利用高分辨率的气象台站观测资料、再分析资料、卫星遥感资料等,结合高分辨率区域气候模式模拟,对西北地区以及祁连山、天山、六盘山和三江源等试验区的降水场、气流场、水汽场等时空特征开展了研究.结果表明:精细化的降水资料能够刻画出西北试验区复杂地形条件下的降水场时空特征,研发的小时降水融合算法对西北地区高频降水分析是有效的;涝年,由于高原抽吸作用,试验区受低层形成的辐合气流所控制,容易形成降水;旱年,高原地表不存在大范围的辐合区,试验区被干冷的偏北风所控制,不利于成云降水.利用模式资料,分析了西北地区及四个试验区水汽场月、季、年气候特征,分析了水汽来源、大气可降水量、水汽收支情况以及年际变化情况.对MODlS和FY卫星反演的水汽产品进行了校准,并对西北地区水汽含量的气候特征进行了分析.

以我国大陆2416个气象观测站点组成的站网为参考,以观测序列的相关性表示对气候变化信号的监测能力,分析不同地区单位经纬度网格内站点数对信号监测能力的影响,得到特定监测能力要求下所需的站点数,为大尺度气候观测站网的站点设置提供科学依据.对2.5°×2.5°网格来说,当要求子集站网气温序列与标准站网气温序列相关系数超过0.99和0.95时,所需的站点数分别为750和377；当要求子集站网降水量序列与标准站网降水量序列的相关系数超过0.95和0.90时,需要的站点数分别为670和417.对2.5°×3.5°和5.0°×5.0°经纬度网格的分析发现,对站点数量要求较高的区域大部分是地形过渡区,一般来说,降水量观测对站点密度的要求高于气温.

The US Climate Reference Network(USCRN) consists of 114 stations developed,deployed,managed, and maintained by the National Oceanic and Atmospheric Administration(NOAA) in the continental United States for the express purpose of detecting the national signal of climate change,focusing solely on precipitation and temperature.The vision of the USCRN program is to reduce uncertainty and error range envelopes in producing the most precise in situ precipitation and temperature records possible,and to do it with the fewest possible stations located in areas of minimal human disturbance and with the least likelihood of human development over the coming 50-100 years.And the key goal of USCRN is to reduce cli- mate uncertainty at the national level to a statistically insignificant level.That is,for precipitation climate uncertainty should be reduced by 95%and for temperature climate uncertainty at the national level should be reduced by 98%. China is in great need of a sustainable high-quality and long-term climate observation network,especially for areas without observations or with little information.Given the complexity of the network development, the overall structure of the climate network should be analyzed first.Therefore,the minimum number of sites and locations which are able to represent national climate characteristics of China are proposed, on the basis of the equilateral triangular mesh employed by the USCRN,in order to provide preliminary advice for adjustment and optimization of China Climate Reference Network.For the purpose of assessing the performance of the network in addressing this goal,the coefficient of determination(r~2) is used as the performance measure(PM).This PM is an assessment of how closely the current and past configuration of the network captures the true national temperature and precipitation signal as defined by an area-averaged time series of annual temperature and precipitation derived from 2416 China observing stations scattered across the continental China.The result is an explained variance that measures how closely the network's time series follows the true time series. Employing the USCRN standard that coefficient of determination exceeds 98%for precipitation and exceeds 95%for temperature,the 2416 stations in the conterminous China are investigated over the period of 1966-1995.Results indicate that China Climate Observing System should consist of at least 103 quasiuniformly distributed stations on a 3.0°equilateral triangular grid in order to reproduce inter-annual variability in temperature and precipitation all over China.And on this structure,the new network will be established after surveys,approval or disapproval assessment,test and evaluation periods for each site at each geographic location.On the other hand,China Climate Reference Network may be adjusted and improved on the basis of the existing observing systems.The optimized network consists of 229 quasi-uniformly distributed stations on a 2.0°triangular grid,founded by the existing 199 stations and 30 new-established stations.The expected new-established stations are mainly located in the southwestern part of the Qinghai-Tibet Plateau,where will be the key areas in the network establishment.Based on the actual history of USCRN establishment,the final climate observing network of China may be formed by less than 103 or 229 stations.

The changing trend of surface air temperature is a critical issue in studies of climate change detection and attribution. Due to the large urbanization effect,however,the current dataset of surface air temperature of many national meteorological stations can hardly meet the demands of climate change researches. Based on the station information from all the meteorological stations of China,the quality of the surface air temperature data is evaluated,and the reference surface stations are selected for the studies of urbanization effect and regional climate change detection.The principles and methodology for selecting the reference stations are discussed. A total of 138 stations across the country have been finally chosen as the reference surface air temperature stations.The data from these stations can represent best the baseline change in surface air temperature in China,and can be used for evaluating the urbanization effects on surface air temperature change of national stations. They can also be used directly for detecting the surface air temperature change in China.

Based on daily snowfall data during 1961-2006,temporal and spatial variation characteristics of snow storms in Heilongjinag Province,China,are investigated. The results show that snow storms in the eastern part of the province are more frequent than in the western part,and more snow storms are found in the mountainous areas than in the low-lying plain areas; the largest snow storm precipitation and frequencies occur in October and the next March,rather than in the mid winter; the largest snow storm intensity is in May and October of the transitional seasons; no significant linear trend of the snow storm frequencies in the past 46 years is found,though an insignificant increase occurs in the snow-prone eastern mountains in springtime; the variability of snow storm precipitation and frequencies significantly increase since the end of the 1970s. It is found that the snow storm frequencies and intensity obviously increase after 2000.

The surface air temperature records are obviously affected by the urbanization in China.The changes of the surface air temperature in Southwest China lag behind the countrywide changes,and air temperature records at some stations even show a dropping trend.It is important to understand the detailed features of surface air temperature change trends and the effect on them of urban development for different stations in that region.Using a data set of monthly mean temperature from 322 stations and corresponding population data,the surface air temperature change trends and the effect of urbanization development on mean surface air temperature records in towns and cities in Southwest China during 1961—2004 are analyzed.Quality control and inhomogeneity adjustment are made for air temperature data.On the basis of calculating air temperature change trends of towns and cities at national reference/baseline stations and rural stations,the extent and relative contribution proportion of urbanization effect are obtained by comparing the differences between the change trends of various stations and rural stations.Results show that there are warming trends of surface air temperature for each of the station groups.The warming rates in towns and cities,and national stations are greater than those in rural areas.In annual mean surface air temperature records in towns and cities,and national stations,urban warming rates are estimated as 0.086 ℃/10a and 0.052 ℃/10a respectively,and their contributions to overall annual mean temperature change are 57.6% and 45.3% respectively.Compared with the other regions in China,the warming rates of temperature and the urban warming rates in Southwest China are relatively low.Although the change of the average heat island intensity in this region is smaller than those in quite a number of regions in China,the contributions of urban warming to the overall mean temperature change trends are generally larger as a result of this feature.In addition,there are obvious season changes in urban warming rates,with the urban warming rates in autumn,spring or winter being the largest and second respectively,and that in summer the smallest.However,the largest contributions(100%) of urban warming to mean temperature in seasons are in spring,second to which are the contributions in summer of 73% and above.Those in autumn and winter are relatively smaller.

A dataset of 282 meteorological stations including all of the ordinary and national basic/reference surface stations of north China is used to analyze the urbanization effect on surface air temperature trends. These stations are classified into rural, small city, medium city, large city, and metropolis based on the updated information of total population and specific station locations. The significance of urban warming effects on regional average temperature trends is estimated using monthly mean temperature series of the station group datasets, which undergo inhomogeneity adjustment. The authors found that the largest effect of urbanization on annual mean surface air temperature trends occurs for the large-city station group, with the urban warming being 0.16 degrees C (10 yr)(-1), and the effect is the smallest for the small-city station group with urban warming being only 0.07 degrees C (10 yr)(-1). A similar assessment is made for the dataset of national basic/reference stations, which has been widely used in regional climate change analyses in China. The results indicate that the regional average annual mean temperature series, as calculated using the data from the national basic/reference stations, is significantly impacted by urban warming, and the trend of urban warming is estimated to be 0.11 degrees C (10 yr)(-1). The contribution of urban warming to total annual mean surface air temperature change as estimated with the national basic/reference station dataset reaches 37.9%. It is therefore obvious that, in the current regional average surface air temperature series in north China, or probably in the country as a whole, there still remain large effects from urban warming. The urban warming bias for the regional average temperature anomaly series is corrected. After that, the increasing rate of the regional annual mean temperature is brought down from 0.29 degrees C (10 yr)(-1) to 0.18 degrees C (10 yr)(-1), and the total change in temperature approaches 0.72 degrees C for the period analyzed.

A brief summary of some recent major research findings of temperature changes over China is made in this paper. The findings come mainly from studies on observed changes of surface air temperature of the last 55 years, 100 years and 1 000 years, and of free atmospheric temperature of the last 50 years, on attribution of surface air temperature change to anthropogenic forcing, and on effect of rapid urbanization on site temperature records and regional average temperature series. Based on a data set of national basic and reference stations, which have been quality-controlled and adjusted for in-homogeneity dominantly induced by relocation of stations, updated surface air temperature time series of the past 55 years and 100 years are established. The new temperature series show a generally more rapid warming than those obtained before, with the rates of change of annual mean temperature reaching 0.22 ℃/10 a. and 0.08 ℃/10 a respectively for the past 55 year and 100 years. The current warming is more significant in Northeast China, North China, Northwest China and the Tibetan Plateau, and the largest increase in temperature occurs in wintertime and springtime. The warming of the last 55 years is the result of more obvious rising of mean minimum temperature. The same change has happened for the country averaged annual extreme low temperature, while the annual extreme high temperature only experiences an insignificant rise. The frequency of temperature-related extreme events such as cold wave, cool summer, hot days generally tends to decrease or to be unchanged in the country as a whole. It is found, however, that significant effects of urbanization on recorded trends of temperature for single stations as well as for region averaged temperature series exist in a few regions investigated so far. In North China which experiences the most remarkable warming in the country, increase of annual mean temperature induced by urbanization for national basic and reference stations reaches 0.44 ℃ in period of 1961—2000, with an increasing rate of temperature of 0.11 ℃/10 a, accounting for 38% of the total warming rate as recorded by these stations. The effects of urbanization might have remained in the other regional changes in annual mean temperature. Regardless the remarkable warming of the surface, mid-to lower troposphere (850—400 hPa) witnesses no significant change in temperature, with a rate of change of only 0.05 ℃/10 a for the period of 1961—2004, and upper troposphere (300—150 hPa) and lower stratosphere (100—50 hPa) are experiencing a significant decrease in temperature at rates of -0.17 ℃/10a and -0.22 ℃/10 a respectively. A slight decrease in temperature is found for the entire troposphere in the period investigated. However, mid-to lower troposphere temperature is increasing in the past 20 years at a much higher rate than before, and the difference of change between surfaces and mid-to lower troposphere is getting smaller. A preliminary temperature series of the past 1 000 years has been reconstructed mainly based on tree ring data in the west and historical record in the east. It shows the warmth of period corresponding to the Medieval Warm Period (MWP) and the marked coldness of the Little Ice Age last from about 1400 to 1900. The warmth of the MWP, however, seems not so evident in the country as a whole as reported before, though the temperature in the end of 11th century and in the mid 13th century might have been higher than that of any decade of 20th century. It is still premature to answer the question of what cause the observed warming on the surface in China. Some evidence support the claim that it has mainly been induced by the increased concentration of greenhouse gases in atmosphere, but the influences of other factors like solar activities and the low-frequency oscillations of ocean-atmospheric system could not be ruled out at present.

The relationships between the atmospheric concentrations of several main contaminations, such as SO_2, NO_2 and PM_ 10, and several meteorological elements, such as wind speed, temperature and precipitation were analysed. Daily data of the contamination concentrations and the meteorological elements from November, 1995 to July, 2003 were used in this study. The results show that the changes of the contamination concentrations and the meteorological elements are significantly correlated in non-linear manners. So, the non-linear regressive equations were developed to describe the relationships. This development distinctly improved the correlations and made the errors of the regressive equations decrease.

文中对多个时间序列的平均序列中常常出现的异常摆动问题进行了探讨.结果表明,给定时间序列集中序列个数的多少会造成其所组成的平均序列的方差的变化,即序列个数越多,平均序列方差越小的可能性就越大,由此定义了方差增长率α.当给定方差增长率限定值α0并使其满足α≤α0时,可以得到最小序列个数m′0,且α0越大或序列间平均相关系数越大,所需要的时间序列数越少.这一结果可应用于气候变化研究中有关平均时间序列建立的研究中,亦可运用到其他相关研究领域.

文中从两个独立的假定导出了距平模式,即:假定年周期气候态为控制实际气候系统演化方程组的解或假定反映年周期气候态的基态量远大于反映气候扰动态的扰动量.第一个假定放宽了导出距平模式的条件,而在第二个假定下距平模式在一定的近似程度下是成立的.另外笔者注意到:距平模式通过引入实际观测到的年周期态,相当于在非距平模中引入了年周期气候态的修正项.

In this paper,the stability of three classes of steady basic states in the two-dimensionalcompressible adiabatic and non-dissipation atmosphere is discussed,and the following property isexactly demonstrated that the stability of these basic states is decided by their engine matrix A intwo ways:（a）the basic states are stable if A is positively definite in set,and（b）the basic statesare unstable if A is negatively definite in set.