Northern Hemisphere winter teleconnections

Explanation of the derivation of the teleconnection climagrams available on Opencharts.

A variety of statistical methods have been used in the literature to define Northern-Hemisphere (NH) teleconnection patterns.  Here, leading variability patterns for the NH winter are defined by an EOF analysis of re-analysis monthly-mean geopotential height at 500 hPa for the December-to-March season, in the 30-year period (1981-2010). 

The analysis has been applied to three sectors within the latitude belt 25N-85N:

  1. the Pacific/North American sector (160E-80W).
  2. the Atlantic/European sector (80W-40E).
  3. the Asian/Pacific sector (40E-160E).

The portion within the grey sector boundary corresponds to the regionally-normalized EOF.  For continuity, regressions of height anomalies onto the corresponding PC are shown over the whole hemisphere.

Data are from the ERA-Interim re-analysis until winter 2009/10, from operational ECMWF analyses thereafter.  


Fig8.3.4.4-1: Northern Hemisphere winter teleconnections


EOF No1 is defined in each of the three sectors and corresponds to a well-documented teleconnection pattern:

  1. the Pacific/North American pattern.
  2. the North Atlantic Oscillation.
  3. the Eurasian pattern.  

The positive phase of these patterns corresponds to an intensification of the westerly winds over:

  1. central and eastern parts of the North Pacific.
  2. central and eastern parts of the North Atlantic.
  3. over central and eastern Siberia.

These patterns are shown in the top row of Fig8.3.4.4-1.  


EOF No2 of the Pacific/North American and the Atlantic/European sector are also retained. This is because they modulate the intensity and position of the stationary-wave ridges over:

  1. the north-eastern parts of the Pacific Ocean.
  2. the north-eastern parts of the Atlantic Ocean.

The positive EOFs correspond to an amplification of stationary-wave ridge pattern.  These are referred to as:

  1. the North Pacific dipole.
  2. the East Atlantic pattern.

These patterns are shown in the bottom row of Fig8.3.4.4-1.