Speaker: Melissa L. Breeden, Postdoctoral Fellow, Chemical Sciences Division, Earth System Research Laboratory, NOAA. Dr. Breeden received her PhD from the University of Wisconsin-Madison in atmospheric sciences. Currently she is a NOAA Climate and Global Change Postdoctoral Fellow, doing important work on atmospheric blocking.

Seminar Title: North Pacific Blocking: Subseasonal Evolution and Contributions from Extratropical and Tropical Teleconnections

Abstract: This talk will overview the literature and ongoing work geared towards understanding midlatitude blocking, and specifically the breakdown of the strong North Pacific jet into wavy, blocked flow in boreal winter. North Pacific blocking can be modeled using a linear inverse model (LIM), inferring the dynamics that drive blocking from an empirical atmospheric operator obtained from time-lagged analysis covariance. It is shown that, on weekly timescales, the LIM can reproduce a similar blocking evolution to that observed in reanalysis with no assumption of linearity. The ‘optimal initial structures’ that precede blocking by two weeks, as determined by the LIM, are explored, followed by consideration of the relative contributions from the tropics and midlatitudes. The role of the features identified by the LIM in facilitating blocking will be examined with a case study of a block that began in mid-February 2006. Connections to ongoing work will be discussed.

This is a virtual event (hosted by Walt Robinson).