A Study of the Extended-range Forecast for the Low Frequency Temperature and High Temperature Weather over the Lower Reaches of Yangtze River Valley in Summer     

Qiuming Yang 《地球科学进展》2018,33(4):385-395

Based on the observational data, the variations of Intraseasonal Oscillation (ISO) of the daily temperatures and its relationships to the high temperature in summer over the lower reaches of the Yangtze River Valley (LYRV) were studied for the period of 1979-2011. It is found that the daily temperatures over LYRV in May-August was mainly of periodic oscillations of 1525, 3060 and 6070 days, and the interannual variation of the intensity of its 3060-day oscillation had a strongly positive correlation with the number of days with daily highest temperature over 35 ℃ in July-August. Low frequency components of daily temperature in the LYRV, and the principal components of the Eastern Asian 850 hPa low frequency temperature, over a time period ranging from 1979 to 2000, were used to establish the Extended Complex Autoregressive model (ECAR) on an extended-range forecast of the 3060-day low frequency temperature over the LYRV. A 11-year independent real-time extended-range forecast was conducted on the extended-range forecast of low frequency component of the temperature over the LYRV in May-August, for the period ranging from 2001 to 2011. These experimental results show that this ECAR model, which is based on a data-driven model, has a good forecast skill at the lead time of approximately 23 days, with a forecast ability superior to the traditional autoregressive (AR) model. Hence, the development and variation of the leading 3060-day modes for the Eastern Asian 850 hPa low frequency temperatures and temporal evolutions of their relationships to low frequency components of the temperature over the LYRV in summer are very helpful in predicting the persistent high temperature over the LYRV at a 20 to 25 days lead.  相似文献   

Defining the Potential of Nanoscale Re‐Os Isotope Systematics Using Atom Probe Microscopy          下载免费PDF全文

Luke Daly  Phil A. Bland  Svetlana Tessalina  David W. Saxey  Steven M. Reddy  Denis Fougerouse  William D.A. Rickard  Lucy V. Forman  Alexandre La Fontaine  Julie M. Cairney  Simon P. Ringer  Bruce F. Schaefer  Daniel Schwander 《Geostandards and Geoanalytical Research》2018,42(3):279-299

Atom probe microscopy (APM) is a relatively new in situ tool for measuring isotope fractions from nanoscale volumes (< 0.01 μm³). We calculate the theoretical detectable difference of an isotope ratio measurement result from APM using counting statistics of a hypothetical data set to be ± 4δ or 0.4% (2s). However, challenges associated with APM measurements (e.g., peak ranging, hydride formation and isobaric interferences), result in larger uncertainties if not properly accounted for. We evaluate these factors for Re‐Os isotope ratio measurements by comparing APM and negative thermal ionisation mass spectrometry (N‐TIMS) measurement results of pure Os, pure Re, and two synthetic Re‐Os‐bearing alloys from Schwander et al. (2015, Meteoritics and Planetary Science, 50, 893) [the original metal alloy (HSE) and alloys produced by heating HSE within silicate liquid (SYN)]. From this, we propose a current best practice for APM Re‐Os isotope ratio measurements. Using this refined approach, mean APM and N‐TIMS ¹⁸⁷Os/¹⁸⁹Os measurement results agree within 0.05% and 2s (pure Os), 0.6–2% and 2s (SYN) and 5–10% (HSE). The good agreement of N‐TIMS and APM ¹⁸⁷Os/¹⁸⁹Os measurements confirms that APM can extract robust isotope ratios. Therefore, this approach permits nanoscale isotope measurements of Os‐bearing alloys using the Re‐Os geochronometer that could not be measured by conventional measurement principles.  相似文献   

GNSS水汽层析的约束条件方程变权代数重构算法     

王昊  丁楠  张文渊  冯遵德 《大地测量与地球动力学》2022,42(8):857-862

基于传统代数重构算法（algebraic reconstruction technique, ART）提出一种约束条件方程变权的代数重构算法(variable weight algebraic reconstruction technique, VWART),利用2019-08香港地区CORS网GNSS观测数据进行实验,选用京士柏探空气象站探空数据进行验证分析。结果表明,相比于传统代数重构算法,变权代数重构算法的精度、稳定性和可靠性均有所提高。以探空数据为例,其RMSE降低20.334%;在不同程度降水条件下,变权代数重构算法反演的垂直水汽廓线分布均优于传统代数重构算法。  相似文献   

A study of track deflection associated with the landfall of Tropical Cyclone Sidr (2007) over the Bay of Bengal and Bangladesh     

《Dynamics of Atmospheres and Oceans》2021

In this study, the dynamics of track deflection associated with Tropical Cyclone (TC) Sidr (2007) are explored using a numerical weather prediction model. It is found that (a) the simulated track of Sidr is sensitive to flow, orographic, and model vertical structure that change the environmental steering flow leading to the track deflection. In particular, the track of TC Sidr is deflected northwestward for cases with lower domain height, horizontal domain covering only part of Himalaya mountains, and varying mountain heights; (b) the simulated track of TC Sidr, when compared with GFS reanalysis data, is mainly controlled by its deep-layer environmental steering flow as a point vortex; (c) the northwestward deflection with lower domain height is caused by an artificially larger high pressure at lower levels in the vicinity of the Himalayas, due to the upward propagation of wave energy being reflected by the upper domain boundary; (d) the significant northwestward deflection associated with the varying mountain height cases is due to the cyclone vortex being advected by the northeasterly monsoonal flow, which is blocked by the mountains in the corresponding cases with mountains; (e) the northeastward track deflection after the landfall of Sidr is explained by the addition of the frictional force.In summary, the model vertical domain height and the Himalaya mountain representation play key roles in influencing the accuracy of TC Sidr track simulation, compared with other factors, such as the vertical resolution, at least for TC Sidr.  相似文献   

冲-洪积平原1:5万区域地质调查技术方法探索     

赵勇 《中国地质调查》2021,8(1):60-70

首都地区规划建设工作主要分布于平原松散地层之上,第四纪地质研究显得尤为重要。依托近几年来在北京地区开展的平原覆盖区1:5万区域地质调查和活动断裂专项调查项目成果,系统总结了平原区第四纪区域地质调查与评价的主要工作手段和技术方法,及其在解决第四纪基础地质问题及生态环境中所起的作用。通过平原区区域地质调查工作,可查明第四纪精细地质结构、含水层分布特征,精确厘定活动断裂位置及其活动时限,探讨自然环境演化序列与人类活动关系等,为城市规划、重大工程建设和应急水源地水资源合理开采提供基础地学数据。研究成果对首都城市减灾防灾、生态环境演变研究具有重要地学支撑作用。  相似文献   

A Review of Atmospheric Electricity Research in China from 2011 to 2018     

Xiushu QIE  Yijun ZHANG 《大气科学进展》2019,36(9):994-1014

Atmospheric electricity research has been conducted actively in China, having profited from the development and application of high temporal and spatial resolution lightning detection and location technologies. This paper reviews the scientific advances made in the field of atmospheric electricity in China from 2011 to 2018, covering the following five aspects:(1)lightning detection and location techniques;(2) discharge processes and parameters associated with rocket-triggered lightning;(3) physical processes in natural lightning and attachment to the ground;(4) lightning activities and charge structure in different thunderstorms; and(5) effects of thunderstorms on the upper atmosphere. In addition, some outstanding questions for future research are outlined.  相似文献   

TanDEM-X双站SAR干涉测量及研究进展     

孙亚飞  江利明  柳林  孙永玲  汪汉胜 《国土资源遥感》2015,(1)

较全面、系统地介绍了Tan DEM-X/Terra SAR-X双站SAR科学计划,重点涉及其科学目标、Tan DEM-X卫星参数、轨道结构以及干涉数据获取模式等相关内容,并讨论了双站SAR成像、极化In SAR和数字波束成形等干涉测量新技术及其研究进展。这些双站SAR新技术的实现将大大地推动SAR干涉测量在全球地形测绘、冰川学、海洋学及地质学等领域中的应用。  相似文献   

Low-order stabilized finite element for the full Biot formulation in soil mechanics at finite strain     

Lluís Monforte  Pedro Navas  Josep Maria Carbonell  Marcos Arroyo  Antonio Gens 《国际地质力学数值与分析法杂志》2019,43(7):1488-1515

This article presents a novel finite element formulation for the Biot equation using low-order elements. Additionally, an extra degree of freedom is introduced to treat the volumetric locking steaming from the effective response of the medium; its balance equation is also stabilized. The accuracy of the proposed formulation is demonstrated by means of numerical analyses.  相似文献   

Analytical solutions for advective–dispersive solute transport in double‐layered finite porous media     

Peter John Cleall 《国际地质力学数值与分析法杂志》2011,35(4):438-460

Analytical solutions for advection and dispersion of a conservative solute in a one‐dimensional double‐layered finite porous media are presented. The solutions are applicable to five scenarios that have various combinations of fixed concentration, fixed flux and zero concentration gradient conditions at the inlet and outlet boundaries that provide a wide number of options. Arbitrary initial solute concentration distributions throughout the media can be considered via explicit formulations or numerical integration. The analytical solutions presented have been verified against numerical solutions from a finite‐element‐based approach and an existing closed‐form solution for double‐layered media with an excellent correlation being found in both cases. A practical application pertaining to advective transport induced by consolidation of underlying sediment layers on contaminant movement within a capped contaminated sediment system is presented. Comparison of the calculated concentrations and fluxes with alternative approaches clearly illustrates the need to consider advection processes. Consideration of the different features of contaminant transport due to varying pore‐water velocity fields in primary consolidation and secondary consolidation stages is achieved via the use of non‐uniform initial concentration distributions within the proposed analytical solutions. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   

基于小波变换的射频干扰消除方法的研究          下载免费PDF全文

林天琪  吴亚军  朱人杰  徐志骏 《天文学报》2021,62(3):29

在射电天文观测中,射频干扰(Radio Frequency Interference, RFI)会以多种形式混入望远镜接收系统,给观测带来误判或者降低观测信噪比.近年来国内国际射电天文快速发展,国内国际大型射电望远镜和阵列先后建设,观测灵敏度大为提高,射频干扰的影响尤为突出.随着科技发展和人类活动的加剧,射频干扰日益严重且不可逆转.提出利用2维离散小波变换的方法分析射电天文观测的数据,对望远镜系统输出的时间频率序列进行小波变换,根据小波系数分离出原始信号中各分量,每个分量统计得到相应的阈值,将各分量与阈值相比较识别干扰成分并标记去除.利用该方法对实际观测数据进行了处理,结果表明该方法能够很好地标记并消减干扰信号,且提高了观测的信噪比.  相似文献