Two-step method for the determination of the differential code biases of COMPASS satellites

The differential code bias (DCB) in satellites of the Global Navigation Satellite Systems (GNSS) should be precisely corrected when designing certain applications, such as ionospheric remote sensing, precise point positioning, and time transfer. In the case of COMPASS system, the data used for estimating DCB are currently only available from a very limited number of global monitoring stations. However, the current GPS/GLONASS satellite DCB estimation methods generally require a large amount of geographically well-distributed data for modeling the global ionospheric vertical total electron content (TEC) and are not particularly suitable for current COMPASS use. Moreover, some satellites with unstable DCB (i.e., relatively large scatter) may affect other satellite DCB estimates through the zero-mean reference that is currently imposed on all satellites. In order to overcome the inadequacy of data sources and to reduce the impact of unstable DCB, a new approach, designated IGGDCB, is developed for COMPASS satellite DCB determination. IGG stands for the Institute of Geodesy and Geophysics, which is located in Wuhan, China. In IGGDCB, the ionospheric vertical TEC of each individual station is independently modeled by a generalized triangular series function, and the satellite DCB reference is selected using an iterative DCB elimination process. By comparing GPS satellite DCB estimates calculated by the IGGDCB approach based on only a handful (e.g., seven) of tracking stations against that calculated by the currently existing methods based on hundreds of tracking stations, we are able to demonstrate that the accuracies of the IGGDCB-based DCB estimates perform at the level of about 0.13 and 0.10?ns during periods of high (2001) and low (2009) solar activity, respectively. The iterative method for DCB reference selection is verified by statistical tests that take into account the day-to-day scatter and the duration that the satellites have spent in orbit. The results show that the impact of satellites with unstable DCB can be considerably reduced using the IGGDCB method. It is also confirmed that IGGDCB is not only specifically valid for COMPASS but also for all other GNSS.     

山东大张矽卡岩型铁矿床中铁的富集机制 ——来自流体包裹体和氢、氧同位素的证据

大张铁矿是鲁西地区近年来新发现的一个重要的矽卡岩型矿床.矿体主要赋存于石英二长闪长岩与奥陶系马家沟组灰岩接触带及其附近.根据脉体穿插关系和交代蚀变特征,将大张矽卡岩型铁矿床成矿过程划分为矽卡岩阶段、氧化物阶段、硫化物阶段和碳酸盐阶段.通过对透辉石、绿帘石、石英和方解石等透明矿物显微观察发现,大张铁矿中流体包裹体类型主要...     

拍摄高质量画面的必备三要素

无论是在编辑电视气象新闻和气象科普专题节目时,我们常常会面对一大堆的拍摄素材,尤其是有一部分初学摄像朋友提供的原始素材而发愁,搜寻很多录象带从中很难找到符合节目制作标准的素材。这些素材带中普遍存在画面上下左右摇晃、抖动,颜色和构图缺乏美感,盲目的推、拉、摇、移而且没有节奏感。想要拍摄出高质量的影像素材,提高后期编辑制作的效率,那就要求我们无论是摄像"发烧友"还是准备从事专业摄像工作的朋友,从拿起摄像机的那一刻开始就要注意培养练就摄像的基本功。     

T213L31全球模式云和对流参数化方案改进试验

针对中国业务中期数值预报模式T213对中雨量级以上的降水预报空报比较明显的问题,文中对此模式预报的降水进行了诊断分析。发现T213模式预报的总降水分布主要是由可分辨尺度降水决定的,且在降水偏多最明显的地区,可分辨尺度的降水即超过或达到了观测的总降水,表明降水空报的主要原因在于可分辨尺度降水偏多。可分辨尺度降水偏多的可能原因有：土壤湿度初始化、云变量的初始化和直接产生降水的云与对流参数化方案存在一定的缺陷。鉴于前两者是目前国际上的难点,文中针对第3个方面的可能原因进行了分析和相应的改进。包括在对流方案之前增加一次云方案的调用;对流参数化方案的闭合由“动力型”改为对流有效位能调整闭合;更复杂的对流触发机制;改进冰沉降和降水通量计算。改进的主要目的是使对流参数化方案更活跃,从而减少格点尺度对流的发生。采用改进的方案,进行了敏感性试验和2005年夏季的连续滚动同化预报试验,并与中国区域400个标准站的降水观测和GPCP的全球降水观测进行了比较。结果表明,改进的方案无论是对中国区域还是全球夏季平均的降水分布预报都好于业务,但四川省和赤道东太平洋降水偏多的问题依然存在。中国区域的降水统计检验还表明,除小雨外,其他量级在大部分时效上降水的TS评分增加,预报偏差降低。     

强弱南海夏季风年水汽输送路径特征分析

采用印度洋偶极子指数（dipole mode index,简称DMI）、Nino3指数和国内学者定义的5种东亚夏季风指数来比较分析印度洋偶极子（Indian Ocean dipole,简称IOD）、ENSO与东亚夏季风年际变化联系的年代际改变,讨论了这种改变的可能成因。结果表明,东亚夏季风指数分别与DMI、Ni-no3指数的年际变化的联系都呈明显的年代际改变。东亚夏季风指数除了在20世纪80年代及90年代初期与DMI联系较弱之外,其余时段均与DMI具有很好的正相关关系。当季风指数与DMI为正相关时,其与Nino3指数则呈负相关,IOD和ENSO对夏季风具有相反的影响。当季风指数与DMI呈较强的正相关时,其与ENSO的相关较弱;而在70年代末至80年代初季风指数与ENSO呈较强的相关时,其与DMI的关系亦较弱。东亚夏季风与IOD、ENSO年际变化之间的联系呈现此强彼弱的特点。1972—1982年和1983—1993年这两个阶段海温分布的显著不同,可能导致了海气相互作用过程中环流变化的周期及分布的改变,使得东亚夏季风与IOD和ENSO的关系发生年代际改变。     

2003年江淮流域强降水过程与30—70d天低频振荡的联系

利用NCEP／NCAR再分析和地面观测站的逐日降水资料,研究了2003年夏季江淮流域强降水过程与低频振荡的联系。结果显示,主周期为30～70d的低频振荡对2003年江淮流域暴雨的形成具有重要贡献：低频涡旋在江淮地区降水期的对流层高、低层呈负、正配置,具有斜压结构,利于降水发生;850hPa上正涡度系统的传播具有明显的北传和西传特征;存在于西太平洋、西北太平洋及其以东地区的低频波列（P—J）的活动过程影响了我国2003年江淮低频强降水的形成;整层低频水汽通量显示来自副热带高压外围的西南季风对水汽输送的贡献较显著,且2003年江淮地区30-70d时间尺度上降水的水汽来源为南海而非孟加拉湾或西太平洋。     

An Adaptive Nonhydrostatic Atmospheric Dynamical Core Using a Multi-Moment Constrained Finite Volume Method

An adaptive 2 D nonhydrostatic dynamical core is proposed by using the multi-moment constrained finite-volume(MCV) scheme and the Berger-Oliger adaptive mesh refinement(AMR) algorithm. The MCV scheme takes several pointwise values within each computational cell as the predicted variables to build high-order schemes based on single-cell reconstruction. Two types of moments, such as the volume-integrated average(VIA) and point value(PV), are defined as constraint conditions to derive the updating formulations of the unknowns, and the constraint condition on VIA guarantees the rigorous conservation of the proposed model. In this study, the MCV scheme is implemented on a height-based, terrainfollowing grid with variable resolution to solve the nonhydrostatic governing equations of atmospheric dynamics. The AMR grid of Berger-Oliger consists of several groups of blocks with different resolutions, where the MCV model developed on a fixed structured mesh can be used directly. Numerical formulations are designed to implement the coarsefine interpolation and the flux correction for properly exchanging the solution information among different blocks. Widely used benchmark tests are carried out to evaluate the proposed model. The numerical experiments on uniform and AMR grids indicate that the adaptive model has promising potential for improving computational efficiency without losing accuracy.     

Fine‐grained precursors dominate the micrometeorite flux

Abstract– We optically classified 5682 micrometeorites (MMs) from the 2000 South Pole collection into textural classes, imaged 2458 of these MMs with a scanning electron microscope, and made 200 elemental and eight isotopic measurements on those with unusual textures or relict phases. As textures provide information on both degree of heating and composition of MMs, we developed textural sequences that illustrate how fine‐grained, coarse‐grained, and single mineral MMs change with increased heating. We used this information to determine the percentage of matrix dominated to mineral dominated precursor materials (precursors) that produced the MMs. We find that at least 75% of the MMs in the collection derived from fine‐grained precursors with compositions similar to CI and CM meteorites and consistent with dynamical models that indicate 85% of the mass influx of small particles to Earth comes from Jupiter family comets. A lower limit for ordinary chondrites is estimated at 2–8% based on MMs that contain Na‐bearing plagioclase relicts. Less than 1% of the MMs have achondritic compositions, CAI components, or recognizable chondrules. Single mineral MMs often have magnetite zones around their peripheries. We measured their isotopic compositions to determine if the magnetite zones demarcate the volume affected by atmospheric exchange during entry heating. Because we see little gradient in isotopic composition in the olivines, we conclude that the magnetites are a visual marker that allows us to select and analyze areas not affected by atmospheric exchange. Similar magnetite zones are seen in some olivine and pyroxene relict grains contained within MMs.     

Predicting Terrestrial Flagstone Reservoirs in the Sha-I Member of the Qibei Depression in the Dagang Oilfield

There are few 3-D seismic profiles and drillings in the middle part of the Qibei depression in the Dagang oilfield, and more than 70% of the 2-D seismic profiles were completed before the 1980s. Meanwhile, changes in the terrestrial formations in this region have been large and complex. These factors have made it difficult to predict reservoirs in this area. The purpose of this paper is to establish a methodology for predicting potential gas and oil reservoirs. Our research combines sequence stratigraphy, well-logs, and seismic analysis to elucidate the prediction of flagstone reservoirs in the S1 (Sha-I) Member in the middle of the Qibei depression. Previous research indicates that these rocks were deposited in an environment that had a semiarid, northern subtropical, and warm, humid climate. The objective strata currently consist mainly of lake fades, deeper lake facies, and shore-shallow lake facies. The study reveals that the lower section of the S1 Member is an important objective region for explora     

煤田火区特征的土地覆盖分类方法 ——以乌达煤田火区为例

土地覆盖变化是土地分析与评价和生态环境变化预测的重要科学基础, 通过精确的土地覆盖分类方法 获取高精度的土地覆盖图是研究煤田火区生态环境变化的必要手段。本文以最大似然法、光谱角度法、面向对象 分类法和基于复合分区的分层分类法进行乌达煤田火区土地覆盖分类的方法研究。研究结果表明, 基于复合分区的 分层分类方法分类精度较高, 总体分类精度为92.97%, kappa 系数为0.9155。该方法通过基于地表热辐射特征、热 异常状况、地貌类型, 以及对生态系统扰动状况等的划分, 减少了地物信息的混淆度, 即通过提