The variations tendencies of seasonal followed the yearly trend in spring and autumn, but had a slight rise tendency in summer. The days of rainstorm increased in southeast, western by west and partly northeast. Considering different climatic zones, the precipitation in north subtropics had similar changing trend to that of the average condition of Chongqing, the high peak of precipitation came later in mid-subtropical zone and mid-temperate zone. The light precipitation days and rainless days in all three climatic zones had similar trend, the days of heavy rain in mid-temperate zone showed up a slight uptrend, and the downtrend of rainstorm days in mid-subtropical is much more significant than that in other two climatic zones.The temperature variations appeared uptrend. The increase rate of minimum temperature was relatively higher. The increase rate of temperature was comparatively higher in spring and autumn, not that obvious in summer. The temperature variations of the average, the maximum and the minimum followed the uptrend in all three climatic zones. The increase speed of average temperature in north subtropics zone was equal to that in the other two climatic zones. The increase speed of maximum temperature in mid-subtropical zone and mid-temperate zone was faster than that in north subtropics zone. The increase speed of minimum temperature in mid-subtropical zone and north subtropics zone was clearly faster than that in mid-temperate zone. The temperature variations in Chongqing had salient phased features. It opposed the trend of the global and the northern hemisphere in 1971-1996 period, but followed the trend afterwards.It's provided with apparent interannual change of the summer flood/drought extreme events in Chongqing.lt became drought during 1960s and 1970s but flood in the early 1980s period,It showed xerasium but relatively wet since late 1980s.Since early 21th, the east area of Chongqing was dry in totality, but turned to wet recently. When the Western Pacific Subtropical High (WPSH) and the ridge line of the South Asia High shift northward (southward), it was likely to cause drought (flood) in Chongqing.The floody/drought also depends on water vapor conveyance, the water vapor convergence and the influence of activities of northen cold air.The extreme high-temperature in summer and the days of high-temperature tended to increase, following the trend of the average temperature variations, appeared certain phased difference. The extreme high-temperature was slightly higher during 1960s and 1970s with narrower fluctuation. In 1980s, the extreme high-temperature was lower than the yearly average of extreme high-temperature and the days of high-temperature were comparatively less. Since 1990s the extreme high-temperature was clearly higher with wider fluctuation. Judging from analyses of circulation system, Western Pacific Subtropical High (WPSH) and the South Asia High are the most important causes of the high temperature in Chongqing, besides of orographic influence, geographic location and human activities.