[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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