Quantitative indices were chosen to analyze the characters of meteorological disasters caused by the extreme synoptic process in early 2008 over China by virtue of the daily temperature, precipitation and weather phenomena dataset at 606 stations in China from 1 January of 1951 to 29 February of 2008. Unusually severe meteorological disasters, including low temperature, heavy snowfall and freezing, happened in the mid-lower reaches of the Yangtze River valley and the areas to the south of the Yangtze River from the middle of January to the first decade of February. In the disaster areas, the maximal persistent low temperature days, snowy days and the freezing days all broke the records since 1951, showing a centennial probability. Especially, board extents, the long persistence and severe damages characterized this synoptic process in early 2008 over China, resulting in heavy losses in many aspects of the social life of China, such as the electric power, the transportation, the agriculture, the forestry, the daily life of the people and so on.

China suffered from severe climate in January 2008 when low temperature, glaze and heavy snowfall significantly struck the transportation, communication and electricity transmission in the south of the country. It stimulates great interest in studying the severe winters. Climatic data show that negative temperature anomaly of this winter probably was moderate, near or less than the threshold of cold (-1.5℃) and much less than that of severe (-2.5℃) winters. However, this has been the coldest one since 1977. The frequencies of type-1a (Rainbelt lies in the eastern China) and type-4 (Rainbelt lies in the north of China) rain patterns in summer, following a severe winter, were greater than their normals, as indicated by the chronology of the last millennium. EOF analysis suggests that the changes in temperature in January of 2008 appeared as a part of interannual variability, which means that probability of occurrence of similar winter pattern in the near future is low.

The trends in daily frequency of maximum and minimum temperatures over the last 44 years were analyzed using the daily maximum and minimum temperature data from 1961 to 2004 in Ningxia, by classifying the temperatures into 38 levels. It was found that daily frequency of maximum temperature below 0℃ decreased while that over 30℃ increased. The annual average minimum temperature increased, meanwhile the daily frequency of extremely low temperature also increased by 350%-275% in 1991-2004 relative to 1961-1990. Therefore, the extreme trends of temperature are obvious in Ningxia.

Based on the daily mean temperature, daily maximum temperature, daily minimum temperature and daily precipitation data at 30 stations in Henan Province from 1957 to 2005, the spatial and temporal characteristics of changes in weather and climate extremes were studied. The main conclusions are summarized as follows: both the numbers of heavy rain days and the extreme intense precipitation events increased, and long dry spell events also increased, but their increasing tendencies were not distinct. There were obvious differences in trends of the extreme intense precipitation and the number of heavy rain days between the south and north parts of Henan Province. The extreme hot days increased, while the extreme cold days decreased, and the tendency of warm winter was remarkable. The days of maximum temperature ≥35℃ and the days of minimum temperatures ≤0℃ significantly decreased. There were very good consistency in the spatial distribution of the extreme temperature events.

Outputs of control experiment and CO₂ increasing experiment from GFDL-CM2.1 coupled model were used to evaluate the effect of CO₂ doubling on the changes in extreme precipitation in China. The results show that CO₂ doubling would cause a prominent increase of annual extreme precipitation amount and precipitation intensity in eastern China, and a prominent increase of annual extreme precipitation frequency except in the south part of North China. Furthermore, CO₂ doubling would bring about severe influence on the distribution of extreme precipitation in spring and summer, leading to the increases of extreme precipitation amount and precipitation intensity, and extreme precipitation frequency in the most parts of eastern China. However, the annual precipitation in the south part of North China and in the mid-lower reaches of the Yangtze River both decreased, due to the decrease of wet days in spring and summer as well as the decreases of light rain and moderate rain.

Temperatures from early March to early July in 1961-2004, at 10 stations in the Yellow River irrigation region of Ningxia were analyzed. The results show that the temperature during the growing season of spring wheat increased obviously. The t-test indicates that the temperature abrupt change occurred in 1989 with a rise of 0.7℃. Over various phenological stages of spring wheat, the temperature increased, but it didn't exceed the suitable range. The temperature-sensitive index of spring wheat was positive from middle March to early April and from May to early June, therefore the climate warming over these periods was favorable to wheat growth. The temperature-sensitive index was negative from middle June to early July and from middle to late April, thus the climate warming over these periods was unfavorable to wheat growth. Overally, the contribution of climate warming to wheat yield was -2.6%.

Based on the summer precipitation data in eastern China during 1880-2006 and at 160 stations in China during 1951-2006, and 500 hPa geopotential height data in the North Hemisphere during 1951-2006, the decadal variation law of summer rain-pattern was explored. The results show that there existed obvious 20-to 40-year period in the eastern monsoon region and the western region, and about 15-year period in the northeastern region of China. Additionally, the main features of geopotential heights at 500 hPa in the Northern Hemisphere for different summer rain-patterns were analyzed. Results show obvious differences of East Asian circulation for four rain-patterns in the eastern monsoon region, and the basically opposite allocation of Eurasia circulation pattern between the two rain-patterns in the western region and the two rain-patterns in the northeastern China.

The change of precipitation in Hunan Province since recent 46 years was analyzed by using linear regression, abrupt change analysis and wavelet analysis. The results showed that the annual precipitation increased at a climatic tendency of 21.8 mm/10a. However, the 11-year running mean curve showed that it will decrease in the future. Precipitations in spring and autumn were decreasing in most of the areas, while summer and winter precipitations both had increasing trends. There existed a wetter trend in summer and winter in Hunan Province in the last 46 years. The abrupt change occurred in summer and in winter during the early 1990s. Generally, both annual precipitation and seasonal precipitation presented four kinds of periodic change.

Based on the observational data of daily fog and visibility at 300 national meteorological observatory stations of China during the period of 1961-2005, spatially and temporally distributive climate characters of fogs of various categories were analyzed through regional division. The frequencies of fog generation and duration in each decade were also calculated. Results show that the fog area was smaller when the visibility of the fog was small. Fog frequencies in most regions generally displayed a evolutional trend of less (the1960s)-more (the 1970s-1980s)-less (since the 1990s) fog days, however, super-dense fog days abruptly increased in the 1970s over the Yangtze River valley and the eastern coastal region. Fogs mostly occurred during 06:00-08:00 o'lock in inland and south coast areas, and 20:00-21:00 o'lock in eastern China and the east coast region. Fogs generally lasted for less than 3 hours in most regions; and those with a duration of more than 12 hours mainly concentrated in the coastal areas, North China, and the Longdong-Shanxi area, and its maximum frequency occurred in the coastal areas, the Sichuan Basin and Yunnan-Guizhou Plateau in the 1990s.

The effects of sulfate aerosols over China on East Asian summer monsoon and precipitation were investigated using the latest version of general circulation model (GCM) CAM3.0 developed by NCAR/UCAR, coupled with an off-line aerosol assimilation system. The model results show that sulfate aerosols over China could bring about an extra global radiative force of -0.25 W/m². In most of China ( about the north of 25°N), the surface temperature universally drops while sea surface temperature increases, which drops the temperature difference between sea and land so that it weakens the East Asian summer monsoon and the precipitation in China. Especially, the cumulus cloud precipitation decreases greatly since sulfate aerosols mainly suppress the convection and cumulus cloud precipitation over China.

The aerosol samples were collected in Hubei University during winter-spring time (from November 2006 to April 2007) and their elemental composition was obtained. The results show that the atmosphere aerosol pollution is light, and the aerosol elements mainly come from the crust element, representative artificial pollutant elements and the salts element in this area. Results of the factor load and correlation analysis show that atmosphere polluants are mostly from construction source, transportation source, and the dining source around the Hubei sci-tech education area.

Morlet wavelet analysis was used to reveal the periodical regulations at different time scales of the temperature time series of Northeast China in the last 100 years. Based on the monthly and annual temperature data at Harbin, Shenyang, Changchun, and Dalian weather stations from 1905 to 2005, the periodic oscillation and the point of abrupt change at different time scales in the temperature time series were discovered, and the main periods for each serial were determined. The research results show that the temperature of Northeast China had an increasing trend of 0.165/10a in the past 100 years, and there were periodical variations of multiple time scales, which displayed different traits at different phases. There were obvious periodic oscillations of 2-3 a, 8-12 a, 20-25 a and 45 a periods for the seasonal and annual temperature variations.