[Eoas-seminar] FW: Honors in the Major defense: Hanna Brasseur, Tuesday, March 30, 3:30 PM on zoom https://fsu.zoom.us/j/92194168456?pwd=WmgrVkdOQW9OZlZGeWpIVFN5ZnVrQT09

[eoas-seminar at lists.fsu.edu]

Honor's in the Major Seminar

Speaker: Hanna Brasseur

Professor: Jon Ahlquist

Title: Disturbances Propagating into the Indian Summer Monsoon: An Observational Study

Time: 3:30 PM, 30 March 2021

Zoom Meeting:   https://fsu.zoom.us/j/92194168456?pwd=WmgrVkdOQW9OZlZGeWpIVFN5ZnVrQT09

Abstract:  This project studied disturbances propagating over the head of the Bay of Bengal (90°E, 20°N), where there are frequent storms during the Indian summer monsoon. Weather data came from the four-times daily global grids in the JRA-55 Japanese Reanalyses. We removed the diurnally-varying annual cycle based on 1 January 1958 through 31 December 2018. Then we identified the 100 largest relative vorticity events at (90°E, 20°N) during the 90-day period 1 June to 29 August for 1958-2018. Events had to be independent in the sense that no two events could occur within a week of each other. Centered around these vorticity maxima, we computed 4-times/day composites beginning 10 days before the maximum and extending to 10 days after the maximum. Time is indexed so that the vorticity maximum at (90°E, 20°N) occurs at t=0. With composites based on vorticity maxima at 850 hPa (approximately z=1.5km), incoming events could be identified at t = -5 days lingering off the coast of Southeast Asia. After a couple days there, the composite broke up when crossing Southeast Asia. This could either be just what it seems, or individual events could move at different speeds so that the composite lost coherency. Over the Bay of Bengal, disturbances lingered again before moving northwest and dissipating over northern India. Composites of the height of pressure surfaces based on the times of vorticity maxima showed low heights, analogous to low pressure, corresponding to vorticity maxima. Composites of upper-tropospheric height and 850-250 hPa thickness reveal mid-latitude connections that are not apparent at 850 hPa.

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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