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891.
南海西部风驱离岸急流次中尺度锋面的动力学分析 总被引:1,自引:0,他引:1
本文利用卫星观测资料和500 m分辨率数值模拟结果,结合理论分析,对南海西部夏季风场驱动的离岸急流海域次中尺度锋面及其不稳定对背景流场的动力学影响进行了研究。卫星观测和模拟结果表明,南海西部(WSCS)存在侧向尺度为O(1-10)km的次中尺度锋面,在地转和非地转运动的共同作用下,次中尺度密度锋面具有一阶Rossby(Ro)和Richardson(Ri)数。锋面诊断结果显示,沿锋面急流方向的风场强迫引起了显著的跨锋面Ekman净输送,有效地在跨锋面方向将表层冷水平流输送至暖水侧,导致海表浮力损失。减弱的垂向层结和增强的水平浮力梯度使得锋面海域出现负Ertel位涡(PV),表明该密度锋面易受次中尺度对称不稳定(SI)的影响。次中尺度锋面不稳定引起的跨锋面次级环流能够显著增强垂向速度,其最大值可达100 m·d-1。能量评估结果表明,次中尺度湍流的两个主要能量源,即地转剪切项(GSP)和垂向浮力通量(BFLUX)在锋面海域显著增强表明在沿锋面急流方向的风场强迫作用下,大尺度地转流的地转剪切动能和锋面有效位能能有效地通过锋面不稳定向次中尺度过程传递。因此,次中尺度锋面及其不稳定有助于增强局地垂向交换和正向串级地转能量,可以为夏季WSCS高叶绿素浓度的相干结构和锋面地转能量的正向传递提供新的动力解释。 相似文献
892.
以受汶川“5.12”地震和“7.10”特大山洪泥石流灾害严重影响的汶川县原草坡乡为例,从农户风险感知现状出发,考察风险感知对搬迁意愿和搬迁行为的不同影响。研究结果表明:农户对自然灾害风险感知越强、对搬迁安置风险感知越弱,其搬迁意愿越强;较高的自然灾害风险感知会提高农户搬离灾害隐患点或风险区的概率,较强的搬迁安置风险感知会降低农户全家搬迁的可能性;搬迁安置风险感知对未搬迁和部分搬迁农户的影响程度超过自然灾害风险感知的影响。基于汶川县原草坡乡的实证研究,提出避灾搬迁安置决策中的“双重风险感知”假说。 相似文献
893.
??????????????????????о??????????????????е?Ч??,???????????????????????????????????????????????????????о????????:1)????????????????????????????о??????????????????Ч??????????????;2)??????????????????Ч?о?????????????????????????????????????????п????;3)??????????????????????????????????????????????????????????? 相似文献
894.
Fine-grained Pleistocene deepwater turbidite channel system on the slope of Qiongdongnan Basin, northern South China Sea 总被引:2,自引:0,他引:2
Yuan Shengqiang Wu Shiguo Lüdmann Thomas Yao Genshun Lv Fuliang Cao Feng Wang Hairong Li Li 《Marine and Petroleum Geology》2009,26(8):1441-1451
Recently, as oil exploitation has become focused on deepwater slope areas, more multi-channel high resolution 2D and 3D seismic data were acquired in the deepwater part of the Qiongdongnan Basin, northern South China Sea. Based on 3D seismic data and coherence time slice, RMS and 3D visualization, a series of deepwater channels were recognized on the slope that probably developed in the late Quaternary period. These channels trend SW–NE to W–E and show bifurcations, levees, meander loops and avulsions. High Amplitude Reflections (HARs), typical for channel–levee complexes, are of only minor importance and were observed in one of the channel systems. Most of the detected channels are characterized by low-amplitude reflections, and so are different from the typical coarse-grained turbidite channels that had been discovered worldwide. The absence of well data in the study area made it difficult to determine the age and lithology of these channels. Using a neighboring drill hole and published data about such depositional systems worldwide, the lithology of these channels is likely to be dominated by mudstones with interbedded thin sandstones. These channels are formed by turbidity currents originated from the little scale mountain river of mid-Vietnam in SW direction and were probably accompanied by a relative sea level drop in the last glacial age. These channels discovered on the northern South China Sea slope are likely to be fine-grained, mud-dominant and low N:G deposits in a deepwater paleogeographic setting. 相似文献
895.
Jun Zhao Wenxi Cao Guifen Wang Dingtian Yang Yuezhong Yang Zhaohua Sun Wen Zhou Shaojun Liang 《Estuarine, Coastal and Shelf Science》2009
For studies in bio-optical oceanography, visible light properties by classes of dissolved organic matter should be characterized. The regional adjustment of model parameters is one approach which is being widely used to refine bio-optical models. In the present study, buoy and laboratory data were acquired, and during the 15-day observation period an algal bloom event occurred. The absorption coefficient of CDOM at 443 nm, ag(443), changed in the range of 0.09–0.35 m−1 and 0.1–0.34 m−1 for two depths, 0.32 m and 2.3 m., respectively, throughout the entire period. CDOM absorption was larger for bloom conditions than for non-bloom conditions. In addition, the fraction of CDOM in total absorption was higher during the bloom event than that of non-bloom conditions. The spectral slope of CDOM absorption, Sg, regressed over 400–500 nm, ranged from 0.015 to 0.0185 nm−1 with an average of 0.0166 nm−1. CDOM fluorescence intensity (Fcdom) was obtained using an internal Raman standard and varied over the range of 467.44–1538.23 in relative units. Variations in Fcdom showed a similar pattern to that of CDOM absorption. A robust non-linear relationship between Fcdom and CDOM absorption was found, with a correlation coefficient of 0.893, throughout the whole observation. An attempt to describe Sg with absorption showed a promising consequence that can be described with a negative correlation during the bloom, however, without any distinguishable tendency for non-bloom time span. A two-band ratio algorithm was also carried out for retrieving CDOM absorption. The variations in optical properties of CDOM may be related to the complicated environment in the estuarine waters, which may result from different sources of CDOM. 相似文献
896.
897.
898.
基于JSCORS的江苏省现代大地坐标框架的建设与维护 总被引:2,自引:2,他引:0
本文结合江苏省现代大地坐标框架的建设和JSCORS的运行维护,通过对江苏省原大地坐标框架的情况分析,介绍了江苏大地坐标框架的建设方案.结合区域稳定基点组的确定、框架维护和复测机制的建立、框架维护系统的建设等内容,提出江苏省大地坐标框架维护的解决方案. 相似文献
899.
900.