Wiener optimal filtering of GRACE data   总被引：4，自引：0，他引：4  

I. Sasgen  Z. Martinec  K. Fleming 《Studia Geophysica et Geodaetica》2006,50(4):499-508

We present a spatial averaging method for Gravity Recovery and Climate Experiment (GRACE) gravity-field solutions based on the Wiener optimal filtering. The optimal filter is designed from the least-square minimization of the difference between the desired and filtered signals. It requires information about the power spectra of the desired gravitational signal and the contaminating noise, which is inferred from the average GRACE degree-power spectrum. We show that the signal decreases with increasing spherical harmonic degree j with approximately j^−b, where b = 1.5 for GRACE data investigations. This is termed the Second Kaula rule of thumb for temporal variations of the Earth’s gravity field. The degree power of the noise increases, in the logarithmic scale, linearly with increasing j. The Wiener optimal filter obtained for the signal model with b = 1.5 closely corresponds to a Gaussian filter with a spatial half width of 4° (∼440 km). We find that the filtered GRACE gravity signal is relatively insensitive to the exponent b of the signal model, which indicates the robustness of Wiener optimal filtering. This is demonstrated using the GFZ-GRACE gravity-field solution for April 2004.  相似文献   

Seismic hazard of the Eastern Mediterranean     

Amr Z. Hamouda 《Acta Geophysica》2006,54(2):165-176

Earthquake hazard parameters such as maximum magnitude, annual mean seismic activity rate, and the Gutenberg-Richter parameter, have been evaluated for the Hellenic and Cyprean Arc regions of the Eastern Mediterranean. The applied maximum likelihood procedure permits the combination of both historical and instrumental data. The collected data from different sources cover earthquakes with magnitude ≥ 3.5 throughout the last two centuries. The historical part of the catalogue only contains the strongest events, whereas the complete part can be divided into several subcatalogues, each assumed complete above a specific threshold of magnitude. The hazard parameters assessment is performed for the two study regions. The Hellenic Arc region was found to be of higher seismicity level than the Cyprean Arc region. The number of annually expected earthquakes with magnitude ≥ 3.5 is much larger in the Hellenic Arc (56±2) than in the Cyprean Arc (35±2). The maximum magnitude calculated in the Hellenic Arc zone is 7.8±0.4 for the time period equal to the length of the catalogue, i.e., 210 years. For the Cyprean Arc zone, the maximum possible magnitude is 6.8±0.4 for the time span of 330 years.  相似文献   

A trigger mechanism of nonlinear mechanoelectric conversions in mineralized faults     

Z. -Yu. Ya. Maibuk 《Izvestiya Physics of the Solid Earth》2006,42(10):838-849

Polymetallic ores yield evidence of semiconductor textures creating irregularly distributed trap zones of electric charges produced by electrochemical reactions and mechanoelectric conversions. Such zones bounded by natural barriers can contain charges concentrated in separate parts of an ore-bearing province and reside in this state for a long time. If this equilibrium is disturbed, the energy (electric charges) is redistributed and signals of pulsed electromagnetic emission in the radiowave frequency range (PEERFR) are radiated. The set of properties of polymetallic ores recorded under in situ conditions and studied in the laboratory suggests a trigger mechanism of PEERFR signal generation. The triggering threshold of this mechanism depends on mining and geological conditions and the concentration and structure of ores. The energy released in ores can be many times larger than the activation energy of this process.  相似文献   

Paleomagnetic studies of Paleolithic site deposits in the Matzuka Cave (Northern Caucasus)     

G. A. Pospelova  L. V. Golovanova  Z. V. Sharonova  V. V. Semenov 《Izvestiya Physics of the Solid Earth》2006,42(7):585-597

As a result of detailed paleomagnetic and magnetic studies of Paleolithic site deposits in the Matuzka Cave, a record of the Matuzka geomagnetic excursion in lithologic layer 7 has been discovered and studied. Such characteristic features as the geomagnetic field direction, position of the virtual geomagnetic pole, geomagnetic field intensity (roughly estimated) after and during the excursion, and climatic conditions coeval with its existence make the Matuzka excursion similar to the ～130-ka Blake excursion. This dates at ～130 ka the formation of layer 7 with ancient archaeological findings.  相似文献   

A numerical model of the partitioning of trace chemical solutes during drop freezing     

A. L. Stuart  M. Z. Jacobson 《Journal of Atmospheric Chemistry》2006,53(1):13-42

Partitioning of volatile chemicals among the gas, liquid, and solid phases during freezing of liquid water in clouds can impact trace chemical distributions in the troposphere and in precipitation. We describe here a numerical model of this partitioning during the freezing of a supercooled liquid drop. Our model includes the time-dependent calculation of the coupled processes of crystallization kinetics, heat transport, and solute mass transport, for a freezing hydrometeor particle. We demonstrate the model for tracer partitioning during the freezing of a 1000 μm radius drop on a 100 μm ice substrate, under a few ambient condition scenarios. The model effectively simulates particle freezing and solute transport, yielding results that are qualitatively and quantitatively consistent with previous experimental and theoretical work. Results suggest that the ice shell formation time is governed by heat loss to air and not by dendrite propagation, and that the location of ice nucleation is not important to freezing times or the effective partitioning of chemical solutes. Even for the case of nucleation at the center of the drop, we found that dendrites propagated rapidly to form surface ice. Freezing then proceeded from the outside in. Results also indicate that the solid-liquid interfacial surface area is not important to freezing times or the effective partitioning of chemical solutes, and that the rate aspects of trapping are more important than equilibrium solid-liquid partitioning to the effective partitioning resulting from freezing.  相似文献   

An objective classification system of air mass types for Szeged, Hungary, with special interest in air pollution levels     

L. Makra  J. Mika  A. Bartzokas  R. Béczi  E. Borsos  Z. Sümeghy 《Meteorology and Atmospheric Physics》2006,92(1-2):115-137

Summary This paper determines the characteristic air mass types over the Carpathian Basin for the winter (December, January, and February) and summer (June, July and August) months dependant on levels of the main air pollutants. Based on the ECMWF data set, daily sea-level pressure fields analysed at 00 UTC were prepared for each air mass type (cluster) in order to relate sea-level pressure patterns with the level of air pollutants in Szeged. The data comprise daily values of twelve meteorological and eight pollutant parameters for the period 1997–2001. Objective definition of the characteristic air mass types is achieved by using the methods of Factor Analysis and Cluster Analysis. According to the results, during the winter months five air mass types (clusters) were detected based on higher concentrations of primary pollutants that occur with high irradiance and low wind speed. This is the case when an anticyclone is found over the Carpathian Basin and over the region south of Hungary, influencing the weather of the country. Low levels of pollutants occur when zonal currents exert influence over Hungary. During the summer months anticyclones and anticyclone ridge situations are found over the Carpathian Basin. (During the prevalence of anticyclone ridge situations, the Carpathian Basin is found at the edge of a high pressure centre.) As a result of high irradiance and very low NO levels, secondary pollutants are highly enriched.  相似文献   

Short-range prediction of a heavy precipitation event by assimilating Chinese CINRAD-SA radar reflectivity data using complex cloud analysis   总被引：5，自引：0，他引：5  

C. Sheng  S. Gao  M. Xue 《Meteorology and Atmospheric Physics》2006,94(1-4):167-183

Summary With the ARPS (Advanced Regional Prediction System) Data Analysis System (ADAS) and its complex cloud analysis scheme, the reflectivity data from a Chinese CINRAD-SA Doppler radar are used to analyze 3D cloud and hydrometeor fields and in-cloud temperature and moisture. Forecast experiments starting from such initial conditions are performed for a northern China heavy rainfall event to examine the impact of the reflectivity data and other conventional observations on short-range precipitation forecast. The full 3D cloud analysis mitigates the commonly known spin-up problem with precipitation forecast, resulting a significant improvement in precipitation forecast in the first 4 to 5 hours. In such a case, the position, timing and amount of precipitation are all accurately predicted. When the cloud analysis is used without in-cloud temperature adjustment, only the forecast of light precipitation within the first hour is improved. Additional analysis of surface and upper-air observations on the native ARPS grid, using the 1 degree real-time NCEP AVN analysis as the background, helps improve the location and intensity of rainfall forecasting slightly. Hourly accumulated rainfall estimated from radar reflectivity data is found to be less accurate than the model predicted precipitation when full cloud analysis is used.  相似文献   

青藏铁路唐古拉山-拉萨段全新世控震断裂研究   总被引：8，自引：0，他引：8  

吴中海吴珍汉  胡道功赵希  叶培盛江万 《地质通报》2006,25(12):1387-1401

地表调查表明,沿青藏铁路唐古拉山-拉萨段存在5条重要的全新世控震断裂带,从北到南分别是温泉盆地西缘断裂带、安多盆地北缘断裂带、崩错断裂带、谷露西缘断裂带和当雄-羊八井断裂带.构造-地貌和年代学分析结果表明,北部的温泉盆地西缘断裂和安多盆地北缘断裂带的活动强度相对比较小,平均垂直活动速率约为0.2～0.5mm/a.南侧的谷露西缘断裂带和当雄-羊八井断裂带的全新世垂直活动速率为约(15±0.5)mm/a.而中部的崩错走滑断裂带的活动强度最大,晚第四纪期间的走滑速率可达(11±4.5)mm/a.全新世断裂活动和古地震研究表明,其中温泉盆地西缘断裂带、安多盆地北缘断裂带、崩错断裂带的西北分支、当雄-羊八井断裂带的当雄段等区域未来发生强震的概率相对更大.  相似文献   

大面积深厚杂填土地基处理技术     

刘焕存  高凤莲  许珩 《岩土工程技术》2006,20(6):307-310

通过一项具体的工程实例,论述了深厚杂填土地基的基本工程特性。介绍了一种处理深厚杂填土地基的新技术———重锤冲扩挤密灰渣土桩复合地基技术,并对施工过程的控制,以及施工效果的检测结果进行了分析,得出了对于大面积深厚杂填土地基采用此技术处理后,能够消除地基深部湿陷性,复合地基承载力可以满足200 kPa。  相似文献   

Environmental Assessments of Trace Metals in Sediments from Dongting Lake, Central China   总被引：1，自引：0，他引：1  

姚志刚  鲍征宇高璞 《中国地质大学学报(英文版)》2006,17(4):50-319

INTRODUCTIONFresh water lakes are one of the planet’s mosti mportant freshwater resources.They support life invarious forms,develop tourism and provide uniquerecreational opportunities.It is also a good source ofthe provision of drinking-water for local communi-ties.Studies on trace elements in rivers,lakes,andsedi ments(Zhou et al.,2004;Gray et al.,2000;Grosheva et al.,2000;Klavins et al.,2000;Aucoinet al.,1999;Bortoli et al.,1998;Elbaz-Poulichet etal.,1996;Johansson et al.,1995;F r…  相似文献