On the Utility of ENSO and PNA Indices for Long-Lead Forecasting of Summer Weather over the Crop-Growing Region of the Canadian Prairies |
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Authors: | E R Garnett M L Khandekar J C Babb |
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Institution: | (1) Canadian Wheat Board, Winnipeg, Manitoba, Canada, CA;(2) Environment Canada, Downsview, Ontario, Canada, CA;(3) Canadian Grain Commission, Winnipeg, Manitoba, Canada, CA |
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Abstract: | Summary The well known ENSO (El Ni?o-Southern Oscillation) phenomenon is quantitatively identified in terms of SST (sea surface temperature)
anomalies over the equatorial central and eastern Pacific and sea level pressure difference over eastern and western regions
of the equatorial Pacific. The PNA (Pacific North American) atmospheric flow pattern, originally identified by Wallace and
Gutzler (1981) is representative of a certain preferred configuration of the mid-tropospheric geopotential height field in
the longitudinal sector extending from the mid-Pacific to the southeastern United States. The PNA index is defined as a linear
combination of normalized geopotential height anomalies at the 700 mb level at four selected locations. Using multiple regression
analysis, suitable linear combinations of predictors based on monthly values of ENSO and PNA indices are obtained which can
foreshadow the summer season’s weather over the crop-growing region of the Canadian prairie provinces with a lead time of
2 to 7 months. The utility of the ENSO and PNA indices for advance indication of summer weather with implications for grain
yields over the Canadian prairies is further discussed.
Received September 10, 1996 Revised October 13, 1997 |
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