Genetic algorithms in seismic waveform inversion   总被引：24，自引：0，他引：24  

Malcolm Sambridge  Guy Drijkoningen 《Geophysical Journal International》1992,109(2):323-342

  相似文献   

从熵原理得出的暴雨面积和雨量的关系   总被引：7，自引：3，他引：7  

张学文  杨秀松 《高原气象》1991,10(3):225-232

  相似文献   

浙江象山海滩岩的发现及其意义   总被引：8，自引：1，他引：8  

高中和  季幼庭 《地震地质》1991,13(1):28-32,T002

作者于浙江象山爵溪首次发现了全新世海滩岩,并对其岩石学特征、同位素年龄、形成环境等进行了初步研究。爵溪海滩岩目前是我国分布位置最北的全新世海滩岩,据14C年龄测出该地3400多年来海岸的相对沉降速率为0.51mm/a  相似文献   

春季北太平洋风暴轴的年际与年代际变化特征及其与太平洋海温异常的关系   总被引：1，自引：0，他引：1       下载免费PDF全文

袁超  徐海明 《Acta Meteorologica Sinica》2016,74(6):860-875

利用20世纪大气再分析资料和欧洲中心海温资料研究了春季西北太平洋风暴轴的年（代）际变化特征以及在不同年代际背景下风暴轴与太平洋海温关系的转变。结果表明,春季西北太平洋风暴轴主要存在两种空间变化模态,即反映其强度变化的第1模态和反映其南北位置变化的第2模态。年代际及以上时间尺度上,风暴轴强度、位置与太平洋海温的关系主要表现为大气对海洋的强迫作用。在不同年代际背景下,风暴轴与太平洋海温的关系则存在明显的年代际转变：1977年以后,风暴轴强度与太平洋海温的关系主要表现为大气对海洋的强迫作用,而在1977年之前则主要表现为海洋对大气的强迫作用,特别是同期冬季日本以东黑潮和黑潮延伸区海温异常的强迫作用;风暴轴南北位置与太平洋海温异常的关系,在1977年以后表现为大气对海洋的强迫作用,主要表现为对北太平洋中部海温的影响,但在1977年以前表现为海洋和大气的共同作用,风暴轴南北位置的变化还与同期的赤道中东太平洋海温异常有关,表明ENSO可能对风暴轴的位置变化存在影响。  相似文献   

Subseasonal variability and predictability of the Arctic Oscillation/North Atlantic Oscillation in BCC_AGCM2.2     

《Dynamics of Atmospheres and Oceans》2016

The subseasonal variability and predictability of the Arctic Oscillation/North Atlantic Oscillation (AO/NAO) is evaluated using a full set of hindcasts generated from the Beijing Climate Center Atmospheric General Circulation Model version 2.2 (BCC_AGCM2.2). It is shown that the predictability of the monthly mean AO/NAO index varies seasonally, with the highest predictability during winter (December–March) and the lowest during autumn (August–November), with respect to both observations and BCC_AGCM2.2 results. As compared with the persistence prediction skill of observations, the model skillfully predicts the monthly mean AO/NAO index with a one-pentad lead time during all winter months, and with a lead time of up to two pentads in December and January. During winter, BCC_AGCM2.2 exhibits an acceptable skill in predicting the daily AO/NAO index of ∼9 days, which is higher than the persistence prediction skill of observations of ∼4 days. Further analysis suggests that improvements in the simulation of storm track activity, synoptic eddy feedback, and troposphere–stratosphere coupling in the Northern Hemisphere could help to improve the prediction skill of subseasonal AO/NAO variability by BCC_AGCM2.2 during winter. In particular, BCC_AGCM2.2 underestimates storm track activity intensity but overestimates troposphere–stratosphere coupling, as compared with observations, thus providing a clue to further improvements in model performance.  相似文献   

Real-time genetic spatial optimization to improve forest fire spread forecasting in high-performance computing environments     

Tomàs Artés  Andrés Cencerrado  Ana Cortés  Tomàs Margalef 《International journal of geographical information science》2016,30(3):594-611

Abstract

Forest fires are a kind of natural hazard with a high number of occurrences in southern European countries. To avoid major damages and to improve forest fire management, one can use forest fire spread simulators to predict fire behavior. When providing forest fire predictions, there are two main considerations: accuracy and computation time. In the context of natural hazards simulation, it is well known that part of the final forecast error comes from uncertainty in the input data. These data typically consist of a set of GIS files, which should be appropriately conflated. For this reason, several input data calibration methods have been developed by the scientific community. In this work, the Two-Stage calibration methodology, which has been shown to provide good results, is used. This calibration strategy is computationally intensive and time-consuming because it uses a Genetic Algorithm as a solution. Taking into account the aspect of urgency in forest fire spread prediction, it is necessary to maintain a balance between accuracy and the time needed to calibrate the input parameters. In order to take advantage of this technique, one must deal with the problem that some of the obtained solutions are impractical, since they involve simulation times that are too long, preventing the prediction system from being deployed at an operational level. A new method which finds the minimum resolution reduction for such long simulations, keeping accuracy loss to a known interval, is proposed. The proposed improvement is based on a time-aware core allocation policy that enables real-time forest fire spread forecasting. The final prediction system is a cyberinfrastructure, which enables forest fire spread prediction at real time.  相似文献   

西伯利亚风暴轴的气候特征及其可能维持机制   总被引：2，自引：1，他引：1  

马阳  朱伟军  李天宇  王森  李欣 《气象科学》2017,37(5):587-597

基于1959—2014年NCEP/NCAR的逐日再分析资料,首先研究了西伯利亚风暴轴各季节的气候平均特征,然后以冬季为例,利用能量诊断方程,从能量学的角度对其的可能维持机制进行了探讨,并在上述分析过程中与北半球两大洋风暴轴的特征进行了对比。结果表明:(1)西伯利亚风暴轴一年四季都独立存在,虽强度要比两大洋风暴轴的强度弱很多且位置偏北,但可以定义为一个弱风暴轴。(2)比较来看,西伯利亚风暴轴强度的季节变化与北太平洋风暴轴的季节变化类似。与两大洋风暴轴位于急流东北侧不同,冬季西伯利亚风暴轴位于东亚温带急流的西侧。(3)进一步的能量分析结果表明,与两大洋风暴轴一样,斜压不稳定的能量转换(Ke4)也是西伯利亚风暴轴区域天气尺度扰动动能的主要来源;而扰动非地转位势通量散度项(Ke3)和时间平均气流对扰动动能的平流输送项(Ke1)也是风暴轴下游发展所需的扰动动能来源之一。  相似文献   

一种渤海风暴潮数值预报模式与试验     

王正林  孙文心 《中国海洋大学学报(自然科学版)》1993,(1)

通过三维模式导出二维数值模式,采用守恒型空间差分格式对渤海风暴潮进行数值模拟。同时采用由三维模式导出的任意形式的底摩擦表达式,找出适用于渤海风暴潮的底摩擦参数。对曾经发生在渤海的四次较严重的风暴潮进行数值后报并与实测资料相比较,证实预报模式的可行性。  相似文献   

Numerical Simulation of Extreme Sea Levels for the Tamil Nadu (India) and Sri Lankan Coasts     

P. Chittibabu  S. K. Dube  P. C. Sinha  A. D. Rao  T. S. Murty 《Marine Geodesy》2002,25(3):235-244

Numerical modeling of extreme sea levels associated with tropical cyclones in the Indian seas has been confined to the northern part of the Bay of Bengal (north of Tamil Nadu). However, limited attempts have been made for modeling of surges along the Tamil Nadu and Sri Lankan coasts. Although, very rarely, cyclones form south of 10°N, there are some instances of severe cyclonic storms hitting these areas and causing widespread destruction to life and property. Keeping this in view, a suitable location-specific, high-resolution, numerical model has been developed for the prediction of storm surges in these regions with a grid resolution of 3 km. Using the model, numerical experiments are performed to simulate the storm surge associated with the 1964 Rameswaram cyclone, the 1978 Batticaloa cyclone, the 1992 Tuticorin cyclone, the 1993 Karaikal cyclone, and the 1994 Madras cyclone. During the years 1964, 1978, and 1992, the cyclones struck both Sri Lanka and Tamil Nadu coasts, while in 1993 and 1994, the cyclones struck only the Tamil Nadu coast. It is found that the computed sea surface elevations are in close agreement with the available observations/estimates.  相似文献   

Effect of fluid column dynamics on longitudinal vibrations of an ultra deepwater riser covered by an orifice plug     

Vadim S. Tikhonov  Alexander I. Safronov 《Ocean Engineering》2002,29(1):99-112

The paper studies longitudinal vibrations of an ultra-deepwater drilling riser whose bottom end is disconnected from the sea floor and covered by a plug (a blind one or the one with a hole). An elastic shell is used as a model of a riser pipe. The fluid column motion in the riser is described by the Navier–Stokes equation for a compressible fluid. Losses of fluid pressure during its flowing through a hole in the plug are taken into account. Solution of the riser equations is carried out in the frequency domain. Analysis of the effect which the riser length, wave period and height, and the plug-hole diameter on the amplitude of the riser's tension vibrations is conducted. A riser manufactured of strong aluminium alloys, some of prospective materials for ultra deepwater drilling, was considered as a prototype. It has been shown that risers 2000–4000 m long, plug-hole, and a riser 6000 m long with plug-hole of 0.087 m in diameter can withstand wave height of >15 m throughout the frequency range.  相似文献