High-resolution atmospheric forcing for regional oceanic model: the Iroise Sea

This study was aimed at modeling, as realistically as possible, the dynamics and thermodynamics of the Iroise Sea by using the Model for Applications at Regional Scale (MARS), a regional ocean 3D model. The horizontal resolution of the configuration in use is 2 km with 30 vertical levels. The 3D model of the Iroise Sea is embedded in a larger model providing open boundary conditions. As regards the atmospheric forcing, the originality of this study is to force the regional ocean model with the high-resolution (6 km) regional meteorological model, Weather Research and Forecasting (WRF). In addition, as the air surface temperature is highly sensitive to the sea surface temperature (SST), this regional meteorological model is improved by taking into account a regional climatologic SST to compute meteorological parameters. By allowing a better coherence between the SST and the temperature of the atmospheric boundary layer while giving a more realistic representation of heat fluxes exchanged at the air/sea interface, this forcing constitutes a noticeable improvement of the Iroise Sea modeling. The different sensitivity tests discussed here pinpoint the importance of entering, in WRF, SST data of sufficiently high quality before the computation of meteorological forcing when the aim is a study of dynamics and thermodynamics far away from the coast. On the other hand, when the target is the reproduction of coastal small-scale features in Iroise Sea modeling, the resolution of the meteorological forcing and the quality of SST are both paramount. The simulation of reference was carried out throughout the Summer and Autumn of year 2005 to allow comparisons with a campaign of surface current measurements by high-frequency radars conducted at the same period.     

Ground-based lidar and atmospheric studies

This review considers the requirements and possibilities for the development of a ground-based network for long-term observations of the atmosphere. This network would be specifically designed to provide early detection of changes in the composition and structure of the stratosphere. The species and parameters identified as being important and amenable to ground-based measurements are summarized, as are the currently available techniques capable of making the required measurements. Ultraviolet laser remote sensing is identified as the most promising technique for the measurement of ozone and temperature profiles which are considered to have the highest priority for network measurements. The laser techniques, and the research at JPL Table Mountain Observatory, to implement ozone and temperature measurements are discussed in greater detail.     

The MST radar technique: Potential for middle atmospheric studies

We examine the potential of the MST (mesosphere-stratosphere-troposphere) radar technique for obtaining detailed information on the middle atmosphere. This technique-which uses very sensitive coherent VHF and UHF radars-is capable of detecting signal returns arising from weak fluctuations in the atmospheric refractive index. With certain limitations the MST technique is capable of continually observing winds, waves, turbulence and atmospheric stability over the height range 1–100 km with good-to-excellent time and space resolution. We examine the relatively large body of literature that has been written over the past few years and outline some aspects of a promising future.     

Antarctica — A unique laboratory for atmospheric studies by optical methods

Optical methods of studying the atmosphere are one valuable means of investigating atmospheric behaviour at heights ranging from less than 1 km to several hundred km. Some examples are given of results from various optical experiments carried out at Halley, Antarctica (76^oS, 27^oW;L=4.2), as is a consideration of the results of some complementary experiments. By combining observations made using different techniques, an improved understanding of atmospheric, ionospheric and magnetospheric processes is obtained.     

Experimental studies related to atmospheric flow around obstacles

Summary Laboratory-scale experiments on a small cylindrical barrier capable of being moved zonally with respect to a rotating hemispherical shell of liquid are described. When the cylinder is moved west relative to the shell at rates approximating 1/10 of the basic rotation a strong anticyclonic circulation developes around the cylinder and pronounced wave motions appear in the remainder of the liquid. When the cylinder is moved eastward at the same relative rates there is no net circulation around it and rapid motions toward the east occur in the latitude zone that it occupies. Velocity discontinuity surfaces on which occasional vortices develop divide this zone from the remainder of the liquid on both sides where much less developed motions occur. General implications of these and certain other types of experiments for problems of flow over large mountain masses are pointed out.     

Preliminary15N studies on atmospheric nitrogenous trace gases

Preliminary nitrogen isotope data for ammonia from animal urine, fuel combustion, fertilizer use and fertilizer factories have been measured or estimated. It turns out that direct nitrogen isotope measurements of atmospheric ammonia at Jülich are in the expected range calculated from the ranges of different sources. For deposition of atmospheric ammonium in Jülich-rain a depletion in¹⁵N with respect to atmospheric ammonia has been found which is explained by isotope fractionations during rainout and washout. In correspondence with this fractionation model are nitrogen isotope data of rain-ammonium from coastal areas, which are enriched in¹⁵N due to the fact that sea water acts as a sink for atmospheric ammonia.For Jülich rain-nitrate a pronounced seasonal trend has been detected with lower¹⁵N data in spring and summer than in autumn and winter. This trend is interpreted by different nitrogen isotope data of anthropogenic and natural nitric oxides which have been measured or estimated from isotope fractionation effects during nitrification and denitrification reactions in soils. It should be possible to get better global estimations for anthropogenic and natural nitric oxides from nitrogen isotope measurements.     

临近空间大气扰动变化特性的定量研究

本文利用TIMED/SABER 2002年1月至2013年1月共11年的卫星温度探测数据,通过全球网格化及在网格内作数学统计的方法,得到了20~100 km高度上全球网格点上温度的平均值和标准差,实现了对临近空间全球大气扰动进行定量刻画的目的.通过定量分析温度标准差的分布特性,文中得到了临近空间大气扰动的全球分布规律,并讨论了与这些分布规律相关的物理过程.结果表明,在20~70 km高度上,温度标准差为1~10 K,有显著的冬季/夏季的差异,冬季的温度标准差比夏季大;大气重力波扰动是最主要来源,同时大气传播性行星波引起的扰动也是来源之一.在70~100 km高度上,温度标准差常年较强,量值为10~30 K,冬季/夏季的差异小,低纬地区的温度标准差高于中高纬度地区,呈现许多局地化的小结构.大气重力波是引起该区域大气总扰动量的主要扰动来源,大气潮汐波、传播性行星波(准2天、准6.5天)也有重要贡献.     

Development and evaluation of airborne microwave refractometer for studies on atmospheric tropical boundary layer radiorefractive index

Observations of high-resolution data on radio refractivity were obtained by the airborne microwave refractometer over the Indian sub-continent (a tropical country) from 1971 to 1988. Detailed vertical and horizontal distributions of radio refractivity on a near-real-time basis in the atmospheric boundary layer were determined. Radiosonde observations cannot detect the thin refractivity gradients which characterize the propagation environment in this low-altitude region. This knowledge is required to design reliable and efficient communication systems for strategic, tactical and operational needs. However, the results demonstrate the layer structures and the variability of the boundary layer in time and space. The radio refractive effects on electromagnetic propagation and the future direction of radio refractivity fine-structure measurements are discussed.     

High-resolution varve studies in Baldeggersee (Switzerland): Project overview and limnological background data

This introduction to a series of high-resolution varve studies in Baldeggersee provides both an overview of the different subprojects as well as background information on relevant limnological trends. The project was based on a new method of in-situ freezing of unconsolidated surficial sediments in deep lakes. With this freeze-core technique a detailed, high-resolution stratigraphy of the varved sediments at the deepest point of Baldeggersee has been established for the period of 1885–1993. Annual and seasonal sediment samples were analyzed. Concentrations of redox active metals in sediments were calibrated as proxy indicators for the reconstruction of hypolimnetic oxygen conditions. Particle size analysis and varve measurements were used to discriminate between the influence of nutrients and climate on sediment formation and accumulation. Baldeggersee is an ideal system for calibrating indicators of deep-water oxygen concentrations because it underwent dramatic changes in nutrient loading and redox conditions during this century. The hypolimnion has been seasonally anoxic for the last 100 years and phosphorus content decreased by a factor of five in the last 20 years. Meromixis was observed between 1960 and 1980. Since 1983 the deep water has been artificially oxygenated. This well documented change in deep-water oxygen concentration represents a unique whole-lake experiment that can be used to analyze the geochemical response of the sediments.     

High-resolution slug testing

The hydraulic conductivity (K) variation has important ramifications for ground water flow and the transport of contaminants in ground water. The delineation of the nature of that variation can be critical to complete characterization of a site and the planning of effective and efficient remedial measures. Site-specific features (such as high-conductivity zones) need to be quantified. Our alluvial field site in the Kansas River valley exhibits spatial variability, very high conductivities, and nonlinear behavior for slug tests in the sand and gravel aquifer. High-resolution, multilevel slug tests have been performed in a number of wells that are fully screened. A general nonlinear model based on the Navier-Stokes equation, nonlinear frictional loss, non-Darcian flow, acceleration effects, radius changes in the wellbore, and a Hvorslev model for the aquifer has been used to analyze the data, employing an automated processing system that runs within the Excel spreadsheet program. It is concluded that slug tests can provide the necessary data to identify the nature of both horizontal and vertical K variation in an aquifer and that improved delineation or higher resolution of K structure is possible with shorter test intervals. The gradation into zones of higher conductivity is sharper than seen previously, and the maximum conductivity observed is greater than previously measured. However, data from this project indicate that well development, the presence of fines, and the antecedent history of the well are important interrelated factors in regard to slug-test response and can prevent obtaining consistent results in some cases.     

一种高分辨率温度传感器

介绍一种基于Pt1000惠斯通平衡电桥的高分辨率温度传感器。 实验测试表明, 该温度传感器具有精确、 稳定、 分辨率高的特点, 测试温度的分辨率可以达到1×10^-5℃。 其温度测试范围可调, 从而可以满足不同测试环境温度测试的需要, 具有较广泛的应用范围, 并可同通用数据采集器连接构成精密温度观测系统。     

Ultraminiature X-ray fluorescence spectrometer for in-situ geochemical analysis on Mars

Determination of the surface composition at various sites on the planet Mars will provide information essential to a better understanding of the geologic history of this complex planet. A spectrometer based upon the X-ray fluorescence method of elemental analysis has been developed in an ultraminiature, rugged form suitable for a spacecraft mission to Mars. The instrument employs two radioisotope sources (⁵⁵Fe and¹⁰⁹Cd) which irradiate adjacent areas on a regolith sample. Fluorescent X-rays emitted by the sample are detected by four thin-window proportional counters. Using pulse-height discrimination, the energy spectra are determined. Virtually all elements above sodium in the periodic table are detected if present at sufficient levels. Minimum detection limits range from 30 ppm to 2%. depending upon the element and the matrix. For most elements, they are below 0.5%. Accuracies also depend upon the matrix, but are generally better than ± 0.5% for all elements of atomic number greater than 14. Elements below sodium are also detected, but as a single group. Ambiguities of identification of the elements producing the observed spectra are minimal. Exotic geological materials are, therefore, just as susceptible to analysis as are the more common rocks. A computer model of the instrument has been developed and tested. This model was used to optimize instrument parameters during the design phase, and has now been expanded to perform automatic analysis of the output data.     

高分辨率浅层人工地震勘探探测隐伏断裂实例

利用高分辨率浅层地震勘探反射波法探测了福建某火电厂场址内的隐伏断裂。结果表明断裂显示清楚,为一走向NE40~55°,上断点埋深为11 m和31 m,断距2~4 m的正断层,为工程避让提供较可靠的依据。     

高分辨磁共振血管壁成像在颅内动脉狭窄病因鉴别中的研究进展

颅内动脉狭窄（ICAS）导致的缺血性脑卒中,具有高致残率和致死率的特点。临床上常规检查方法包括经颅多普勒超声、CT血管造影、磁共振血管造影和X射线数字减影血管造影等,上述方法都是针对血管狭窄,不能显示血管壁病变。高分辨磁共振血管壁成像技术（HR-VWI）是一种新出现的影像学检查手段,能够无创性显示血管壁病变,对判断ICAS病变性质具有重要价值。本文针对HR-VWI在ICAS病因鉴别中的应用研究进展进行综述。

     

High-resolution unmanned aerial vehicle aeromagnetic surveys for mineral exploration targets

Recent advancements in geophysical exploration have been realized through reliably integrating unmanned aerial vehicle platforms with lightweight, high-resolution magnetometer payloads. Unmanned aerial vehicle aeromagnetic surveys can provide a contemporary data product between the two end-members of coverage and resolution attained using manned airborne and terrestrial magnetic surveys. This new data product is achievable because unmanned aerial vehicle platforms can safely traverse with magnetometer payloads at flight elevations closer to ground targets than manned airborne surveys, while also delivering an increased coverage rate compared to walking conventional terrestrial surveys. This is a promising new development for geophysical and mineral exploration applications, especially in variable terrains. A three-dimensional unmanned aerial vehicle aeromagnetic survey was conducted within the Shebandowan Greenstone Belt, northwest of Thunder Bay, Ontario, Canada, in July 2017. A series of two-dimensional grids (∼500 m × 700 m) were flown at approximate elevations of 35, 45 and 70 m above ground level using a Dà-Jiāng Innovations multi-rotor unmanned aerial vehicle (S900) and a GEM Systems, Inc., Potassium Vapour Magnetometer (GSMP-35U). In total, over 48 line-km of unmanned aerial vehicle aeromagnetic data were flown with a line spacing of 25 m. The collected aeromagnetic data were compared to a regional heliborne aeromagnetic survey flown at an elevation of approximately 85 m above the terrain, with a line spacing of 100 m, as well as a follow-up terrestrial magnetic survey. The first vertical derivative of the gathered unmanned aerial vehicle total magnetic field data was calculated both directly between each of the different flight elevations, and indirectly by calculating the values predicted using upward continuation. This case study demonstrates that low flight elevation unmanned aerial vehicle aeromagnetic surveys can reliably collect industry standard total magnetic field measurements at an increased resolution when compared to manned airborne magnetic surveys. The enhanced interpretation potential provided by this approach also aided in delineating structural controls and hydrothermal fluid migration pathways (a pair of adjacent shear zones) related to gold mineralization on site. These structural features were not clearly resolved in the regional manned airborne magnetic data alone, further demonstrating the utility of applying high-resolution unmanned aerial vehicle aeromagnetic surveys to mineral exploration applications. The conclusions and interpretations drawn from the unmanned aerial vehicle aeromagnetic data, coupled with historical data, were applied to make a new gold mineralization discovery on the site, assayed at 15.7 g/t.     

A new radiometer for atmospheric long waves

Summary A new radiometer has been designed which employs a black plate whose radiation towards the night sky is balanced by infrared radiation transferred in vacuo. The instrumental characteristics are described by a simplified theory and by laboratory tests making use of large surfaces with known emissivities. The instrument allows the incoming IR atmospheric flux to be measured with a high degree of accuracy and independently of the ventilation rate.     

High-resolution ensemble forecasting for the Gulf of Mexico eddies and fronts

High-resolution models and realistic boundary conditions are necessary to reproduce the mesoscale dynamics of the Gulf of Mexico (GOM). In order to achieve this, we use a nested configuration of the Hybrid Coordinate Ocean Model (HYCOM), where the Atlantic TOPAZ system provides lateral boundary conditions to a high-resolution (5 km) model of the GOM . However, such models cannot provide accurate forecasts of mesoscale variability, such as eddy shedding event, without data assimilation. Eddy shedding events involve the rapid growth of nonlinear instabilities that are difficult to forecast. The known sources of error are the initial state, the atmospheric condition, and the lateral boundary condition. We present here the benefit of using a small ensemble forecast (10 members) for providing confidence indices for the prediction, while using a data assimilation scheme based on optimal interpolation. Our set of initial states is provided by using different values of a data assimilation parameter, while the atmospheric and lateral boundary conditions are perturbed randomly. Changes in the data assimilation parameter appear to control the main position of the large features of the GOM in the initial state, whereas changes in the boundary conditions (lateral and atmospheric) appears to control the propagation of cyclonic eddies at their boundary. The ensemble forecast is tested for the shedding of Eddy Yankee (2006). The Loop Current and eddy fronts observed from ocean color and altimetry are almost always within the estimated positions from the ensemble forecast. The ensemble spread is correlated both in space and time to the forecast error, which implies that confidence indices can be provided in addition to the forecast. Finally, the ensemble forecast permits the optimization of a data assimilation parameter for best performance at a given forecast horizon.     

The application of least squares analysis for the estimation of low atmospheric concentrations of short-lived radon daughters and studies on their disequilibrium

The application of the weighted and unweighted least-squares method to the analysis of the individual concentrations of short-lived radon daughters in the open atmosphere, where, unlike in the mines the levels are low, is discussed. The method can be optimized to give minimum counting errors by proper choice of collection times and counting periods. By analysing a large number of samples it is shown that the least squares method gives better accuracy than the simultaneous equations method generally in use. The calculation can be simplified by using the unweighted least-squares analysis without significant loss in accuracy. The levels of RaA, RaB and RaC in surface air at Bombay during the period January-June 1975, calculated using the least-square method, are presented. The activity ratios of RaC/RaB are shown to have an average value around 0.6–0.9 even at 18 m height. The RaB/RaA activity ratios however show a much larger scatter than the RaC/RaB values. The possible reasons for these differences are discussed. The application of the least-squares method to the analysis of Th-B and Th-C is also described.     

High-resolution depth imaging with sparseness-constrained inversion

An imaging technique is developed which exceeds the resolution limitation prescribed by conventional seismic imaging methods. The high‐resolution imaging is obtained by introducing a sparseness‐constrained least‐squares inversion into the imaging process of prestack depth migration. This is implemented by a proposed interference technique. In contrast to conventional depth migration, a decomposed signal or combined event, instead of the source wavelet, is needed in the proposed scheme. The proposed method aims to image a small local region with a higher resolution using the prestack data set. It should be applied following conventional depth imaging if a higher resolution is needed in a target zone rather than replacing the conventional depth imaging for the entire medium. Synthetic examples demonstrate the significant improvements in the resolution using the proposed scheme.     

The evidence for auroral effects on atmospheric electricity

Summary The possibility of atmospheric electrical effects due to the aurora has been considered by investigators since 1875. An unsatisfactory theoretical basis for an explanation of observed effects and the measurements of only a few of the related parameters for short periods of time has led to uncertainty in the matter. Nevertheless, since the IGY²), new discoveries related to the aurora portray an unusual complexity, and a wide range of energy input. When considered with recent discussions on atmospheric electrification some interesting interpretations of the observed effects are suggested. On the ground, large negative excursions of the atmospheric electric field (E) during fair weather, and above 100 mb³) peculiar increases in negative ion densities and variations in air-earth current density (I) all appear to be related to auroral activity. A difference in (I) measured simultaneously at geomagnetic latitudes 55° and 68°N which is greater than what one would expect from a difference in conductivity due to cosmic rays may also be due to the aurora. Several models of the observed effects will be considered: (1) the high influx of negative space charge, i.e. a precipitation of around 10¹⁴ elementary charges m^–2 s^–1; (2) the auroral bremsstrahlung flux acts as an atmospheric current generator; (3) plasma instability in the auroral electrojet; (4) a combination of (2) and (3). The infrequent observation of the auroral effects on atmospheric electricity is probably due to limitations in detecting an extreme local fluctuation in such a large-scale complex phenomenon.