Application of principal component analysis to understand variability of rainfall     

R. N. Iyengar 《Journal of Earth System Science》1991,100(2):105-126

The usefulness of principal component analysis for understanding the temporal variability of monsoon rainfall is studied. Monthly rainfall data of Karnataka, spread on 50 stations for a period of 82 years have been analysed for interseasonal and interannual variabilities. A subset of the above data comprising 10 stations from the coherent west zone of Karnataka has also been investigated to bring out statistically significant interannual signals in the southwest monsoon rainfall. Conditional probabilities are proposed for a few above normal/below normal transitions. A sample prediction exercise for June–July using such a transition probability has been found to be successful.  相似文献   

西昆仑山地区太阳分光辐射分布特征   总被引：1，自引：0，他引：1  

魏耀宏  林振耀 《高原气象》1992,11(3):249-258

  相似文献   

冰力模型实验   总被引：2，自引：0，他引：2  

史庆增  徐继祖  宋安 《冰川冻土》1990,(4)

本文首先简述了冰力模型实验的概况,然后介绍了在国内第一座冰池实验中进行的首次冰力模型实验——渤海辽东湾抗冰平台冰力模型实验的设备、模型冰制取技术和实验结果。实验中,冰排的破坏符合一般规律,它预示了现场冰的破坏现象;冰力值稍低于计算值,但更合理,可供设计参考;冰力谱中存在着明显的主频率,它集中于0.8HZ左右。  相似文献   

On the use of maximum entropy/autoregressive spectrum in harmonic analysis of time series     

B. Fong Chao 《Pure and Applied Geophysics》1990,134(2):303-311

The maximum entropy (ME) spectrum, or its equivalent form of the autoregressive (AR) spectrum, has been used as a tool for harmonic analysis of time series in geophysics. This paper critically examines its usage in estimating the amplitude and the exponential decay rate of a harmonic function. The argument is based upon Prony's relation, which relates a complex-conjugate pair of poles for the AR model of the time series on one hand, to the complex frequency of one harmonic component in the time series on the other. It is found that: (i) the ME spectrum can be used as an estimator for the decay rate in a way similar to the Fourier spectral analysis; (ii) the ME spectrum contains no information whatsoever about the amplitude, contrary to what has been claimed and practiced in geophysical applications.  相似文献   

NUMERICAL EXPERIMENTS FOR THE IMPACT OF ANTARCTIC ICE COVER AND SEA SURFACE TEMPERATURE ON CLIMATE VARIABILITY^*          下载免费PDF全文

Miao Qun  Chen Longxun 《Acta Meteorologica Sinica》1997,11(1):23-34

By using a three-level atmospheric general circulation model(AGCM),we have completed several numerical experiments to study the impacts of sea surface temperature anomaly(SSTA) and antarctic ice cover anomaly(AICA) during 1981-1983 on climate variability.The results show that during the El Nino period of 1982-1983 the impact of SSTA overrides that of AICA.SSTA mainly affects equatorial zonal circulation and produces PNA wave train,and SE-NW wave train in East Asia to influence the weather of China.AICA produces west-east anomalous vortex streets in the middle latitudes of both hemispheres and affects the intensity of the polar vortex of Southern Hemisphere.  相似文献   

国外有关海气系统年代际变率的机制研究   总被引：13，自引：1，他引：13  

江志红  屠其璞 《地球科学进展》2001,16(4):569-573

对近期国外有关年代际变率机制的诊断和模拟研究作了综合评述 ,着重介绍形成年代际变率的 5种主要机制 ,即热带海洋的强迫作用、中纬度的海气相互作用、温盐环流的作用、热带—中纬度的相互作用、海气之间的随机强迫作用机制 ,并简单阐述了作者的有关看法  相似文献   

Three-dimensional slope reliability and risk assessment using auxiliary random finite element method     

《Computers and Geotechnics》2016

This paper aims to propose an auxiliary random finite element method (ARFEM) for efficient three-dimensional (3-D) slope reliability analysis and risk assessment considering spatial variability of soil properties. The ARFEM mainly consists of two steps: (1) preliminary analysis using a relatively coarse finite-element model and Subset Simulation, and (2) target analysis using a detailed finite-element model and response conditioning method. The 3-D spatial variability of soil properties is explicitly modeled using the expansion optimal linear estimation approach. A 3-D soil slope example is presented to demonstrate the validity of ARFEM. Finally, a sensitivity study is carried out to explore the effect of horizontal spatial variability. The results indicate that the proposed ARFEM not only provides reasonably accurate estimates of slope failure probability and risk, but also significantly reduces the computational effort at small probability levels. 3-D slope probabilistic analysis (including both 3-D slope stability analysis and 3-D spatial variability modeling) can reflect slope failure mechanism more realistically in terms of the shape, location and length of slip surface. Horizontal spatial variability can significantly influence the failure mode, reliability and risk of 3-D slopes, especially for long slopes with relatively strong horizontal spatial variability. These effects can be properly incorporated into 3-D slope reliability analysis and risk assessment using ARFEM.  相似文献   

应用全型散度方程诊断鄂东北一次梅雨强降雨     

张端禹  许建玉  赵玉春 《气象科技》2016,44(6):1009-1015

利用0.5°×0.5°GFS分析资料和常规气象观测资料,分析2013年7月5—7日鄂东北梅雨连续暴雨过程。结果表明:1降雨具有比较明显的日变化,夜间加强,白天减弱;鄂东北低层辐合也有与降雨强度一致的日变化特点。2散度变率在高层出现正值、中低层出现负值有利于降雨加强,且这种变化比暴雨发生稍有提前。一般傍晚散度变率在低层即出现负值,这有利于夜间低层辐合加强。3利用全型散度方程2项组合诊断发现,虽然非线性平衡方程偏差项确是散度变率的主要项,但在降雨开始阶段只有余项在低层出现较为明显的负值。4利用全型散度方程4项组合诊断发现,边界层水平风场辐合是降雨启动因子之一;非地转平衡项在近地面出现较大正值对于降雨减弱有较好的指示;与垂直运动有关的项在降雨峰值阶段中层负值较大。  相似文献   

夏玉米生长过程曲线重建研究——以鹤壁市为例     

李颖  李耀辉  王金鑫 《气象与环境科学》2016,39(4):7-13

增强型植被指数(EVI)时间序列数据(即植被生长曲线)是整个生育期内植被各种生物学特征的综合反映。由于太阳位置、大气、地表和传感器位置与性能等的影响,根据遥感数据计算的EVI值往往比实际值偏低(存在大量噪声),并不能反映植被生长的真实情况,应用前需进行去噪重建工作。针对目前生长曲线重建研究大多是针对MODIS等国外遥感数据的情况,在综合分析重建方法的基础上,利用风云3号卫星的MERSI中分辨率遥感卫星数据构建鹤壁市夏玉米的EVI生长过程曲线。首先,用最大值合成法(MVC)对原始EVI时间序列数据进行初步的去云处理。接着,利用基于时间域的Savitzky-Golay滤波(简称SG滤波)对该EVI序列进行进一步的平滑去噪处理,结果发现,在噪声点EVI数值提高了,但同时在其他不是噪声点的地方EVI的值降低了。针对这种不合理的情况,利用基于SG迭代滤波取上包络线的改进方法进行处理,很好地克服了上述缺陷,在非噪声点EVI数值适当提高,且曲线平滑,达到了生长曲线重建的目的。然后,采用基于频率域的小波变换方法进行实验对比,结果发现,小波变换存在着与经典SG滤波类似的缺陷,而且在曲线末端存在突变情况。经过比较分析发现,针对研究区的实际情况,改进SG迭代滤波是较优的去噪方法。  相似文献   

蚀变矿物近红外光谱特征对地质找矿的指示意义——以甘肃岗岔金矿为例     

彭自栋  申俊峰  曹卫东  李金春  刘廷 《地质通报》2016,35(5):822-831

甘肃岗岔金矿位于秦岭造山带之碌曲-成县逆冲推覆构造带的西段北侧,是典型的构造蚀变岩型金矿床,目前储量可达中型。在矿区地质填图的基础上,采用BJKF-1型近红外矿物分析仪对矿区7号勘探线ZK07-4钻孔、8号勘探线ZK08-6钻孔及27号勘探线的ZK27-1、ZK27-3、ZK27-4钻孔岩心进行蚀变特征研究,识别出的主要蚀变矿物为伊利石、云母类、地开石、高岭石等。蚀变矿物分布及含量变化特点表明,与矿化有关的蚀变主要是绢英岩化,其中已探明矿体多位于采用近红外分析技术圈出的绢英岩化带内。此外,伊利石反射光谱特征参数计算结果表明,伊利石结晶度和Al-OH特征吸收峰形态呈现有规律的变化,即含矿段和近矿段伊利石结晶度大(SWIR-IC值5.5~5.7),Al-OH吸收峰尖锐;远矿段和无矿段伊利石结晶度小(SWIR-IC值1.3~1.5),Al-OH吸收峰平缓,显示含矿段伊利石形成温度较高。上述结果表明,矿区内绢英岩化蚀变及伊利石结晶度、Al-OH峰形是有利找矿标志,对找矿具有实际指导意义。  相似文献