Observation and a numerical study of gravity waves during tropical cyclone Ivan~(2008)

Abstract

Activity and spectral characteristics of gravity-waves (GWs) are analyzed during tropical cyclone (TC) Ivan (2008) in the troposphere and lower stratosphere using radiosonde and GPS radio occultation data, ECMWF outputs and simulations of French numerical model Meso-NH with vertical resolution varying between 150 m near the surface and 500 m in the lower stratosphere. Conventional methods for GW analysis and signal and image processing tools provide information on a wide spectrum of GWs with horizontal wavelengths of 40–1800 km and short vertical wavelengths of 0.6–10 km respectively and periods of 20 min–2 days. MesoNH model, initialized with Aladin-Réunion analyses, produces realistic and detailed description of TC dynamics, GWs, variability of the tropospheric and stratospheric background wind and TC rainband characteristics at different stages of TC Ivan. In particular a dominant eastward propagating TC-related quasi-inertia GW is present during intensification of TC Ivan with horizontal and vertical wavelengths of 400–600 km and 1.5–3.5 km respectively during intensification. A wavenumber-1 vortex Rossby wave is identified as a source of this medium-scale mode while short-scale modes located at north-east and south-east of the TC could be attributed to strong localized convection in spiral bands resulting from wavenumber-2 vortex Rossby waves. Meso-NH simulations also reveal high-frequency GWs with horizontal wavelengths of 20–80 km near the TC eye and high-frequency GWs-related clouds behind TC Ivan. In addition, GWs produced during landfall are likely to strongly contribute to background wind in the middle and upper troposphere as well as the stratospheric quasi-biennial oscillation

Gravity Wave Behavior in Lower Stratosphere During Tropical Cyclones Over the Bay of Bengal

“…The characteristics of low‐frequency GW in UT/LS is related to the temporal and spatial extent of the cyclone (Chane‐Ming et al, ). Chane Ming et al () showed that low‐frequency GWs of periods of 4.6–13 hr and vertical wavelengths of 0.7–3 km occurred during TC Ivan. Vertical wavelengths ranging from 0.8 to about 3 km prevailed during the cyclones Dina and Faxai in the LS over the affected region (Chane‐Ming et al, ).…”

Quantifying the global impact of tropical cyclone‐associated gravity waves using HIRDLS, MLS, SABER and IBTrACS data

“…The spectral range of stratospheric GWs observed or modelled in association with TCs is extremely broad and spans multiple orders of magnitude both in terms of vertical wavelengths (from as short as 0.7 km (e.g, Chane Ming et al . ) to as long as 10 km or more [e.g. Wu and Zhang, ; Hecht et al .…”

Satellite Observations of Stratospheric Gravity Waves Associated With the Intensification of Tropical Cyclones

“…TC‐induced gravity waves (GWs) have been widely studied with model simulations, satellite, and ground‐based observations, as well as reanalysis data (Chen et al, ; Chane Ming et al, , ; Kuester et al, ; Kim et al, ; Miller et al, ; Nolan & Zhang, ; Wu et al, ; Yue et al, ). Typical characteristics, namely, the vertical and horizontal wavelength, period, and propagation direction have been assessed.…”