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21.
ZhenMing Wu Lin Zhao Lin Liu Rui Zhu ZeShen Gao YongPing Qiao LiMing Tian HuaYun Zhou MeiZhen Xie 《寒旱区科学》2018,10(2):114-125
Differential Interferometric Synthetic Aperture Radar(D-In SAR) has been widely used to measure surface deformation over the Tibetan Plateau. However, the accuracy and applicability of the D-In SAR method are not well estimated due to the lack of in-situ validation. In this paper, we mapped the seasonal and long-term displacement of Tanggula(TGL) and Liangdaohe(LDH) permafrost regions with a stack of Sentinel-1 acquisitions using the Small Baseline Subset In SAR(SBAS-In SAR) method. In the TGL region, with its dry soils and sparse vegetation, the In SAR-derived surface-deformation trend was consistent with ground-based leveling results; long-term changes of the active layer showed a settlement rate of around 1 to 3 mm/a due to the melting of ground ice, indicating a degrading permafrost in this area. Around half of the deformation was picked up on monitoring, in contrast with in-situ measurements in LDH, implying that the D-In SAR method remarkably underestimated the surface-deformation. This phenomenon may be induced by the large soil-water content, high vegetation coverage, or a combination of these two factors in this region. This study demonstrates that surface deformation could be mapped accurately for a specific region with Sentinel-1 C-band data, such as in the TGL region.Moreover, although the D-In SAR technology provides an efficient solution for broad surface-deformation monitoring in permafrost regions, it shows a poor performance in the region with high soil-water content and dense vegetation coverage. 相似文献
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The relationship of N2O distributions with the Arctic vortex breakup is first analyzed with a probability distribution function (PDF) analysis. The N2O concentration shows different distributions between the early and late vortex breakup years. In the early breakup years, the N2O concentration shows low values and large dispersions after the vortex breakup, which is related to the inhomogeneity in the vertical advection in the middle and high latitude lower stratosphere. The horizontal diffusion coefficient (Kyy) shows a larger value accordingly. In the late breakup years, the N2O concentration shows high values and more uniform distributions than in the early years after the vortex breakup, with a smaller vertical advection and Kyy after the vortex breakup. It is found that the N2O distributions are largely affected by the Arctic vortex breakup time but the dynamically defined vortex breakup time is not the only factor. 相似文献
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Thomas K. Flesch Lowry A. Harper Raymond L. Desjardins Zhiling Gao Brian P. Crenna 《Boundary-Layer Meteorology》2009,132(1):11-30
Inverse-dispersion calculations can be used to infer atmospheric emission rates through a combination of downwind gas concentrations
and dispersion model predictions. With multiple concentration sensors downwind of a compound source (whose component positions
are known) it is possible to calculate the component emissions. With this in mind, a field experiment was conducted to examine
the feasibility of such multi-source inferences, using four synthetic area sources and eight concentration sensors arranged
in different configurations. Multi-source problems tend to be mathematically ill-conditioned, as expressed by the condition
number κ. In our most successful configuration (average κ = 4.2) the total emissions from all sources were deduced to within 10% on average, while component emissions were deduced
to within 50%. In our least successful configuration (average κ = 91) the total emissions were calculated to within only 50%, and component calculations were highly inaccurate. Our study
indicates that the most accurate multi-source inferences will occur if each sensor is influenced by only a single source.
A “progressive” layout is the next best: one sensor is positioned to “see” only one source, the next sensor is placed to see
the first source and another, a third sensor is placed to see the previous two plus a third, and so on. When it is not possible
to isolate any sources κ is large and the accuracy of a multi-source inference is doubtful. 相似文献
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香山绝对点周围的局部地壳变形及其对重力测量结果的影响 总被引:1,自引:0,他引:1
为了监视北京地区的地壳稳定性,北京测绘院对10多个基岩点和北京市区进行了多次沉降观测,结果表明香山点近10多年来高程变化只有几毫米,其重力效应可略而不计,但测点东北和东南方有两个较大的下沉区。用线积分法计算了两个局部沉降的重力效应,在沉降区中心其影响可达0.38μms^-2,但对香山点的重力效应非常小,完全可以忽略。因此得出如下结论:香山点观测到的重力变化不是地壳变形引起的。 相似文献
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本文报道的微体化石产于湖北宜昌樟村坪万家沟剖面埃迪卡拉纪陡山沱组第10层的硅磷质结核中,化石组合包括疑源类Appendisphaera grandis、Ericiasphaera spjeldnaesii、Knollisphaeridium maxi mum、Leiosphaeridia tenuissi ma、Meghystrichosphaeridium perfectum、Tianzhushania polysiphonia、T.spinosa、T.ornata;丝状蓝藻Oscillatoriopsis obtusa、Polytrichoides induviatus、P.lineatus、Salome hubeiensis、Siphonophycustypicum;多细胞藻类Sarcinophycus palilloformis、Wengania minuta。该微体化石组合面貌与黄陵背斜东、南翼陡山沱组二段硅质结核中以大型具刺疑源类Tianzhushania为特征的组合相同,与贵州瓮安地区陡山沱组上磷块岩下部保存的微体化石组合面貌基本一致。 相似文献
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