Wave-Modified Flux and Plume Dispersion in the Stable Boundary Layer

The effects of a pressure jump and a following internal gravity wave on turbulence and plume diffusion in the stable planetary boundary layer are examined. The pressure jump was accompanied by a sudden increase in turbulence and plume dispersion. The effects of wave perturbations on turbulence statistics are analysed by calculating fluxes and variances with and without the wave signal for averaging times ranging from 1 to 30 min. The wave signals are obtained using a band-pass filter. It is shown that second-order turbulence quantities calculated without first subtracting the wave perturbations from the time are greater than those calculated when the wave signal is separated from the turbulence. Estimates of the vertical dispersion of an elevated tracer plume in the stable boundary layer are made using an elastic backscatter lidar. Plume dispersion observed 25 m downwind of the source increases rapidly with the arrival of the flow disturbances. Measured plume dispersion and plume centreline height correlate with the standard deviation of the vertical velocity but not with the wave signal.     

Model Simulations of the Transport of Odra Flood Water through the Szczecin Lagoon into the Pomeranian Bight in July/August 1997

The Odra river flood of July through August 1997 transported a large additional volume of water into the Szczecin Lagoon area for a period of about one month. The dispersion of this water in the Szczecin Lagoon and Pomeranian Bight was simulated using the operational hydrodynamic model of the North Sea and Baltic Sea operated by the Federal Maritime and Hydrographic Agency of Germany (BSH). The model system receives as input meteorological forecast fields from the EUROPA model of the German Weather Service. As a result of the model simulation, the temporal development of the river plume can be described as follows: First the eastern part of Szczecin Lagoon, the Zalew Wielki, filled with flood water displacing θnormalρ Odra river water from that area. After about a week, Odra river flood water started to flow into the Pomeranian Bight. Its dispersion within Szczecin Lagoon was by no means uniform. The Kleines Haff, the western part of the Lagoon, was not much affected at first. When large labelled water masses had already left the Zalew Wielki area through the Swina river, at most only about half the water volume in Kleines Haff had been replaced by Odra flood water. In the Pomeranian Bight, the concentration was higher at the coast of Usedom – at least initially – than at the coast of Wolin. After 30 August 1997, northwesterly winds caused undiluted Baltic water to flow from the northern to the southern part of the Pomeranian Bight, pushing the water body marked, or distinguished, by Odra water eastward along the coast of Wolin. At the same time, outflow began from Kleines Haff through the Peenestrom into the Greifswalder Bodden. Due to light winds, and hence limited vertical mixing in summer, the proportion of freshwater in Baltic surface water reached about 50% in the southern Pomeranian Bight. Near Rügen, it fell below 10%. Within 2 months of stronger wind caused major shifts of the water bodies concerned. The scale considerations and model simulations discussed in this paper allowed qualitative estimates to be made in the course of the flood event, which were later confirmed by measurements, presented at a HELCOM (Helsinki Commission, Baltic Marine Environment Protection Commission) Scientific Workshop in January 1998.     

南海北部夏季叶绿素a分布规律及影响因素

采用2002—2016年6—9月Aqua/MODIS叶绿素a产品分析珠江冲淡水在南海北部生态效应的季节及年际变化特征。6月来自陆源的营养物质在西南季风作用下向河口以东陆架区输运, 浮游植物增殖, 叶绿素a含量增大; 7月河口以东高浓度叶绿素a覆盖面积达到最大; 8月在减弱的珠江径流和环境风场共同影响下, 口门外海高浓度叶绿素a覆盖面积明显减小; 9月北部陆架区处于东北季风影响之下, 河口以西覆盖面积逐渐增大。通过线性回归分析可知, 珠江径流量是口门外海高浓度叶绿素a覆盖面积的主要影响因素, 且这种影响有一个月左右的滞后效应。显著大于(小于)多年平均的珠江径流量和环境风场等因素共同作用, 导致2008(2004)年表现为高浓度叶绿素a覆盖面积的极大值(极小值)年份。叶绿素a在南海北部陆架区的时空变化特征主要受冲淡水过程影响, 订正过的卫星叶绿素a产品可以用来讨论珠江冲淡水的季节及年际变化。     

A Comparison Of The Detailed Structure In Dispersing Tracer Plumes Measured In Grid-Generated Turbulence With A Meandering Plume Model Incorporating Internal Fluctuations

A meandering plume model that explicitly incorporatesinternal fluctuations has been developed and used to model the evolutionof concentration fluctuations in point-source plumes in grid turbulenceobtained from a detailed water-channel simulation. This fluctuating plumemodel includes three physical parameters: the mean plume spread in fixedcoordinates, which represents the outer plume length scale; the meaninstantaneous plume spread in coordinates attached to the instantaneousplume centroid, which represents the inner plume length scale; and, theconcentration fluctuation intensity in the meandering reference frame,which represents the in-plume fluctuation scale. These parameters arespecified in terms of a set of coupled dynamical equations that modeltheir development with downstream distance from the source. Explicitexpressions for the concentration moments of arbitrary integral orderand the concentration probability density function have been obtainedfrom the fluctuating plume model. Detailed comparisons of model predictionsagainst water-channel measurements for the first four concentrationmoments and the concentration probability distributions generally showvery good overall quantitative agreement. Exact quantitative conditions,expressed in terms of the physical parameters of the fluctuating plumemodel, have been derived for the emergence of off-centreline peaks inthe concentration variance profile. These quantitative conditions havebeen illustrated in terms of a diagram of states of the dispersing plume,and the qualitatively different regimes of plume concentration variancebehaviour on this state diagram have been identified and characterized.     

地幔柱假说及其发展

Ｍｏｒｇａｎ提出的地幔柱假说之后，基于流体力学基本方程组的定常地幔柱模式研究，认为地幔柱是地幔对流的一个组合部分。组分差异驱动的地幔柱模拟实验结果，限制了地幔柱在地球动力学中的应用。热浮力驱动的模拟实验结果得到了新的动态地幔柱模式。     

渤海第三纪裂谷扩张的地球物理分析

根据重磁计算的结果，对渤海第三纪裂谷扩张问题做了分析。在研究中还注意参考了渤海地热流和地壳上地幔电性高导层抬升的研究成果。认为由于深部岩浆的上涌，在渤海及其相邻的陆地共有渤中、渤海湾、庙西、辽东湾和垦利５个较大的地幔柱拱起，它们在华北新生代拗陷区形成了一个走向明显、形态独特、规模较大而又相对集中的地幔柱群     

Electrical resistivity imaging of conductive plume dilution in fractured rock

Electrical resistance tomography (ERT) was used to monitor a conductive plume dilution experiment that was conducted in fractured basalt in order to assess its applications in this type of fractured-rock environment. Tap water was injected into an injection well for 34 days to dilute a pre-existing potassium chloride (KCl) plume at a site in Idaho, USA. No further fluids were introduced artificially during a 62-day monitoring period. Both surface ERT and cross-borehole ERT were used to monitor dilution and displacement of the plume. A square grid of land-surface electrodes was used with the surface ERT. Three-dimensional images of surface ERT delineated areas of increased and decreased resistivities. Increasing resistivities are attributed to dilution/displacement of the KCl solution by tap-water invasion or the influx of seasonal recharge. Decreasing resistivities resulted from redistribution of residual KCl solution. Cross-borehole ERT was conducted between the injection well and each of seven surrounding monitoring wells. Polar plots of the injection-well resistivity data in the direction of each monitoring well delineate specific locations where tap water seeped from the injection well via preferential flow paths determined by time-dependent resistivity increases. Monitoring-well data indicate locations of clustered and isolated regions of resistivity changes.     

Comparison of Wind-tunnel and Water-channel Simulations of Plume Dispersion through a Large Array of Obstacles with a Scaled Field Experiment

We report on measurements of the near-field dispersion of contaminant plumes in a large array of building-like obstacles at three scales; namely, at full-scale in a field experiment, at 1:50 scale in a wind-tunnel simulation, and at 1:205 scale in a water-channel simulation. Plume concentration statistics extracted from the physical modelling in the wind-tunnel and water-channel simulations are compared to those obtained from a field experiment. The modification of the detailed structure of the plume as it interacts with the obstacles is investigated. To this purpose, measurements of the evolution of the mean concentration, concentration fluctuation intensity, concentration probability density function, and integral time scale of concentration fluctuations in the array plume obtained from the field experiment and the scaled wind-tunnel and water-channel experiments are reported and compared, as well as measurements of upwind and within-array velocity spectra. Generally, the wind-tunnel and water-channel results on the modification of the detailed plume structure by the obstacles were qualitatively similar to those observed in the field experiments. However, with the appropriate scaling, the water-channel simulations were able to reproduce quantitatively the results of the full-scale field experiments better than the wind-tunnel simulations.     

云南铂族元素找矿基础问题

云南省铂族元素矿床成矿地质条件较好，已有不少已知矿床、矿点、找矿信息及地球化学异常。找矿重点以基性超基性岩型为主，也应考虑其它类型，如热液型、黑色页岩型、煤岩型等。找矿重点地区除在峨眉山玄武岩分布区及其周边外，应注意康滇地轴中部及边缘中新生代断裂带通过的地区。峨眉山玄武岩分布区外围的卡林型金矿和浅成低温热液型矿床分布区亦值得重视，如滇东南地区。此外，寒武系黑色岩系及含磷层位的含铂性是一个具有挑战性的新课题，值得加强研究。云南铂族元素矿床的成矿时代，可能从元古代到新生代均有，对云南找铂来说非常有利，其它省区无法与之相比。新生代构造可能将深埋的矿体错动到浅部，找矿中需要特别注意。不妨“沿河找矿”。第四纪的风化壳中是否有铂族元素的富集也可探索。