Rapid earthquake focal mechanism inversion using high-rate GPS velometers in sparse network

In this study, we demonstrate an approach for inverting earthquake source parameters based on high-rate global positioning system(GPS) velocity seismograms. The velocity records obtained from single-station GPS velocity solutions with broadcast ephemeris are used directly for earthquake source parameter inversion using the Cut and Paste method, without requiring conversion of the velocity records into displacement records. Taking the El Mayor-Cucapah earthquake as an example, GPS velocity records from 10 stations with reasonable azimuthal coverage provide earthquake source parameters very close to those from the Global centroid moment tensor(Global CMT) solution. In sparse network tests, robust source parameters with acceptable bias can be achieved with as few as three stations. When the number of stations is reduced to two, the bias in rake angle becomes appreciable, but the magnitude and strike estimations are still robust. The results of this study demonstrate that rapid and reliable estimation of earthquake source parameters can be obtained from GPS velocity data. These parameters could be used for early earthquake warning and shake map construction, because such GPS velocity records can be obtained in real time.     

Quantifying the effect of thermospheric parameterization in a global model

Global climate models have become useful tools for studying the important physical processes that affect the Earth's upper atmosphere. However, the results produced by all models contain uncertainty that stems for the manner in which the model is driven, as well as in the treatment of the internal physics and numerics. In order to fully understand the scientific value of the model results then, it is necessary to have a quantitative understanding of the uncertainty in the model. In this study, the global ionosphere–thermosphere model is used to investigate how uncertainty in the use of parameters in a large scale model can affect the model results. Eight parameters are studied that ultimately have an effect on the thermospheric temperature equation. It is found that among these, uncertainty in the thermal conductivity, NO cooling, and NO binary diffusion coefficients most strongly translate to uncertainty in the temperature and density results. In addition, variations in the eddy diffusion coefficient are shown to result in significant uncertainty in the thermospheric composition, and ultimately the electron density.     

Inferring Low Cloud Base Heights at Night for Aviation Using Satellite Infrared and Surface Temperature Data

A nighttime image product that depicts areas of the lowest cloud base heights has been developed by combining brightness temperature data from the Geostationary Operational Environmental Satellite (GOES) Imager InfraRed (IR) bands centered at 3.9 μm and 10.7 μm, with hourly shelter temperatures from surface observing sites and offshore marine buoys. A dependent data sample showed a good correlation between the surface temperature minus IR cloud top temperature differences versus measured cloud base heights. Histogram analysis indicated that a temperature difference of less than 4-C related to a > 50% frequency of ceilings below 1000 ft above ground level, the threshold for Instrument Flight Rules (IFR). Using this result as a model, an experimental Low Cloud Base image product was developed that highlights regions of likely IFR ceilings. Validation of the Low Cloud Base product for two separate periods resulted in Probabilities of Detection of 67% and 72% and False Alarm Rates of 6% and 11%, respectively. Some regional variation observed could be related to the relative frequency of multi-layered overcast conditions. The biggest factor leading to underdetection of IFR ceilings by the GOES Low Cloud Base product is the presence of overlying clouds, including thin cirrus contamination. The GOES Low Cloud Base product shows potential for use as guidance for aviation meteorologists over both continental and marine areas.     

Some Thoughts on the Earthquake Science Experimental Site——The Underground Cloud Map

The Western Yunnan Earthquake Predication Test Site set up jointly by the China Earthquake Administration, the National Science Foundation Commission of America, and United States Geological Survey has played an important role in development of early earthquake research work in China. Due to various objective reasons, most of the predicted targets in the earthquake prediction test site have not been achieved, and the development has been hindered. In recent years, the experiment site has been reconsidered, and renamed the “Earthquake Science Experimental Site”. Combined with the current development of seismology and the practical needs of disaster prevention and mitigation, we propose adding the “Underground Cloud Map” as the new direction of the experimental site. Using highly repeatable, environmentally friendly and safe airgun sources, we could send constant seismic signals, which realizes continuous monitoring of subsurface velocity changes. Utilizing the high-resolution 3-D crustal structure from ambient noise tomography, we could obtain 4-D (3-D space + 1-D time) images of subsurface structures, which we termed the “Underground Cloud Map”. The “Underground Cloud Map” can reflect underground velocity and stress changes, providing new means for the earthquake monitoring forecast nationwide, which promotes the conversion of experience-based earthquake prediction to physics-based prediction.     

Daytime precipitation identification scheme based on multiple cloud parameters retrieved from visible and infrared measurements

Visible and infrared (VIR) measurements and the retrieved cloud parameters are commonly used in precipitation identification algorithms, since the VIR observations from satellites, especially geostationary satellites, have high spatial and temporal resolutions. Combined measurements from visible/infrared scanner (VIRS) and precipitation radar (PR) aboard the Tropical Rainfall Measuring Mission (TRMM) satellite are analyzed, and three cloud parameters, i.e., cloud optical thickness (COT), effective radius (Re), and brightness temperature of VIRS channel 4 (BT4), are particularly considered to characterize the cloud status. By associating the information from VIRS-derived cloud parameters with those from precipitation detected by PR, we propose a new method for discriminating precipitation in daytime called Precipitation Identification Scheme from Cloud Parameters information (PISCP). It is essentially a lookup table (LUT) approach that is deduced from the optimal equitable threat score (ETS) statistics within 3-dimensional space of the chosen cloud parameters. South and East China is selected as a typical area representing land surface, and the East China Sea and Yellow Sea is selected as typical oceanic area to assess the performance of the new scheme. It is proved that PISCP performs well in discriminating precipitation over both land and oceanic areas. Especially, over ocean, precipitating clouds (PCs) and non-precipitating clouds (N-PCs) are well distinguished by PISCP, with the probability of detection (POD) near 0.80, the probability of false detection (POFD) about 0.07, and the ETS higher than 0.43. The overall spatial distribution of PCs fraction estimated by PISCP is consistent with that by PR, implying that the precipitation data produced by PISCP have great potentials in relevant applications where radar data are unavailable.     

云平台下地震监测台网软件系统的应用方案研究

针对数字化地震台网JOPENS软件系统的技术特点及功能需求,在对当前各种主流云计算平台进行比较的基础上,基于较为合适的阿里云计算平台,提出了在云环境下部署JOPENS系统的应用方案。测试结果表明JOPENS系统部署在云环境下能够提升测震台网中心运行的稳定性及可扩展性,并节约运行维护成本。该研究对于当前三网融合新形势下云南省地震台网的建设及运行工作具有借鉴意义。     

Cloud-Radiation Studies During the European Cloud and Radiation Experiment (EUCREX)

The dominant role of clouds in modulating and interacting with radiative energy transports within the atmosphere, in providing precipitation, transporting water and influencing air-chemical processes is still not understood well enough to be accurately represented within atmospheric circulation and climate models over all regions of the globe. Also the extraction of real-world cloud properties from satellite measurements still contains uncertainties. Therefore, various projects have been developed within the Global Energy and Water Cycle Experiment (GEWEX), to achieve more accurate solutions for this problem by direct measurements within cloud fields and other complementary studies. They are based on the hypothesis, that most relevant properties of cloud fields can be parametrized on the basis of the prognostic field variables of atmospheric circulation models, and that the cloud microphysical properties can directly be related – with additional parameters on the particle shapes etc. – to the radiative transfer properties.One of these projects has been the European Cloud and Radiation Experiment (EUCREX) with its predecessor ICE (International Cirrus Experiment).The EUCREX and ICE provided a common platform for research groups from France, Germany, Sweden and the United Kingdom to concentrate their efforts primarily on high, cold cirrus. They showed, with data from satellites, that this cloud species enhances the atmospheric greenhouse-effect. Numerical mesoscale models were used in sensitivity studies on cloud developments. In-situ measurements of cloud properties were made during more than 30 aircraft missions, where also in-flight comparisons of various instruments were made to ensure the quality of data sets measured from different aircraft. The particle sampling probes, used for in-cloud measurements, showed a disagreement in total number density in all ranges between about 20–50%, while all other instruments agreed quite satisfactorily. A few measured holographic data provided information on typical ice-crystal shapes, which were used in numerical simulations of their absorption and scattering properties.Several new instruments for both in-situ and remote measurement, such as a polar nephelometer, a chopped pyrgeometer and an imaging multispectral polarimeter (POLDER) for cloud and radiation measurements were tested and improved. New algorithms were developed for cloud classifications in multispectral satellite images and also for simulations of the scattering of radiation by non-spherical particles.This paper primarily summarizes the EUCREX results obtained between 1989 and 1996, and provides examples of the many results which have been obtained so far. It is not a complete review of the world-wide state in this field, but it tries to place the EUCREX results into the world-wide development. Therefore many references are made to the results of other groups, which in turn influenced the work within EUCREX.     

Holocene slip rate and paleoearthquake records of the Salt Lake segment of the Northern Zhongtiaoshan Fault,Shanxi Province

The Northern Zhongtiaoshan Fault is a major deep fault at the southern margin of the Yuncheng Basin. There have been few studies on the fault, and the historical earthquakes are few and weak. However, the intensity of activity on the fault should never be underestimated. Through interpretations of aerial images, topography measurements and excavation of trenches, this paper studied the fault distribution, the surface deformation and the activity of the normal fault south of Salt Lake near the city of Yuncheng. By tracing faults in the three trenches, it was found that there had been at least three large paleoseismic events, at 1–3.5, 3.6–4.4 and 7.4–8.8 ka BP. Employing 14 C dating, we determined the same gravel layers in the uplifted side and downthrown side. Making differential Global Positioning System measurements of the vertical difference and topographic profile, we obtained the mean slip rate of the Northern Zhongtiaoshan Fault since 24.7 ka BP(0.75±0.05 mm/a). Using the results of relevant studies, we calculated the possible vertical fault displacement of one earthquake(2.35 m) and obtained the recurrence interval of characteristic earthquakes as 2940–3360 a after dividing the displacement by the mean slip rate.     

内地核物质的状态参数及其量子效应的研究

采用与现有地震学数据一致的地核物质状态方程,计算了300K时压强-不可压缩系数的关系图,并与地核环境下PREM、PEM模型的数据加以比较;给出了内地核环境下温度-摩尔体积、温度-热压等参数的关系曲线,研究了地核物质的热学参数;应用计算所得到的热压值,借助量子统计物理的方法,列表给出了与内地核物质量子效应有关的各项参数.量子计算表明:巨大的地球自引力压强只是破坏了Fe原子的最外层和极少一部分Fe原子的次外层结构,并没有像白矮星一样使所有的核外电子发生全部的公有化.     

Mesospheric planetary wave effects on global PMC variability inferred from AIM–CIPS and TIMED–SABER for the northern summer 2007 PMC season

Polar Mesospheric Cloud (PMC) observations from the Cloud Imaging and Particle Size (CIPS) instrument on the Aeronomy of Ice in the Mesosphere (AIM) spacecraft are used to investigate the role of planetary wave activity on global PMC variability in the summer polar mesosphere during the 2007 Northern hemisphere season. This is coupled with an analysis of contemporaneous measurements of atmospheric temperature by the Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) instrument onboard the Thermosphere–Ionosphere–Mesosphere–Energetics and Dynamics (TIMED) spacecraft to characterize the importance of temperature as a dominant forcing mechanism of the dynamical state of the summer polar mesosphere. The study confirms results from a recent study using PMC data from the Student Nitric Oxide Explorer (SNOE) and temperature data from SABER, such that planetary wave activity is present in both PMCs and mesospheric temperature and that are strongly coherent and anti-correlated. The dominant wave present in the polar summer mesosphere in both PMCs and temperature is the 5-day wavenumber 1 Rossby normal mode. The maximum amplitude of the variation of the 5-day wave in temperature is small at 3 K but has a significant effect on PMC albedo. The phase relationship between PMC and temperature is variable between 150° and 180° out of phase, with PMC albedo reaching a maximum ～10 h before the minimum in temperature. We have identified two additional waves, the westward propagating 2-day wavenumber 2 (2DW2) and the eastward propagating 2-day wavenumber 1 (2DE1) are both present in PMC and temperature variability in the 2007 NH season. The 2DW2 wave is consistent with a Rossby normal mode excited by the instability in the zonal mean zonal wind. However, the source of the 2DE1 wave could be a nonlinear interaction of the 2DW2 with the migrating diurnal tide. This is the first time these two wave features have been detected in coincident PMC and temperature measurements. Analysis of the zonal variation of PMC occurrence and temperature shows they are also anti-correlated and supporting the conclusion that temperature is an important forcing mechanism in zonal variability.     

地震期间电离层扰动现象研究

介绍了大量的关于地震电离层扰动现象研究的最新进展,研究表明地震发生前的几天或者几个小时电离层扰动被观测到,电离层前兆是确实存在.但要将震前的电离层扰动作为地震短临预报的工具,还有许多值得我们去深入研究和解决的问题.应用空间技术开展大区域范围内电离层参数的实时观测,如用地震电磁卫星、GPS台网、并和地面电离层垂测仪观测相结合,建立“电离层地震前兆监测系统”,无疑会加速这项研究的进程.     

舒曼共振：测量全球热带气温的最新方法

全球气候突变已成为全世界科学家、企业家和政治家共同关注的焦点问题之一。为了准确地预测全球温度的变化趋势和变化速度，我们必须对全球大气温度进行更为广泛更为精确的测量，研究和发展测量大气温度的新方法。由于全球年平均温度变化不过零点几度，相当于其绝对温度的千分之几，由直接测量全球数千个测点的气温来准确估算全球大气平均温度及其变化是困难的。因此，找出一些依赖于气温的涨落而非线性变化的物理参量是很有用的。这样，测量那些参量的明显变化可以准确地确定温度的细微变化。同地球一电离层谐振腔以及全球范围的闪电活动相联系的舒曼共振的振幅就是这样一种物理量。舒曼共振是一种全球性的电磁现象，它能敏感地反映整个热带大气的温度变化。这就是说，在全球任何一个背景噪声较低的地点设置一个舒曼共振台站，可由这一台站纪录的舒曼共振幅度的明显变化推断全球热带大气气温的细微变化。     

Airflow pattern and droplet trajectories about an electrostatic cloud droplet probe

Summary This study considers the numerical results for the airflow pattern to obtain droplet trajectories around and into a leading edge hole of a cloud droplet sampling probe. The probe was initially conceived at MIT and developed into a practical airborne system in the Cloud Physics Program at the National Center for Atmospheric Research. The probe is designed to be an ellipsoid of revolution with a circular sampling hole at the forward stagnation point. The external flow field is assumed to be steady, axisymmetric, irrotational and incompressible and depends on four parameters: the hole radius, axial speed in the hole, free stream velocity and the fineness ratio of the ellipsoid. The trajectory calculations are based on a three-dimensional gravity field with a fluid resistance computed from experimental drag coefficients on spheres. Both numerical and theoretical solutions for the flow field have been obtained for various combinations of the above parameters. For these flow fields, trajectories for droplets have been obtained. From the trajectory calculations we have obtained collection efficiencies for the probe and have compared these trajectories with experimental trajectories obtained at NCAR.The National Center for Atmospheric Research is sponsored by the National Science Foundation.     

Analytical fragility assessment using unscaled ground motion records

It is desirable that nonlinear dynamic analyses for structural fragility assessment are performed using unscaled ground motions. The widespread use of a simple dynamic analysis procedure known as Cloud Analysis, which uses unscaled records and linear regression, has been impeded by its alleged inaccuracies. This paper investigates fragility assessment based on Cloud Analysis by adopting, as the performance variable, a scalar demand to capacity ratio that is equal to unity at the onset of limit state. It is shown that the Cloud Analysis, performed based on a careful choice of records, leads to reasonable and efficient fragility estimates. There are 2 main rules to keep in mind for record selection: to make sure that a good portion of the records leads to a demand to capacity ratio greater than unity and that the dispersion in records' seismic intensity is considerable. An inevitable consequence of implementing these rules is that one often needs to deal with the so‐called collapse cases. To formally consider the collapse cases, a 5‐parameter fragility model is proposed that mixes the simple regression in the logarithmic scale with logistic regression. The joint distribution of fragility parameters can be obtained by adopting a Markov Chain Monte Carlo simulation scheme leading directly to the fragility and its confidence intervals. The resulting fragility curves compare reasonably with those obtained from the Incremental Dynamic Analysis and Multiple Stripe Analysis with (variable) conditional spectrum–compatible suites of records at different intensity levels for 3 older reinforced concrete frames with shear‐, shear‐flexure‐, and flexure‐dominant behavior.     

A global empirical model for mapping zenith wet delays onto precipitable water vapor using GGOS Atmosphere data

The importance of water vapor in research of global climate change and weather forecast cannot be over emphasized; therefore substantial efforts have been made in exploring the optimal methods to measure water vapor. It is well-established that with a conversion factor, zenith wet delays can be mapped onto precipitable water vapor(PWV). However, the determination of the exact conversion factor depends heavily on the accurate calculation of a key variable, weighted mean temperature of the troposphere(T_m). As a critical parameter in Global Positioning System(GPS) meteorology, T_m has recently been modeled into a global grid known as GWMT. The GWMT_model only requires the location and the day of year to calculate T_m. Despite the advantages that the GWMT_model offers, anomalies still exist in oceanic areas due to low sampling resolution. In this study, we refine the GWMT_model by incorporating the global T_m grid from Global Geodetic Observing System(GGOS) and obtain an improved model, GWMT-G. The results indicate that the GWMT-G model successfully addresses the anomaly in oceanic areas in the GWMT_model and significantly improves the accuracy of T_m in other regions.     

Global warming: a review of this mostly settled issue

Global warming and attendant climate change have been controversial for at least a decade. This is largely because of its societal implications since the science is largely straightforward. With the recent publication of the Fourth Assessment Report of the United Nations’ Intergovernmental Panel on Climate Change (Working Group 1) there has been renewed interest and controversy about how certain the scientific community is of its conclusions: that humans are influencing the climate and that global temperatures will continue to rise rapidly in this century. This review attempts to update what is known and in particular what advances have been made in the past 5 years or so. It does not attempt to be comprehensive. Rather it focuses on the most controversial issues, which are actually few in number. They are:

• Is the surface temperature record accurate or is it biased by heat from cities, etc.?
• Is that record significantly different from past warmings such as the Medieval Warming Period?
• Are human greenhouse gases changing the climate more than the sun?
• Can we model climate and predict its future, or is it just too complex and chaotic?
• Are there any other changes in climate other than warming, and can they be attributed to the warming?

Finally there is a very brief discussion of the societal policy response to the scientific message. Note that much of the introductory material in each section is essentially the same as that which appears in Keller 2003 (hereafter referred to as OR = original review) and its update (Keller 2007). Despite continued uncertainties, the review finds an affirmative answer to these questions. Of particular interest are advances that seem to explain why satellites do not see as much warming as surface instruments, how we are getting a good idea of recent paleo-climates, and why the twentieth century temperature record was so complex. It makes the point that in each area new information could come to light that would change our thinking on the quantitative magnitude and timing of anthropogenic warming, but it is unlikely to alter the basic conclusions.     

Cloud water interception in the high altitude tree heath forest (Erica arborea L.) of Paul da Serra Massif (Madeira,Portugal)

Cloud water interception (CWI) occurs when cloud droplets are blown against the forest canopy, where they are retained on the vegetation surface, forming larger water droplets that drip into the forest floor. CWI was measured from 1 October 1997 to 30 September 1999, on a first‐line tree heath (Erica arborea), at Bica da Cana, Madeira Island. Rainfall was corrected for wind‐loss effect and compared with throughfall and other climatological normals. The CWI depletion rate along a forest stand transect was also analysed during three distinct fog events in 2008. Cloud water was 28 mm day^?1, corresponding to 68% of total throughfall and 190% of the gross precipitation. Cloud water correlates directly with monthly normals of fog days and wind speed and correlates inversely with the monthly air temperature normal. CWI has an exponential correlation with monthly relative humidity normal. Cloud water capture depletion along the stand shows a logarithmic decrease. Although a forest stand does not directly relate to a first‐line tree heath, this study shows that CWI is a frequent phenomenon in the Paul da Serra massif. Restoration and protection of high altitude ecosystems in Madeira should be a priority, not only for biodiversity, ecological and economical purposes but also for its role in regional water resources. Copyright © 2011 John Wiley & Sons, Ltd.     

Assessing the Current Evolution of the Greenland Ice Sheet by Means of Satellite and Ground-Based Observations

The present study utilises different satellite and ground-based geodetic observations in order to assess the current evolution of the Greenland Ice Sheet (GIS). Satellite gravimetry data acquired by the Gravity Recovery and Climate Experiment are used to derive ice-mass changes for the period from 2003 to 2012. The inferred time series are investigated regarding long-term, seasonal and interannual variations. Laser altimetry data acquired by the Ice, Cloud, and land Elevation Satellite (ICESat) are utilised to solve for linear and seasonal changes in the ice-surface height and to infer independent mass-change estimates for the entire GIS and its major drainage basins. We demonstrate that common signals can be identified in the results of both sensors. Moreover, the analysis of a Global Positioning System (GPS) campaign network in West Greenland for the period 1995–2007 allows us to derive crustal deformation caused by glacial isostatic adjustment (GIA) and by present-day ice-mass changes. ICESat-derived elastic crustal deformations are evaluated comparing them with GPS-observed uplift rates which were corrected for the GIA effect inferred by model predictions. Existing differences can be related to the limited resolution of ICESat. Such differences are mostly evident in dynamical regions such as the Disko Bay region including the rapidly changing Jakobshavn Isbræ, which is investigated in more detail. Glacier flow velocities are inferred from satellite imagery yielding an accelerated flow from 1999 to 2012. Since our GPS observations cover a period of more than a decade, changes in the vertical uplift rates can also be investigated. It turns out that the increased mass loss of the glacier is also reflected by an accelerated vertical uplift.     

Seasonal cycle of cloud cover analyzed using Meteosat images

A cloud-detection method was used to retrieve cloudy pixels from Meteosat images. High spatial resolution (one pixel), monthly averaged cloud-cover distribution was obtained for a 1-year period. The seasonal cycle of cloud amount was analyzed. Cloud parameters obtained include the total cloud amount and the percentage of occurrence of clouds at three altitudes. Hourly variations of cloud cover are also analyzed. Cloud properties determined are coherent with those obtained in previous studies.     

基于单站多系统的GNSS硬件延迟估算方法及其应用

随着全球导航卫星系统（Global Navigation Satellite Systems,GNSS）的不断发展,中国地区单个GNSS接收站在一个时刻可以接收到超过30颗GNSS卫星的信号,这为单站GNSS硬件延迟估算方法的研究提供了有利条件.本文首先通过GNSS硬件实验,分析了不同温度条件下GNSS系统硬件延迟的变化特征,研究结果显示：当温度快速变化时,硬件延迟变化比较剧烈,变化幅度可达12.53 TECU（1 TECU=10 ¹⁶el·m^-2）;在恒温条件或室温条件下,硬件延迟变化比较缓慢,变化幅度在1.00 TECU左右.在GNSS系统硬件延迟实验的基础上,充分利用单站多星观测的特点,提出了一种基于单站多系统的GNSS硬件延迟的估算方法——单站三角分解与差分消元法,并将该方法应用于河北保定站2015-2017年GNSS系统硬件延迟的求解中.通过对估算的GNSS系统硬件延迟进行分析显示：单站三角分解与差分消元法具有计算速度快、独立性好的特点;在北斗系统上硬件延迟的求解效果优于GPS、GLONASS系统,硬件延迟求解的结果整体上比利用欧洲定轨中心全球电离层地图校正的结果大2.50~3.00TECU左右;同时,该方法在消除GNSS系统硬件延迟后,获得的垂直总电子含量（Total Electron Content,TEC）能较好地反映电离层TEC的周日变化、日出增强、半年变化、年变化和春秋分不对称性等特征.