Tropical Cyclone Structure

Tropical cyclones are observed to have outward propagating signals at cloud-top height that in phase with the diurnal cycle (the daily rising and setting of thesun). There is some evidence that these signals, visible in upper level clouds, reflect a diurnal cycle in tropical cyclone structure throughout the depth of the troposphere. We have investigated wavelike responses of the tropical cyclone to diurnal forcing in cloud-resolving numerical simulations. The structure of the tropical cyclone wind field supports the propagation of internal inertial gravity waves excited by diurnal and semi-diurnal (second harmonic) forcing only in certain areas (generally away from the TC center). The figure at the right (from O'Neill et al. (2017) shows cross sections of eddy temperature fields in three tropical cyclone simulations, which indicate semi-diurnal gravity wave propagation in the two simulations with diurnal forcing (right two). Variability in the structure of the TC wind field significantly affects the ability of diurnal waves to propagate away from the TC center, which is the subject of continued investigation.

Papers on this topic
Diurnal Waves
O'Neill, M.E., D. Perez-Betancourt, and A.A.Wing (2017), Accessible environments for diurnal-period waves in simulated tropical cyclones, J. Atmos., Sci., 74, 2489-2505, doi:10.1175/JAS-D-16-0294.1.
TCs in GCMs
Moon, Y., D. Kim, S. J. Camargo, A. A. Wing, A. H. Sobel, H. Murakami, K. A. Reed, E. Scoccimarro, G. A. Vecchi, M. F. Wehner, C. M. Zarzycki, and M. Zhao (2020), Azimuthally averaged wind and thermodynamic structures of tropical cyclones in global climate models and their sensitivity to horizontal resolution, J. Climate, 33, 1575–1595, doi:10.1175/JCLI-D-19-0172.1.
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