Anomaly Detection in MODIS Land Products via Time Series Analysis     

ZHANG Jingxiong David Roy Sadashiva Devadiga ZHENG Min 《地球空间信息科学学报》2007,10(1):44-50

With remote sensing information products becoming increasingly varied and arguably improved, scientific applications of such products rely on their quality assessment. In an operational context such as the NASA (National Aeronautics and Space Administration) information production based on the MODIS (Moderate Resolution Imaging Spectroradiometer) instrument on board Earth Observing System (EOS) Terra and Aqua satellites, efficient ways of detecting product anomaly, i.e., to discriminate between product artifacts and real changes in Earth processes being monitored, are extremely important to assist and inform the user communities about potential unreliability in the products. A technique for anomaly detection, known as MAD (the median of absolute deviate from the median), in MODIS land products via time series analysis is described, which can handle intra- and in-ter-annual variation in the data by using MAD statistics of the original data and their first-order difference. This method is shown to be robust and work across major land products, including NDVI, active fire, snow cover, and surface reflectance, and its applicabil-ity to multi-disciplinary products is anticipated.  相似文献   

Quadrant analysis of the scalar and momentum fluxes in the stable marine atmospheric surface layer     

George D. Katsouvas  Costas G. Helmis  Qing Wang 《Boundary-Layer Meteorology》2007,124(3):335-360

The quadrant technique, a conditional sampling approach that allocates Reynolds stresses into four different types of events (ejections or bursts, sweeps, inward interactions and outward interactions), is applied to stable marine atmospheric boundary-layer data, collected in the framework of the Coupled Boundary Layer Air—Sea Transfer, Low wind component experiment at Nantucket Island, Massachusetts, USA. The general properties of both scalar and momentum transport are analyzed under the scope of quadrant analysis experimentally and theoretically. It is shown that the third-order Gram–Charlier series is necessary and even sufficient in most of the cases, in describing the experimental time and flux contributions of each quadrant to the total transfer, for both scalar and momentum transport, while the ability of the Gaussian distribution is limited to outlining the general pattern of these quantities. Moreover, a threshold value is applied to the conditional analysis, separating the most important events from the less significant ones and the sensitivity of the flux and especially the time fraction of each quadrant on the choice of this value is presented and discussed. Also, a set of numerically extracted equations, completing the analytical relations, is derived, enabling the prediction of the time and flux fractions of each quadrant, for a wide range of correlation coefficient and threshold values. Finally, the sensitivity of the analysis to the atmospheric stability and the Reynolds averaging scales showed that correlated and uncorrelated motions tend to balance for increasingly stable conditions and/or for large time scales.  相似文献   

Hardy-Hilbert不等式一个新的改进     

王祥  张太忠 《南京气象学院学报》2007,30(4):575-578

研究关于重级数型Hardy-Hilbert不等式改进的问题。通过给出如下形式的权系数的估计式∞研究关于重级数型Hardy-Hilbert不等式改进的问题。通过给出如下形式的权系数的估计式ω(q,n)=∑∞m=11m nnm1q<πsinπp-12np1 2en-q1,q>1,1p q1=1,n∈N,从而得到Hardy-Hilbert不等式的一个新的改进形式∑∞m=1∑∞n=1ambnm n<∑∞n=1πsinπp-12n1p 2en-1qanp1p∑∞n=1πsinπp-12n1q 2en-1pbnq1q。  相似文献   

闽中地区次火山-热液金（银）矿床成矿系列及资源潜力   总被引：3，自引：0，他引：3       下载免费PDF全文

黄树峰陈玉水  林美龙李秋平 《中国地质》2005,32(1):115-121

闽中地区是福建省金银成矿集中区,其上规模成矿主要集中于晚侏罗世次火山活动阶段。次火山-热液金(银)矿床的形成,矿、热、水“三源”是基本必要条件,北西、北东向两组构造带的复合是成矿定位的关键。在断隆带、坳中隆、坳中凹不同构造环境中,相应地递次形成(次)辉绿岩-闪长玢岩、(次)英安斑岩、(次)流纹斑岩等区域次火山-热液金(银)矿床成矿系列的3个亚系列;在垂向空间分布上,自上而下构成(微)细粒浸染型、石英脉型、破碎带蚀变岩型、隐爆角砾岩型、次火山岩型等工业矿床类型分带序列。金矿资源潜力在50t以上。  相似文献   

Reconstruction of Nineteenth Century Summer Temperatures in Norway by Proxy Data from Farmers'Diaries   总被引：2，自引：0，他引：2  

P.Ø. Nordli 《Climatic change》2001,48(1):201-218

Proxy data from five farmers; diaries in the Møre, Dovre and Trøndelag regions in central Norway were used for climatic reconstruction purposes. The method chosen was "simple linear regression analysis" with the start of the grain harvest (barley or oats) as predictor and summer temperature (May – August) as predictand. Overlapping periods with modern instrumental observations (starting 1858 or later) were used for calibration of the model. The model was tested on independent data by establishing the regression on one half of the overlapping period and applying the regression on the other half. The standard deviation in the residuals varied from 0.3°C to 0.7°C and the biases of the mean values from –0.3°C to +0.3°C. Climatic reconstructions were established for the early- and mid-nineteenth century summer temperature, i.e. during the last part of what has come to be regarded as the "Little Ice Age", in this article considered to end around 1880.By use of the proxy data model, huge inhomogeneities of the "classical" Trondheim series were detected, the early nineteenth century part of the series evidently being too warm. The inhomogeneity was removed by use of adjustment terms. The adjusted series indicates that in the Trondheim region the summer temperature during the last part of the "Little Ice Age" phase was about 1°C lower than the latest 60 years. This is in serious contradiction to the classical Trondheim series.  相似文献   

湖南江永铅锌矿床岩溶成矿构造系列及其演化   总被引：3，自引：0，他引：3       下载免费PDF全文

汪劲草  汤静如  彭恩生  常家良  雷衍国 《地质找矿论丛》2000,15(2):159-165

文章从解析已知矿体入手,认为江永铅锌矿床外接触带主矿体不是脉型矿体,而是岩溶型矿体。岩溶成矿构造受石磴子组中厚层灰岩控制。一组岩溶由两个岩厅组成,一个发育于２００～３２０ｍ标高,另一个发育于４００～５５０ｍ标高。根据近等距性原则,分别于已知岩溶型矿体（Ⅱ、Ⅲ）的南、北两侧预测了Ⅰ、Ⅳ及Ⅴ号岩溶组。建立了岩溶成矿构造系列、结构及坑睛鉴别标志,并探讨了岩溶的形成与演化。预测结论与物探激电异常结果吻合。  相似文献   

Statistical assessment of trends and oscillations in rainfall dynamics: Analysis of long daily Italian series   总被引：1，自引：0，他引：1  

M. Cislaghi  C. De Michele  A. Ghezzi  R. Rosso 《Atmospheric Research》2005,77(1-4):188

Since the 18th century systematic measurements of rainfall have been collected in Italy. The daily rainfall series observed in Milan (1835–2001), Genoa (1833–2000), Bologna (1813–2001) and Palermo (1797–1999) are examples of available long rainfall records. These data series can help analyzing the evolution of precipitation. The present paper deals with long term evolution of: (i) annual rainfall amount; (ii) annual number of rainy events; (iii) intensity of rainfall, (iv) inter-annual rainfall partitioning, i.e. the duration of wet and dry periods, and (v) maximum annual values of daily rainfall amount, duration of wet and dry periods. The evolution is studied analyzing the first two order statistics and the 30-year return period quantiles via moving window analysis. Confidence intervals are introduced to check the statistical significance of the estimated statistics and quantiles. The results are compared with those provided by the traditional Mann-Kendall test. The analysis shows how the annual precipitation exhibits a negative trend in the first half of 20th century, with a subsequent positive trend in northern Italy (Genoa, Milan and Bologna). Conversely, the dataset for Palermo (southern Italy) displays only a negative trend. Because the number of precipitation episodes is found to decrease in the investigated period, the average rain rate is significantly increasing especially in northern Italy. This is also associated with shorter duration of rain episodes with an evident effect on rainfall extremes. Dry periods tend to be longer with increasing variability. The Mann-Kendall test and its progressive form have shown to be well suited for monotonic trend, but the confidence interval analysis, introduced here, is more appropriate if oscillations are significant.  相似文献   

对水文时间序列混沌特征参数估计问题的讨论   总被引：15，自引：0，他引：15       下载免费PDF全文

王文  许武成 《水科学进展》2005,16(4):609-616

水文过程到底是不是低维混沌过程一直是个有争议的问题。相关文献在混沌特征参数估计中存在不少问题,包括:时延量估计的主观性很强,不同研究者的估计值差别很大;在关联维估计中,很多研究者有意无意地忽略了一个基本原则,即只有在关联维估计图上存在明确的标度区的情况下才能准确判断存在有限关联维;很多研究者在计算水文时间序列的关联维时仍采用原始的G-P计算公式,而没有采用Theiler提的修正公式,从而可能误将相点在时序上的相关性当做一种状态空间几何特征,造成关联维估计错误;国内相关研究中还普遍存在序列长度偏短的问题,对这些问题进行了讨论并给出了相应的结论。  相似文献   

西江流域硝酸盐氮输出规律研究   总被引：2，自引：0，他引：2       下载免费PDF全文

刘凌  贺国庆 《水科学进展》2005,16(5):655-660

以西江流域为研究对象,研究流域出口断面硝酸盐氮浓度时间变化规律,采用非平稳时间序列分析方法,分析流域系统行为对氮输出的影响,结果发现:西江硝酸盐氮浓度存在线性增加的确定性趋势,其季节增加量最大值出现在每年5月,与降雨季节增加量最大值时间基本一致,表明降雨造成的地表冲刷、土壤侵蚀以及5月施加的氮肥量大,是造成流域硝酸盐氮输出增大的主要原因。对西江高要断面输出的硝酸盐氮浓度建立了非平稳自回归-滑动平均混合模型,即ARIMA(1,0,1)(2,1,1)12模型,模型通过了高要站硝酸盐氮浓度实测数据的验证,利用模型,预测了西江硝酸盐氮输出的时间变化规律。  相似文献   

地下圆形衬砌隧道对沿线地震动的影响(Ⅰ):级数解   总被引：8，自引：4，他引：8  

梁建文  纪晓东  Vincent W Lee 《岩土力学》2005,26(4):520-524

利用波函数展开法，给出了地下圆形衬砌隧道对入射平面P波和SV波散射问题的一个级数解答，当衬砌与半空间介质相同时，该解答退化为文献中的无衬砌隧道的解答。级数解答为进一步定量研究隧道对入射平面P波和SV波的放大作用以及入射波长、入射角度、隧道直径和衬砌刚度等参数对隧道沿线地震动的影响奠定了理论基础。  相似文献