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It also allows for better continuity of the time series from one month to the next, than if the patterns were calculated based on the data for each month independently.
This analysis accounts for variability in the structure and amplitude of the teleconnection patterns associated with the annual cycle of the extratropical atmospheric circulation. These patterns are referred to as the North Atlantic Oscillation, the Pacific/North American teleconnection pattern, the East Atlantic pattern, the West Pacific pattern, the East Pacific - North Pacific pattern, the East Atlantic/ Western Russia pattern, the Tropical/ Northern Hemisphere pattern, the Polar-Eurasian pattern, the Scandinavia pattern, and the Pacific Transition pattern. Click here for additional discussion on how the teleconnection indices are calculated.Īn examination of all twelve sets of rotated modes revealed ten dominant teleconnection patterns, of which eight to nine appear in each of the twelve calendar months. Therefore, these ten leading rotated modes for each calendar month are based on 153 (51 x 3) monthly standardized anomaly maps. A Varimax rotation is then applied to these ten leading un-rotated modes, yielding the ten leading rotated modes and their time series for that calendar month. The anomalies are standardized by the 1950-2000 base period monthly means and standard deviations.įor each of the twelve calendar months, the ten leading unrotated EOFs are first determined from the standardized monthly height anomaly fields in the three-month period centered on that month. For our monitoring purposes, we apply the RPCA technique to monthly mean standardized 500-mb height anomalies obtained from the CDAS in the analysis region 20°N-90°N between January 1950 and December 2000. This procedure isolates the primary teleconnection patterns for all months and allows time series of the patterns to be constructed. The procedure used to identify the Northern Hemisphere teleconnection patterns and indices is the Rotated Principal Component Analysis -RPCA (Barnston and Livezey 1987, Mon. Technique for Identifying the Northern Hemisphere Teleconnection Patterns.
Northern Hemisphere Teleconnection Patterns > Teleconnection Pattern Calculations
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