一次强沙尘暴活动对中国城市空气质量的影响

对2006年4月8—12日发生在中国北方地区的一次强沙尘暴天气过程及其对中国大陆城市空气质量的影响进行了分析研究。结果表明：①造成此次沙尘天气过程的直接原因是伴随着西伯利亚强冷空气南下的冷锋自西北向东南方向的移动。沙尘暴鼎盛时期卫星观测的中国境内大气沙尘气溶胶指数（AI）的分布存在一个高值区和两个次高值区。高值区位于内蒙古西部地区、河西走廊和河套地区;两个次高值区分别位于塔克拉玛干沙漠及华北至东北地区。与此同时,地面观测的最小能见度小于10 km的气象站点分布最密集的地区也主要分布在上述3个区域。AI的分布与最小能见度的分布之间有着很好的一致性。②这次沙尘天气过程的影响范围主要在33°N以北。从西到东沙尘天气影响的程度逐渐减轻,受污染最严重的城市集中在西北地区东部。根据锋面过境时间与发生大气污染事件时间的对比可将受沙尘天气影响的城市大致分为两类：第一类城市大气污染事件发生在冷锋过境期间（Ⅰ类城市）,第二类城市大气污染事件发生在冷锋过境前（Ⅱ类城市）。Ⅰ类城市受沙尘过程影响发生空气污染事件的持续时间相对较短,空气污染事件主要出现在锋面过境前后。Ⅱ类城市受沙尘过程影响发生空气污染事件的持续时间相对较长,空气污染事件的出现时间要明显超前于锋面过境时间。两类城市的共同特征是能见度与空气污染指数（API）之间存在着良好的反位相关系。     

Increased Particle Fluxes at the INDEX Site Attributable to Simulated Benthic Disturbance

Particle fluxes were measured 7 m above the sea bottom during the predisturbance, disturbance, and postdisturbance periods by using time series sediment traps attached to seven deep-sea moorings deployed in the INDEX experiment site in the Central Indian Basin. The predisturbance particle fluxes varied between 22.3 to 55.1 mg m -2 day -1 . Increased and variable particle fluxes were recorded by the sediment traps during the disturbance period. The increase observed was 0.5 to 4 times more than the background predisturbance fluxes. The increases in particle fluxes (~4 times) recorded by the sediment trap located in the southwestern direction (DMS-1) were the greatest, which could be the result of preferential movement of resuspended particles generated during the deep-sea benthic disturbance along the general current direction prevailing in this area during the experimental period. Also, the traps located closer to the disturbance area recorded greater fluxes than did the traps far away, across the Deep Sea Sediment Resuspension System path. This variability in recorded particle fluxes by the traps around the disturbance area clearly indicates that physical characteristics such as grain size and density of the resuspended particles produced during the disturbance had an important effect on particle movement. The postdisturbance measurements during ~5 days showed a reduction in particle fluxes of ~50%, indicating rapid particle settlement.     

Development of a fish-based multimetric index to assess the ecological quality of marine habitats: the Marine Fish Community Index

In this paper the Marine Fish Community Index (MFCI) for the assessment of ecological status of marine environment is proposed. The MFCI was divided into 4 typologies: Rocky subtidal; shallow, intermediate and deep soft-bottoms. Based on the typical community associated to each typology and the DPSIR analysis performed, a set of metrics were selected and tested through a multiple correlation matrix (Pearson’s coefficient) and the core ones included in the index. The MFCI was applied in all typologies and the scores obtained with each metric were analyzed. In order to test the robustness of the MFCI the final ecological value of each zone was recalculated by removing successively one metric at a time. The MFCI showed a sensitive and robust response in the ecological status assessment. Since it incorporates both functional and structural community information, the MFCI can be useful in the context of the Marine Strategy Framework Directive as well as in other contexts of conservation and sustainable management of the marine environment.     

广西中部岩溶区农业干旱成因与治旱对策

桂中岩溶区降水资源和地下水资源丰富,但是,几乎每年都发生旱灾,受旱耕地面积达12. 5× 104hm2 ,占全广西受旱面积的55. 9% ,严重地影响农业经济的发展。综合分析研究表明,桂中岩溶平原区农业生产受旱成灾是气候性、岩溶地质性、工程性因素综合影响的结果。针对致旱原因,提出了①完善和改造水利工程设施,提高水利工程综合利用效率;② 充分利用水资源的时空分布规律,实施地表、地下水联合开发;③恢复与重建水源生态环境,调节水循环系统的物流机制,减少水资源流失,增强系统供水功能;④调整土地利用结构,建设良好的农田生态体系,促进资源利用与环境改善的良性循环; ⑤调整种植结构,推广节水旱作、土壤改良、农艺节水抗旱技术; ⑥调整农业产业结构,形成多元化的农业经济体系;⑦ 建立完善农村抗早服务体系等综合治旱措施,从抓好水资源的开发、利用、治理、配置、节约、保护和管理七方面入手,提高水资源利用率、完善水土资源优化配置和改善水源生态环境,以增强农业生产的防旱抗旱能力,实现农村经济和社会可持续发展。      

南半球中高纬大气环流年代际变率的研究

利用近百年全球海平面气压图和再分析海平面气压等资料,建立了自1871年以来1,4,7和10月份的南极涛动指数（AOI）序列。近百年来1月AOI有明显增强的趋势,7月AOI则有明显减弱的趋势。最近40多年来,1,4和10月AOI都有较强的上升趋势。4个月份的AOI都有20～30a左右的准周期波动,表现出显著的年代际尺度的变化。用1,4,7和10月的平均可以近似反映年平均南极涛动指数的变化。在年代际尺度上,年平均指数在1894～1901年、1910～1935年左右是强的负指数时期。1880～1893年、1936～1945年左右是较强的正指数时期,1980年代以来,强的正指数已经持续了近20a,且1990年代以来还有加强的趋势。模拟结果的功率谱显示气候系统内部产生的低频变化主要体现在年际尺度变率上,年代际尺度变率的谱值则远远低于观测结果,但不排除在个别情况下,通过Hasselmann机制产生AOI年代际变率的可能性。     

Multilevel assessment of spatiotemporal variability of vegetation in subtropical mountain-hill region

The complex spatiotemporal vegetation variability in the subtropical mountain-hill region was investigated through a multi-level modeling framework. Three levels - parcel, landscape, and river basin levels- were selected to discover the complex spatiotemporal vegetation variability induced by climatic, geomorphic and anthropogenic processes at different levels. The wavelet transform method was adopted to construct the annual maximum Enhanced Vegetation Index and the amplitude of the annual phenological cycle based on the 16-day time series of a5om Moderate Resolution Imaging Spectroradiometer Enhanced Vegetation Index datasets during 2OOl-2OlO. Results revealed that land use strongly influenced the overall vegetation greenness and magnitude of phenological cycles. Topographic variables also contributed considerably to the models, reflecting the positive influence from altitude and slope. Additionally, climate factors played an important role： precipitation had a considerable positive association with the vegetation greenness, whereas the temperature difference had strong positive influence on the magnitude of vegetation phenology. The multilevel approach leads to a better understanding of the complex interaction of the hierarchical ecosystem, human activities and climate change.     

地震应急评估与决策指标体系的构建

Loss assessment and decision-making are essential for earthquake emergency rescues,and for scientific prediction of seismic damage and determination of rescue objectives.In practice,however,there exist some problems,such as basic data not being precise and rich enough and decision making not having systematic and complete criteria.This paper tries to solve these problems using the method of data indexation by constructing an index system for earthquake emergency loss assessment and decision-making.     

中国集装箱多门户港口区域空间结构的形成与机理

运用港口首位度和修正的赫希曼-赫芬达尔指数, 从箱流的角度对1998-2010 年中国集装箱港口体系的空间结构转型进行了定量测度。结果表明:① 集装箱港口体系的重心由珠三角地区向长三角地区缓慢转移;② 集装箱港口体系总体进入“边缘挑战阶段”, 箱流的分散化成为中国集装箱港口体系空间变化的主流倾向, 但7 大港区首位港的极辐作用存在显著差异;③ 中国集装箱港口体系空间结构呈现低级均衡、单门户、多门户并存的多样化特征, 其中, 长三角、珠三角地区形成集装箱多门户港口区域的空间结构已成事实。政府宏观调控与政策引导, 枢纽港资源瓶颈约束, 边缘港口的设施、服务趋同, 港航企业网络扩展和腹地交通网络拓展与完善等因素是多门户空间结构形成的主要动力。     

天水城市扩张的时空特征及动因分析

以不同时期的天水市地形图和TM遥感影像为基础,提取城市建设用地信息。并利用年均扩展指数（AGI）分析各时期城市空间扩展的分异特征。结果表明：天水城市用地由小范围到大范围、AGI 强度由低到高再趋缓。1996 年前,城区人口密度一直下降,此后又开始上升,与AGI 的变化相对应。受“两山夹一川”的地形限制,天水经历了由二点向多点分散扩展、内部填充与沿河谷延伸的空间演变过程。形成了南北窄、东西长的带状格局,不同于平原型城市以同心圆外扩模式。不同时期城市扩张的动因不同,初期是人口和工商业迁入,中期是行政力量和市场机制,近期是人口、经济的增长带来的社会需求。为了适应重点开发的需要,天水需要走出河谷、开发新区,提升综合功能。     

Inversion of potential field data using the structural index as weighting function rate decay

Nonparametric inverse methods provide a general framework for solving potential‐field problems. The use of weighted norms leads to a general regularization problem of Tikhonov form. We present an alternative procedure to estimate the source susceptibility distribution from potential field measurements exploiting inversion methods by means of a flexible depth‐weighting function in the Tikhonov formulation. Our approach improves the formulation proposed by Li and Oldenburg (1996, 1998) , differing significantly in the definition of the depth‐weighting function. In our formalism the depth weighting function is associated not to the field decay of a single block (which can be representative of just a part of the source) but to the field decay of the whole source, thus implying that the data inversion is independent on the cell shape. So, in our procedure, the depth‐weighting function is not given with a fixed exponent but with the structural index N of the source as the exponent. Differently than previous methods, our choice gives a substantial objectivity to the form of the depth‐weighting function and to the consequent solutions. The allowed values for the exponent of the depth‐weighting function depend on the range of N for sources: 0 ≤N≤ 3 (magnetic case). The analysis regarding the cases of simple sources such as dipoles, dipole lines, dykes or contacts, validate our hypothesis. The study of a complex synthetic case also proves that the depth‐weighting decay cannot be necessarily assumed as equal to 3. Moreover it should not be kept constant for multi‐source models but should instead depend on the structural indices of the different sources. In this way we are able to successfully invert the magnetic data of the Vulture area, Southern Italy. An original aspect of the proposed inversion scheme is that it brings an explicit link between two widely used types of interpretation methods, namely those assuming homogeneous fields, such as Euler deconvolution or depth from extreme points transformation and the inversion under the Tikhonov‐form including a depth‐weighting function. The availability of further constraints, from drillings or known geology, will definitely improve the quality of the solution.