太行山对北京“7.21”特大暴雨的影响及水汽敏感性分析的数值研究

运用GRAPES_Meso模式对2012年7月21—22日发生在北京地区附近的特大暴雨过程进行数值模拟和地形、水汽的敏感性试验。地形敏感性试验发现,在这次特大暴雨过程中,由于太行山北端的阻挡作用,使得气流和水汽辐合、抬升,加强了对流过程;对流层低层山前东南风和西南风、北风的辐合带增大了气旋性涡度,使东移到北京的低涡稳定维持5 h左右,对降水有明显的增幅作用;而且地形起伏和地形海拔高度对降水都有明显增幅作用,地形起伏的增幅作用较地形高度的大。水汽敏感性试验发现在这次特大暴雨过程中,水汽条件较小的变化,会导致水汽输送的明显差异,从而导致降水量显著地改变。     

福建锦城187Ma花岗岩的发现——对华南沿海早侏罗世构造演化的制约

本文对福建沿海福清地区的锦城花岗岩和牛头尾花岗闪长岩进行了岩石地球化学、锆石U-Pb-Hf同位素分析.LA-ICP-MS锆石U-Pb定年结果显示锦城花岗岩的年龄为187±1Ma,为福建沿海首次发现的早侏罗世岩浆活动;牛头尾花岗岩形成时代为130±1Ma,代表燕山晚期(白垩纪)的一期岩浆活动.锦城花岗岩具有高5iO2、偏碱、高Fe2OT3等特征,为高钾钙碱性系列,岩石相对富集轻稀土,亏损Nb、Ta、Ti等高场强元素,富集Ba、Sr等大离子亲石元素,具高Rb/Sr( 1.31 ～ 1.93)比值及低Rb/Ba(0.26 ～0.29)、Eu/Eu*(0.30 ～0.56)、La/Yb(5.69 ～ 18.39),Sr/Y(2.24 ～2.29)比值,为典型的Ⅰ型花岗岩,且具有火山孤花岗岩的地球化学特征,很可能形成于与俯冲相关的构造背景.牛头尾花岗岩相比锦城花岗岩低SiO2,贫钾,而富镁、钙,属于花岗闪长岩.其更亏损Nb、Ta及富集Ba、Sr,具较低Rb/Sr(0.27)、Rb/Ba(0.09)比值和较高的Eu/Eu*(0.98)、La/Yb( 16.87),Sr/Y( 19.08)比值,同样为具有弧特征的钙碱性Ⅰ型花岗岩,也形成于与大洋俯冲有关的构造背景.锦城花岗岩和年头尾花岗闪长岩具有相似的锆石Hf同位素组成,εHf(t)分别为2.18～4.73和1.25 ～4.15,tDMC均为～ 1.0Ga,表明二者起源于相同的新元古代新生地壳.结合已有的资料,本次研究发现锦城花岗岩与南岭地区同时代岩浆岩( 194 ～ 172Ma)在成因上有密切的联系,暗示古太平洋板决的俯冲很可能自早侏罗世开始.这样,华南古特提斯构造域向古太平洋构造域的转换很可能发生在早侏罗世之前,大致在205 ～ 190Ma期间.     

尾矿坝稳定性的可靠度分析

以极限平衡理论和传统的安全系数方法为基础,将可靠度理论引入尾矿坝稳定性分析中。通过敏感性分析和可靠度计算分析发现,尾矿材料的内摩擦角的变异性将显著地影响尾矿坝稳定性分析的可靠指标,重度的变异性对可靠指标的影响大于粘聚力的变异性的影响。简述了尾矿坝稳定性分析中利用可靠度理论的重要性,并建议在尾矿坝的可靠度分析中,将尾矿材料的抗剪强度指标c, 和重度 作为基本随机变量。     

气候变化对黄土碳库效应影响的敏感性研究

中国黄土分布广、厚度大,是古气候变化的良好记录载体,然而黄土在大气CO2循环中到底是源还是汇一直是困扰人们的一个问题.本文利用陆相生态系统中的生物地球化学模型,通过敏感性试验,模拟了土壤有机碳对气候变化的响应.结果表明:1)在各种稳定的气候条件下黄土的土壤有机质都是持续增加的,因此可以认为自然条件下黄土是大气CO2的一个汇;2)温度和降水对黄土中土壤有机质含量的影响正好相反,表明湿度是影响黄土地区生态环境的主要因素,温度和降水都是通过对湿度的影响来影响植被生态的;3)地表植被和土壤有机质是黄土碳库与大气CO2之间的重要媒介.黄土表层的生物地球化学过程是影响黄土碳汇效应的主要过程;4)黄土碳库的主要存在形式以次生碳酸盐为主,其次是土壤有机质,气态CO2只占很小比例.     

中国大陆科学钻探主孔1200米构造柱及变形构造初步解析

在利用成象测井资料准确地恢复岩心空间位置的基础上，建立了位于江苏省东海县毛北村的中国大陆科学钻探主孔岩心1200m精细构造柱。划分了由榴辉岩与超镁铁质岩组成的第一岩性-构造单元及由副片麻岩夹榴辉岩与超镁铁质岩透镜体组成的第二岩性-构造单元，自上而下岩石的面理产状由向东陡倾变为向南东缓倾。第一岩性-构造单元的榴辉岩与超镁铁质岩是毛北榴辉岩杂岩体的组成部分，在榴辉岩中发现以南北向拉伸线理及由北往南的剪切指向为特征的超高压变质岩早期变形举止。位于第二岩性一构造单元下部(770-1130m深度)300多米厚的韧性剪切带是地表出露的毛北韧性剪切带在孔下的延伸，剪切应变及石英组构分析表明，在伴随的退变质角闪岩相一绿帘角闪岩相一绿片岩相的转换过程中，剪切应变由自SE往NW的“逆冲”转为NW向SE的正向滑移。结合钻孔围区地质，重塑了上部由毛北榴辉岩杂岩体与副片麻岩围岩组成的轴面向SE倾斜的同斜倒转褶皱系，以及下部为韧性剪切带的构造模型。钻孔验证了VSP地震反射剖面中850-1200m深度的强反射层与韧性剪切带相吻合。结合苏鲁超高压变质地体的折返构造的研究，提出该构造模型的成因与折返阶段超高压变质地体的斜向上的挤出及后折返阶段的穹隆形成有关。     

内蒙古地区干旱风险评估

分析了形成旱灾风险的有关因素,表明旱灾风险不仅与缺雨程度及持续时间有关,而且还有明显的季节性差异。用单位评价期内的降水距平百分率反映缺雨程度,用作物和生态系统不同季节的缺雨敏感度反映干旱影响的季节性差异,并以干旱持续期内单位时段旱灾风险的累加反映其累积效应,从而建立起旱灾风险的识别指数。应用旱灾风险指数对60年来内蒙古的旱灾风险进行了初步评估。给出了各级旱灾发生的概率,并统计出及各级旱灾对应的后果。对影响范围大、跨经两个以上作物生长年份、最大旱灾风险指数双倍于特旱的极端干旱在内蒙古的发生情况进行了分析。结果表明,20世纪80年代中期以来,内蒙古的极端干旱过程在逐渐东扩,内蒙古东部地区的旱灾出现了增多增强的趋势。     

Study on the Effects of Land Surface Heterogeneitiesin Temperature and Moisture on Annual Scale Regional Climate Simulation

The ``combined approach', which is suitable to represent subgrid land surface heterogeneity in both inter-patch and intra-patch variabilities, is employed in the Biosphere/Atmosphere Transfer Scheme (BATS) as a land surface component of the regional climate model RegCM3 to consider the heterogeneities in temperature and moisture at the land surface, and then annual-scale simulations for 5 years (1988--1992) were conducted. Results showed that on the annual scale, the models response to the heterogeneities is quite sensitive, and that the effect of the temperature heterogeneity (TH) is more pronounced than the moisture heterogeneity (MH). On the intraannual scale, TH may lead to more (less) precipitation in warm (cold) seasons, and hence lead to larger intraannual variability in precipitation; the major MH effects may be lagged by about 1 month during the warm, rainy seasons, inducing ～6% more precipitation for some sub-regions. Additionally, the modeled climate for the northern sub-regions shows larger sensitivities to the land surface heterogeneities than those for the southern sub-regions. Since state-of-art land surface models seldom account for surface intra-patch variabilities, this study emphasizes the importance of including this kind of variability in the land surface models.     

Species sensitivity distributions: data and model choice

Species sensitivity distributions (SSDs) are increasingly incorporated into ecological risk assessment procedures. Although these new techniques offer a more transparent approach to risk assessment they demand more and superior quality data. Issues of data quantity and quality are especially important for marine datasets that tend to be smaller (and have fewer standard test methods) when compared with freshwater data. An additional source of uncertainty when using SSDs is appropriate selection from the range of methods used in their construction. We show through examples the influence of data quantity, data quality, and choice of model. We then show how regulatory decisions may be affected by these factors.     

Conditional nonlinear optimal perturbation: Applications to stability,sensitivity, and predictability

Conditional nonlinear optimal perturbation (CNOP) is a nonlinear generalization of linear singular vector (LSV) and features the largest nonlinear evolution at prediction time for the initial perturbations in a given constraint. It was proposed initially for predicting the limitation of predictability of weather or climate. Then CNOP has been applied to the studies of the problems related to predictability for weather and climate. In this paper, we focus on reviewing the recent advances of CNOP’s applications, which involves the ones of CNOP in problems of ENSO amplitude asymmetry, block onset, and the sensitivity analysis of ecosystem and ocean’s circulations, etc. Especially, CNOP has been primarily used to construct the initial perturbation fields of ensemble forecasting, and to determine the sensitive area of target observation for precipitations. These works extend CNOP’s applications to investigating the nonlinear dynamical behaviors of atmospheric or oceanic systems, even a coupled system, and studying the problem of the transition between the equilibrium states. These contributions not only attack the particular physical problems, but also show the superiority of CNOP to LSV in revealing the effect of nonlinear physical processes. Consequently, CNOP represents the optimal precursors for a weather or climate event; in predictability studies, CNOP stands for the initial error that has the largest negative effect on prediction; and in sensitivity analysis, CNOP is the most unstable (sensitive) mode. In multi-equilibrium state regime, CNOP is the initial perturbation that induces the transition between equilibriums most probably. Furthermore, CNOP has been used to construct ensemble perturbation fields in ensemble forecast studies and to identify sensitive area of target observation. CNOP theory has become more and more substantial. It is expected that CNOP also serves to improve the predictability of the realistic predictions for weather and climate events plays an increasingly important role in exploring the nonlinear dynamics of atmospheric, oceanic and coupled atmosphere-ocean system. Supported by National Basic Research Program of China (Grant Nos. 2006CB403606, 2007CB411800), National Natural Science Foundation of China (Grant Nos. 40830955, 40675030, 40505013), Institute of Atmospheric Physics, Chinese Academy of Sciences (Grant No. IAP07202), and LASG State Key Laboratory Special Fund     

青藏高原北侧地区干湿年夏季垂直环流差异的对比分析及青藏高原的热力影响

为了分析西北干旱的形成原因，本文首先利用高原北侧地区５站历年夏季的降水量资料等，制定了该区的干湿标准，划分了历年夏季的干湿等级。接着又利用ＥＣＭＷＦ的格点资料等对比分析了该区干湿年夏季间垂直环流的差异，也探讨了青藏高原地面热状况与高原北侧干湿状况的联系。其主要结论是：１）文中制定的以降水标准差为判据的干湿标准适合西北干旱区；２）高原北侧干湿年夏季间在高原北侧和高原上的垂直环流存在明显差异；３）青藏高原地面热状况与上列差异有关，也即青藏高原的热力作用是西北干旱的重要成因之一。