小冰期以来羌塘高原中西部冰川变化图谱分析   总被引：10，自引：2，他引：8  

李德平  王利平  刘时银  谢自楚  丁良福  吴立宗 《冰川冻土》2009,31(1):40-47

运用地理信息图谱理论与方法,以地形图、航空相片、Lantlsat TM和ETM+遥感数据为基础数据源,分析了羌塘高原中西部小冰期至2000年代的冰川变化.结果表明:这里虽仍有部分冰川存在前进,但冰川整体呈萎缩状态,而且近几十年来,冰川退缩加剧.与同一区域的普若岗日相比,研究区冰川更为稳定.与其它山区冰川相比,这里由于是极大陆型冰川区,所以冰川较其它山区冰川相对稳定.气温升高和降水减少是该区冰川退缩的主要原因.  相似文献   

Modeling of gravity-wave tail spectra in the middle atmosphere via numerical and Doppler-spread methods     

《Journal of Atmospheric and Solar》2004,66(11):933-948

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Comparison of different algorithms for calculating the shading effects of topography on solar irradiance in a mountainous area     

Yanlin Zhang  Xiaoli Chang  Ji Liang 《Environmental Earth Sciences》2017,76(7):295

In mountainous areas, topographic shading effects exert significant influence on the spatial distribution of solar irradiance on the land surface, which should be considered in estimating and modeling physical, biological, and hydrological processes. Various algorithms have been proposed for quantitative assessment of the impact of topography on the arriving solar radiation on slopes in mountainous area based on digital elevation model (DEM). However, different algorithms tend to produce different results even based on the same DEM. In this study, two algorithms for determining the maximum horizontal viewing angle of terrain obstruction were compared in a catchment in the Qilian Mountains, Northwest China, which were identical except for the way in interpreting DEM. Two algorithms for calculating sky view factor were also compared. Then, different algorithm combinations were compared and their sensitivities to the horizontal resolution of DEM were investigated. Results showed that the differences in outputs of different algorithms and combinations were significant and cannot be ignored in estimating the spatial distribution of solar irradiance in mountainous areas. A simple ground validation concluded that the algorithm assuming a linear variation in elevation was a little better than that assuming a stepped variation in elevation in and among neighboring DEM cells. For calculating diffuse solar radiation, the algorithm based on a sloped coordinate system was theoretically better than that based on a horizontal coordinate system. It is worth noting that even though the estimated annual mean of solar irradiance over the study area was almost the same among some algorithm combinations, the difference in spatial distribution was significant, which may lead to consequent difference in assessing or modeling some other environmental variables relevant to surface energy exchange, e.g., evaporation, snowmelt, and ground temperature. However, the analysis in this study was mainly theoretical, and further ground-based validations should be made in future.  相似文献   

System probabilistic model of rock slope stability considering correlated failure modes     

《Computers and Geotechnics》2017

In this paper, a system reliability analysis of rock slope stability with considering all input parameters as stochastic parameter is presented. To perform reliability analysis a cut-set system has been used. For this purpose, Sequential Compounding Method (SCM) as a powerful method for reducing the computational time and accurate evaluation is employed to determine the reliability indices with considering correlations between failure modes which are calculated by defining equivalent linear safety margin for each failure mode. Furthermore, the 3-D system probability of failure surface is presented and the probabilistic model is developed to evaluate the rock slope probability of failure.  相似文献   

四川省汶川地震极重灾区次生山地灾害分布规律与发育趋势   总被引：1，自引：0，他引：1  

韩用顺  朱颖彦  孔亚平  韩军  薛蛟  曾思美 《中国地质灾害与防治学报》2010,21(4):14-21

通过对汶川地震极重灾区次生山地灾害的实地考察、遥感调查和综合分析,阐述了次生山地灾害类型与特征,分析了次生山地灾害的时空分布规律,并结合灾害活动特性,探讨了次生山地灾害的发育趋势,提出了灾区防灾减灾和恢复重建的对策与建议。研究结果表明:(1)汶川地震在极重灾区诱发次生山地灾害逾万处,其分布具有点多面广、类型多样、成灾迅速、危害严重、监测预报困难等特点;(2)次生山地灾害的分布受地震烈度、地质构造、地形地貌、地层岩性的制约,并具有明显的滞后性和延续性;(3)利用GIS和遥感技术,能够快速有效地进行地震次生山地灾害的动态监测与灾情评估,从而为防灾减灾管理和灾后重建工作提供科学依据和借鉴参考。  相似文献   

Aerosol optical thickness retrieval over non-Lambertian land surface with synergistic use of AATSR radiance measurements and MODIS derived Albedo Model Parameters     

Yong Xue  Jianping Guo  Xiaoye Zhang 《Atmospheric Research》2009,93(4):736-746

Various algorithms have recently been developed in order to retrieve the aerosol optical thickness (AOT) at continental scales. However, they are, to some extent, subject to large uncertainties resulting from some necessary physical assumptions on land surface anisotropy and level of brightness. In fact, disentangling aerosol and surface signals contained in the top of atmosphere (TOA) radiance received at the satellite level are a matter of difficulty because a single sensor itself cannot gather all required spatial, temporal, spectral and angular information. In particular, each instrument yields limited scanning configuration due to its platform's orbital characteristics. In this regard, a synergetic approach is presented which merges Advanced Along-Track Scanning Radiometer (AATSR) TOA radiances and the MODerate resolution Imaging Spectroradiometer (MODIS) Bi-directional Reflectance Distribution Function (BRDF)/Albedo Model Parameters Product for the retrieval of AOT at 0.55, 0.66, and 0.87 µm wavelengths over non-Lambertian land surface at a 5 km spatial resolution. In this approach, BRDF products serve to assess the surface reflectance in the AATSR geometry as a boundary layer. The peculiarity of the approach is that no specific assumption is required about the spectral characteristics of land surface, thus allowing for a quantitative retrieval of aerosol particles over any arbitrary land unit in virtue of combining forward and nadir AATSR observations. We obtain on average differences within 0.1τ compared to in situ AErosol RObotic NETwork (AERONET) measurements and 36 retrievals corresponding to 27 January, 12 February, 16 March, 28 May, 26 June, and 21 July 2006, respectively, over the city of Beijing in China. Pearson's correlation coefficient is 0.94 and 0.96 for nadir and forward AATSR, respectively. These suggest that AOT retrieval over land is indeed feasible by taking benefit of the validated MODIS BRDF. Besides, the first results indicate that the AATSR retrievals might be used to evaluate the spectral behaviour of the AOT.  相似文献   

洞庭湖流域不同水体中同位素研究   总被引：4，自引：1，他引：3  

黄一民  宋献方  章新平  何清华  韩青  凡非得  贺伟 《地理科学》2016,36(8):1252-1260

在洞庭湖流域内的长沙、汨罗、怀化对大气降水、地表水（河水）、地下水（泉水、井水）进行了取样,分析了流域内不同水体中稳定水同位素的变化特征以及它们之间的转化关系。研究发现地处亚热带季风区的洞庭湖流域,地表水、地下水中同位素继承了降水同位素冬半年富集、夏半年贫化的特征,但存在不同程度的滞后。同时,降水同位素的变化幅度及波动性明显大于地表水及地下水,而地表水、地下水中同位素较降水中要富集。流域内河水中同位素大致表现出随纬度升高而贫化的趋势,这主要受降水同位素场的影响。流域内长沙河水、井水、泉水中同位素组成均位于大气水线附近且分别大致位于一直线上,这说明大气降水是这3种水体的主要补给源。不同季节河水、井水、泉水中同位素组成与大气水线的比较则进一步反映出了不同水体在不同季节的转化关系。  相似文献   

Influence of spatial and temporal scales on statistical analyses of rainfall variability in the River Nile basin     

《Dynamics of Atmospheres and Oceans》2017

In this study, empirical orthogonal function was applied to analyze rainfall variability in the Nile basin based on various spatio-temporal scales. The co-occurrence of rainfall variability and the variation in selected climate indices was analyzed based on various spatio-temporal scales. From the highest to the lowest, the cumulative amount of variance explained by the first two principal components (PCs) for any selected size of the spatial domain was obtained for the annual, seasonal, and monthly rainfall series respectively. The variability in the annual rainfall of 1° × 1° spatial coverage explained by only the first PC was about 55% on average. However, this percentage reduced to about 40% on average across the study area when the size of the spatial domain was increased from 1° × 1° to 10° × 10°. The variation in climate indices was shown to explain rainfall variability more suitably at a regional than location-specific spatial scale. The magnitudes and sometimes signs of the correlation between rainfall variability and the variation in climate indices tended to vary from one time scale to another. These findings are vital in the selection of spatial and temporal scales for more considered attribution of rainfall variability across the study area.  相似文献   

Geochronological and petrogeochemical constraints on the skarn deposits in Tongshanling ore district,southern Hunan Province: Implications for Jurassic Cu and W metallogenic events in South China     

《Ore Geology Reviews》2016

Southern Hunan Province, South China, is located in the central part of the Qin–Hang metallogenic belt and is characterized by abundant Cu–Pb–Zn and W–Sn polymetallic ore deposits. The Cu–Pb–Zn deposits are associated with Jurassic granodiorite porphyries whereas the W–Sn deposits occur within Jurassic granite porphyries. Here we present geochronologic and geochemical data for the Tongshanling Cu–(Mo)–Pb–Zn deposit and the Weijia W deposit in the district of Tongshanling, southern Hunan. Zircon U–Pb dating and molybdenite Re–Os geochronology indicate that the emplacement of the Tongshanling granodiorite porphyry and the associated Cu mineralization occurred at 162–160 Ma, slightly earlier than the formation of the Xianglinpu granite porphyry and associated W mineralization at 159–158 Ma. The Tongshanling granodiorite is high-K calc-alkaline, weakly peraluminous, and weakly fractionated with zircon ε_Hf(t) values of − 15.1 to − 5.6. In contrast, the Xianglinpu granite is alkaline, peraluminous, and highly fractionated, with ε_Hf(t) values of − 9.5 to 0.9. Our data indicate that the Tongshanling granodiorite is relatively oxidized and was formed by the partial melting of Paleoproterozoic crustal material with inputs of mafic magma which was derived from a subduction-modified lithospheric mantle. In contrast, the Xianglinpu granite porphyry is relatively reduced and was formed by direct interaction between the crust and asthenospheric mantle. The difference in magma generation and tectonics is considered to have resulted in the different types of mineralization associated with these two intrusive bodies.  相似文献   

长沙桃子湖湖水稳定同位素的变化及其影响因素     

华明权  章新平  姚天次  罗紫东  周慧  饶志国  贺新光 《湖泊科学》2018,30(6):1766-1778

基于对长沙桃子湖湖水和降水中稳定同位素的监测数据,分析了湖水中稳定同位素的变化特征及其与降水和蒸发的关系,旨在了解湿润气候条件下小型湖泊的湖水稳定同位素的变化规律,揭示降水和蒸发对湖水稳定同位素变化的具体影响.在时间变化上,湖水稳定同位素具有明显的季节变化,湖水中δ¹⁸O的最大值出现在春季,最小值出现在冬季;湖水中过量氘的最大值出现在5-6月,最小值出现在9-10月.在空间变化上,桃子湖不同深度和不同空间点上的湖水中δ¹⁸O差异很小,说明湖水基本处于均匀混合状态.当5日累计降水量≥ 20.3 mm时,湖水中δ¹⁸O的变化与5日累计降水量之间的负相关关系非常显著,但与5日累计蒸发量之间呈弱正相关;湖水中过量氘的变化与5日累计降水量之间无显著相关关系,但与5日累计蒸发量之间呈弱的相关性;相比于平均湖水蒸发线,该降水段的蒸发线斜率和截距均有明显增加.当累计降水量<20.3 mm时,湖水中δ¹⁸O的变化与5日累计降水量之间的相关程度明显降低,但与5日累计蒸发量之间的相关程度则明显提高;湖水中过量氘的变化与5日累计降水量以及与5日累计蒸发量之间的相关关系显著提高;相比于平均湖水蒸发线,该组蒸发线的斜率和截距均有明显减小.  相似文献