云南降雨型滑坡县级预警雨量阈值分析

根据云南省华坪县滑坡灾害历史数据和同期气象站实测小时降雨资料,以滇西北的华坪县为例动态地计算了每次滑坡灾害的有效降雨天数和对应前期的有效降雨量;并应用主成分分析法对44场降雨型滑坡进行分析,结果表明间接前期雨量、发生雨量和激发雨量对诱发滑坡都有重要影响,得出诱发滑坡的降水有短时强降雨和长时低强度降雨两种类型。由此建立了含有两类降雨特点的华坪县I〖CD*2〗D（降雨强度〖CD*2〗历时）阈值曲线,并在此过程中提出了确定降雨历时D结束时刻的方法和有待进一步研究的问题。通过对华坪县滑坡预警雨量研究,为其他县级滑坡灾害预警雨量阈值的确定提供一种方法。     

Palomar and Table Mountain observations of 9P/Tempel 1 during the Deep Impact encounter: First results

We present the first results of the Palomar Adaptive Optics observations taken during the Deep Impact encounter with 9P/Tempel 1 in July 2005. We have combined the Palomar near-IR imaging data with our visual wavelength images obtained simultaneously at JPL's Table Mountain Observatory to cover the total wavelength range from 0.4 to 2.3 μm in the B, V, R, I, J, H, and K filter bands, spanning the dates from 2005 July 03-07. We also include in our overall analysis images taken on the pre-encounter dates of June 1 and June 15, 2005. The broad wavelength range of our observations, along with high temporal resolution, near-IR sensitivity, and spatial resolution of our imaging, have enabled us to place constraints on the temperature of the impact flash and incandescent plume of >700 K, and to provide mean dust velocities of order approximately 1.25 h after impact derived from our 1.64 μm observations. Our ejected dust mass estimates, as derived from our near-IR observations, are an order of magnitude less than those previously reported for visual wavelength observations.     

基于动态阈值的HJ-1B图像云检测算法研究

针对环境与灾害监测预报小卫星星座1B星(HJ-1B)的传感器波段特征,通过对云检测阈值的年度波动性分析,提出了一种基于波谱标准差异常的“动态阈值云检测算法”.该算法的实现主要是采用图像配准、波段运算、线性回归和误差分析等方法,获取云异常区域,进而剔除图像中的云像元.研究结果表明,该算法可以很好地检测出不同时相、不同类型下垫面上空的云像元,为有效利用HJ-1B数据并提高其图像分类精度发挥作用.     

基于SPOT5遥感影像的浅层滑坡体自动提取方法

本文在前人研究的基础上,对浅层滑坡体的提取方法进行了改进。首先利用改进的MSAVI算法提取SPOT5影像中的裸地信息,进而对提取的结果进行去阴影、坡度筛选、形态学滤波、栅-矢转换、面积和顺坡性筛选,并基于改进的多峰直方图阈值自动选取算法实现了滑坡体信息的自动提取。经过实验比较表明,改进的方法既有效地去除非滑坡体等干扰信息,又真正实现了滑坡体信息的自动提取,从而极大地提高了已发生滑坡体的识别、提取效率和精度。     

美国科罗拉多河高速水流实验对下游水生生态系统的影响及启示

科罗拉多河的适应性管理处于世界领先水平。美国为研究格伦峡谷大坝对下游水生生态系统的影响而进行了3次高速水流实验,取得了显著的生态效益,也积累了许多宝贵经验。分析显示,利益相关方参与是该实验成功的体制保障,跟踪监测与评估是实验成功的技术保障,闸坝适应性调度是河流保护与管理的有效手段。该实验的实施过程和效果对我国闸坝调度有许多有益的启示。例如,对下游水生生物和湿地生态系统的保护应作为闸坝调度的目标之一,应加强闸坝适应性调度的实验和研究,促进利益相关方参与河流保护与管理。     

The determinants of vulnerability and adaptive capacity at the municipal level: Evidence from floodplain management programs in the United States

This article provides a quantitative test of the relationship between adaptive capacity and socio-economic status (SES) at the municipal level. Local participation in a U.S. floodplain management program, the Community Rating System (CRS), is used as an indicator of adaptive capacity. The relationship between aggregated measures of SES and CRS participation is tested using probit, OLS and tobit models. The analysis indicates that socio-economic characteristics of a municipality's population are associated with the capacity of municipal leaders to effect collective action in response to environmental challenges. More theoretical work and case studies are needed to fully explain the reasons for this association.     

Estimation of the Threshold Friction Velocities over Various Dust Storm Source Areas in Northwest China

The emission of dust particles into the atmosphere is governed by the aerodynamic and resistant factors,which are quantified by the friction velocity u＊ and the threshold friction velocity u＊t, respectively. The threshold friction velocity u＊t influences the vertical dust flux and dust transport. Based on the micrometeorological data obtained in the springs of 2004 and 2006 over Hunshandake desert area, Loess Plateau,and Gobi desert area, the relationship between dust concentration and friction velocity for the dust events that occurred over Hunshandake desert area was investigated, and the threshold friction velocities over the three different dust source areas were estimated. The results show that the value of dust concentration is low during the preemission stage of a dust storm event, and the rapid increase of friction velocity provides favorable dynamic conditions for dust emission. During the dust emission stage, the dust concentration increases sharply due to mechanical and thermal turbulent mixing. At the calm-down stage, the dust concentration drops nearly linearly with the decreasing friction velocity, on account of the gravitational deposition of larger dust particles. When the dust concentration is higher than 200 μg m-3, it is considered as a dust emission process. According to the criteria, the values of threshold friction velocity over Hunshandake desert area and Gobi region are 0.6 and 0.45 m s-1, respectively. The threshold friction velocity over Loess Plateau depends on the wind direction, due to the complex terrain and inhomogeneous surface. The northwest wind shows the effects of the Mu Us desert in the northwest. The corresponding u＊t is 0.35 m s-1. The south wind exhibits the characteristics of the Loess hilly dunes in the south, and the u＊t is 0.7 m s-1.The large roughness length of the Loess hilly dunes and the large inter-particle cohesion for the clay soil texture increases the local friction velocity. Different threshold friction velocities and occurrence frequencies of strong wind account for different dust emission capabilities for various source areas.     

Physical properties of (2) Pallas

Ground-based high angular-resolution images of asteroid (2) Pallas at near-infrared wavelengths have been used to determine its physical properties (shape, dimensions, spatial orientation and albedo distribution).We acquired and analyzed adaptive optics (AO) J/H/K-band observations from Keck II and the Very Large Telescope taken during four Pallas oppositions between 2003 and 2007, with spatial resolution spanning 32-88 km (image scales 13-20 km/pixel). We improve our determination of the size, shape, and pole by a novel method that combines our AO data with 51 visual light-curves spanning 34 years of observations as well as archived occultation data.The shape model of Pallas derived here reproduces well both the projected shape of Pallas on the sky (average deviation of edge profile of 0.4 pixel) and light-curve behavior (average deviation of 0.019 mag) at all the epochs considered. We resolved the pole ambiguity and found the spin-vector coordinates to be within 5° of [longitude, latitude] = [30°, −16°] in the Ecliptic J2000.0 reference frame, indicating a high obliquity of about 84°, leading to high seasonal contrast. The best triaxial-ellipsoid fit returns ellipsoidal radii of , and . From the mass of Pallas determined by gravitational perturbation on other minor bodies , [Michalak, G., 2000. Astron. Astrophys. 360, 363-374], we derive a density of significantly different from the density of C-type (1) Ceres of [Carry, B., Dumas, C., Fulchignoni, M., Merline, W.J., Berthier, J., Hestroffer, D., Fusco, T., Tamblyn, P., 2008. Astron. Astrophys. 478 (4), 235-244]. Considering the spectral similarities of Pallas and Ceres at visible and near-infrared wavelengths, this may point to fundamental differences in the interior composition or structure of these two bodies.We define a planetocentric longitude system for Pallas, following IAU guidelines. We also present the first albedo maps of Pallas covering ∼80% of the surface in K-band. These maps reveal features with diameters in the 70-180 km range and an albedo contrast of about 6% with respect to the mean surface albedo.     

‘Strange changes’: Indigenous perspectives of climate change and adaptation in NE Arnhem Land (Australia)

Despite growing global attention to the development of strategies and policy for climate change adaptation, there has been little allowance for input from Indigenous people. In this study we aimed to improve understanding of factors important in integration of Yolngu perspectives in planning adaptation policy in North East Arnhem Land (Australia). We conducted workshops and in-depth interviews in two ‘communities’ to develop insight into Yolngu peoples’ observations and perspectives on climate change, and their ideas and preferences for adaptation. All participants reported observing changes in their ecological landscape, which they attributed to mining, tourism ‘development’, and climate change. ‘Strange changes’ noticed particularly in the last five years, had caused concern and anxiety among many participants. Despite their concern about ecological changes, participants were primarily worried about other issues affecting their community's general welfare. The results suggest that strategies and policies are needed to strengthen adaptive capacity of communities to mitigate over-arching poverty and well-being issues, as well as respond to changes in climate. Participants believed that major constraints to strengthening adaptive capacity had external origins, at regional, state and federal levels. Examples are poor communication and engagement, top-down institutional processes that allow little Indigenous voice, and lack of recognition of Indigenous culture and practices. Participants’ preferences for strategies to strengthen community adaptive capacity tended to be those that lead towards greater self-sufficiency, independence, empowerment, resilience and close contact with the natural environment. Based on the results, we developed a simple model to highlight main determinants of community vulnerability. A second model highlights components important in facilitating discourse on enhancing community capacity to adapt to climatic and other stressors.