Statistical Analysis of Convective Updrafts in Tropical Cyclone Rainbands Observed by Airborne Dual-Doppler Radar
Open Access
- Author:
- Barron, Nicholas
- Graduate Program:
- Meteorology and Atmospheric Science
- Degree:
- Master of Science
- Document Type:
- Master Thesis
- Date of Defense:
- November 09, 2020
- Committee Members:
- Anthony Carl Didlake, Jr., Thesis Advisor/Co-Advisor
George Spencer Young, Committee Member
Kelly Lombardo, Committee Member
David Jonathan Stensrud, Program Head/Chair
James H Ruppert Jr., Special Signatory - Keywords:
- Tropical Cyclones
Convection
Tropical Meteorology - Abstract:
- Ten years of airborne Doppler radar observations are used to study the kinematic and reflectivity structures of convective updrafts in tropical cyclone (TC) rainbands. An automated algorithm is developed to identify the strongest rainband updrafts across 12 TCs. The selected updrafts are then collectively analyzed by their frequency, radius, azimuthal location (relative to the 200-850 hPa environmental wind shear), structural characteristics, and secondary circulation (radial/vertical) flow pattern. Rainband updrafts become deeper and stronger with increasing radius. A wavenumber-1 asymmetry arises showing that in the downshear (upshear) quadrants of the TC, updrafts are more (less) frequent and deeper (shallower). Low-level radial flows near the updrafts correspond to the background vortex-scale radial flow asymmetry, being predominantly inflow (outflow) in the downshear (upshear) quadrants. Moreover, the downshear inflow layer decreases in depth traveling from the downshear-right to downshear-left quadrants. In the right-of-shear quadrants, updrafts tend to have either in-up-out or in-up-in secondary circulation patterns, with the in-up-out circulation generally having the deepest updraft and reflectivity tower. In the downshear-left quadrant, the dominant updraft circulation type shifts from primarily in-up-out to out-up-out. It is hypothesized that this shift is due to the decrease in radial inflow layer depth, the bottom-up decay of older updrafts, and the increase in stratiform precipitation surrounding the updrafts. In particular, the stratiform region encourages cold-pool dynamics that support new convective updrafts with a preferred out-up-out circulation. The findings presented in this study support the previous literature regarding organized rainband convection in a mature and sheared TC.