Influence of Cloud-Radiative Forcing on Tropical Cyclone Development in Moderate Vertical Wind Shear
Date of Award
Spring 2025
Language
English
Embargo Period
5-14-2025
Document Type
Dissertation
Degree Name
Doctor of Philosophy (PhD)
College/School/Department
Department of Atmospheric and Environmental Sciences
Program
Atmospheric Science
First Advisor
Brian H. Tang
Second Advisor
Robert G. Fovell
Committee Members
Brian H. Tang, Robert G. Fovell, Kristen L. Corbosiero, Ryan D. Torn
Keywords
Tropical Cyclones, Cloud-Radiative Forcing, Vertical Wind Shear, Longwave Radiation, TC Development
Subject Categories
Atmospheric Sciences | Meteorology
Abstract
This research seeks to better understand how cloud–radiative forcing (CRF) influences the structural evolution and intensity change of tropical cyclones (TCs) during the organizaional stage, with a particular focus on environments characterized by moderate vertical wind shear. While CRF has been shown to impact TC development during genesis and mature stages, its role during the transitional post-genesis phase—when TCs exhibit disorganized convection and are highly sensitive to environmental influences—remains poorly understood. Moreover, forecasting TC intensity in moderate shear environments continues to present substantial challenges, underscoring the need for focused investigation of TC development in the moderate-shear regime.
The Weather Research and Forecasting (WRF) model is used to examine how CRF influences TC development in moderate shear environments using idealized ensemble experiments with and without CRF.
For weak TCs in the organizational stage, the response to moderate vertical wind shear is indirectly modulated by CRF, particularly at the higher end of the moderate shear spectrum. Key findings reveal a bifurcation in TC structural and intensity evolution: CRF-on TCs exhibit greater resilience to shear-induced vortex tilt and undergo sustained intensification, while CRF-off TCs experience prolonged stagnation in development and ultimately reach lower peak intensities.
CRF-on TCs are marked by reduced vortex tilt, broader outer-core wind fields, and stronger secondary circulations, resulting in a more vertically aligned and dynamically robust vortex. In contrast, CRF-off TCs undergo a brief period of rapid spin-up and radius of maximum wind contraction, but this is followed by a breakdown in structural coherence due to enhanced vulnerability to shear-induced radial and downdraft ventilation. These effects delay intensification by up to 72 hours and limit TC intensity. The initial intensification in CRF-off TCs thus represents a short-lived phase, whereas CRF-on TCs achieve a more persistent spin-up, leading to broader and stronger wind fields.
Nighttime longwave radiative processes play a key role in driving these differences. In CRF-off TCs, enhanced longwave cooling promotes downdraft development via evaporative cooling and boundary-layer destabilization, resulting in stronger low-entropy air intrusion into the core that suppresses convection. Conversely, the "greenhouse effect" associated with CRF increases ascent, enhances core moistening in typically subsident upshear regions, and accelerates the spin-up of the tangential wind field. These findings underscore the indirect but relevant role of CRF in shaping TC structure, thermodynamic resilience, and intensity evolution under moderate vertical shear.
License
This work is licensed under the University at Albany Standard Author Agreement.
Recommended Citation
Richardson, Jannetta C., "Influence of Cloud-Radiative Forcing on Tropical Cyclone Development in Moderate Vertical Wind Shear" (2025). Electronic Theses & Dissertations (2024 - present). 216.
https://scholarsarchive.library.albany.edu/etd/216
