Investigations on coastal upwelling off Northwest Africa and Portugal with empirical orthogonal functions

1980 ◽  
Vol 33 (5) ◽  
pp. 210-221 ◽  
Author(s):  
Holger Detlefsen ◽  
Peter Speth
Keyword(s):  
Coastal Upwelling ◽  
Empirical Orthogonal Functions ◽  
Orthogonal Functions ◽  
Northwest Africa

On the dynamics of wind-driven shelf currents

1981 ◽  
Vol 302 (1472) ◽  
pp. 617-634 ◽  
Keyword(s):  
Sea Level ◽  
Momentum Equation ◽  
Bottom Friction ◽  
Empirical Orthogonal Functions ◽  
Rate Of Change ◽  
Time Dependent ◽  
Momentum Balance ◽  
Orthogonal Functions ◽  
Northwest Africa ◽  
Coastal Sea

Measurements of currents, wind, and coastal sea level from off Oregon, northwest Africa and Peru are used to examine characteristics of the depth-integrated momentum balance at mid-shelf locations. Attention is focused on determining the nature of the balance, as a function of frequency, of time-dependent terms in the alongshore momentum equation. Decomposition of the estimated terms into empirical orthogonal functions, and regression of terms on the wind stress to obtain the wind-forced component, are methods used in an attempt to assess objectively the type of balance present. It is found, for Oregon, that there is a relatively large amount of variance in the depth-integrated cross-shelf velocity which is not balanced by other estimated terms. In addition, a substantial component of the flow is wind-forced, with bottom friction insignificant for periods less than 11 days. For northwest Africa, the motion is strongly wind-driven, with bottom friction playing an important role for periods greater than 6 days and with a quasi-steady response evident for periods longer than 10 days. For Peru, the motion is dominated by an inviscid, unforced balance which, for the 5- to 11-day frequency band, is primarily between the alongshore pressure gradient and the rate of change with time of the alongshore velocity.

scholarly journals Improving the Remote Sensing Retrieval of Phytoplankton Functional Types (PFT) Using Empirical Orthogonal Functions: A Case Study in a Coastal Upwelling Region

2018 ◽  
Vol 10 (4) ◽  
pp. 498 ◽  
Author(s):  
Marco Correa-Ramirez ◽  
Carmen Morales ◽  
Ricardo Letelier ◽  
Valeria Anabalón ◽  
Samuel Hormazabal
Keyword(s):  
Remote Sensing ◽  
Coastal Upwelling ◽  
Empirical Orthogonal Functions ◽  
Orthogonal Functions ◽  
Functional Types

Empirical Methods in Short-Term Climate Prediction

2006 ◽  
Author(s):  
Huug van den Dool
Keyword(s):  
Climate Prediction ◽  
Empirical Orthogonal Functions ◽  
Data Sets ◽  
Seasonal Forecasts ◽  
Short Term ◽  
Orthogonal Functions ◽  
Ocean Atmosphere Interaction ◽  
Global Coverage ◽  
Atmosphere Interaction ◽  
Global Data

This clear and accessible text describes the methods underlying short-term climate prediction at time scales of 2 weeks to a year. Although a difficult range to forecast accurately, there have been several important advances in the last ten years, most notably in understanding ocean-atmosphere interaction (El Nino for example), the release of global coverage data sets, and in prediction methods themselves. With an emphasis on the empirical approach, the text covers in detail empirical wave propagation, teleconnections, empirical orthogonal functions, and constructed analogue. It also provides a detailed description of nearly all methods used operationally in long-lead seasonal forecasts, with new examples and illustrations. The challenges of making a real time forecast are discussed, including protocol, format, and perceptions about users. Based where possible on global data sets, illustrations are not limited to the Northern Hemisphere, but include several examples from the Southern Hemisphere.

scholarly journals Spatio-Temporal Patterns of Mass Changes in Himalayan Glaciated Region from EOF Analyses of GRACE Data

2021 ◽  
Vol 13 (2) ◽  
pp. 265
Author(s):  
Harika Munagapati ◽  
Virendra M. Tiwari
Keyword(s):  
Temperature Anomaly ◽  
Mass Gain ◽  
Snow Accumulation ◽  
Empirical Orthogonal Functions ◽  
Total Water ◽  
Orthogonal Functions ◽  
Grace Data ◽  
Grace Satellite ◽  
Spatio Temporal ◽  
Gravity Recovery

The nature of hydrological seasonality over the Himalayan Glaciated Region (HGR) is complex due to varied precipitation patterns. The present study attempts to exemplify the spatio-temporal variation of hydrological mass over the HGR using time-variable gravity from the Gravity Recovery and Climate Experiment (GRACE) satellite for the period of 2002–2016 on seasonal and interannual timescales. The mass signal derived from GRACE data is decomposed using empirical orthogonal functions (EOFs), allowing us to identify the three broad divisions of HGR, i.e., western, central, and eastern, based on the seasonal mass gain or loss that corresponds to prevailing climatic changes. Further, causative relationships between climatic variables and the EOF decomposed signals are explored using the Granger causality algorithm. It appears that a causal relationship exists between total precipitation and total water storage from GRACE. EOF modes also indicate certain regional anomalies such as the Karakoram mass gain, which represents ongoing snow accumulation. Our causality result suggests that the excessive snowfall in 2005–2008 has initiated this mass gain. However, as our results indicate, despite the dampening of snowfall rates after 2008, mass has been steadily increasing in the Karakorum, which is attributed to the flattening of the temperature anomaly curve and subsequent lower melting after 2008.

Identifying VIV Vibration Modes by Use of the Empirical Orthogonal Functions Technique

2002 ◽  
Author(s):  
Gudmund Kleiven
Keyword(s):  
Model Test ◽  
Vibration Mode ◽  
Multivariate Data ◽  
Empirical Orthogonal Functions ◽  
Mode Shapes ◽  
Data Sets ◽  
Vibration Modes ◽  
Ocean Engineering ◽  
Orthogonal Functions ◽  
Related Technique

The Empirical Orthogonal Functions (EOF) technique has widely being used by oceanographers and meteorologists, while the Singular Value Decomposition (SVD being a related technique is frequently used in the statistics community. Another related technique called Principal Component Analysis (PCA) is observed being used for instance in pattern recognition. The predominant applications of these techniques are data compression of multivariate data sets which also facilitates subsequent statistical analysis of such data sets. Within Ocean Engineering the EOF technique is not yet widely in use, although there are several areas where multivariate data sets occur and where the EOF technique could represent a supplementary analysis technique. Examples are oceanographic data, in particular current data. Furthermore data sets of model- or full-scale data of loads and responses of slender bodies, such as pipelines and risers are relevant examples. One attractive property of the EOF technique is that it does not require any a priori information on the physical system by which the data is generated. In the present paper a description of the EOF technique is given. Thereafter an example on use of the EOF technique is presented. The example is analysis of response data from a model test of a pipeline in a long free span exposed to current. The model test program was carried out in order to identify the occurrence of multi-mode vibrations and vibration mode amplitudes. In the present example the EOF technique demonstrates the capability of identifying predominant vibration modes of inline as well as cross-flow vibrations. Vibration mode shapes together with mode amplitudes and frequencies are also estimated. Although the present example is not sufficient for concluding on the applicability of the EOF technique on a general basis, the results of the present example demonstrate some of the potential of the technique.

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