The planetary wave amplification hypothesis and its relationship to heat waves and polar air outbreaks over North America

Northern Hemisphere synoptic weather patterns are hypothesized to respond to Arctic amplification. As the Arctic warms disproportionately to the rest of the Northern Hemisphere, the weakened north-south temperature gradient may favor larger amplitude planetary waves, a northward shift in the jet stream, and as a result, a change in the mid-latitude weather systems and patterns in the Northern Hemisphere. Larger amplitude planetary waves may lead to a stagnation of the patterns, resulting in an increase in persistent cold air outbreaks, or, on the other hand, heat waves, and therefore, drought. Several studies have explored this relationship and its complexities, and even used that information to attempt to attribute extreme events such as cold air outbreaks or heat waves. This study will explore the climatology using a different method entirely. This hypothesis will be analyzed using the self-organizing map (SOM) technique to create a relevant climatology of these weather patterns. Daily NCEP/NCAR reanalysis data will be fed into the SOM algorithm to identify the synoptic weather patterns commonly seen in the Northern Hemisphere, with a focus on North America. These patterns will then be analyzed for any increased frequency in high-amplitude patterns. Finally, the 2013-14 extreme winter with the anomalously cool eastern half of the United States and dry west coast will be analyzed in the context of the climatology.