甘肃省富硒土壤标准研究与探讨   总被引：1，自引：0，他引：1  

李春亮  李洚  杨菁  王巧薇  杨景宇 《西北地质》2021,(1):242-246

建立富硒土壤地方标准对促进富硒产业发展具有积极意义.笔者分析了西北各省富硒土壤标准制定现状,基于在甘肃全省范围内协同采集的304件土壤及小麦籽实样品分析数据,通过富硒小麦的下限值及籽实与根系土中Se的线性相关模型,推导出0.28×10-6作为甘肃省富Se 土壤标准下限,对甘肃省富Se 土壤地方标准的建立及富Se 土壤资...  相似文献   

LANDSAT7ETM+图像的光谱模式分析与应用——以北京密云地区土地覆盖为例     

张香平  杨小唤 《地球信息科学学报》2005,7(1):107-110

采用模式分解的方法(PDM),对北京密云地区2002年3月19日ETM+图像进行光谱模式提取与分解,得到研究区各个像元的植被、水和土壤系数;并通过不同系数的组合和判别分析的条件确定了研究区的土地覆盖状况以及不同土地覆盖类型的面积。结果表明,在降低ETM+数据维的情况下,光谱模式分解可以更直接的反映地物的类型。  相似文献   

顾及多因子影响的中国西部地区大气加权平均温度模型精化研究     

莫智翔  黎杏  黄良珂  刘立龙  韦欣怡  周清华 《大地测量与地球动力学》2021,41(2):145-151

针对中国西部地区地形起伏较大等情况,分析大气加权平均温度(Tm)与测站高程、地面温度的关系,利用2014?2016年探空数据,在Bevis模型基础上建立一种与地面温度、高程和季节变化有关的新Tm模型.以2017年探空数据为参考值,对新模型进行精度分析,并与广泛使用的Bevis模型和GPT2w模型进行精度比较.结果表明,...  相似文献   

高分多模卫星大气校正总体设计与在轨验证     

余婧  杨文涛  李正强  侯伟真  裘桢炜  李雨廷  葛邦宇 《遥感学报》2022,26(5):1039-1050

高分多模卫星搭载中国首台民用大气同步校正仪,可以对同平台的高分辨率相机观测区域进行时间同步、视场覆盖的大气参数测量,实现对高分辨率图像的大气校正。文章论述了高分多模卫星大气同步校正的总体设计思路,并给出了时空同步、多谱段、多偏振通道探测体制的设计方案和地面验证结果。高分多模卫星入轨以后,对大气同步校正仪的大气参数反演效果和高分辨率图像的校正效果进行了分析,结果表明利用大气同步校正仪测量数据对大气气溶胶光学厚度（AOD）和大气水汽含量（CWV）的反演结果可信,对高分辨率图像有较好的大气校正效果。  相似文献   

Three-dimensional on-line chemical modeling in a Mars general circulation model     

Y. Moudden  J.C. McConnell 《Icarus》2007,188(1):18-34

In this paper we present the design and some results of an on-line chemical model of the atmosphere of Mars using a three-dimensional dynamical-chemical model. A chemistry module has been added to the 3D Mars Global Multiscale Model (GM3), a general circulation model based on the Canadian weather forecast model. As water is a major fuel for chemistry on Mars, we have taken care to simulate the atmospheric water vapor content, taking into account evaporation from and condensation to the polar caps and in the atmosphere we allow for freezing and formation of a bulk cloud and sedimentation. The chemical module includes the main neutral carbon-oxygen-hydrogen-nitrogen species and associated relevant reactions. The outputs of the model are analyzed in the light of our current understanding of the chemistry on Mars. The results are in general accordance with 1D models and with two other 3D models with more limited chemistry. The model does not require elevated diffusion coefficients to fit observational data in the thermosphere as was suggested in some 1D studies. The large scale transport and the downward thermospheric transport in the winter pole appear to have a significant role in the concentrations of some trace species.  相似文献   

Velocity and vorticity measurements of Jupiter's Great Red Spot using automated cloud feature tracking     

David S. Choi  Don Banfield  Adam P. Showman 《Icarus》2007,188(1):35-46

We have produced mosaics of the Great Red Spot (GRS) using images taken by the Galileo spacecraft in May 2000, and have measured the winds of the GRS using an automated algorithm that does not require manual cloud tracking. Our technique yields a high-density, regular grid of wind velocity vectors that is advantageous over a limited number of scattered wind vectors that result from manual cloud tracking. The high-velocity collar of the GRS is clearly seen from our velocity vector map, and highest wind velocities are measured to be around 170 m s⁻¹. The high resolution of the mosaics has also enabled us to map turbulent eddies inside the chaotic central region of the GRS, similar to those mapped by Sada et al. [Sada, P.V., Beebe, R.F., Conrath, B.J., 1996. Icarus 119, 311-335]. Using the wind velocity measurements, we computed particle trajectories around the GRS as well as maps of relative and absolute vorticities. We have discovered a narrow ring of cyclonic vorticity that surrounds the main anti-cyclonic high-velocity collar. This narrow ring appears to correspond to a ring surrounding the GRS that is bright in 5 μm [Terrile, R.J., Beebe, R.F., 1979. Science 204, 948-951]. It appears that this cyclonic ring is not a transient feature of the GRS, as we have discovered it in a re-analysis of Galileo data taken in 1996 first analyzed by Vasavada et al. [Vasavada, A.R., and 13 colleagues, 1998. Icarus 135, 265-275]. We also calculate how absolute vorticity changes as a function of latitude along a trajectory around the GRS and compare these measurements to similar ones performed by Dowling and Ingersoll [Dowling, T.E., Ingersoll, A.P., 1988. J. Atmos. Sci. 45, 1380-1396] using Voyager data. We show no dramatic evolution in the structure of the GRS since the Voyager era except for additional evidence for a counter-rotating GRS core, an increase in velocity in the main velocity collar, and an overall decrease in the length of the GRS.  相似文献   

地理空间元数据的探讨     

吴金华 《地球科学与环境学报》2002,24(2):59-61

地理空间数据内容繁杂且数据量庞大,建立地理空间数据元数据是对其进行管理及共享的有效、可行的方法。因而对地理空间数据元数据的概念、研究现状、内容进行了探讨,对已有的元数据标准做出了简单的比较,并建立了一个地理空间元数据管理系统的框架。  相似文献   

Titan's surface and rotation: new results from Voyager 1 images     

James Richardson  Ralph D. Lorenz  Alfred McEwen 《Icarus》2004,170(1):113-124

We present an analysis of images of Saturn's moon Titan, obtained by the Voyager 1 spacecraft on November 8-12, 1980. Orange filter (590-640 nm) images were photometrically corrected and a longitudinal average removed from them, leaving residual images with up to 5% contrast, and dominated by surface reflectivity. The resultant map shows the same regions observed at 673 nm by the Hubble Space Telescope (HST). Many of the same albedo features are present in both datasets, despite the short wavelength (600 nm) of the Voyager 1 images. A very small apparent longitudinal offset over the 14 year observation interval places tight constraints on Titan's rotation, which appears essentially synchronous at 15.9458±0.0016 days (orbital period =15.945421±0.000005 days). The detectability of the surface at such short wavelengths puts constraints on the optical depth, which may be overestimated by some fractal models.  相似文献   

涡旋系统运动可预报性的一种简单动力学分析     

肖天贵 《成都信息工程学院学报》1997,(1)

运用简单的动力学方程，考察了旋转运动和辐合运动的初值问题，由此探讨了天气系统（尤其是涡旋系统）运动的可预报时限。对于天气尺度系统，确定性可预报时限约２～５天；对于１０７ｍ量级天气系统，可预报时限约１０多天；对于中小尺度天气系统，可预报时限约１天。其结果同Ｓｍａｇｏｒｉｎｓｋｙ等、Ｆｒａｅｄｒｉｃｈ等的结论基本一致。讨论还发现，在不同外部参数条件下，涡旋运动可预报性是有差异的  相似文献   

Life cycles of spots on Jupiter from Cassini images     

Liming Li  Andrew P. Ingersoll  Carolyn C. Porco  Shawn P. Ewald 《Icarus》2004,172(1):9-23

Using the sequence of 70-day continuum-band (751 nm) images from the Cassini Imaging Science System (ISS), we record over 500 compact oval spots and study their relation to the large-scale motions. The ∼100 spots whose vorticity could be measured—the large spots in most cases—were all anticyclonic. We exclude cyclonic features (chaotic regions) because they do not have a compact oval shape, but we do record their interactions with spots. We distinguish probable convective storms from other spots because they appear suddenly, grow rapidly, and are much brighter than their surroundings. The distribution of lifetimes for spots that appeared and disappeared during the 70-day period follows a decaying exponential with time constant (mean lifetime) of 3.5 days for probable convective storms and 16.8 days for all other spots. Extrapolating the exponential beyond 70 days seriously underestimates the number of spots that existed for the entire 70-day period. This and other evidences (size, shape, distribution in latitude) suggest that these long-lived spots with lifetime larger than 70 days are from a separate population. The zonal wind profile obtained manually by tracking individual features (this study) agrees with that obtained automatically by correlating brightness variations in narrow latitude bands (Porco et al., 2003). Some westward jets have developed more curvature and some have developed less curvature since Voyager times, but the number of westward jets that violate the barotropic stability criterion is about the same. In the northern hemisphere the number of spots is greatest at the latitudes of the westward jets, which are the most unstable regions according to the barotropic stability criterion. During the 70-day observation period the Great Red Spot (GRS) absorbed nine westward-moving spots that originated in the South Equatorial Belt (SEB), where most of the probable convective storms originate. Although the probable convective storms do not directly transform themselves into westward-moving spots, their common origin in the SEB suggests that moist convection and the westward jet compose a system that has maintained the GRS over its long lifetime.  相似文献