The effects of spring Eurasian snow cover on Northern Hemispheric atmospheric circulation and summer rainfall in China have been explored using the latest version of general circulation model (GCM) CAM3.1 developed by NCAR. Model results show that snow anomaly in spring can cause the thickness anomaly in the troposphere and trigger a wave train of geopotential height anomalies from western Europe extending to East Asia at 500 hPa by changing the distribution of the soil moisture and temperature in succeeding summer. As a result, 500 hPa height anomalies with opposite sign are located in southern and northern China. Meanwhile, summer precipitation anomaly in southern China is out of phase with that in northern China. The results demonstrate that spring Eurasian snow cover anomaly acts as an important factor affecting the distribution of summer rainfall in China.

The distributive pattern of the alpine ecosystem in the source regions of the Yangtze River and Yellow River was analyzed based on the aerial photo in 1967 and the TM remote sensing data obtained in 1986 and 2000; the relationship of changes in the alpine ecosystem with climate was then analyzed based on the climatic observation data; and the effect of changes in the land surface terrestrial ecological system on the hydrological process of the river source region was analyzed using runoff coefficient, rainfall-runoff relationship, flow duration curve, and water conservation index etc. Results show that the alpine ecosystem persistently degraded over the last 40 years, the area of high coverage alpine meadow and alpine steppe decreased, while wetland shrunk and desertified meadow increased. The permafrost thawing due to temperature rise is one of the main factors which led to the degradation of the alpine ecosystem. The changing of temperature was significantly negatively correlated with the areas of high coverage alpine meadow, alpine steppe and alpine swamp meadow. The degradation of land surface terrestrial ecosystem has significantly affected the hydrological process in the source regions; under the condition that precipitation changed slightly, the relation between the persistent decline of runoff coefficient and precipitation-runoff attenuated, the frequency of flood increased, and the outflow and water conservation index persistently decreased. It is urgent to pay much attention to cope with the climatic change and to sustain the alpine ecosystem's function in the source regions.

Based on the temperature and precipitation observation data during 1961-2007 and projection during 2011-2060 by the ECHAM5/MPI-OM model, changing tendencies of temperature and precipitation in the Pearl River basin were analyzed. The results show that the annual average air temperature increased by 1.8℃ during the past 47 years, with a maximum increase in winter and a minimum increase in summer. Annual temperature would rise by 1.9℃ under the SRES-A1B scenario in the next 50 years (2011-2060); at the same time, inter-annual variability would enhance. Seasonal temperature would rise most significantly in autumn and most weakly in winter under the SRES-A2 and SRES-B1 scenarios; however, under the SRES-A1B scenario, the opposite is true. In the past 47 years, except that autumn precipitation decreased, spring, summer, winter and annual precipitation increased. Precipitation would overally increase about 230 mm in 2011-2060 by the ECHAM5/MPI-OM model under the SRES-A1B scenario. However, the seasonal percentages of annual rainfall would not change obviously. On the other hand, the inter-annual variability of annual and winter precipitation would enhance, but that of autumn precipitation would weaken.

Based on observed temperature and precipitation data from 1961-2000 and climate projection in the first 50 years of the 21st century by ECHAM5/MPI-OM, changes of annual temperature and precipitation in the Songhua River basin were analyzed. The results show that annual temperature has increased dramatically since the beginning of the 1980s under global warming, but annual precipitation had no significant change trends except small decadal variations from 1961 to 2000. Relative to 1961-1990, annual temperature will increase significantly in the first 50 years of the 21st century, with an increment of more than 1℃ before the end of the 2040s; and annual precipitation will show no obvious trends in the first 50 years of the 21st century, but winter precipitation and temperature will increase, and spring precipitation will also increase.

This study investigated future spatial distribution of dryness/wetness in China during the first 50 years of 21st century according to standardized precipitation index (SPI) which was calculated from the monthly precipitation data projected by the ECHAM5/MPI-OM climate model under the SRES-A2 (high emission), SRES-A1B (mediate emission) and SRES-B1 (low emission) scenarios of anthropogenic greenhouse gas emissions. The results show that the projected dryness/wetness pattern in the future 50 years under the SRES-A2 scenario is similar to the observed one in 1961-2000, i.e. there is a SW-NE oriented drought belt from Southwest China to Northeast China; but the projected patterns under the SRES-A1B and SRES-B1 scenarios are different, especially under the SRES-B1 scenario, a north-wetness-south-dryness pattern was projected. The area of drought was projected to weakly increase under the SRES-A2 scenario but to decline under the SRES-A1B and SRES-B1 scenarios. Spatial distributions of the frequency of droughts were also projected to be different from each other.

Based on the statistical information of meteorological and agricultural inundation disaster data from 1951 to 2006, the characteristics of the spatial and temporal distribution of the occurrence frequency of rain-waterlogging process (defined as 10-day accumulated rainfall ≥250 mm (150 mm in Northwest China) or 20-day accumulated rainfall ≥350 mm (250 mm in Northwest China)) in the Yellow River and the Yangtze River basins were analyzed, the results show that rain-waterlogging in the two river basins has continually increased during the last 50 years, especially after the 1980s due to the impact of climate change; inundated cropland areas and economic losses showed increasing trends. The rain-waterlogging range was larger and the occurrence frequency of rain-waterlogging was higher in the Yangtze River basin in comparison with the Yellow Rive basin. Summer was a season in one year when the occurrence frequency of rain-waterlogging was the highest and its range was the largest due to the influence of rainstorms. Since the end of the 1980s, rainstorm disaster has distinctively increased in the Yellow Rive basin, and since the early 1980s inundated cropland area has remarkably increased in the Yangtze River basin. The inundation ratios of rain-waterlogging in the two river basins gradually increased from the upper reaches to lower reaches, and the impacts of rain-waterlogging disaster were relatively larger in the middle and lower reaches of the Yangtze River basin.

Based on meteorological data and social-economic statistical data, influence factor analysis of urban residential cooling energy consumption in Beijing was performed. Some conclusions are drawn: under given architecture design standard, four factors, including cooling intensity, urban population, per capita urban housing area and air conditioner ratio, directly affect the urban residential cooling energy consumption by air conditioners. In general, the amount of cooling energy consumption tends to increase inevitably because the later three factors increase continuously. Among four factors, climate is the only one that can act to save energy sometimes. In Beijing, the speed of urbanization is large, the contribution of the air conditioner ratio to increase in cooling energy consumption ranks the first in most years.

The analyses of high wind days in Yingkou Prefecture from 1971 to 2000 indicate that days of wind speed above 6 and 8 categories in one year reduced successively from spring, winter, autumn to summer. Annual days of wind speed above 6 and 8 categories in the recent 30 years (1971-2000) reduced at a linear change rate of 27.4 d /10a and 6.7 d /10a, but in the recent 20 years (1981-2000), the annual high wind days reduced at a linear trend of 13.1 d/10a and 6.1 d/10a, respectively, suggesting that the reducing trends of high wind days in the recent 30 years are more significant than those in the recent 20 years; and the reducing trends in spring and early summer (March to June) are more remarkable than those in autumn and winter. The weakening of local general circulation associated with the reduction in diurnal range might be one of the reasons for the decline in high wind days in Yingkou Prefecture.