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.

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

Atmospheric Chemistry and Physics ◽

10.5194/acp-14-641-2014 ◽

2014 ◽

Vol 14 (2) ◽

pp. 641-658 ◽

Cited By ~ 24

Author(s):

F. Chane Ming ◽

C. Ibrahim ◽

C. Barthe ◽

S. Jolivet ◽

P. Keckhut ◽

...

Keyword(s):

Tropical Cyclone ◽

Gravity Waves ◽

Radio Occultation ◽

Numerical Study ◽

Wide Spectrum ◽

Wave Number ◽

Southwest Indian Ocean ◽

Gps Radio Occultation ◽

Occultation Data ◽

Radio Occultation Data

Abstract. Gravity waves (GWs) with horizontal wavelengths of 32–2000 km are investigated during tropical cyclone (TC) Ivan (2008) in the southwest Indian Ocean in the upper troposphere (UT) and the lower stratosphere (LS) using observational data sets, radiosonde and GPS radio occultation data, ECMWF analyses and simulations of the French numerical model Meso-NH with vertical resolution < 150 m near the surface and 500 m in the UT/LS. Observations reveal dominant low-frequency GWs with short vertical wavelengths of 0.7–3 km, horizontal wavelengths of 80–400 km and periods of 4.6–13 h in the UT/LS. Continuous wavelet transform and image-processing tools highlight a wide spectrum of GWs with horizontal wavelengths of 40–1800 km, short vertical wavelengths of 0.6–3.3 km and periods of 20 min–2 days from modelling analyses. Both ECMWF and Meso-NH analyses are consistent with radiosonde and GPS radio occultation data, showing evidence of a dominant TC-related quasi-inertia GW propagating eastward east of TC Ivan with horizontal and vertical wavelengths of 400–800 km and 2–3 km respectively in the LS, more intense during TC intensification. In addition, the Meso-NH model produces a realistic, detailed description of TC dynamics, some high-frequency GWs near the TC eye, variability of the tropospheric and stratospheric background wind and TC rainband characteristics at different stages of TC Ivan. A wave number 1 vortex Rossby wave is suggested as a source of dominant inertia GW with horizontal wavelengths of 400–800 km, while shorter scale modes (100–200 km) located at northeast and southeast of the TC could be attributed to strong localized convection in spiral bands resulting from wave number 2 vortex Rossby waves. Meso-NH simulations also reveal GW-related clouds east of TC Ivan.

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On the Spectra of Gravity Waves Generated by Two Typical Convective Systems

Atmosphere ◽

10.3390/atmos10070405 ◽

2019 ◽

Vol 10 (7) ◽

pp. 405

Author(s):

Yuan Wang ◽

Lifeng Zhang ◽

Jun Peng ◽

Yun Zhang ◽

Tongfeng Wei

Keyword(s):

High Resolution ◽

Tropical Cyclone ◽

Gravity Waves ◽

Spectral Characteristics ◽

Wave Source ◽

Convective Systems ◽

Spectral Distributions ◽

The Waves

Spectral characteristics of lower-stratospheric gravity waves generated in idealized mei-yu front and tropical cyclone (TC) are compared by performing high-resolution simulations. The results suggest that the systems which organize convection in different forms can generate waves with distinctly different presentation. The mei-yu front appears as a linear zonal wave source and gravity waves are dominated by cross-frontal (meridional) propagating components. The northward (southward) components have dominant meridional wavelengths of 125–333 km (>250 km), periods of 100–200 min (83–143 min), and phase speeds of 0–15 m s−1 (15–20 m s−1). The TC appears as a point wave source and gravity waves propagate equally in various horizontal directions. The waves exhibit greater power and broader spectral distributions compared with those in the mei-yu front, with dominant horizontal wavelengths longer than 62.5 km, periods of 33–600 min, and phase speeds slower than ~40 m s−1.

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On the presence of equatorial waves in the lower stratosphere of a general circulation model

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-13-22607-2013 ◽

2013 ◽

Vol 13 (8) ◽

pp. 22607-22637 ◽

Cited By ~ 1

Author(s):

P. Maury ◽

F. Lott

Keyword(s):

Gravity Waves ◽

General Circulation ◽

Lower Stratosphere ◽

Circulation Model ◽

Atmospheric Model ◽

Kelvin Waves ◽

Flux Analysis ◽

Equatorial Waves ◽

Quasi Biennial Oscillation ◽

The Waves

Abstract. To challenge the hypothesis that equatorial waves in the lower stratosphere are essentially forced by convection, we use the LMDz atmospheric model extended to the stratosphere and compare two versions having very different convection schemes but no quasi biennial oscillation (QBO). The two versions have realistic time mean precipitation climatologies but very different precipitation variabilities. Despite these differences, the equatorial stratospheric Kelvin waves at 50 hPa are almost identical in the two versions and quite realistic. The Rossby-gravity waves are also very close but significantly weaker than in observations. We demonstrate that this bias on the Rossby-gravity waves is essentially due to a dynamical filtering occurring because the model zonal wind is systematically westward: during a westward phase of the QBO, the Rossby-gravity waves in ERA-Interim compare well with those in the model. These results suggest that in the model the effect of the convection scheme on the waves is in part hidden by the dynamical filtering and the waves are produced by other sources than equatorial convection. For the Kelvin waves, this last point is illustrated by an Eliassen and Palm flux analysis, showing that in the model they come more from the subtropics and mid-latitude regions whereas in the ERA-Interim reanalysis the sources are more equatorial. We also show that non-equatorial sources are significant in reanalysis data, and we consider the case of the Rossby-gravity waves. We identify situations in the reanalysis where here are large Rossby-gravity waves in the middle stratosphere, and for dates when the stratosphere is dynamically separated from the equatorial troposphere. We refer to this process as a "stratospheric reloading".

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On the presence of equatorial waves in the lower stratosphere of a general circulation model

Atmospheric Chemistry and Physics ◽

10.5194/acp-14-1869-2014 ◽

2014 ◽

Vol 14 (4) ◽

pp. 1869-1880 ◽

Cited By ~ 7

Author(s):

P. Maury ◽

F. Lott

Keyword(s):

Gravity Waves ◽

General Circulation ◽

Lower Stratosphere ◽

Circulation Model ◽

Atmospheric Model ◽

Kelvin Waves ◽

Flux Analysis ◽

Equatorial Waves ◽

Quasi Biennial Oscillation ◽

The Waves

Abstract. To challenge the hypothesis that equatorial waves in the lower stratosphere are essentially forced by convection, we use the LMDz atmospheric model extended to the stratosphere and compare two versions having very different convection schemes but no quasi-biennial oscillation (QBO). The two versions have realistic time mean precipitation climatologies but very different precipitation variabilities. Despite these differences, the equatorial stratospheric Kelvin waves at 50 hPa are almost identical in the two versions and quite realistic. The Rossby gravity waves are also very similar but significantly weaker than in observations. We demonstrate that this bias on the Rossby gravity waves is essentially due to a dynamical filtering occurring because the model zonal wind is systematically westward. During a westward phase of the QBO, the ERA-Interim Rossby gravity waves compare well with those in the model. These results suggest that (i) in the model the effect of the convection scheme on the waves is in part hidden by the dynamical filtering, and (ii) the waves are produced by other sources than equatorial convection. For the Kelvin waves, this last point is illustrated by an Eliassen and Palm flux analysis, showing that in the model they come more from the subtropics and mid-latitude regions, whereas in the ERA-Interim reanalysis the sources are more equatorial. We show that non-equatorial sources are also significant in reanalysis data sets as they explain the presence of the Rossby gravity waves in the stratosphere. To illustrate this point, we identify situations with large Rossby gravity waves in the reanalysis middle stratosphere for dates selected when the stratosphere is dynamically separated from the equatorial troposphere. We refer to this process as a stratospheric reloading.

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Mesoscale Horizontal Kinetic Energy Spectra of a Tropical Cyclone

Journal of the Atmospheric Sciences ◽

10.1175/jas-d-17-0391.1 ◽

2018 ◽

Vol 75 (10) ◽

pp. 3579-3596 ◽

Cited By ~ 2

Author(s):

Yuan Wang ◽

Lifeng Zhang ◽

Jun Peng ◽

Saisai Liu

Keyword(s):

Tropical Cyclone ◽

Kinetic Energy ◽

Gravity Waves ◽

Lower Stratosphere ◽

Wrf Model ◽

Weather Research And Forecasting ◽

Physical Processes ◽

Upper Troposphere ◽

Mature Period ◽

Vertically Propagating

A high-resolution cloud-permitting simulation with the Weather Research and Forecasting (WRF) Model is performed to investigate the mesoscale horizontal kinetic energy (HKE) spectra of a tropical cyclone (TC). The spectrum displays an arc-like shape in the troposphere and a quasi-linear shape in the lower stratosphere for wavelengths below 500 km during the mature period of the TC, while they both develop a quasi −5/3 slope. The total HKE spectrum is dominated by its rotational component in the troposphere but by its divergent component in the lower stratosphere. Further spectral HKE budget diagnosis reveals a generally downscale cascade of HKE, although a local upscale cascade gradually forms in the lower stratosphere. However, the mesoscale energy spectrum is not only governed by the energy cascade, but is evidently influenced also by other physical processes, among which the buoyancy effect converts available potential energy (APE) to HKE in the mid- and upper troposphere and converts HKE to APE in the lower stratosphere, the vertically propagating inertia–gravity waves transport the HKE from the upper troposphere to lower and higher layers, and the vertical transportation of convection always transports HKE upward.

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Equatorial wave analysis from SABER and ECMWF temperatures

Atmospheric Chemistry and Physics ◽

10.5194/acp-8-845-2008 ◽

2008 ◽

Vol 8 (4) ◽

pp. 845-869 ◽

Cited By ~ 80

Author(s):

M. Ern ◽

P. Preusse ◽

M. Krebsbach ◽

M. G. Mlynczak ◽

J. M. Russell

Keyword(s):

Gravity Waves ◽

Lower Stratosphere ◽

Spectral Power ◽

Space Time ◽

Special Focus ◽

Kelvin Wave ◽

Quasi Biennial Oscillation ◽

Planetary Scale ◽

Equatorial Wave ◽

Wave Modes

Abstract. Equatorial planetary scale wave modes such as Kelvin waves or Rossby-gravity waves are excited by convective processes in the troposphere. In this paper an analysis for these and other equatorial wave modes is carried out with special focus on the stratosphere using temperature data from the SABER satellite instrument as well as ECMWF temperatures. Space-time spectra of symmetric and antisymmetric spectral power are derived to separate the different equatorial wave types and the contribution of gravity waves is determined from the spectral background of the space-time spectra. Both gravity waves and equatorial planetary scale wave modes are main drivers of the quasi-biennial oscillation (QBO) in the stratosphere. Temperature variances attributed to the different wave types are calculated for the period from February 2002 until March 2006 and compared to previous findings. A comparison between SABER and ECMWF wave analyses shows that in the lower stratosphere SABER and ECMWF spectra and temperature variances agree remarkably well while in the upper stratosphere ECMWF tends to overestimate Kelvin wave components. Gravity wave variances are partly reproduced by ECMWF but have a significant low-bias. For the examples of a QBO westerly phase (October–December 2004) and a QBO easterly phase (November/December 2005, period of the SCOUT-O3 tropical aircraft campaign in Darwin/Australia) in the lower stratosphere we find qualitatively good agreement between SABER and ECMWF in the longitude-time distribution of Kelvin, Rossby (n=1), and Rossby-gravity waves.

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Equatorial wave analysis from SABER and ECMWF temperatures

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-7-11685-2007 ◽

2007 ◽

Vol 7 (4) ◽

pp. 11685-11723 ◽

Cited By ~ 4

Author(s):

M. Ern ◽

P. Preusse ◽

M. Krebsbach ◽

M. G. Mlynczak ◽

J. M. Russell III

Keyword(s):

Gravity Waves ◽

Lower Stratosphere ◽

Spectral Power ◽

Space Time ◽

Kelvin Waves ◽

Special Focus ◽

Quasi Biennial Oscillation ◽

Planetary Scale ◽

Equatorial Wave ◽

Wave Modes

Abstract. Equatorial planetary scale wave modes such as Kelvin waves or Rossby-gravity waves are excited by convective processes in the troposphere. In this paper an analysis for these and other equatorial wave modes is carried out with special focus on the stratosphere using temperature data from the SABER instrument as well as ECMWF temperatures. Space-time spectra of symmetric and antisymmetric spectral power are derived to separate the different equatorial wave types and the contribution of gravity waves is determined from the spectral background of the space-time spectra. Both gravity waves and equatorial planetary scale wave modes are main drivers of the quasi-biennial oscillation (QBO) in the stratosphere. Temperature variances attributed to the different wave types are calculated for the period from February 2002 until March 2006 and compared to previous findings. A comparison between SABER and ECMWF wave analyses shows that in the lower stratosphere SABER and ECMWF spectra and temperature variances agree remarkably well while in the upper stratosphere ECMWF tends to overestimate Kelvin wave components. Gravity wave variances are partly reproduced by ECMWF but have a significant low-bias. A case study for the time period of the SCOUT-O3 tropical aircraft measurement campaign in Darwin/Australia (in November and December 2005) is performed and we find that in the lower stratosphere also the longitude-time distribution of the Kelvin waves is correctly reproduced by ECMWF.

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