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HOME > Climate & Weather Linkage > Teleconnections > Pacific/North American Pattern > Monthly Mean PNA Index
The monthly mean PNA index is constructed by following modified pointwise method:

PNA = Z*(15°N-25°N,180-140°W)-Z*(40°N-50°N,180-140°W)


where Z* denotes monthly mean 500 mb height anomaly that is obtained by subtracting the calendar mean value for each month during 1950-2000 base period.

The index is normalized using 1950-2000 base period statistics.

The correlation coefficients between PNA indices using different methods for the 1950-2000 base period.

  REOF Modified Pointwise Pointwise
REOF   0.92 0.92
Modified Pointwise     0.98

cf) The PNA index using Pointwise method following Wallace and Gutzler (1981):

PNA = Z*(20°N,160°W)-Z*(45°N,165°W)+Z*(55°N,115°W)-Z*(30°N,85°W).

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Page Author: Climate Prediction Center Internet Team
Page last modified: December 12, 2005
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