Persistent Wave Structures and Western Droughts

We propose that anomalous sea surface temperatures and polar ice extent caused and maintained the highly persistent large-scale tropospheric wave structure over North America during the winter of 2014. This wave structure led to a persistent regime of dry weather in the western US and cold, wet weather in the Midwest and eastern US. The sea surface temperature anomalies acted as waveguides. The polar ice extent anomaly acted to maintain a meridional feedback of polar wave energy, oriented along a narrow longitudinal range, which stabilized and reinforced the existing stationary wave over North America.

The research testing this conjecture is ongoing, based on analyses of archived sea surface temperature data, polar ice extent data, and comparisons between similarly persistent winter weather patterns during other years. It is our hope that this effort will contribute to a broader understanding of dominant large-scale wave modes in the troposphere—modes that are determined in any particular case by a finite roster of thermal and geographic forcings.