Automated Classification Scheme for Wind Fields

Abstract

In earlier works of several authors, wind fields or flow patterns were grouped by means of trajectory calculations or by use of a principal component analysis. A new automated classification method is proposed that makes use only of wind observations and does not require predefined circulation patterns, a priori rules, or spatial or temporal interpolation. A distance measure is defined between pairs of wind fields, represented by a set of observations. Based on the resulting distance matrix, a hierarchical cluster analysis is performed that also provides an indication for the choice of an appropriate number of clusters. The classification method is applied to a monthly record of 1-h averages of wind measurements in the region of Basel, Switzerland. Different clustering schemes are tested, and the complete linkage method is chosen as most appropriate. For the test case a relatively small number of classes (12) provides a sufficient description of the different flow patterns in this complex topography. The strong channeling of flow in the valleys of the Basel region seems to result in only a small number of distinguishable flow patterns.