Using the snow cover fraction(SNC) output from eight WCRP CMIP3 climate models under SRES A2,A1B,and B1 scenarios,the future trend of SNC over East Asia is analyzed.Results show that SNC is likely to decrease in East Asia,with the fastest decrease in spring,then winter and autumn,and the slowest in summer.In spring and winter the SNC decreases faster in the Qinghai-Xizang Plateau than in northern East Asia,while in autumn there is little difference between them.Among the various scenarios,SRES A2 has the largest decrease trend,then A1B,and B1 has the smallest trend.The decrease in SNC is mainly caused by the changes in surface air temperature and snowfall,which contribute differently to the SNC trends in different regions and seasons.
An overview of basic research on climate change in recent years in China is presented. In the past 100 years in China, average annual mean surface air temperature (SAT) has increased at a rate ranging from 0.03℃ (10 yr)-1 to 0.12℃ (10 yr)-1 . This warming is more evident in northern China and is more significant in winter and spring. In the past 50 years in China, at least 27% of the average annual warming has been caused by urbanization. Overall, no significant trends have been detected in annual and/or summer precipitation in China on a whole for the past 100 years or 50 years. Both increases and decreases in frequencies of major extreme climate events have been observed for the past 50 years. The frequencies of extreme temperature events have generally displayed a consistent pattern of change across the country, while the frequencies of extreme precipitation events have shown only regionally and seasonally significant trends. The frequency of tropical cyclone landfall decreased slightly, but the frequency of sand/dust storms decreased significantly. Proxy records indicate that the annual mean SAT in the past a few decades is the highest in the past 400-500 years in China, but it may not have exceeded the highest level of the Medieval Warm Period (1000-1300 AD). Proxy records also indicate that droughts and floods in eastern China have been characterized by continuously abnormal rainfall periods, with the frequencies of extreme droughts and floods in the 20th century most likely being near the average levels of the past 2000 years. The attribution studies suggest that increasing greenhouse gas (GHG) concentrations in the atmosphere are likely to be a main factor for the observed surface warming nationwide. The Yangtze River and Huaihe River basins underwent a cooling trend in summer over the past 50 years, which might have been caused by increased aerosol concentrations and cloud cover. However, natural climate variability might have been a main driver for the mean and extreme precipitation variations obser
This paper describes the construction of a 0.5°×0.5°daily temperature dataset for the period of 1961- 2005 over China's Mainland for the purpose of climate model validation. The dataset is based on the in- terpolation from 751 observing stations in China and comprises 3 variables: daily mean,minimum,and maximum temperature.The"anomaly approach"is applied in the interpolation.The gridded climatology of 1971-2000 is first calculated and then a gridded daily anomaly for 1961-2005 is added to the climatologY to obtain the final dataset.Comparison of the dataset with CRU (Climatic Research Unit) observations at the monthly scale shows general agreement between the two datasets.The differences found can be largely attributed to the introduction of observations at new stations.The dataset shows similar interannual vari- ability as does CRU data over North China and eastern part of the Tibetan Plateau,but with a slightly larger linear trend. The dataset is employed to validate the simulation of three extreme indices based on daily mean,minimum,and maximum temperature by a high-resolution regional climate model. Results show that the model reproduces these indices well.The data are available at the National Climate Center of China Meteorological Administration,and a coarser resolution(1°×1°)version can be accessed via the World Wide Web.
The regional climate change index(RCCI)is employed to investigate hot-spots under 21st century global warming over East Asia.The RCCI is calculated on a 1-degree resolution grid from the ensemble of CMIP3 simulations for the B1,A1B,and A2 IPCC emission scenarios.The RCCI over East Asia exhibits marked sub-regional variability.Five sub-regional hot-spots are identified over the area of investigation:three in the northern regions(Northeast China,Mongolia,and Northwest China),one in eastern China,and one over the Tibetan Plateau.Contributions from different factors to the RCCI are discussed for the sub-regions. Analysis of the temporal evolution of the hot-spots throughout the 21st century shows different speeds of response time to global warming for the different sub-regions.Hot-spots firstly emerge in Northwest China and Mongolia.The Northeast China hot-spot becomes evident by the mid of the 21st century and it is the most prominent by the end of the century.While hot-spots are generally evident in all the 5 sub-regions for the A1B and A2 scenarios,only the Tibetan Plateau and Northwest China hot-spots emerge in the B1 scenario,which has the lowest greenhouse gas(GHG)concentrations.Our analysis indicates that sub- regional hot-spots show a rather complex spatial and temporal dependency on the GHG concentration and on the different factors contributing to the RCCI.
