Magnetic history of a dyke on Mount Etna (Sicily)

During the 1989 eruption of Mount Etna, two fracture systems, trending c. N45°E and N150°E, opened at the foot of its 3000 m high SE Crater and propagated quickly downslope to distances of ≈3 and 7 km, respectively. The northeastern fracture fed a flank eruption, whereas the southeastern fracture remained dry and offered contrasting volcanological and geophysical evidence of the presence of magma at a shallow depth. During the opening of this non-eruptive fracture system, a differential magnetic network was set up on a short profile across its distant extremity. Initially, the magnetic field did not display any change along the profile between frequent surveys. However, repeated measurements at intervals of about 3 months for two years revealed the slow build-up of a 130 nT anomaly. The anomaly vanishes laterally within 0.2 km of the surface expression of the fracture system. This exceptional set of observations constrains the location and time of cooling of a shallow dyke. The increase in magnetization of the dyke inferred by the rate of growth of the anomaly leads to the interpretation that the dyke was emplaced near the end of the eruption.     

对化探异常评价的思考

化探异常评价是地质普查找矿中的一项重要工作,异常评价的主要工作环节为异常筛选阶段,异常源追踪,定位阶段和异常起因研究,高质量地完成三个环节的各项工作,除掌握好地球化学本学科的基础理论之外,尚需地质,地球物理等其它多学科的基础理论的支持,尤其是现代成矿理论和地质找矿技术的支持。     

基于智能手机GNSS双频原始观测值的电离层延迟提取与分析

基于智能手机GNSS（全球导航卫星系统）观测值的研究主要集中于观测值质量分析和定位算法,在大气应用方面关注度则较为有限.本文基于全球首款支持GNSS双频信号的小米8智能手机和超短基线的Trimble Alloy测地型接收机,利用原始GNSS双频载波相位观测值,考虑连续历元间电离层变化较小从而进行观测值质量控制策略,评估了小米8智能手机电离层提取精度.研究结果表明：卫星高度角或载噪比较高的条件下,智能手机观测值可能依然是无效的,设置卫星高度角或载噪比阈值的方法进行质量控制不再适用.小米8提取的电离层延迟与测地型接收机呈现了很好的一致性,但其波动幅度略高于测地型接收机,提取精度优于0.2 TECU,表明智能手机GNSS观测值用于大气应用是可行的.     

On the Second-Year Warming in Late 2019 over the Tropical Pacific and Its Attribution to an Indian Ocean Dipole Event※

After its maturity, El Ni?o usually decays rapidly in the following summer and evolves into a La Ni?a pattern. However, this was not the case for the 2018/19 El Ni?o event. Based on multiple reanalysis data sets, the space-time evolution and triggering mechanism for the unusual second-year warming in late 2019, after the 2018/19 El Ni?o event, are investigated in the tropical Pacific. After a short decaying period associated with the 2018/19 El Ni?o condition, positive sea surface temperature anomalies (SSTAs) re-intensified in the eastern equatorial Pacific in late 2019. Compared with the composite pattern of El Ni?o in the following year, two key differences are evident in the evolution of SSTAs in 2019. First, is the persistence of the surface warming over the central equatorial Pacific in May, and second, is the re-intensification of the positive SSTAs over the eastern equatorial Pacific in September. Observational results suggest that the re-intensification of anomalous westerly winds over the western and central Pacific, induced remotely by an extreme Indian Ocean Dipole (IOD) event, acted as a triggering mechanism for the second-year warming in late 2019. That is, the IOD-related cold SSTAs in the eastern Indian Ocean established and sustained anomalous surface westerly winds over the western equatorial Pacific, which induced downwelling Kelvin waves propagating eastward along the equator. At the same time, the subsurface ocean provided plenty of warm water in the western and central equatorial Pacific. Mixed-layer heat budget analyses further confirm that positive zonal advection, induced by the anomalous westerly winds, and thermocline feedback played important roles in leading to the second-year warming in late 2019. This study provides new insights into the processes responsible for the diversity of El Ni?o evolution, which is important for improving the physical understanding and seasonal prediction of El Ni?o events.     

基于GNSS的空间环境参数反演平台及精度评估

基于全球和区域全球导航卫星系统（GNSS）参考站网进行对流层和电离层参数反演实现空间环境变化监测具有成本低、精度高、实时性好等优点,得到了广泛应用.本文基于南京信息工程大学的北斗/GNSS空间环境监测平台Xsensing,以国际GNSS服务组织提供的对流层产品为参考,评估了不同气象条件下对流层参数反演精度,在此基础上采用固定非差模糊度的精密单点定位技术（PPP）实现高精度电离层参数反演.实验结果表明,基于全球参考站的对流层估计误差偏差为0.05 mm,对应的标准差为5.6 mm,在平稳和剧烈的气象条件下均能反映水汽变化趋势特征.基于短基线进行电离层延迟反演精度评估,结果表明浮点解PPP反演电离层延迟误差的平均偏差为-0.09 TECU,精度为0.38 TECU,采用非差模糊度固定技术对电离层延迟提取精度提高达84.2％;静态模拟动态解算模式下电离层估计精度与静态相当.上述结果表明该平台可实现高精度空间环境参数反演,下一步将融合机载、船载等多种平台观测实现中小尺度空间变化监测.     

ITG-CHAMP01: a CHAMP gravity field model from short kinematic arcs over a one-year observation period

Global gravity field models have been determined based on kinematic orbits covering an observation period of one year beginning from March 2002. Three different models have been derived up to a maximum degree of n=90 of a spherical harmonic expansion of the gravitational potential. One version, ITG-CHAMP01E, has been regularized beginning from degree n=40 upwards, based on the potential coefficients of the gravity field model EGM96. A second model, ITG-CHAMP01K, has been determined based on Kaulas rule of thumb, also beginning from degree n=40. A third version, ITG-CHAMP01S, has been determined without any regularization. The physical model of the gravity field recovery technique is based on Newtons equation of motion, formulated as a boundary value problem in the form of a Fredholm-type integral equation. The observation equations are formulated in the space domain by dividing the one-year orbit into short sections of approximately 30-minute arcs. For every short arc, a variance factor has been determined by an iterative computation procedure. The three gravity field models have been validated based on various criteria, and demonstrate the quality of not only the gravity field recovery technique but also the kinematically determined orbits.     

新疆艾肯达坂物化探综合异常的再解释

新疆和静县艾肯达坂39号铜矿点东南第四系大面积覆盖区存在1个物化探综合异常,多年来备受关注．2002年钻探查证后,对异常进行了再解释,查明了引起异常的原因．该高极化低电阻率激电异常是由下志留统依南里克组一套浅变质岩中的弱金矿化、弱石墨化、弱黄铁矿化碳质粉砂岩引起;低重力异常是由下志留统依南里克组中的次生石英岩、硅质岩和硅化大理岩引起;磁异常主要由厚达20m左右的下二叠统艾肯达坂组中基性火山岩砾石、岩块及碎屑等第四系堆积物引起,而下志留统依南里克组浅变质岩基本为无磁性岩石;全铜、有机铜和活动态铜异常主要是由第四系堆积物中大量铜矿转石和含铜高的中基性火山岩引起;壤中汞气和热释汞气异常是由断裂引起．证实了艾肯达坂物化探综合异常处于拉尔墩深大断裂带上．区域成矿地质条件对比表明,西南天山下志留统依南里克组一套浅变质岩具有形成“黑色岩系”型金矿的有利地质条件,是突破“库姆托尔式”金矿的有利地层,建议加强该区的金矿普查工作．     

A new ellipsoidal gravimetric, satellite altimetry and astronomic boundary value problem, a case study: The geoid of Iran

A new gravimetric, satellite altimetry, astronomical ellipsoidal boundary value problem for geoid computations has been developed and successfully tested. This boundary value problem has been constructed for gravity observables of the type (i) gravity potential, (ii) gravity intensity (i.e. modulus of gravity acceleration), (iii) astronomical longitude, (iv) astronomical latitude and (v) satellite altimetry observations. The ellipsoidal coordinates of the observation points have been considered as known quantities in the set-up of the problem in the light of availability of GPS coordinates. The developed boundary value problem is ellipsoidal by nature and as such takes advantage of high precision GPS observations in the set-up. The algorithmic steps of the solution of the boundary value problem are as follows:

- Application of the ellipsoidal harmonic expansion complete up to degree and order 360 and of the ellipsoidal centrifugal field for the removal of the effect of global gravity and the isostasy field from the gravity intensity and the astronomical observations at the surface of the Earth.

- Application of the ellipsoidal Newton integral on the multi-cylindrical equal-area map projection surface for the removal from the gravity intensity and the astronomical observations at the surface of the Earth the effect of the residual masses at the radius of up to 55 km from the computational point.

- Application of the ellipsoidal harmonic expansion complete up to degree and order 360 and ellipsoidal centrifugal field for the removal from the geoidal undulations derived from satellite altimetry the effect of the global gravity and isostasy on the geoidal undulations.

- Application of the ellipsoidal Newton integral on the multi-cylindrical equal-area map projection surface for the removal from the geoidal undulations derived from satellite altimetry the effect of the water masses outside the reference ellipsoid within a radius of 55 km around the computational point.

- Least squares solution of the observation equations of the incremental quantities derived from aforementioned steps in order to obtain the incremental gravity potential at the surface of the reference ellipsoid.

- The removed effects at the application points are restored on the surface of reference ellipsoid.

- Application of the ellipsoidal Bruns’ formula for converting the potential values on the surface of the reference ellipsoid into the geoidal heights with respect to the reference ellipsoid.

- Computation of the geoid of Iran has successfully tested this new methodology.

Comments on the Synergism Between the Analytic Planetary Boundary-Layer Model and Remote Sensing Data

This paper is adapted from a presentation at the session of the European Geophysical Society meeting in 2002 honouring Joost Businger. It documents the interaction of the non-linear planetary boundary-layer (PBL) model (UW-PBL) and satellite remote sensing of marine surface winds from verification and calibration studies for the sensor model function to the current state of verification of the model by satellite data. It is also a personal history where Joost Businger had seminal input to this research at several critical junctures. The first scatterometer in space was on SeaSat in 1978, while currently in orbit there are the QuikSCAT and ERS-2 scatterometers and the WindSat radiometer. The volume and detail of data from the scatterometers during the past decade are unprecedented, though the value of these data depends on a careful interpretation of the PBL dynamics. The model functions (algorithms) that relate surface wind to sensor signal have evolved from straight empirical correlation with simple surface-layer 10-m winds to satellite sensor model functions for surface pressure fields. A surface stress model function is also available. The validation data for the satellite model functions depended crucially on the PBL solution. The non-linear solution for the flow of fluid in the boundary layer of a rotating coordinate system was completed in 1969. The implications for traditional ways of measuring and modelling the PBL were huge and continue to this day. Unfortunately, this solution replaced an elegant one by Ekman with a stability/finite perturbation equilibrium solution. Consequently, there has been great reluctance to accept this solution. The verification of model predictions has been obtained from the satellite data.