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Figure 2. Left: the hemispheric 500-hPa height field regressed upon the standardized time series at the reference gridpoint (45 N, 165 W) based on monthly wintertime (DJFM) data for the period of record 1958-99. Note that the familiar PNA pattern appears in combination with a wavetrain extending across the Atlantic and Eurasia that appears to be reflected from the tropics in the Atlantic sector. The Atlantic center is stronger than the Florida center used in the conventional definition of the PNA pattern. Right: 500-hPa height regressed upon the standardized second principal component of SLP. Contour interval 10 m (-5, 5, 15...). Negative contours are dashed. From [10].
"Fig3.eps"
Figure 3. Wintertime (DJFM) sea-level pressure and surface air temperature trends for the period of record 1959-99 as calculated separately by linear regression for warm (58, 66, 69, 70, 73, 77, 78, 83, 87, 88, 92, 93, 95, 98 ) and cold (63, 67, 68, 71, 74, 75, 76, 84, 85, 86, 89, 96) years of the ENSO cycle as defined by JFM (?).
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Figure 3. Multiple realizations of the 522 dam contour in 10-day mean maps for the 30 most extreme high-index (left) and low-index (right) polarity of the NAM. Note the higher variability and the more frequent incidence of blocking under low-index conditions.
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Fig. XX. a) Regression of wintertime daily precipitaion anomalies onto normalized values of the AO, and b) the density of daily precipitation observations, shown for Washington state only, available for analysis. The major topographic features of the region are indicated schematically in panel a). The data employed in a) is the NOAA NCEP unified raingauge analysis and in b) the NOAA NCDC cooperative stations.
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Figure 6. A vectorial representation of the linear relationships between local wintertime (DJFM) 850-hPa temperature (T) and the two leading PC's of the hemispheric SLP field. The zonal component of the vectors relates to the first mode (the NAM) and the meridional component to the second (PNA-like) mode. Hence a vector directed from SW to NE indicates that T is positively correlated with both PC's: it tends to be above normal when SLP is below normal both over the Arctic and the North Pacific. In analyzing impacts of these modes upon temperature in such a region it might be worthwhile using a linear combination of PC1 and PC2 as a basis for stratifying the data.
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Figure 7. SLP (upper panels) and SAT (lower panels) wintertime (DJFM) 1958-99 trends based on NCEP-Reanalysis and University of Delaware data. Left: Linear trend. Center: The component of that trend that is linearly congruent with the two leading PC's of the SLP field and is hence presumed to be dynamically induced. Right: The residual trend.
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Figure 7. Left: Linear trend in wintertime (DJFM) surface air temperature 1958-99 based on University of Delaware data. Center: The component of that trend that is linearly congruent with the two leading PC's of the SLP field (data are detrended before being regressed) and is hence presumed to be dynamically induced. Right: The residual trend.
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Figure XX. April-May minus October-November difference in normalized aerosol concentrations based on NASA SeaWifs imagery for 1998-2001. Values are normalized by dividing by the annual mean optical depth at each gridpoint. Light and dark shading indicates difference magnitudes in excess of 25 and 50%, respectively; thick contour 0%, and dashed contours for decreases in aerosol.
