The Spatial and Temporal Variability of Atmospheric Teleconnection Patterns: A Continuum Perspective

• Main Author: Johnson, Nathaniel Charles
• Other Authors: Johannes Verlinde, Eugene E. Clothiaux, Steven B. Feldstein, Jerry Y. Harrington, David Pollard, Hampton N. Shirer
• Format: Text
• Language: English
• Published: Penn State 2009
• Subjects: Meteorology; Pacific; aleutian low; North Atlantic; North Atlantic oscillation
• Online Access: http://etda.libraries.psu.edu/theses/approved/WorldWideIndex/ETD-3881/index.html

The continuum perspective of atmospheric teleconnection patterns provides a simpler framework than the commonly used discrete modal perspective for understanding the spatial and temporal variability of the two dominant Northern Hemisphere teleconnection patterns, the North Atlantic Oscillation (NAO) and the Pacific/North American pattern (PNA). The continuum perspective suggests that the spatial and temporal variability of atmospheric teleconnection patterns occur through the changes in the frequency distribution within the continuum of these patterns. This dissertation demonstrates that two similar methods, self-organizing map (SOM) analysis and k-means clustering combined with linear unidimensional scaling (LUS), provide an attractive framework for this perspective because each method provides a visualization of the continuum in a spatially ordered manner. A SOM analysis of daily, wintertime Northern Hemisphere sea level pressure (SLP) reveals that the interdecadal variability of the NAO arises from changes in the frequency distribution of the NAO-like SOM patterns within the NAO continuum. In particular, this analysis shows that the secular, eastward shift of the NAO that began in the 1970s may be understood as arising from a change in dominance from westward-displaced, negative NAO-like patterns to eastward-displaced, positive NAO-like patterns, although westward- and eastward-displaced NAO-like patterns existed during all time periods and for both phases. The application of k-means clustering with LUS to North Pacific SLP reveals that the intraseasonal, interannual, and interdecadal variability of the PNA similarly arises from changes in the frequency of the cluster patterns that compose the PNA continuum, each of which has a timescale of about 10 days. A SOM analysis of coupled SLP and outgoing longwave radiation data shows that many of these patterns are associated with convection in the tropical Indo-Pacific region. On intraseasonal timescales, the frequency distribution of the North Pacific SLP patterns, in particular the PNA-like patterns, is influenced strongly by the Madden-Julian Oscillation (MJO). On interannual timescales, the El Niño-Southern Oscillation (ENSO) impacts the North Pacific continuum, with warm ENSO episodes resulting in the increased frequency of easterly displaced Aleutian low pressure anomaly patterns, and cold ENSO episodes resulting in the increased frequency of southerly displaced Aleutian high pressure anomaly patterns. In addition, the results of this analysis suggest that the interdecadal variability of the North Pacific SLP field, including the well known regime shift of 1976/77, also results from changes in the frequency distribution within the continuum of SLP patterns.