Simplified EOFs-three alternatives to rotation

Jolliffe, Ian T.; Uddin, Mudassir; Vines, S. K.

doi:10.3354/cr020271

Cited by 28 publications

(15 citation statements)

References 20 publications

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“…To identify which large-scale structures, or variability modes, are connected with TX90 and TN10 we computed the unrotated and rotated (with varimax) EOFs (Jolliffe et al 2002). The association between PC_ TX90 and PC_TN10 with the large-scale variables is measured not only temporally but also spatially.…”

Section: Methodsmentioning

confidence: 99%

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Trends in warm days and cold nights over the Iberian Peninsula: relationships to large-scale variables

et al. 2009

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The aims of this study are to identify the trend of warm days and cold nights over the Iberian Peninsula and to connect the variations with large-scale variables. The reasons for performing this analysis are the effects that extremes events have on different ecosystems. Here, we present the results on spatial and temporal variability of warm days (TX90), or those exceeding the 90th percentile of maximum temperature, and cold nights (TN10), or those falling below the 10th percentile of minimum temperature. The extreme indices were derived from daily observations at stations and gridded data over land area for the period 1950 to 2006. Significant trends of more warm days and fewer cold nights were found. The trend to fewer cold nights is within the interval of global results given by the IPCC AR4 report; however, the trend to warm days is greater than the corresponding global trend. The influence of large-scale variables on these extreme indices was examined by means of the Empirical Orthogonal Function, correlation, composite maps and multiple regression analyses. Changes in TX90 are connected with the Scandinavian teleconnection index and a preferred mode of geopotential height at 500 hPa over the North Atlantic. Changes in TN10 are connected with the East Atlantic teleconnection index and the leading mode of Sea Surface Temperature (SST) variability over the North Atlantic area. Based on the links between the extreme indices and the large-scale variables we derived statistical models to describe the response of TX90 and TN10 to atmospheric circulation and SST variations. The 668 Climatic Change (2010) 100:667-684 models characterized the observed variations of TX90 and TN10 reasonably well. The results of this study encourage us to analyze, in further work, how temperature extremes might change over the Iberian Peninsula under warmer climate conditions.

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Section: Methodsmentioning

confidence: 99%

“…We used Empirical Orthogonal Functions to extract the signals of the TX90 and TN10 variability (Hannachi et al 2007;Jolliffe 2002). The first mode of TX90 and TN10 accounts for a large amount of variance, 72% and 67%, respectively, with spatial patterns significant in 99% of the total area at the 95% significance level.…”

Section: Methodsmentioning

confidence: 99%

Trends in warm days and cold nights over the Iberian Peninsula: relationships to large-scale variables

et al. 2009

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“…A detailed comparison of the new technique, SCoT, rotated PCA, and Vines' (2000) simple components is given for an example involving sea surface temperatures in Jolliffe, Uddin, and Vines (2002). Tibshirani (1996) studied the dif culties involved in the interpretation of multiple regression equations.…”

Section: A Motivating Examplementioning

confidence: 99%

A Modified Principal Component Technique Based on the LASSO

Jolliffe

Trendafilov

Uddin³

2003

Journal of Computational and Graphical Statistics

711

522

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In many multivariate statistical techniques, a set of linear functions of the original p variables is produced. One of the more dif cult aspects of these techniques is the interpretation of the linear functions, as these functions usually have nonzero coef cients on all p variables. A common approach is to effectively ignore (treat as zero) any coef cients less than some threshold value, so that the function becomes simple and the interpretation becomes easier for the users. Such a procedure can be misleading. There are alternatives to principal component analysis which restrict the coef cients to a smaller number of possible values in the derivationof the linear functions,or replace the principalcomponentsby "principal variables." This article introduces a new technique, borrowing an idea proposed by Tibshirani in the context of multiple regression where similar problems arise in interpreting regression equations. This approach is the so-called LASSO, the "least absolute shrinkage and selection operator," in which a bound is introduced on the sum of the absolute values of the coef cients, and in which some coef cients consequently become zero. We explore some of the propertiesof the new technique,both theoreticallyand using simulation studies, and apply it to an example.

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“…For the rotation, the varimax criterion was used. This form of rotation is the most frequently used in climatological studies because it has been found to be entirely independent of the domain (Kaiser, 1958), and simplifies the structure of the loadings (Jolliffe et al, 2002) by maximising the variance of the squared correlation coefficients (i.e. loadings) between each rotated component with each original component (Horel, 1981).…”

Section: Pca Applicationmentioning

confidence: 99%

Comprehensive analysis of the climate variability in the eastern Mediterranean. Part I: map‐pattern classification

Κωστοπούλου

Jones

2007

Intl Journal of Climatology

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Abstract:This paper provides an extended study of the dominant daily circulation patterns governing the climate variability in the eastern Mediterranean. The methodology adopted to determine the circulation patterns is based on combined analysis of the spatial and temporal variation of rotated principal components of sea-level pressure. A catalogue of characteristic seasonal composites is presented and discussed. It is found that, during winter and spring, large scale features situated in northern Europe affect the atmospheric circulation over the domain of study, whereas the Atlantic (Azores) anticyclone and the Asian Thermal Low define most of the observed circulation types in summer. In autumn, the area exhibits a rapid transition from the warm to cold season showing climatic features from both extreme seasons. Similarities between winter and spring/autumn patterns are detected and correlation analyses are employed between their spatial patterns to reveal that similar circulation patterns occur amongst the three seasons, which usually appear more pronounced during winter. Frequencies and trends of the proposed circulation types are examined for each season. A linear trend analysis for the overall period exhibits a significant increase in the anticyclonic types particularly in winter. With respect to the cyclonic types, statistically significant negative trends have been found in all seasons especially for types associated with depressional activity in central the Mediterranean.

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Simplified EOFs-three alternatives to rotation

Cited by 28 publications

References 20 publications

Trends in warm days and cold nights over the Iberian Peninsula: relationships to large-scale variables

Trends in warm days and cold nights over the Iberian Peninsula: relationships to large-scale variables

A Modified Principal Component Technique Based on the LASSO

Comprehensive analysis of the climate variability in the eastern Mediterranean. Part I: map‐pattern classification

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