Directional Correlation Coefficient for Channeled Flow and Application to Wind Data over Complex Terrain

Pirmin Kaufmann Paul Scherrer Institute, Villigen, Switzerland

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Rudolf O. Weber Paul Scherrer Institute, Villigen, Switzerland

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Abstract

Analysis of vector quantities or directional data, such as the variables characterizing flow, is of significant interest to geophysical fluid dynamicists. For flows with strong channeling, a new simple correlation coefficient is defined. It is demonstrated by application to a model of channeled flow that the new correlation captures the flow features in the case of channeling better than other correlations taken from the literature. The new correlation coefficient is applied to wind data from a mesoscale network of anemometers in complex terrain. A cluster analysis based on the correlation matrix is used to group observation sites into classes with similar behavior of the channeled flow. Sites within the same class are not necessarily geographically close. A similar behavior of the wind directions indicated by these classes seems to be more closely related to the orographic features and to the altitude of the sites than to the horizontal distance between them.

Corresponding author address: Dr. Rudolf O. Weber, Paul Scherrer Institute, CH-5232 Villigen PSI, Switzerland.

Email: rudolf.weber@psi.ch

Abstract

Analysis of vector quantities or directional data, such as the variables characterizing flow, is of significant interest to geophysical fluid dynamicists. For flows with strong channeling, a new simple correlation coefficient is defined. It is demonstrated by application to a model of channeled flow that the new correlation captures the flow features in the case of channeling better than other correlations taken from the literature. The new correlation coefficient is applied to wind data from a mesoscale network of anemometers in complex terrain. A cluster analysis based on the correlation matrix is used to group observation sites into classes with similar behavior of the channeled flow. Sites within the same class are not necessarily geographically close. A similar behavior of the wind directions indicated by these classes seems to be more closely related to the orographic features and to the altitude of the sites than to the horizontal distance between them.

Corresponding author address: Dr. Rudolf O. Weber, Paul Scherrer Institute, CH-5232 Villigen PSI, Switzerland.

Email: rudolf.weber@psi.ch

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