Analysis Of Climate Change Characteristics Over Southwest China Under The Background Of Global Warming

Based on the monthly, annual temperature, precipitation data at 135 stations from 1961 to 2005 in southwest China, and in accordance with altitude and topographical features, southwest China is divided into four regions. The linear trend method, conventional statistical methods and R/S analysis method in fractal theory are used to estimate trends, continuing strength, interdecadal variation characteristics, regional characteristics and the spatial distribution characteristics of temperature and precipitation in southwest China, while the abrupt change of all time series are tested. The fractal dimension, saturated embedding dimension and Kolmogorov entropy of each time series are figured out, and educed the effective freedom degrees number of dynamic system, the least number of independent state variables for the dynamic system model, the predictable time length of chaotic systems. The results showed that:1. The long-term changes of annual mean temperature is significant upward trend, and average annual precipitation is a weak downward trend in southwest China. Their H-indexes are greater than 0.5, indicated that the continuing strength is stronger, and belived that the annual average temperature will continue to rise, while the annual precipitation will continue to maintain a weak downward trend.2. The warming of the annual average temperature is relatively obvious during 90 years and after 2000, seasonal temperatures are also reflected in a clear upward trend, and the warming in winter is faster than in summer. The growth of precipitation in dry season is greater than in wet season.3. According to the spatial distribution of the linear trend, we can see that the linear trend of annual average temperature are more obvious upward trend in most areas, the largest warming regional are Tibet, western Sichuan and western Yunnan. In the northeastern Sichuan and the junction both Sichuan and north Yunnan, there is a downward trend in temperatures, and have a clear cooling centers, indicated that there is some existence of non-synchronous with global warming. The spatial distribution of precipitation trends also showed that the linear trend is greater in West than in East, the increasing centers are located in Tibet and western Sichuan region. 4. The time series of both annual average temperature and precipitation in southwest China showed the fractal features. Their effective freedom degrees number of dynamic system are 7, the least number of independent state variables for the dynamic system model are 3, the predictable time length of chaotic systems are 16 and 8 years.5. For each district, zone-Ⅰ(altitude≥2000 m), zone-Ⅱ(1000m≤altitud<2000 m), zone-Ⅲ-1 and zone-Ⅲ-2 (altitud<2000 m), their long-term changes of annual mean temperature is significant upward trend, and there is a strong continuity, particularly in zone-Ⅰ, warming trend is most apparent, in addition to the spring, the warming rates of others quarters are higher or closer than national means during last 50 years, followed by zone-Ⅱand zone-Ⅲ-2. It has shown in each district that the warming is faster in winter than in summer. The summer in zone-Ⅲ-1 is also showing a weak cooling trend. In addition, the annual precipitation of zone-Ⅰhave shown the upward trend, others appeared the weak downward trend, and there is a strong continuity. For all districts, the growth of precipitation in dry season is greater than in wet season.6. For all districts, these time series of temperature and precipitation in each season have shown the fractal features. Their effective freedom degrees number of dynamic system are 5-8, the least number of independent state variables for the dynamic system model are 3-4, the predictable time length of chaotic systems are 7～17 years.7. The results of abrupt test:the abrupt time zone of annual average temperature in southwest have existed since 1998, but did not detect the start time, while the reduced abrupt point of annual average precipitation have tested at 1987, the increased abrupt point at 1996, its abrupt time zone have not detected. For each districts, the abrupt time zone of annual average temperature have detected, zone-Ⅰis after 1987, zone-Ⅱis after 2000, zone-Ⅲ-2 is after 2003, zone-Ⅲ-1 have not detected, increased abrupt point are none,1995,2001 and 1997. The abrupt time zone of annual average precipitation are after 2000, none, after 1996 and none, their increased abrupt point are 1997,1998, none and 1962, reduced abrupt point are 1969, 1968 and 2002,1984,2003.