Autocorrelation Functions Computed from Daily 500 mb Geopotential Height Analyses

Juhani Rinne Department of Meteorology, University of Helsinki, Finland

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Simo Järvenoja Department of Meteorology, University of Helsinki, Finland

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Abstract

A method of computing autocorrelation fields with the aid of empirical orthogonal functions (EOF) is applied. The isotropic parts of the fields are separated, and a one-parameter model of the isotropic autocorrelation field is constructed. The approximation is compared with the Bessel representations discussed by others. The present model requires fewer parameters (one as against four) and gives a more realistic representation at greater distances. In other respects, the results are quite similar. At midlatitudes, the present model is a good approximation of the autocorrelation fields. Over the Himalayas, the fields are exceptionally anisotropic. The results substantiate the importance of the Himalayas in teleconnectivity.

Abstract

A method of computing autocorrelation fields with the aid of empirical orthogonal functions (EOF) is applied. The isotropic parts of the fields are separated, and a one-parameter model of the isotropic autocorrelation field is constructed. The approximation is compared with the Bessel representations discussed by others. The present model requires fewer parameters (one as against four) and gives a more realistic representation at greater distances. In other respects, the results are quite similar. At midlatitudes, the present model is a good approximation of the autocorrelation fields. Over the Himalayas, the fields are exceptionally anisotropic. The results substantiate the importance of the Himalayas in teleconnectivity.

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