[Eoas-seminar] Meteorology MS Defense for Evan Jones, Monday, June 29, 2020, 3:00 PM, on Zoom 93373177597

[eoas-seminar at lists.fsu.edu]

Meteorology Seminar

Evan Jones

M.S. Meteorology Candidate



Title:  REPRESENTATION OF TROPICAL CYCLONE PRECIPITATION IN GLOBAL REANALYSIS DATASETS

Major Professor:  Dr. Allison Wing and Dr. Rhys Parfitt

Date: Monday, June 29, 2020                           Time: 3:00 PM


Location: Zoom Meeting URL: https://fsu.zoom.us/j/93373177597

ABSTRACT
Each year, tropical cyclones (TCs) impact communities around the world by producing rainfall with devastating damage, loss of life and can contribute a non-trivial amount to climatological annual mean rainfall. The representation of TC precipitation in datasets such as reanalyses is thus crucial for both forecasting purposes and climate projections. This study quantifies the spread in TC precipitation across eight different reanalysis datasets: CFSR, ERA-20C, ERA-40, ERA5, ERA-Interim, JRA-55, MERRA-2 and NOAA-20C. TC precipitation is assigned using two TC tracking methods, manual tracking and objective tracking, via a fixed radius.

Climatological TC precipitation and TC precipitation fraction assigned using TempestExtremes is generally lower than that assigned using IBTrACS, owing to the fewer number of TCs tracked in TempestExtremes and position differences between the best-track and reanalyses, as well as the underestimation of reanalysis TC intensity. Both methods capture the same general spatial patterns of TC precipitation and TC precipitation fraction globally. Compared to TRMM, assignment from both methods provides less annual average TC precipitation and TC precipitation fraction over most areas, with the exception of land and some ocean basins. In most basins, with the exception of the West Pacific (WPAC), and most reanalyses, with the exception of MERRA-2, the systematic bias toward IBTrACS-derived TC precipitation is greatly minimized by considering TC precipitation normalized by TC density.

The relative spread across reanalyses in TC precipitation is larger for TC precipitation derived from TempestExtremes than from IBTrACS, where the East Pacific (EPAC) has a higher relative spread than the WPAC with both tracking methods. Partitioning by Saffir-Simpson best-track intensity, the largest relative spread across reanalyses in TC precipitation is from TCs of major hurricane strength. A comparison of IBTrACS-derived extratropical phase TC precipitation in the North Atlantic shows that there is a large relative spread across the reanalyses, likely a limitation of the fixed radius method when assigning extratropical phase precipitation. Finally, a comparison of mean precipitation rate in TCs as a function of reanalysis MSLP shows that the spread across reanalyses is larger for higher intensity TCs, but that the inability of reanalyses to properly represent highest intensity and very weak TCs also contributes.  Overall, TC precipitation in reanalyses is not only a function of their resolution or any TC pre-processing that is done, but also how it assimilates data, parameterizes complex processes, and configures model physics.




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

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