Extratropical Impacts of the Madden-Julian Oscillation

Speaker: Stephanie Henderson, Assistant Professor, Atmospheric and Oceanic Sciences, UW-Madison

The Pacific-North American (PNA) pattern is a large-scale wave-like pressure pattern that forms over the North Pacific and across North America with important implications for precipitation and temperatures. In this work, we examine PNA development by considering both the role of tropical variability and the mid-latitude circulation. Using linear inverse modeling (LIM), we find that the PNA pattern optimally grows when there is an El Niño-Southern Oscillation (ENSO) event, which persists through a winter season, and concurrently, a Madden-Julian Oscillation (MJO) event, which evolves on weekly timescales.  These two tropical phenomena independently force teleconnection patterns that evolve from destructive towards constructive interference as the MJO propagates eastward, leading to the rapid growth of a PNA pattern.