甘肃民勤自动站与人工站气象观测数据差异分析

从自动站与人工站观测方式的区别人手,对民勤国家基准气候站观测的数据进行整理与对比分析得出：（1）2种观测方式数据序列中,本站气压2a平均差值为0．1hPa,差值变幅在～0．3～0．5hPa;气温2a平均差值-0．1℃,差值变幅在-0．1～0．0℃之间;相对湿度2a平均差值为-1％,差值变幅在一4％～2％之间;2min平均风速2a平均差值为0．5m／s,差值变幅在0．3～0．7m／s之间,10min平均风速2a平均差值为0．4m／s,差值变幅在0．4～0．5m／s之间;地面温度2a平均差值为0．6℃,差值变幅在0．0～1．2℃之间。本站气压、气温、相对湿度、风向风速、地温差值虽然不固定,但对历史资料的序列连续性影响不显著;（2）各要素中差值最大的是地面最高温度,2a平均差值为1．8oC,差值变幅在-1．7～4．3℃之间;（3）自动站的观测结果比人工观测更真实、准确、科学,更接近大气中的实际情况。     

夏季索马里越赤道气流垂直结构的变化特征及其与东亚夏季风活动的关系

采用NCEP/NCAR和ERA40再分析月平均资料,对比分析夏季垂直尺度上五层(1000 hPa、925 hPa、850 hPa、700 hPa、600 hPa)索马里越赤道气流(SMJ)的时空演变特征。指出对流层中低层SMJ存在不同的垂直结构,且具有年际、年代际变化特征。夏季SMJ垂直结构主要呈现出全区一致、上下反相两种分布型(“A”型和“B”型),细分为一致增强型(“A+”型)、一致减弱型(“A-”型)、上弱下强型(“B+”型)和上强下弱型(“B-”型)。进一步分析指出,SMJ垂直结构与东亚夏季风活动关系密切,SMJ“A+”(“A-”)型垂直结构对应东亚夏季风偏强(弱),我国内蒙古东部、华北地区降水偏多(少);夏季SMJ“B+”(“B-”)型垂直结构对应东亚夏季风偏弱(强),我国江南、日本地区降水偏少(多)。     

THE HYDROLOGICAL CHARACTERISTICS AND WATER BUDGET OF QINGHAI LAKE DRAINAGE BASIN

The rapid shrinkage of the surface area reflects the long-term deficit water budget of Qinghai Lake. Study of the yearly hydrology and meteorology in the lake catchment basin and the hydrologic factors as well as water budget led to the conclusion that evaporation exceeding the water input resulted in the drop of lake level, thai the obvious decrease of runoff to the lake and precipitation on the catchment accelerated the falling of lake level before 1987. and that increase of about 6.7% in rainfall on the whole basin will balance the lake's water budget.     

Processes affecting deposition of sediment in a small, morphologically complex lake

Devil Lake is morphologically complex as a result of Pleistocene glacial erosion of the Frontenac Axis of the Canadian Shield. In order to assess the processes causing highly variable sedimentation in the lake, we monitored currents, suspended sediment and temperature in the lake before and during autumn overturn in 2002. Strong summer thermal stratification (stability number to 0.11 s^–1 declining with the approach of overturn) was insufficient to prevent a dynamic response in the hypolimnion to wind forcing. Superimposed on a gradual increase in suspended sediment concentration in the last weeks of stratification from less than 2 g/l to about 30 g/l were shorter-term rises lasting up to several days. Associated with these events was an increase in particle size of the sediment from a mode of 40–50 to 150–200 m ascribed to flocculation from primary particles. These events culminated in rapid (<1 h) clearing of the water associated with strong, sustained winds over the lake, especially from the southwest. After overturn, the events were more frequent, and flocculation was unable to develop as well in the more vigorous circulation. However, currents in the hypolimnion occurred throughout the period before, during and after overturn with speed related to wind speed, but direction largely independent of wind direction. The results represent an approach to understanding the nature of sedimentary processes and thus to strengthening the use of sedimentary records as proxy in environmental and paleoenvironmental assessment.     

汶川地震诱发的地面塌陷成因

针对目前由汶川地震诱发的地面塌陷研究尚少的现状,以北川县安昌镇开茂村水没河流域地面塌陷坑群为研究对象,根据所处的地质环境条件,通过现场调查、工程勘察及钻孔岩土试验,探讨了地震诱发的地面塌陷成因及机制。认为塌陷区第四系松散层上部含细颗粒的饱和粉土、粉质粘土和下部粗颗粒的饱和砂层、砂砾层等的存在是产生地面塌陷的前提,强烈的地震诱发了砂土液化是产生地面塌陷的内因,而塌陷坑的陆续出现说明了地面塌陷一般都有个时间发展过程,是一种渐进性质的破坏;且地下水动力条件的改变、真空吸蚀作用、余震作用以及强降雨加剧了潜蚀作用,最终导致地面塌陷的产生与发展。结果表明:这些塌陷坑群的出现主要是由地震砂土液化和潜蚀作用共同作用的结果。     

A Simulation Study on the Extreme Temperature Events of the 20th Century by Using the BCC_AGCM

Extreme temperature events are simulated by using the Beijing Climate Center Atmospheric General Circulation Model (BCC AGCM) in this paper. The model has been run for 136 yr with the observed external forcing data including solar insolation, greenhouse gases, and monthly sea surface temperature (SST). The daily maximum and minimum temperatures are simulated by the model, and 16 indices representing various extreme temperature events are calculated based on these two variables. The results show that the maximum of daily maximum temperature (TXX), maximum of daily minimum (TNX), minimum of daily maximum (TXN), minimum of daily minimum (TNN), warm days (TX90p), warm nights (TN90p), summer days (SU25), tropical nights (TR20), and warm spell duration index (WSDI) have increasing trends during the 20th century in most regions of the world, while the cold days (TX10p), cold nights (TN10p), and cold spell duration index (CSDI) have decreasing trends. The probability density function (PDF) of warm/cold days/nights for three periods of 1881-1950, 1951- 1978, and 1979-2003 is examined. It is found that before 1950, the cold day/night has the largest probability, while for the period of 1979-2003, it has the smallest probability. In contrast to the decreasing trend of cold days/nights, the PDF of warm days/nights exhibits an opposite trend. In addition, the frost days (FD) and ice days (ID) have decreasing trends, the growing season has lengthened, and the diurnal temperature range is getting smaller during the 20th century. A comparison of the above extreme temperature indices between the model output and NCEP data (taken as observation) for 1948-2000 indicates that the mean values and the trends of the simulated indices are close to the observations, and overall there is a high correlation between the simulated indices and the observations. But the simulated trends of FD, ID, growing season length, and diurnal temperature range are not consistent with the observations and their correlations are low or even negative. This indicates that the model is incapable to simulate these four indices although it has captured most indices of the extreme temperature events.     

西北中部半干旱区兴隆山森林岛降水机理的数值模拟

通过WRF V2.1.2模式数值模拟试验并结合长期观测数据,研究了中国西北半干旱区长期存在和维持的森林山区(兴隆山区,103.84°E、35.86°N)的降水特征及其与周边地区的降水差异,并探讨了造成这种差异的主要原因。结果表明,兴隆山区与周边地区的降水差异主要表现在夏、秋季。在夏、秋季兴隆山区受东南湿润气流的影响,获得较多的水汽输入和较稳定的水汽来源,而山地地形则有利于截留东南气流携带的水汽并形成降水;兴隆山区及其周边地区局地的蒸散差异对二者之间降水差异的贡献不大。另外,兴隆山区土壤堆积覆盖的石质山构造和森林下垫面也有利于降水的截留和贮存以及植被的生长。因此,有利于水汽输入的大尺度环流形势、地形对空中水汽的截留以及特殊的地质因素是兴隆山山区孤立森林岛在半干旱区长期存在和维持的原因。     

玛曲地区夏季强降水的环流分型及水汽轨迹分析

利用青藏高原(下称高原)东北边坡玛曲地区1967—2008年12个常规气象观测站的降水资料和NCEP/NCAR再分析资料,在环流分型的基础上,应用后向轨迹模型分析了不同等级降水的不同环流型的水汽输送轨迹。结果表明:(1)暴雨发生的环流型以高原低槽型为主,大雨的发生以切变型为主。(2)暴雨的不同环流型的水汽输送轨迹差异较大,同一型暴雨不同等压面水汽轨迹较一致;大雨的不同环流型之间水汽轨迹无明显差异,同一型大雨不同等压面的水汽轨迹差异很大。(3)通过追踪不同时间长度的水汽输送的后向轨迹发现,可以用向前追踪360h的水汽输送轨迹代表玛曲地区的水汽输送,水汽轨迹以偏南气流为主。由此可见,虽然不同等级、不同环流型强降水之间的水汽轨迹存在差异,但是玛曲地区强降水的水汽主要来自印度洋-孟加拉湾和南海-孟加拉湾的偏南气流。     

长治高温气候特征及分析预报

通过对长治市1977年-2004年6月-8月出现≥35℃的高温天气的地理分布特征、时间和强度等统计研究,给出了高温天气的气候背景。从500hPa高空形势分析,归纳出造成高温天气的四种主要环流形势（两槽一脊型、纬向环流型、大陆暖高型、副高控制型）;分析了风、云、降水等气象要素与高温天气的内在联系。通过850hPa高温预报指标站的选取及数值预报产品的统计分析,给出了高温天气的综合性预报模型。     

人工观测与自动仪器观测的对比分析

文章利用察右中旗2010年人工观测与自动仪器观测的对比分析,分析两种观测技术获取的气象数据所存在的差异,确保结果的科学性,为自动站业务化运行和气候资料的连续性提供一定参考依据。