北极薄冰-煎饼冰区域中不同重力波驱动形成海流的敏感性分析     

张雪妍  戴海瑨  赵军  殷何卿 《海洋学报(英文版)》2020,39(3):123-129

A coupled ocean-ice-wave model is used to study ice-edge jet and eddy genesis during surface gravity wave dissipation in a frazil-pancake ice zone. With observational data from the Beaufort Sea, possible wave dissipation processes are evaluated using sensitivity experiments. As wave energy dissipated, energy was transferred into ice floe through radiation stress. Later, energy was in turn transferred into current through ocean-ice interfacial stress. Since most of the wave energy is dissipated at the ice edge, ice-edge jets, which contained strong horizontal shear, appeared both in the ice zone and the ocean. Meanwhile, the wave propagation direction determines the velocity partition in the along-ice-edge and cross-ice-edge directions, which in turn determines the strength of the along-ice-edge jet and cross-ice-edge velocity. The momentum applied in the along-ice-edge(cross-ice-edge)direction increased(decreased) with larger incident angle, which is favorable condition for producing stronger mesoscale eddies, vice versa. The dissipation rate increases(decreases) with larger(smaller) wavenumber, which enhances(reduces) the jet strength and the strength of the mesoscale eddy. The strong along-ice-edge jet may extend to a deep layer(> 200 m). If the water depth is too shallow(e.g., 80 m), the jet may be largely dampened by bottom drag, and no visible mesoscale eddies are found. The results suggest that the bathymetry and incident wavenumber(magnitude and propagation direction) are important for wave-driven current and mesoscale eddy genesis.  相似文献   

Change in Precipitation over the Tibetan Plateau Projected by Weighted CMIP6 Models     

Yin ZHAO  Tianjun ZHOU  Wenxia ZHANG  Jian LI 《大气科学进展》2022,39(7):1133-1150

Precipitation over the Tibetan Plateau (TP) is important to local and downstream ecosystems. Based on a weighting method considering model skill and independence, changes in the TP precipitation for near-term (2021–40), mid-term (2041–60) and long-term (2081–2100) under shared socio-economic pathways (SSP1-1.9, SSP1-2.6, SSP2-4.5, SSSP3-7.0, SSP5-8.5) are projected with 27 models from the latest Sixth Phase of the Couple Model Intercomparison Project. The annual mean precipitation is projected to increase by 7.4%–21.6% under five SSPs with a stronger change in the northern TP by the end of the 21st century relative to the present climatology. Changes in the TP precipitation at seasonal scales show a similar moistening trend to that of annual mean precipitation, except for the drying trend in winter precipitation along the southern edges of the TP. Weighting generally suggests a slightly stronger increase in TP precipitation with reduced model uncertainty compared to equally-weighted projections. The effect of weighting exhibits spatial and seasonal differences. Seasonally, weighting leads to a prevailing enhancement of increase in spring precipitation over the TP. Spatially, the influence of weighting is more remarkable over the northwestern TP regarding the annual, summer and autumn precipitation. Differences between weighted and original MMEs can give us more confidence in a stronger increase in precipitation over the TP, especially for the season of spring and the region of the northwestern TP, which requires additional attention in decision making.  相似文献   

Deformation mechanism of strain localization in 2D numerical interface tests     

Huaxiang Zhu  Wan-Huan Zhou  Zhen-Yu Yin 《Acta Geotechnica》2018,13(3):557-573

Heterogeneity arises in soil subjected to interface shearing, with the strain gradually localizing into a band area. How the strain localization accumulates and develops to form the structure is crucial in explaining some significant constitutive behaviors of the soil–structural interface during shearing, for example, stress hardening, softening, and shear-dilatancy. Using DEM simulation, interface shear tests with a periodic boundary condition are performed to investigate the strain localization process in densely and loosely packed granular soils. Based on the velocity field given by grains’ translational and rotational velocities, several kinematic quantities are analyzed during the loading history to demonstrate the evolution of strain localization. Results suggest that tiny concentrations in the shear deformation have already been observed in the very early stage of the shear test. The degree of the strain localization, quantified by a proposed new indicator, α, steadily ascends during the stress-hardening regime, dramatically jumps prior to the stress peak, and stabilizes at the stress steady state. Loose specimen does not develop a steady pattern at the large strain, as the deformation pattern transforms between localized and diffused failure modes. During the stress steady state of both specimens, remarkable correlations are observed between α and the shear stress, as well as between α and the volumetric strain rate.  相似文献   

Cyclic degradation and non-coaxiality of soft clay subjected to pure rotation of principal stress directions     

Jian-Gu Qian  Zi-Bo Du  Zhen-Yu Yin 《Acta Geotechnica》2018,13(4):943-959

Foundation soils are often under non-proportional cyclic loadings. The deformation behaviour and the mechanism of non-coaxiality under continuous pure principal stress rotation for clays are not clearly investigated up to now. In order to study the effect of pure principal stress rotation, a series of cyclic undrained tests on Shanghai soft clay subjected to cyclic rotation of principal stress directions keeping the deviatoric stress constant under the pure rotation condition were conducted using hollow cylinder apparatus. Based on this, the evolutions of excess pore pressure and strains during cyclic loading were investigated, together with the effects of the intermediate principal stress parameter and the deviatoric stress level on stress–strain stiffness and non-coaxiality. The result can provide an experimental basis for constitutive modelling of clays describing the behaviour under non-proportional loadings.  相似文献   

A simple approach to evaluating leakage through thin impervious element of high embankment dams     

Gang Deng  Kui Cao  Rui Chen  Xingxing Zhang  Qi Yin  Hao Zhou 《Environmental Earth Sciences》2018,77(1):25

Internal erosion is the most common reason which induces failure of embankment dams besides overtopping. Relatively large leakage is frequently concentrated at defects of impervious element, and this will lead to eventual failure. The amount of leakage depends not only on integrity of impervious element, but also on dam height, shape of valley, shape of impervious element and water level in reservoir. The integrity of impervious element, which represents the relative level of seepage safety, is not easy to be determined quantitatively. A simple method for generalization of steady seepage state of embankment dams with thin impervious element is proposed in this paper. The apparent overall value of permeability coefficient for impervious element can be obtained by this method with reasonable accuracy and efficiency. A defect parameter of impervious element is defined as an index to characterize seepage safety of embankment dams. It equals the ratio of the apparent overall value of permeability coefficient to the measured value in laboratory for intact materials. Subsequently, seepage safety of three dams is evaluated and the evolution of defect level of impervious element of dams is investigated. It is proved that the newly proposed method in this paper is feasible in the evaluation of relative seepage safety level of embankment dams with thin impervious element.  相似文献   

碳市场顶层设计路线图     

邹骥  柴麒敏  陈济  傅莎  葛兴安  胡敏  李昂  林丹妮  林殷  刘冬惠  刘俊伶  刘爽  祁悦  王克  王庶  张俊杰 《气候变化研究进展》2019,15(3):217-221

中国正面临着低碳减排和保持经济增速的双重挑战。为利用碳排放权交易机制以最低的社会成本实现减排目标,我国自2013年起开始建设碳排放权交易试点,并于2017年12月起宣布正式启动全国碳市场。然而碳市场的顶层设计不可一蹴而就,需要在我国宏观经济改革的大背景下分阶段逐步推进。短期（2020年前）碳市场建设重在强化产权制度建设,完善市场交易基础。中期（2021—2030年）碳市场建设要形成活跃的市场氛围,充分降低我国的温室气体达峰成本。长期（2031—2050年）碳市场建设要形成稳定上升的碳价趋势,为我国的低碳转型提供长期动力。  相似文献   

1617号鲇鱼台风登陆后引发不同性质暴雨的成因对比分析          下载免费PDF全文

王毅  张晓美  杨寅  曹勇  张芳华  周庆亮 《大气科学学报》2019,42(2):245-254

2016年9月28日1617号台风"鲇鱼"登陆后由台风本体环流和外围环流引发了不同性质的暴雨,这是本次秋季登陆台风暴雨预报的难点。利用常规气象观测资料以及NCEP的1°×1°再分析资料等,对不同性质暴雨的成因进行了诊断对比分析。结果表明:浙江东南部对流性降水和江西南部稳定性降水的大气层结结构具有明显的差异。中高纬度低槽距离台风较远,冷空气主要从低层入侵台风西北侧,破坏台风低层的暖心结构。台风外围中层干冷空气随东南风向浙江东南部输送,并叠加在低层暖湿气流之上,形成上冷下暖的不稳定层结,同时在对流层上层有干冷空气下沉至台风环流中下层(干侵入),导致浙江文成附近出现了局地特大暴雨。江西南部由于低层被湿冷空气占据,层结较为稳定,降水发展平缓。低空东南急流为台风外围环流暴雨提供了充足的水汽,浙江东南部地形对降水起到了增幅作用。不稳定层结及中层冷空气的输送对对流性暴雨的激发作用可以为登陆台风降水性质和强度预报提供参考依据。  相似文献   

Slow earthquakes,tectonic tremors,and rheology of the lower continental crust     

An Yin 《《地质学报》英文版》2018,92(Z1):3-3

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Three-Dimensional Lithospheric Resistivity Structure of the NE Tibetan Plateau and the Western North China Block and its Geological Significance     

Gaofeng Ye  Yuancheng Zhao  Sheng Jin  Wenbo Wei  Hao Dong  Letian Zhang  Yaotian Yin 《《地质学报》英文版》2018,92(Z1):38-39

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Structural evolution of a triclinic-type transpressional high strain zone and its role in exhuming the root of the Paleoproterozoic Trans-North China Orogen     

Jian Zhang  Guochun Zhao  Min Sun  Sanzhong Li  Shuwen Liu  Chunjing Wei  Changqing Yin 《《地质学报》英文版》2018,92(Z1):117-117

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