Contour Analysis: A New Approach for Melding Geophysical Fields

Arthur J. Mariano Harvard University, Cambridge, Massachusetts

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Abstract

This paper introduces a new approach, contour analysis, for combining independent estimates of a geophysical field to produce a single realization incorporating data from all sources. Contour analysis divides the field estimates into contours and then calculates the average position of each contour: it is shown that this method avoids the smearing and weakening of important dynamical features which can result from the traditional method of simply averaging data values at fixed geographical coordinates. The paper begins with an overview of how contour points are determined and averaged; this is followed by an illustrative example showing the basic steps one must go through to automate the process on a computer. The remainder of the paper presents comparisons between the traditional approach and the contour analysis approach over a wide range of data types: combining numerical model fields, averaging one-dimensional curves, space-time interpolation of Gulf Stream north wall positions and an application to data assimilation in the Gulf Stream ring and meander region.

Abstract

This paper introduces a new approach, contour analysis, for combining independent estimates of a geophysical field to produce a single realization incorporating data from all sources. Contour analysis divides the field estimates into contours and then calculates the average position of each contour: it is shown that this method avoids the smearing and weakening of important dynamical features which can result from the traditional method of simply averaging data values at fixed geographical coordinates. The paper begins with an overview of how contour points are determined and averaged; this is followed by an illustrative example showing the basic steps one must go through to automate the process on a computer. The remainder of the paper presents comparisons between the traditional approach and the contour analysis approach over a wide range of data types: combining numerical model fields, averaging one-dimensional curves, space-time interpolation of Gulf Stream north wall positions and an application to data assimilation in the Gulf Stream ring and meander region.

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