[Crib-list] VIRTUAL Event...SPEAKER: Justin Finkel (Univ. of Chicago) / CRIBB Seminar / 12:00 PM - 1:00 PM / Friday, March 4, 2022 (fwd)

[Shirley Entzminger]

    VIRTUAL...

 	      COMPUTATIONAL RESEARCH in BOSTON and BEYOND SEMINAR
 				 (CRIBB)


   ZOOM meeting info...

 	https://mit.zoom.us/j/96155042770

 	Meeting ID: 961 5504 2770

====================================

DATE:	Friday, March 4, 2022

TIME:	12:00 PM - 1:00 PM


TITLE:	Short weather forecasts inform long-term climatology of sudden
 	stratospheric warming



SPEAKER:   Justin Finkel  (University of Chicago)


ABSTRACT:

In some physical systems such as the Earth's atmosphere, the most extreme and
rare events matter a great deal, both for their human impact and for their
dynamical consequences. A prototypical example is sudden stratospheric warming
(SSW), a rapid breakdown of the winter stratospheric polar vortex, which causes
extreme mid-latitude cold spells and alters surface weather for months. The
historical scarcity of observations, and an unusually SSW-rich 2000's decade,
lead to uncertain SSW climatology: when do they occur, how often, and how
predictably? Long, expensive model runs could answer these statistical
questions, but with a tradeoff between cost and bias. We instead utilize weather
forecast ensembles that are high-resolution, but short (subseasonal) in
duration. A simple coarse-graining procedure chains them together to estimate
key climate statistics, such as annual frequencies and timing distributions of
SSW events, as formulated in Transition Path Theory. Using forecast ensembles
initialized between 1996 and 2018, we find that the SSW statistics match well
with 20th-century reanalysis. Our method extrapolates the climatology well
beyond what is possible with the short observational dataset that initialized
the forecasts, yielding accurate estimates of 1 in a century events. This
suggests exciting new uses for ensemble forecasts in rare event analysis


=======================================

For information about the "Computational Research in Boston and Beyond Seminar"
(CRIBB), please visit:

 		https://math.mit.edu/sites/crib/


=================

Shirley A. Entzminger
Administrative Assistant II
Department of Mathematics
Massachusetts Institute of Technology
77 Massachusetts Avenue
Building 2, Room 350A
Cambridge, MA 02139
PHONE: 	(617) 253-4994
E-mail:	daisymae at math.mit.edu
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