胶州湾北部滨海湿地分布特征及质量评价

以胶州湾北部滨海湿地为研究区域,运用RS和GIS技术提取湿地信息,研究时空变化特征,建立湿地定量评价系统,并对湿地质量进行分析。研究表明,自1997年到2007年,该地湿地类型变化较大,沿岸湿地退化现象严重,人为活动影响增大,非湿地面积大量增加,湿地质量不断下降。     

北疆积雪深度和积雪日数的变化趋势

 选取新疆北疆20个站1961-2006年积雪及稳定积雪日数、最大积雪深度资料,同时选择冬季降水量和气温稳定通过0℃以下的日数作为积雪的影响因子,分析了46 a来北疆积雪的变化趋势。结果表明：46 a来最大积雪深度呈显著增加趋势,平均年增长0.8%,其变化与冬季降水量增加有关,呈正相关;积雪日数和稳定积雪日数也呈稍增加趋势,增加主要发生在1960-1980年代,1990年代以来有所减少,其变化与气温稳定通过0℃以下的日数呈显著正相关。     

南、北半球环状模月内活动的主要时间尺度

基于“大气环状活动带” 的概念, 利用逐日再分析资料对南、 北半球环状模 (简称SAM、 NAM) 的季节活动特征及月内活动的主要时间尺度 (Submonthly timescales) 进行了研究, 结果表明, NAM具有冬季强、 夏季弱的年循环特征, 而SAM则表现出明显的准半年循环特征。并且, 逐年的功率谱分析进一步显示: NAM的月内活动的主要时间尺度以准1周和准2周为主, 且它们具有共生性, 准3周为相对次要的周期; 而SAM的月内活动周期与NAM相似, 准2周和准1周较强, 准3周次之。NAM和SAM的月内活动在不同特征时间尺度上的空间特征及其时间演变值得进一步研究。     

Rainfall yield characteristics of electrical storm observed in the Spanish Basque Country area during the period 1992–1996

This paper is focused on the study of rainfall yield characteristics of electrical storms observed over the Northern Iberian Peninsula during 1992–1996. To this aim Principal Components Analysis (PCA) and Self-Organizing Maps (SOM) method have been used. The SOM method is a group of artificial neural networks based on the topological properties of the human brain. Results clearly suggest that there exist three different meteorological patterns that are linked to the characteristics of electrical events found in the study area. In winter, most of the electrical events are formed under oceanic advection (NW air fluxes). On these cases, mean rainfall yield estimates reach values of 700 10⁴ m³ per cloud to ground lightning flash (CG flash). During summer most frequent electrical storms are associated to local instability shooting by surface heating with advection of humidity coming from the Iberian Peninsula. Under these meteorological situations, rain is scarcer if compared with oceanic events but lightning CG counts reach the maximum values found in the area (about 10 CG counts per 20 × 20 km² and day) giving this way the smallest rainfall yield with a mean value of 15 10⁴ m³ per CG flash. Iberian air fluxes associated with cold air in upper parts of the atmosphere represent the third meteorological pattern found. This pattern is most common in spring and autumn but is not unusual in the rest of the seasons. In those cases mean rainfall yield in the area is about 150 10⁴ m³ per CG flash. In all electrical episodes K instability index is greater than 15 °C but in the most lightning producing events, this index reaches in the area values greater than 24 °C. PCA results pointed out that there exists a relationship between rain and CG counts expressed by the first principal component computed from standardized data. However, we must notice that no event is solely linked to this axis, since a seasonal influence which decreases lightning production when rain increases is always present. Results found are of great interest for short term forecasting of flashfloods in mountainous areas like the Spanish Basque Country region.     

北非地区海-陆热力差异与夏季江淮流域旱涝的关系

基于NCEP/NCAR月均再分析资料和中国743站降水资料,根据夏季江淮流域51 a(1954-2004年)区域旱涝指数的年代际变化特征,确定北非地区作为研究的关键区.分析发现,关键区的地表温度异常在冬季具有较好的持续性,冬季北大西洋涛动是导致这种异常持续性的重要原因之一.通过对前冬北非地区地表温度和夏季江淮流域降水的SVD分析发现:当北非大陆地区偏冷,其西北侧的海区偏暖时,江淮流域夏季的降水将整体偏多;反之,江淮流域夏季的降水整体偏少.进一步研究发现,北非地区海陆地表温度异常的对比,要比其中单一海洋或陆地区域的异常对夏季江淮流域的旱涝有更好的指示能力.文中定义了一个海陆热力差异指数来表征这种地表温度异常的对比程度,该指数和夏季江淮流域旱涝指数呈较好的正相关关系,并且对夏季江淮流域极端旱涝年份也有较好的指示,认为该指数可以作为一个指示江淮流域整体旱涝事件的预报因子.     

Consistency of observed winter precipitation trends in northern Europe with regional climate change projections

Often it is claimed that the recent changes in northern European climate are at least partly anthropogenic even though a human influence has not yet been successfully detected. Hence we investigate whether the recent changes are consistent with regional climate change projections. Therefore, trends in winter (DJF) mean precipitation in northern Europe are compared to human induced changes as predicted by a set of four regional climate model simulations. The patterns of recent trends and predicted changes match reasonably well as indicated by pattern correlation and the similarity is very likely not random. However, the model projections generally underestimate the recent change in winter precipitation. That is, the signal-to-noise ratio of the anthropogenic precipitation change is either rather low or the presently used simulations are significantly flawed in their ability to project changes into the future. European trends contain large signals related to the North Atlantic Oscillation (NAO), of which a major unknown part may be unrelated to the anthropogenic signal. Therefore, we also examine the consistency of recent and projected changes after subtracting the NAO signal in both the observations and in the projections. It turns out that even after the removal of the NAO signal, the pattern of trends in the observations is similar to those projected by the models. At the same time, the magnitude of the trends is considerably reduced and closer to the magnitude of the change in the projections.     

藏北地区近地层大气和土壤特征量分析

利用"全球协调加强观测期亚澳季风青藏高原试验研究(CAMP/Tibet)"4个台站2003年大气和土壤的观测资料,详细分析了藏北高原不同下垫面上的气温、相对湿度、土壤温度、土壤湿度等的季节变化及年变化特征。近地层大气各气象要素变化剧烈;4个站气温高低的差异显示了纬度和高度的明显影响;各站冻土冻融过程存在地域差别,尤其是春季冻结消融阶段的持续时间相差可达1个月;土壤质地的差别对土壤湿度影响也较大,黏土土壤含水量要高些,粉土和砂土要低些。     

桂北地区剪切带型金矿成矿机理研究

桂北地区金矿划分为石英脉型、石英细脉带型和构造蚀变岩型金矿.不同级别剪切带构造控制矿化集中区、矿床、矿体分布以及矿脉形态、产状和矿化类型,具有上部石英脉型、中部石英细脉带型、下部构造蚀变岩型金矿的矿化分带模式.金质矿源主要来源于上地壳围岩,硫源主要来自深部,金矿成矿溶液主要来源于大气降水,热源来自变质和构造运动,成矿时代主要为燕山期.矿床成因属是产于前寒武纪浅变质碎屑岩系的与脆一韧性剪切带有关的中低温热液脉状金矿.     

Paleoclimatic changes in southern Africa during the intensification of Northern Hemisphere glaciation: evidence from ODP Leg 175 Site 1085

Pliocene age sediments from Ocean Drilling Program Leg 175, Site 1085-A and B in the Cape Basin were analyzed to investigate the impact of the intensification of Northern Hemisphere glaciation (INHG) on the South Atlantic Benguela Current system from 4 to 2 Ma. Proxies for productivity (concentrations and mass accumulation rates of total organic carbon, carbon to nitrogen ratios, percent calcium carbonate, and percent biogenic silica) as well as weight percent sand (a proxy for preservation or winnowing) peak at 3.2, 3.0, 2.4, and 2.25 Ma. Normative calculations of allied trace and major elemental determinations indicate synchronous increases in productivity peaks, as well as high concentrations and accumulations of terrigenous sediments. Coeval increases in hemipelagic sedimentation and productivity indicators could be the result of enhanced eolian sedimentation resulting from strengthened winds, leading to elevated rates of upwelling and enhanced productivity. However, rapid burial, as indicated by high sedimentation rates, could also enhance preservation. The very high concentrations (>30%) and accumulations (up to 60 g/cm²/kyr) limit the likelihood that eolian sedimentation was the only transport mechanism, invoking an additional fluvial source. Rapid burial by either eolian or fluvial transport links these intervals of enhanced preservation and productivity with continental climate changes resulting from (1) increased winds and/or dust availability due to higher aridity in the Namibia/northern South Africa region; (2) lowered sea-level related to increased ice volume; (3) increased sediment load due to wetter conditions in the continental interior; or (4) some combination. Peaks at 3.2, 2.4 and 2.25 Ma are coincident with maximum precession, suggesting a link between hemipelagic sedimentation and enhanced monsoonal circulation over southern Africa. The Site 1085 sedimentary record during the INHG seems to be controlled by low-latitude processes linked to precession rather than hig-latitude processes.