Lightning and special peat bog phenomena on Andøya,northern Norway

In 1982 a c.5 m² slab of peat, c.25 cm thick, was discovered on a peat bog on the island of Andøya in northern Norway. The peat slab, which weighed c.1 ton, was found 4 m to 5 m from a hole having precisely the same shape. Investigations on Andøya to date have provided information on six quite similar phenomena with slab weights varying between 100 kg and 4 tons. Outside Andøya, five similar phenomena have been recorded in Norway, and pieces of earth displaced from their original locations have been reported in Britain, Germany and the United States. Lightning is hypothesized to have caused these phenomena.     

Laboratory simulations of prebiotic molecule stability in the jarosite mineral group; end member evaluation of detection and decomposition behavior related to Mars sample return

Recently, the prebiotic amino acid glycine has been found associated with natural jarosite samples from locations around the world. Since the discovery of jarosite on Mars, extensive research focuses on linking this mineral group with possible detection of biosignatures in the geologic record on Earth and Mars. Multiple analytical methods, including extraction and mass spectrometry techniques, have identified glycine and other biomolecules in jarosite samples. The jarosite end members jarosite (sensu stricto-potassium jarosite), natrojarosite (sodium jarosite), and ammoniojarosite (ammonium jarosite) have different thermodynamic stabilities, decompose at different rates, and have potentially different susceptibilities to substitution. The relationship between the thermodynamic stability of the jarosite end members and the effect that glycine has on the thermal decomposition behavior of each end member was investigated using thermal gravimetric analysis. Introducing glycine into the synthesis procedure (75 ppm) of the potassium, sodium, and ammonium jarosite end member has elucidated the effects that glycine has on the thermal stability of the mineral group. Potassium jarosite appears to be the least susceptible to the effects of glycine, with the sodium and ammonium end members showing marked changes in thermal decomposition behavior and decomposition rates. These results suggest that the sodium and ammonium jarosites are more suitable targets for identifying signs of prebiotic or biotic activity on Mars and Earth than the potassium jarosites. These results have implications for current in situ investigations of the martian surface and future sample return missions.     

Triple F—a comet nucleus sample return mission

The Triple F (Fresh From the Fridge) mission, a Comet Nucleus Sample Return, has been proposed to ESA’s Cosmic Vision program. A sample return from a comet enables us to reach the ultimate goal of cometary research. Since comets are the least processed bodies in the solar system, the proposal goes far beyond cometary science topics (like the explanation of cometary activity) and delivers invaluable information about the formation of the solar system and the interstellar molecular cloud from which it formed. The proposed mission would extract three sample cores of the upper 50 cm from three locations on a cometary nucleus and return them cooled to Earth for analysis in the laboratory. The simple mission concept with a touch-and-go sampling by a single spacecraft was proposed as an M-class mission in collaboration with the Russian space agency ROSCOSMOS.     

基于copula函数的区域干旱分析方法

提出不同网格干旱等级影响下的区域干旱指数。采用copula函数,建立了区域干旱历时和干旱强度的联合分布,计算联合分布的重现期,并对实际重现期作区间估计。所提出的区域干旱指数能够反映研究区域内发生干旱的严重程度和该区内不同干旱等级所影响面积的大小,且联合分布同时考虑了干旱历时和干旱强度,更全面地反映区域的干旱状况。重庆市2006年干旱实证分析表明,区域干旱指数能够较好地描述本次干旱的发生发展过程,并计算出联合分布的重现期为118年。     

Understanding salt mobilization from an irrigated catchment in south‐eastern Australia

Groundwater discharge from the Riverine Plains of the southern Murray‐Darling Basin is a major process contributing salt to the Murray River in Australia. In this study, data from an irrigated 60 000 ha catchment in the Riverine Plains were analysed to understand groundwater discharge into deeply incised drains, the process dominating salt mobilization from the catchment. We applied three integrated methodologies: classification and regression trees (CART), conceptual modelling and artificial neural networks (ANNs) to a comprehensive, spatially lumped, monthly data set from July 1975 to December 2004. Using CART analysis, it was shown that rainfall was the most important variable consistently explaining the salt load patterns at the catchment outlet. Using the conceptual model representing spatially lumped groundwater discharge into deeply incised drains, we demonstrated that salt mobilization from the study catchment can be well represented by a rainfall contribution, influenced by the hydraulic head in the deep regional aquifer and potential evapotranspiration. Using ANNs, it was confirmed that rainfall had a much higher impact on salt loads at the catchment outlet than irrigation water use. All these results demonstrate that under conditions similar to those experienced from 1975 to 2004, it is rainfall rather than irrigation water use that governs salt mobilization from the study catchment. Management of salt mobilization from irrigated catchments has traditionally focussed on the improvement of irrigation practices but it could be equally important to further understand the scope for management to control groundwater discharge in these irrigation areas. Copyright © 2010 John Wiley & Sons, Ltd.     

Approaches for defining thresholds and return periods for rainfall‐triggered shallow landslides

Probabilistic thresholds for triggering shallow landslides by rainfall are developed using two approaches: a logistic regression model and Iverson's physically based model. Both approaches are applied to a 180 km² area in northern Italy. For the physically based model a Monte Carlo approach is used to obtain probabilities of slope failure associated with differing combinations of rainfall intensity and duration as well as differing topographic settings. For the logistic regression model hourly and daily rainfall data and split‐sample testing are used to explore the effect of antecedent rainfall on triggering thresholds. It is demonstrated that both the statistical and physically based models provide stochastic thresholds that express the probability of landslide triggering. The resulting thresholds are comparable, even though the two approaches are conceptually different. The physically based model also provides an estimate of the percentage of potentially unstable areas in which failure can be triggered with a certain probability. The return period of rainfall responsible for landslide triggering is studied by using a Gumbel scaling model of rainfall intensity–duration–frequency curves. It is demonstrated that antecedent rainfall must be taken into account in landslide forecasting, and a method is proposed to correct the rainfall return period by filtering the rainfall maxima with a fixed threshold of antecedent rainfall. This correction produces an increase of the return periods, especially for rainstorms of short duration. Copyright © 2009 John Wiley & Sons, Ltd.     

钻孔温度恢复及平衡态温度确定

多年冻土温度场在气候变化研究重要意义，因为多年冻土具有记忆古温度场的能力。钻探过程对冻土原状温度具有深刻影响，深钻孔在几个内难以恢复到天然状态。热扩散理论表明，５０年后钻孔温度才能恢复至平衡状态。控制钻孔温度恢复的对数方程为求得冻土平衡态温度场提供了有效手段。     

不同还田方式下稻草的腐解速率及养分释放规律

采用尼龙网袋法和砂滤管法研究了稻草不同还田方式下的腐解及养分释放规律。结果表明：稻草还田后，前期腐解快，后期较慢。翻埋还田的稻草腐解速率明显快于覆盖还田稻草，整个试验期间（210d）翻埋还田的稻草腐解率达到76．55％，而覆盖还田的稻草仅为53．50％。稻草覆盖与翻埋两种还田方式下养分释放速率均以钾（K）最快，磷（P）次之，氮（N）最慢。还田10d内，两种方式下K分别释放了50．32％和90．13％。稻草与土壤充分混合条件下，稻草和土壤矿化释放的氮以NO3-N为主（〉80％），NH4-N和可溶性有机氮较少；在稻草还田后的前40d存在土壤微生物与作物竞争土壤矿质氮的现象，40d之后此现象消失，稻草开始氮的净矿化；在稻草埋入土壤时同时配施适量的氮肥，则不会出现微生物的夺氮现象。整个试验期间，该土壤氮净矿化量达90．4mg／kg土。     

利用机载LIDAR双次回波高程之差分类激光脚点

机载LIDAR技术已经引起了测绘界的浓厚兴趣,有可能给测绘领域带来一场新的技术革命。机载LI-DAR技术的硬件设备在国外已相对成熟,而机载LIDAR的数据后处理算法仍然处于研究发展阶段,还有诸多问题没有得到解决,其关键之一就是机载LIDAR数据的滤波与分类。本文首先对已有的滤波分类方法进行了综合评价,并指出了各自的局限。然后提出利用两次回波信号的高程数据来实现对机载LIDAR数据的分类。首次分类后得到植被激光脚点点集和地面及房屋激光脚点点集。而房屋上的激光脚点要高出地面上的激光脚点数米之多,简单利用阈值法就可以进一步分类出房屋激光脚点和地面激光脚点。也可以先经过滤波处理将地面激光脚点去掉,然后利用两次回波信号的高程数据来分类自然植被激光脚点和人工地物激光脚点。实验证明所提方法简单有效,算法简单实用,特别适用于分类植被激光脚点。     

日照地区风暴潮增水重现值计算

为给政府、规划、设计部门决策提供参考,采用组合分布法对日照地区风暴潮增水的重现值进行了计算。提出了以台风发生强烈的季节和月份进行统计抽样统计的替代方法,简化了工程设计初期的数据处理工作量;并给出了适用于日照地区风暴潮增水的分布模式。与传统的年极值法和过阈法相比,该方法考虑了风暴潮增水的季节变化,物理意义更趋明确。