Inversion, error analysis, and validation of GPS/MET occultation data

The global positioning system meteorology (GPS/MET) experiment was the first practical demonstration of global navigation satellite system (GNSS)-based active limb sounding employing the radio occultation technique. This method measures, as principal observable and with millimetric accuracy, the excess phase path (relative to propagation in vacuum) of GNSS-transmitted radio waves caused by refraction during passage through the Earth’s neutral atmosphere and ionosphere in limb geometry. It shows great potential utility for weather and climate system studies in providing an unique combination of global coverage, high vertical resolution and accuracy, long-term stability, and all-weather capability. We first describe our GPS/MET data processing scheme from excess phases via bending angles to the neutral atmospheric parameters refractivity, density, pressure and temperature. Special emphasis is given to ionospheric correction methodology and the inversion of bending angles to refractivities, where we introduce a matrix inversion technique (instead of the usual integral inversion). The matrix technique is shown to lead to identical results as integral inversion but is more directly extendable to inversion by optimal estimation. The quality of GPS/MET-derived profiles is analyzed with an error estimation analysis employing a Monte Carlo technique. We consider statistical errors together with systematic errors due to upper-boundary initialization of the retrieval by a priori bending angles. Perfect initialization and properly smoothed statistical errors allow for better than 1 K temperature retrieval accuracy up to the stratopause. No initialization and statistical errors yield better than 1 K accuracy up to 30 km but less than 3 K accuracy above 40 km. Given imperfect initialization, biases ≫ 2 K propagate down to below 30 km height in unfavorable realistic cases. Furthermore, results of a statistical validation of GPS/MET profiles through comparison with atmospheric analyses of the European Centre for Medium-range Weather Forecasts (ECMWF) are presented. The comparisons indicate the high utility of the occultation data in that very good agreement of upper troposphere/lower stratosphere temperature (better than 1.5 K rms, ≪ 0.5 K bias) is found for a region (Europe+USA) where the ECMWF analyses are known to be good, but poorer agreement for a region (Southern Pacific) where the analyses are known to be degraded.     

MIDAS-W: a workstation-based incoherent scatter radar data acquisition system

The Millstone Hill Incoherent Scatter Data Acquisition System (MIDAS) is based on an abstract model of an incoherent scatter radar. This model is implemented in a hierarchical software system, which serves to isolate hardware and low-level software implementation details from higher levels of the system. Inherent in this is the idea that implementation details can easily be changed in response to technological advances. MIDAS is an evolutionary system, and the MIDAS hardware has, in fact, evolved while the basic software model has remained unchanged. From the earliest days of MIDAS, it was realized that some functions implemented in specialized hardware might eventually be implemented by software in a general-purpose computer. MIDAS-W is the realization of this concept. The core component of MIDAS-W is a Sun Microsystems UltraSparc 10 workstation equipped with an Ultrarad 1280 PCI bus analog to digital (A/D) converter board. In the current implementation, a 2.25 MHz intermediate frequency (IF) is bandpass sampled at 1 s intervals and these samples are multicast over a high-speed Ethernet which serves as a raw data bus. A second workstation receives the samples, converts them to filtered, decimated, complex baseband samples and computes the lag-profile matrix of the decimated samples. Overall performance is approximately ten times better than the previous MIDAS system, which utilizes a custom digital filtering module and array processor based correlator. A major advantage of MIDAS-W is its flexibility. A portable, single-workstation data acquisition system can be implemented by moving the software receiver and correlator programs to the workstation with the A/D converter. When the data samples are multicast, additional data processing systems, for example for raw data recording, can be implemented simply by adding another workstation with suitable software to the high-speed network. Testing of new data processing software is also greatly simplified, because a workstation with the new software can be added to the network without impacting the production system. MIDAS-W has been operated in parallel with the existing MIDAS-1 system to verify that incoherent scatter measurements by the two systems agree. MIDAS-W has also been used in a high-bandwidth mode to collect data on the November, 1999, Leonid meteor shower.     

改进型中心管模型能量转换性能试验及样机设计

为了提高中心管振荡水柱波浪能利用技术能量转换效率,基于新的认识和目前常用的2.4米导航灯标,对中心管尾部设计了三种模型并在造波水槽中进行能量转换性能试验。试验结果表明:直管型中心管俘获宽度比最高达到了70.25%,但通频带宽度窄;加长喇叭口型中心管略好于喇叭口型中心管;在喷咀比为0.02条件下,加长喇叭口型中心管浮体有较高双峰俘获宽度比,波峰为40.0%,波谷为31.6%,通频带宽,为随机波下高效转换创造了条件。最高俘获宽度比和双峰通频带特性实验数据结果都优于历史文献值。根据试验数据对一些适合小型海洋仪器供电的样机进行了设计,设计的样机具有较高的性价比。     

基于卷积对抗降噪网络的塔里木盆地沙漠地震资料消噪方法研究

塔里木盆地作为我国重要的油气勘探地区, 其地表主要由沙漠覆盖.塔里木地区获取的沙漠地震资料通常表现为低信噪比, 并且有效信号与背景噪声在低频段存在严重的混叠现象.这两点给沙漠地震资料的消噪带来了巨大的困难, 进而影响后期的反演、成像以及解释等工作.为了压制沙漠背景噪声并完整恢复有效信号, 本文采用生成对抗网络(Generative Adversarial Network, GAN)的基本思路并利用去噪器代替GAN中的生成器, 提出一种针对沙漠地震资料的全新消噪网络, 命名为沙漠地震卷积对抗降噪网络(Desert Seismic Convolutional Adversarial Denoising Network, DSCA-Net).在DSCA-Net中, 我们将去噪器的均方误差损失与去噪器、鉴别器之间的对抗损失相结合, 提出了一种全新损失函数; 利用该损失函数来优化网络, 进而得到适合沙漠地震资料去噪的模型.模拟与实际实验均表明本文提出的DSCA-Net可以有效地压制沙漠地震资料中的背景噪声, 同时显著增强同相轴的连续性; 经过DSCA-Net处理后的沙漠地震资料信噪比得到显著提升.

     

最小传递路径的正射影像色彩一致性处理方法

针对区域范围内多幅正射影像之间色彩不一致问题,设计了一种基于重叠区域的正射影像匀色方法,提取正射影像的有效区域外部轮廓并进行多边形拟合,利用Wallis滤波器根据有效区域的重叠区域进行处理。为了减小多次匀色造成的积累误差,提出一种结合Voronoi图和Dijkstra算法的方法确定最小传递路径。最后,通过相应实验验证了最小传递路径的正射影像色彩一致性处理方法的有效性。     

Climate policy strength compared: China,the US,the EU,India, Russia,and Japan

The few systematic international comparisons of climate policy strength made so far have serious weaknesses, particularly those that assign arbitrary weightings to different policy instrument types in order to calculate an aggregate score for policy strength. This article avoids these problems by ranking the six biggest emitters by far – China, the US, the EU, India, Russia, and Japan – on a set of six key policy instruments that are individually potent and together representative of climate policy as a whole: carbon taxes, emissions trading, feed-in tariffs, renewable energy quotas, fossil fuel power plant bans, and vehicle emissions standards. The results cast strong doubt on any idea that there is a clear hierarchy on climate policy with Europe at the top: the EU does lead on a number of policies but so does Japan. China, the US, and India each lead on one area. Russia is inactive on all fronts. At the same time climate policy everywhere remains weak compared to what it could be.

Policy relevance

This study enables climate policy strength, defined as the extent to which the statutory provisions of climate policies are likely to restrict GHG emissions if implemented as intended, to be assessed and compared more realistically across space and time. As such its availability for the six biggest emitters, which together account for over 70% of global CO₂ emissions, should facilitate international negotiations (1) by giving participants a better idea of where major emitters stand relative to each other as far as climate policy stringency is concerned, and (2) by identifying areas of weakness that need action.     

Lower thermospheric nitric oxide concentrations derived from WINDII observations of the green nightglow continuum at 553.1 nm

Vertical profiles of nitric oxide in the altitude range 90 to 105 km are derived from 553 nm nightglow continuum measurements made with the Wind Imaging Interferometer (WINDII) on the Upper Atmosphere Research Satellite (UARS). The profiles are derived under the assumption that the continuum emission is due entirely to the NO+O air afterglow reaction. Vertical profiles of the atomic oxygen density, which are required to determine the nitric oxide concentrations, are derived from coordinated WINDII measurements of the atomic oxygen OI 557.7 nm nightglow emission. Data coverage for local solar times ranging from 20 h to 04 h, and latitudes ranging from 42°S to 42°N, is achieved by zonally averaging and binning data obtained on 18 nights during a two-month period extending from mid-November 1992 until mid-January 1993. The derived nitric oxide concentrations are significantly smaller than those obtained from rocket measurements of the airglow continuum but they do compare well with model expectations and nitric oxide densities measured using the resonance fluorescence technique on the Solar Mesosphere Explorer satellite. The near-global coverage of the WINDII observations and the similarities to the nitric oxide global morphology established from other satellite measurements strongly suggests that the NO+O reaction is the major source of the continuum near 553 nm and that there is no compelling reason to invoke additional sources of continuum emission in this immediate spectral region.     

利用多源城市数据划定地铁站点吸引范围

随着时代的发展,世界城市规模不断扩大,各大城市的交通需求陡然增加,而地面出行所带来的堵塞和环保问题导致政府部门把目光转向地下交通发展,其中地铁是地下交通发展中最重要的交通工具.准确划定地铁站点吸引范围,分析影响地铁站点吸引范围主要因素,不仅对于优化地铁交通服务和规划地铁周边建成环境具有重要意义,同时对于新建地铁站点设施...     

露天煤矿截水帷幕防渗膜垂向隐蔽铺设施工工艺

防渗膜（HDPE土工膜）目前广泛应用于防污染、防渗漏、防扩散为主的防渗工程中,且铺设形式复杂多样。在我国某露天煤矿地下截水帷幕工程中,将防渗膜进行大深度垂向隐蔽铺设,深度可突破50 m,作为帷幕墙防渗主体;利用接头箱技术,实现了不同槽段间的防渗膜叠覆连接;通过注浆回填工艺,在压紧防渗膜的同时,提高了帷幕墙的抗渗性;最后采用围井抽水试验验证了墙体的防渗性,结果表明,防渗膜帷幕墙渗透系数仅为8.6×10^-7 cm/s,达到设计要求。防渗膜帷幕墙具有施工效率高、成本低、绿色环保等优点,其成功应用对其他类似项目具有推广借鉴意义。     

21世纪重力与磁法勘探的展望

对21世纪重力与磁法勘探的仪器，数据处理技术，解释理论与方法，应用领域等方面的发展方向进行了分析与展望，发展航空标量，矢量，梯度重力测量和航空全梯度磁力测量，三分量磁力测量，提高综合信息采集能力；开展卫星重磁测量，综合卫星，航空，地面重磁测量资料研究地球结构与构造；发展高精度数据处理技术；重磁异常弱信号的提取，不同深度重磁异常的划分，低纬底变倾角化磁极以及位场面延拓；发展复杂条件下三维重磁场多参数综合反演可视化技术以及快速自动反演技术；探索磁性多参数的应用新领域，充分发挥磁法在环境污染调查中的作用并开拓应用新领域。