[Eoas-seminar] Meteorology MS Defense for Gwen Dmitruk, Monday, November 9, 2020, 11:30 AM, on Zoom https://fsu.zoom.us/j/99786563905?pwd=RWlYeWZLRGE4V1Vja0duK3l0UWZkQT09

[eoas-seminar at lists.fsu.edu]

Meteorology Seminar

Gwendolyn Dmitruk

M.S. Meteorology Candidate



Title:  A globe-circling synoptic-Scale winter disturbance In Northern hemisphere midlatitudes



Major Professor: Dr. Jon Ahlquist

Date: Monday, November 9, 2020                               Time: 11:30 AM



Location: Zoom Meeting (URL: https://fsu.zoom.us/j/99786563905?pwd=RWlYeWZLRGE4V1Vja0duK3l0UWZkQT09)



ABSTRACT

Preliminary studies by former FSU students Lydia Stefanova and Alec Bogdanoff documented a synoptic-scale disturbance that can travel eastward long distances around the globe with a period of about 20 days (roughly 9-10 days to go halfway around). These earlier studies looked at only at one pressure level, 500 hPa. The present study extends this work by adding multiple levels with a better, longer data set (1958-2018 from JRA-55 reanalysis on 1.25-degree lat-lon grid) and removing the annual cycle. The two centers of action are off the northeastern coasts of Asia and North America, where relative vorticity and height fluctuations are large. The starting point was identifying the 100 most prominent during 61 years of 150-day cold seasons beginning on 1 November of 1958-2018.  Global composites spanning 25 days before to 25 days after the 100 most extreme relative vorticity maxima at 500 hPa were computed for multiple pressure levels. This allowed for observation of the disturbance from 1000 hPa to 1 hPa. At the time of the vorticity maxima, the composite shows an untilted feature about 560 km in diameter extending from 1000 hPa to 100 hPa, decaying rapidly above that level. Composites confirmed the existance of the wave pattern, which travels eastward across the Atlantic with maintained strength after reaching a peak off the cost of Nova Scotia (t = 0). It rapidly loses this strength and gains a notable southward component to its trajectory after reaching the European coastline, but still visibly treks eastward across Asia in its weakened state. Upon reaching the Pacific (at t = 9), it surges in relative vorticity strength again. This strength is likewise maintained across the North Pacific, until it similarly and significantly weakens in strength and attains a southeastern trajectory upon contact with the North America, only to reemerge in a week's time to repeat the pattern once again (t = 19) increasing and maintaining strength along the North Atlantic. Similar results are repeated using height fall composites, with wave signal location, speed, and strength mirroring that of the relative vorticity composites. Case studies of individual events allow for the indexing and chronicling of the events life cycle.


Shel McGuire
Florida State University
Academic Program Specialist
Department of Earth, Ocean, & Atmospheric Science
1011 Academic Way, 2019 EOA Building
Tallahassee, FL 32306
850-644-8582
To make an appointment please login to my.fsu.edu and choose the Campus Connect (CC) icon

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