几何光学冠层反射建模中的光谱分量特征的参数化(英文)

该文用几何光学与辐射传输混合模型研究不连续植被冠层的几何光学反射模型的四分量（承照树冠、承照地面、阴影树冠、阴影地面）的参数化。用一个修正的均匀介质层路径散射（反射与传输）参数的解析算法估计路径散射参数（反射与传输），其中也考虑了冠层间隙的影响。光谱分量特征是不连续植被冠层的传输与反射，背景反照率，以直射光通量与天空漫射光通量比例的函数。光谱分量特征的模型与在美国缅因州Ｈｏｌａｎｄ采集的针叶林数据吻合。基于ＬｉＳｔｒａｈｌｅｒ几何光学相互遮蔽模型，用参数化的光谱分量特征对老松林和老云杉林的方向反射进行估计，其结果与在不同太阳与观测方向上的ＰＡＲＡＢＯＬＡ测量值匹配得很好。     

用航空POLDER测量仪获取的方向性信息增强对北方森林冠层的识别(英文)

ＰＯＬＤＥＲ（地球反射极化和方向）仪器在ＢＯＲＥＡＳ实验中曾搭载ＮＡＳＡ的一架Ｃ１３０飞机飞行。在ＢＯＲＥＡＳ的南部地区，ＰＯＬＤＥＲ获取了各种实验场地上的ＢＲＤＦ测量值。森林覆盖地区的大的热点特征，以及十个地区上的镜面反射分量得到了描述。该文通过ＰＯＬＤＥＲ的测量数据，对向常规的光谱特征中加入通过遥感获得的方向性特征后，对各种森林覆盖的分类和区分能力的提高给出了定量化的解。当将方向信息加入常规光谱信息后，采用无监督分类时，类间耦合矩阵的各项显著减小（减小倍数为２－５倍）。这一事实证明了用遥感方向特征可以增强对ＢＯＲＥＡＬ森林覆盖的区分能力。     

Petrology and Geochemistry of Early Cretaceous Bimodal Continental Flood Volcanism of the NW Etendeka, Namibia. Part 1: Introduction, Mafic Lavas and Re-evaluation of Mantle Source Components

The bimodal NW Etendeka province is located at the continentalend of the Tristan plume trace in coastal Namibia. It comprisesa high-Ti (Khumib type) and three low-Ti basalt (Tafelberg,Kuidas and Esmeralda types) suites, with, at stratigraphicallyhigher level, interstratified high-Ti latites (three units)and quartz latites (five units), and one low-Ti quartz latite.Khumib basalts are enriched in high field strength elementsand light rare earth elements relative to low-Ti types and exhibittrace element affinities with Tristan da Cunha lavas. The unradiogenic²⁰⁶Pb/²⁰⁴Pb ratios of Khumib basalts are distinctive, most plottingto the left of the 132 Ma Geochron, together with elevated ²⁰⁷Pb/²⁰⁴Pbratios, and Sr–Nd isotopic compositions plotting in thelower ¹⁴³Nd/¹⁴⁴Nd part of mantle array (EM1-like). The low-Tibasalts have less coherent trace element patterns and variable,radiogenic initial Sr (     

Using hydrogeochemical signatures of stream water to assess pathways for rainfall events: towards a predictive model

Thanks to its simple division into agricultural and forestry land use, the Corbeira catchment (Galicia, Spain) is used as a case study to build a predictive model using hydrogeochemical signatures. Stream data acquired under recessional flow conditions over a one year period were obtained from a sampling station near the downstream end of the catchment, and using principal component analysis, it is shown that some of the analytical parameters are covariant, and some are negatively correlated. These findings support inferences about the pathways of rainfall in the catchment. Specific signatures may be associated with the dominant hydrological source, either surface runoff or subsurface waters: additionally, the dominant land use in that part of the catchment, where the flow originated, can also be predicted. The dominant runoff shows a strong covariance between suspended solids (SS) and particulate phosphorus (PP), with a clear negative correlation with pH. Dissolved organic carbon (DOC) data are associated with this covariant set when these compounds are available in the soils in question. Dissolved phosphorus, total organic nitrogen and dissolved nitrates are also associated with the same covariant set when the runoff flows through areas of extensive agricultural use. The SS ? PP covariance is less significant at lower flows. Typical base flow regimes show a significant covariance between salinity and pH, with a marked negative correlation with SS ? PP set, confirming the dominance of subsurface waters in the baseflow, as expected. Seasonally divergent DOC ? SS behaviour proves to be a useful tracer for rainfall regimes. The DOC trend shows a sinusoidal annual variation in amplitude, determined by the rainfall regime. As a result, flow from the catchment is dominated by surface water whenever there is synchronicity between the peaks of DOC and SS. Copyright © 2013 John Wiley & Sons, Ltd.     

基于目标时域散射特性的土地覆盖类型分类研究

目标散射特性随时间变化的规律称之为目标时域散射特性。目标时域散射特征是利用多时相雷达遥感图像进行目标识别的基础。本研究以广东肇庆为试验区,利用多时相单参数雷达图像进行土地覆盖类型分类研究,分析了试验区内典型植被的结构、形态及其散射机理等特征,总结了各类目标的时域散射特性,区分识别了多种目标,制作了土地覆盖类型分类图.     

Indian Ocean-MORB-type isotopic signature of Yushigou ophiolite in North Qilian Mountains and its implications

Many researchers have focused on the tectonic evolution of North Qilian Mountains (NQM) since the 1970s[1―7]. However, the tectonic affinity of the an- cient oceanic mantle in early Paleozoic remains in de-bate. Three general explanations for it have been pro- posed. The first one suggests that the ancient ocean was a part of Proto-Tethys, and the tectonic evolution of NQM should be regarded as a portion of the562 Science in China: Series D Earth Sciences Tethyan tectonic domain[1]. …     

Long-arc analyses of SLR observations of the Etalon geodetic satellites

In this paper we describe the results of an analysis of a 2.5-year set of satellite laser range observations of the two Etalon geodetic satellites. We fit continuous orbits to the range observations, and map the range residuals into series of equivalent orbital element residuals, considering in detail the orbital longitude, eccentricity and nodal residuals. We use the longitude residuals to study thermal effects acting on the satellites and compare the results with those published for the Lageos satellites. We discuss the differences between the two series of eccentricity residuals, and again compare the results with those from Lageos. Finally we use the nodal residuals to investigate the potential for determination of UT1 of the reference frame defined by the orbits of the Etalon satellites. Received: 30 January 1997 / Accepted: 11 December 1997     

Progressive Transformation of a Flux Rope to an ICME

The solar wind conditions at one astronomical unit (AU) can be strongly disturbed by interplanetary coronal mass ejections (ICMEs). A subset, called magnetic clouds (MCs), is formed by twisted flux ropes that transport an important amount of magnetic flux and helicity, which is released in CMEs. At 1 AU from the Sun, the magnetic structure of MCs is generally modeled by neglecting their expansion during the spacecraft crossing. However, in some cases, MCs present a significant expansion. We present here an analysis of the huge and significantly expanding MC observed by the Wind spacecraft during 9 – 10 November 2004. This MC was embedded in an ICME. After determining an approximate orientation for the flux rope using the minimum variance method, we obtain a precise orientation of the cloud axis by relating its front and rear magnetic discontinuities using a direct method. This method takes into account the conservation of the azimuthal magnetic flux between the inbound and outbound branches and is valid for a finite impact parameter (i.e., not necessarily a small distance between the spacecraft trajectory and the cloud axis). The MC is also studied using dynamic models with isotropic expansion. We have found (6.2±1.5)×10²⁰ Mx for the axial flux and (78±18)×10²⁰ Mx for the azimuthal flux. Moreover, using the direct method, we find that the ICME is formed by a flux rope (MC) followed by an extended coherent magnetic region. These observations are interpreted by considering the existence of a previously larger flux rope, which partially reconnected with its environment in the front. We estimate that the reconnection process started close to the Sun. These findings imply that the ejected flux rope is progressively peeled by reconnection and transformed to the observed ICME (with a remnant flux rope in the front part).     

Multi-objective autocalibration of SWAT model for improved low flow performance for a small snowfed catchment

ABSTRACT

A reliable modelling framework needs to ensure that the model is simulating reality with limited uncertainty, thus enhancing its predictive ability. In the literature, hydrological model assessment using one or more metrics is reported to be inadequate when the river flow regime is required to be reproduced comprehensively. This research is aimed to: (a) calibrate the Soil and Water Assessment Tool (SWAT) based on the concept of multi-objective optimization by applying the Borg multi-objective evolutionary algorithm (MOEA); (b) apply hydrological signatures as objective functions; and (c) adopt a multi-metric approach for model evaluation. The SWAT model was coupled with a relatively newer and powerful Borg MOEA. The inclusion of hydrological signatures as objective functions along with the conventional statistical functions assisted in improving the performance for low flows by 135% in terms of volume efficiency and 65% for flow time series simulation.