基于地理探测器的青藏高原多年冻土分布影响因子分析     

肖瑶  赵林  邹德富  刘世博  马露  应雪  刘艺阗 《冰川冻土》2021,43(1):311-321

多年冻土的分布会受到局地地质、地形地貌和地表覆被等因素的影响.为探究各因子对多年冻土分布的影响强弱,选择青藏高原五个典型多年冻土区为研究区,基于MODIS和SRTM DEM数据提取研究区内2003—2012年平均地表温度、NDVI、地表反照率、积雪日数和坡度、坡向等因子,并采用地理探测器模型研究了各因子对研究区多年冻土...  相似文献   

大型坳陷湖盆“洪水—河漫湖”沉积——以干旱背景下的松南泉四段为例     

潘树新  卫平生  王天奇  王建功  梁苏娟  赵志魁  赵占银  黄世伟 《地质论评》2012,58(1):41-52

本文建立了一种干旱背景下坳陷湖盆全新的沉积充填模式,即"洪水—河漫湖"沉积模式。在干旱背景下,物源区的河流主要表现为季节性的洪水,大多数河流都消失在荒漠中,河水主要以地表蒸发、植被生态消耗、地下渗流、河流终端湖以及河漫湖等形式排泄,坳陷湖盆内并未形成统一大面积的汇水中心和湖相沉积。这种背景条件下,湖盆的沉积充填特征明显不同于经典的坳陷湖盆和浅水湖盆沉积。下白垩统泉头组四段沉积时期,松辽盆地具有气候干旱、地势平坦、生物单调贫乏等特征,盆地南部存在5大沉积体系及7条主要的水系。除在盆地西部古龙凹陷地区河流汇水形成小范围浅水湖泊外,在盆地南部主要为"洪水—河漫湖"的河流相沉积。坳陷湖盆"洪水—河漫湖"沉积具有以下特点:①全盆地没有统一的汇水中心,因而缺乏大面积分布的湖相和三角洲沉积;②河流表现为季节性的洪水,部分河流由于地形变缓,并未进入汇水中心,而是消失在荒漠中,河流相为盆地沉积充填的主要类型;③湖盆具有多物源、多漫湖、满盆含砂的沉积特点;④河漫湖与河流在空间分布上存在3种关系,即河流终止于河漫湖、河流穿过河漫湖、河流绕过河漫湖等。坳陷湖盆"洪水—河漫湖"是一种中—新生代陆相坳陷湖盆沉积充填的新模式,具有重要的理论和实践意义。  相似文献   

Solutions of the linearized geodetic boundary value problem for an ellipsoidal boundary to order e 3     

B. Heck  K. Seitz 《Journal of Geodesy》2003,77(3-4):182-192

q6yhv2fw7xe40and/xxlarge8194.gif" alt="ensp" align="MIDDLE" BORDER="0">The geodetic boundary value problem (GBVP) was originally formulated for the topographic surface of the Earth. It degenerates to an ellipsoidal problem, for example when topographic and downward continuation reductions have been applied. Although these ellipsoidal GBVPs possess a simpler structure than the original ones, they cannot be solved analytically, since the boundary condition still contains disturbing terms due to anisotropy, ellipticity and centrifugal components in the reference potential. Solutions of the so-called scalar-free version of the GBVP, upon which most recent practical calculations of geoidal and quasigeoidal heights are based, are considered. Starting at the linearized boundary condition and presupposing a normal field of Somigliana–Pizzetti type, the boundary condition described in spherical coordinates is expanded into a series with respect to the flattening f of the Earth. This series is truncated after the linear terms in f, and first-order solutions of the corresponding GBVP are developed in closed form on the basis of spherical integral formulae, modified by suitable reduction terms. Three alternative representations of the solution are discussed, implying corrections by adding a first-order non-spherical term to the solution, by reducing the boundary data, or by modifying the integration kernel. A numerically efficient procedure for the evaluation of ellipsoidal effects, in the case of the linearized scalar-free version of the GBVP, involving first-order ellipsoidal terms in the boundary condition, is derived, utilizing geopotential models such as EGM96.  相似文献   

Outstanding Issues on Pulsations in Young Stars     

M. Marconi  F. Palla 《Astrophysics and Space Science》2003,284(1):245-255

We briefly summarize the impact of protostellar evolution on the initialconditions of pre-main-sequence (PMS) contraction and identifytwo different kinds of instability in young stars closely connected to thePMS physical conditions. These are the q323141nppjv6713/xxlarge948.gif" alt="delta" align="BASELINE" BORDER="0"> Scuti type pulsations in intermediate-mass PMS stars (Herbig Ae stars) and the pulsation instability of brown dwarfs and very low mass stars. For the former, we review recentobservational and theoretical work and provide the location in the H-Rdiagram of known candidates. For the latter, the possibility that deuteriumcan be an efficient driving mechanism of the instability is explored.  相似文献   

一维气温时间序列的多重分形研究   总被引：10，自引：0，他引：10  

严绍瑾  彭永清  张运刚 《热带气象学报》1996,12(3):207-211

采用武汉１９５１－１９７０年日平均气温序列作多重分形分析，从计算ｑ阶分数维Ｄｑ着和，得到了多重分形谱ｆ（ａ）曲线，反映了大气运动确定是一个层次分明的过程，具有多标度结构。  相似文献   

Oxidation and Origin of Organic Matter in Surficial Eastern Mediterranean Hemipelagic Sediments     

P. J. M. Van Santvoort  G. J. De Lange  J. Thomson  S. Colley  F. J. R. Meysman  C. P. Slomp 《Aquatic Geochemistry》2002,8(3):153-175

Aerobic mineralisation of C_org in surface sedimentsof the deep (>2000 m water depth) eastern Mediterranean Sea has been quantified by analysis of detailedbox core C_org concentration versus depth profiles and the modelling environment for early diageneticproblems MEDIA. The reactive fraction comprises 60–80% of the total C_org reachingthe sediments and is largely oxidised within the surficial 10 cm. A non-reactive C _orgfraction (G_NR) dominates at depths >10 cm, and makes up20–40% of the total C _org flux to the sediments. First-order rateconstants for decomposition of the reactive fraction calculated from theC _org profiles range from 5.4 × 10^-3 to8.0 × 10^-3 y^-1 to 8.0 × 10^-3 y^-1. Total mineralization rates in thesurface sediment are between 1.7 and 2.6 q70857jm363g/xxlarge956.gif" alt="mgr" align="MIDDLE" BORDER="0">mol C cm^-2 y^-1 and thus are typical for oligotrophic, deep-seaenvironments. The low fluxes and rapid remineralisation of C _org are accompanied by²¹⁰Pb_excess surface mixed layers which are only 2 cm deep, among the thinnest reported for oxygenated marine sediments.Model results indicate a mismatch between the C _org profiles and O₂ microprofileswhich were measured onboard ship. This can be attributed to a combination of decompression artefactsaffecting onboard measurement of the O₂ profiles or the leakage ofoxygen into the core during handling on deck. Furthermore, the used D_b values, based on ²¹⁰Pb, may not befully appropriate; calculations with higher D_b values improve the O₂ fits. The surficial sedimentq70857jm363g/xxlarge948.gif" alt="delta" align="BASELINE" BORDER="0">¹³C _org values of q70857jm363g/xxlarge8764.gif" alt="sim" align="MIDDLE" BORDER="0"> -22q70857jm363g/xxlarge8240.gif" alt="permil" align="MIDDLE" BORDER="0"> become less negative with increasing depth and decreasing C _orgconcentrations. The major q70857jm363g/xxlarge948.gif" alt="delta" align="BASELINE" BORDER="0">¹³C change occurs in the top 3 to 4 cm and coincides with the interval weremost of the organic carbon oxidation takes place. This indicates that the reactive fractionof organic matter, commonly assumed to be marine, has a more negative q70857jm363g/xxlarge948.gif" alt="delta" align="BASELINE" BORDER="0">¹³C _orgthan the refractory fraction, usually held to be terrestrial. Palaeoproductivity estimates calculated from thesediment data by means of literature algorithms yield low surface productivities(12–88 gC m^-2 y^-1), which are in good agreement with field measurements of primary productivity in otherstudies. Such values are, however, significantly lower than those indicated by recent productivitymaps of the area derived from satellite imagery (>100 gC m^-2 y^-1).  相似文献   

A daily rainfall occurrence process   总被引：1，自引：0，他引：1  

W. Jakubowski 《Stochastic Environmental Research and Risk Assessment (SERRA)》1988,2(1):1-16

A model for the periodic (annual cycle), discrete rainfall occurrence process is presented. Using this model the probabilistic properties of the process in q191731063746j58/xxlarge8467.gif" alt="ell" align="BASELINE" BORDER="0">-day intervals can be investigated. In such an interval the rainfall occurrence process is approximated by some stationary processa _t ,tq191731063746j58/xxlarge8707.gif" alt="exist" align="MIDDLE" BORDER="0">IN. The processa _t ,tq191731063746j58/xxlarge8707.gif" alt="exist" align="MIDDLE" BORDER="0">IN is described by the distributions of the lengths of wet and dry sequences. It is assumed that the lengths of successive wet and dry sequences are independent. For this process the distribution of the number of wet days in q191731063746j58/xxlarge8467.gif" alt="ell" align="BASELINE" BORDER="0">-day intervals is calculated. The model is fitted to 50-year rainfall data from Wroclaw, Poland. Rainfall amounts of 0.1, 1.0 and 2.0 mm are considered as thresholds defining a wet day. To estimate the distribution of the length of wet and dry sequences the family of Pascal distribution is chosen.  相似文献   

Local Sensitivity Analysis of a Numerical Model of Volcanic Plinian Columns through Automatic Differentiation     

Isabelle Charpentier  Juan Manuel Espíndola 《Mathematical Geology》2005,37(1):95-113

Numerical simulation of geological phenomena are nowadays widely used to understand them. A good example are the numerous codes developed to model mass motion in different processes. Such models are approximations to the real phenomena because the physical conditions are simplified or because the values of the parameters intervening in the modeling are known only approximately. For this reason, an obligatory step in the application of these models is the assessment of their sensitivity to changes in the parameters. Sensitivity analysis is also required to evaluate the influence of the different input variables in the outcome of the model. In general this analysis is carried out by repeated computation of the model to different sets of input variables and settings of the model. A more fruitful procedure to carry out such analysis can be achieved by automatic differentiation. In this paper we illustrate such approach through its application to the model of an eruptive plinian column. The results of the analysis allow to assess, in a systematic and efficient manner, the relevance of the different boundary values and parameters of the model. The analysis reveals the effects on velocity, temperature, gas fraction, radius and ultimately column height, by changes in their boundary value (i.e. at the vent). The effect of changes in the value of the gas constants, density of pyroclasts and specific heat of the erupted material is also evidenced. Alternatively, the results can be regarded as a mean to estimate the values of the variables for different set of boundary values without recurring to new runs of the model. Automatic differentiation is shown to be a convenient scheme to obtain derivatives of model variables. This type of analysis forms in addition the basis for further work in inversion schemes.  相似文献   

NOAA Weather Radio (NWR) – A Coastal Solution to Tsunami Alert and Notification     

George?L.?CrawfordEmail author 《Natural Hazards》2005,35(1):163-171

The Washington State/Local Tsunami Work Group adopted the NOAA Weather Radio q/xxlarge8220.gif" alt="ldquo" align="MIDDLE" BORDER="0">All-Hazardsq/xxlarge8221.gif" alt="rdquo" align="MIDDLE" BORDER="0"> Warning System to warn citizens quickly and effectively of not only tsunami hazards but also other natural or man-made hazards. In concert with an array of deep ocean tsunami detectors, land-based seismic sensors, and warning messages issued by the tsunami warning centers, NWR provides a means to expeditiously get critical decision-making information to emergency managers, elected officials, and first responders. To implement the NWR strategy effectively, a partnership was developed to add a repeater to the NWR system to provide complete coverage to the coast of Washington and to shipping lanes off the coast. The Work Group also recognized the need to disseminate time critical hazard information on tsunamis to the public on beaches and in high traffic areas, so it developed a new notification system, with the first prototype installed on 2 July 2003 in Ocean Shores, Washington. A public education program also was developed to improve the impacted communitiesq/xxlarge8217.gif" alt="rsquo" align="BASELINE" BORDER="0"> understanding of the tsunami hazard, the warning system, and actions they should take if a tsunami occurs.  相似文献   

A Friedmann-Lemaître Universe Model with a Positive Cosmological Constant     

M.G. Larionov 《Astrophysics and Space Science》1997,252(1-2):139-149

The possibility of using a Friedmann-Lemaître model with a non-zero cosmological constant q3t7k63165qt56q1/xxlarge947.gif" alt="gamma" align="MIDDLE" BORDER="0"> is investigated on the basis of analyses of the RATAN-600 and 87GB radio surveys and optical constraints. A zero deceleration parameter and critical matter density are features of the model. The model is in agreement with current observational data, including estimates of the age of the Universe, Hubble constant measurements, and the q3t7k63165qt56q1/xxlarge920.gif" alt="THgr" align="BASELINE" BORDER="0"> - z relation. A value for the cosmological constant is determined and its physical nature discussed.  相似文献