GFDL - Geophysical Fluid Dynamics Laboratory

Publication 8401

Harnack, R., and J. Lanzante, 1984: Specification of seasonal mean
700 mb heights over North America by North Pacific and North Atlantic sea
surface temperature.
Mon. Wea. Rev., 112, 1626-1633.


North Pacific and North Atlantic SST (sea surface temperature) were used
separately and in combination to specify seasonal-mean North American 700
mb heights. One of the goals was to quantify these relationships so that the
importance of North Atlantic versus North Pacific SST could be assessed.
Sea surface temperature predictors were in the form of EOF (empirical
orthogonal function) amplitudes, while the predictands consisted of
seasonal-mean 700 mb heights at each of 25 locations over North America.
Linear regression analysis was used in the data period 1949-77 to build three
kinds of models: 1) using the first five North Pacific SST EOF’s, 2) using
the first five North Atlantic SST EOF’s and 3) using five EOF’s from each
field, but screening to produce the best five predictor models.

The principal findings can be summarized as:

  1. Based on area-averaged skill and percent area of significant skill, North
    Pacific SST is a better specifier of 700 mb height than North Atlantic
  2. Pacific SST models have significant overall skill for all seasons except
    spring, with area-averaged true skill being greatest in winter (S=0.247)
    and least in spring (S=0.061).
  3. Atlantic SST models do not attain field significance in any season, but
    perform best overall in winter (S=0.095).
  4. A portion of the region studied for winter and summer contained gridpoint
    locations where testing indicated that Atlantic SST adds significant
    information to that of Pacific SST in explaining variations of 700 mb
    height. This amounted to 13 and 15% of the total area, respectively,
    which was not enough to declare field significance.