Anomalously deep earthquakes in northwestern Italy     

Marco Cattaneo  Paolo Augliera  Stefano Parolai  Daniele Spallarossa 《Journal of Seismology》1999,3(4):421-435

It is usually assumed that earthquakes in intraplate regions occur in the upper crust, and northwestern Italy is generally assigned to this kind of normal seismicity. In this work, the depth distribution of the events localized in this area by the Istituto Geofisico Geodetico (IGG) seismic network in the period 1991–1997 is analyzed in detail. In particular, the location capability of the network is discussed, adopting as reference quarry blasts (for the epicentral position) and the locations obtained from a dense temporary network (for the depth estimate). Within the so-obtained error limits, the depth distribution of events show a characteristic pattern: while for most of the area covered by the network the well-located seismicity lies within the first 20 km of depth, in a band following the inner arc of the Western Alps, numerous events have anomalously large focal depths, reaching a maximum of 114 km. These depth determinations cannot be attributed to instabilities of the location procedure: different choices of the propagation models used for the hypocentral determination led to very similar depth values, always significantly larger than the standard values for the surrounding areas. A strong correlation has been found between the 3-dimensional distribution of these foci and the P-wave propagation anomalies obtained from tomographic studies, suggesting a direct link between elastic and rheological properties of lower crust and upper mantle in this area.  相似文献   

卡尔曼滤波模型误差的识别   总被引：3，自引：1，他引：2  

陶本藻 《大地测量与地球动力学》1999,19(4):15-20

本文在简述卡尔曼滤波模型基础上讨论了模型误差的检验和估计问题,提出了检验卡尔曼滤波模型误差显著性的几种统计假设检验方法,探讨并给出了估计模型误差的方法和公式。  相似文献   

基于集合预报的台风“利奇马”登陆后远距离暴雨预报的敏感性分析     

王毅  张晓美  陶亦为  刘爽  邓国 《气象科学》2020,40(1):22-29

2019年第9号台风“利奇马”在8月10日登陆后引发了远距离大范围的暴雨,本文利用ECMWF(EC)和GRAPES全球集合预报模式等资料对暴雨短期预报的误差及原因进行了分析。此次台风远距离暴雨主要集中在8月10日夜间的山东中部地区,EC集合预报对该区域的降水量预报效果总体优于GRAPES集合预报。集合敏感性分析可以识别出和预报变量高相关(敏感)的天气系统,结果表明山东区域平均降水量对同期500 hPa副高、台风西北侧海平面气压和山东北部低层温度较为敏感,而对流层高层的高度及经向风存在更大范围的敏感区。根据暴雨预报TS评分选取EC集合预报成员作为优势组和劣势组,结果表明优势组预报成员表现为山东上空300 hPa低槽前倾,北侧高空偏南急流更强,同时配合低层台风外围偏东风急流,形成高层辐散、低层辐合的有利条件。另外,优势组预报的中纬度低层冷空气和斜压锋区更强,导致优势组在山东中部预报出暴雨,更加接近于实况。  相似文献   

复杂地形条件下嵌套细网格模式35例数值预报的总结     

钱正安  陈玉春 《高原气象》1994,13(2):144-152

本文利用一适合复杂地形区的有限区域预报模式系统，分别采用欧洲中期天气预报中心的格点资料和我国国家气象中心的ＤＣＤ电码资料，对１９８１年７月１－３０日和１９８８年８月１０－１４日两时段共３５天作了４８小时预报。形势场和降水预报的主客观评分表明，该模型系统已具备了在业务环境下作预报的可能，该模型预报性能良好，具有较好的强降水预报的能力。  相似文献   

轨道误差对近实时GPS遥感水汽的影响研究   总被引：5，自引：3，他引：5  

曹云昌  方宗义夏青 《气象科技》2004,32(4):229-232

利用GPS技术近实时探测水汽对于气象预报、气候研究具有重要的应用价值，而近实时探测需要使用GPS卫星的预报星历，预报星历的误差会直接影响到实时水汽探测的精度。利用从IGS资料处理中心下载的精密预报星历和最终星历，对2000年北京GPS水汽试验中的资料进行了解算，并结合探空资料计算的水汽进行了分析。结果表明：以探空为标准，使用精密预报星历计算的水汽总量均方根误差为0．31cm，最终星历为0．30cm，二者差别不大，为0．01cm，证明使用精密预报星历可以满足近实时探测水汽的要求。  相似文献   

动态Kalman滤波模型误差的影响   总被引：4，自引：11，他引：4  

杨元喜 《测绘科学》2006,31(1):17-18

动态Kalman滤波模型误差的影响与静态平差模型误差影响不同。它包括观测异常误差影响和动力学模型异常的影响。本文分别讨论了观测异常误差和动力学模型异常误差对当前历元滤波结果的影响及对后续历元滤波结果的影响;构建了异常误差影响表达式,并对各类异常误差的检测方法进行了分析。  相似文献   

A New Method for the Determination of Area-Averaged Turbulent Surface Fluxes from Low-Level Flights Using Inverse Models     

Jens Bange  Peter Zittel  Thomas Spieß  Jörg Uhlenbrock  Frank Beyrich 《Boundary-Layer Meteorology》2006,119(3):527-561

The low-level flight method (LLF) has been combined with linear inverse models (IM) resulting in an LLF+IM method for the determination of area-averaged turbulent surface fluxes. With this combination, the vertical divergences of the turbulent latent and sensible heat fluxes were calculated from horizontal flights. The statistical errors of the derived turbulent surface fluxes were significantly reduced. The LLF+IM method was tested both in numerical and field experiments. Large-eddy simulations (LES) were performed to compare ‘true’ flux profiles with ‘measurements’ of simulated flights in an idealised convective boundary layer. Small differences between the ‘true’ and the ‘measured’ fluxes were found, but the vertical flux divergences were correctly calculated by the LLF+IM method. The LLF+IM method was then applied to data collected during two flights with the Helipod, a turbulence probe carried by a helicopter, and with the research aircraft Do 128 in the LITFASS-98 field campaign. The derived surface fluxes were compared with results from eddy-covariance surface stations and with large-aperture scintillometer data. The comparison showed that the LLF+IM method worked well for the sensible heat flux at 77 and 200 m flight levels, and also for the latent heat flux at the lowest level. The model quality control indicated failures for the latent heat flux at the 200 m level (and higher), which were probably due to large moisture fluctuations that could not be modelled using linear assumptions. Finally the LLF+IM method was applied to more than twenty low-level flights from the LITFASS-2003 experiment. Comparison with aggregated surface flux data revealed good agreement for the sensible heat flux but larger discrepancies and a higher statistical uncertainty for the latent heat flux  相似文献   

Accuracy assessment and refinement of the JGM-2 and JGM-3 gravity fields for radial positioning of ERS-1     

P. Moore  S. Ehlers  S. Carnochan 《Journal of Geodesy》1998,72(7-8):373-384

ERS-1 radial positioning using the JGM-2 and JGM-3 gravity fields is assessed by analysing dual crossovers with TOPEX/Poseidon, neither field containing ERS-1 data. This method allows a more complete recovery of ERS-1 radial orbit error, specifically of the previously unattainable mean geographical error. The global analysis shows that the theoretical error derived from the JGM-2 covariance matrix is realistic and that JGM-3 represents a slight improvement, at least at the inclination of ERS-1. A latitudinal-based study in the southern ocean indicates possible weaknesses in both fields, notably for low and resonant geopotential orders m. A refinement of JGM-2, RGM-2, is undertaken through inclusion of ERS-1 and STELLA laser tracking and ERS-1 altimetry, reducing several of its deficiencies. Received: 14 May 1996 / Accepted: 17 February 1997  相似文献   

复杂岩性解释模型稳定性和可靠性评价   总被引：2，自引：0，他引：2       下载免费PDF全文

汪宏年 《地球物理学报》1998,41(4):561-569

对解释模型进行评价以及如何选择合适的解释模型是复杂岩性解释中非常重要的问题。本文应用统计学的理论以及非线性优化技术,系统研究了在线性约束条件下对储层参数的置信区域和误差大小进行估计的问题,通过将梯度投影算法与奇异值分解技术相结合的方法给出了计算储层参数置信区域与误差大小的公式,以及对复杂岩性解释模型的稳定性和可靠性进行合理评价的具体方法。最后通过数值计算实例研究了一种能够有效提高解释模型稳定性和可靠性的措施,数值计算结果证明解释模型响应函数的最小非零奇异值大小是影响稳定性和可靠性的一个重要参数,当最小非零奇异值较大时,模型的稳定性往往较好,否则较差,因此通过对解释模型进行适当组合并选取最小非零奇异值较大的综合解释模型,可以大大提高其稳定性和可靠性。  相似文献   

各种物理强迫激发的平均经圈环流特征及其对数值天气预报模式系统误差的贡献     

张绍晴  刘还珠 《大气科学》1996,20(1):112-122

本文证明7种强迫作用激发经圈环流的线性叠加性，分项考察了各种物理强迫激发经圈环流的特征，通过考察一个数值模式的模式大气和实际大气各种物理强迫激发经圈环流的差异，分析了模式系统误差的成因，这种建立在动力背景之上的模式误差分析方法，其物理意义明确，具有较为普遍的适用性。  相似文献