Characteristics of high‐frequency gravity waves generated by tropical deep convection: Case studies

Dutta, Gopa; Kumar, Mukesh; Kumar, P. Vinay; Ratnam, M. Venkat; Chandrashekar, M.; Shibagaki, Yoshiaki; Salauddin, M.; Basha, H. Aleem

doi:10.1029/2008jd011332

Cited by 38 publications

(30 citation statements)

References 64 publications

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“…In a few studies (Kumar, 2006(Kumar, , 2007Dhaka et al, 2002;Venkat Ratnam et al, 2008;Debashis Nath et al, 2009;Dutta et al, 2009;Leena et al, 2012a, b), possible sources in the troposphere for their generation are identified which include convection, wind shear and topography.…”

Section: Introductionmentioning

confidence: 99%

Evidence for tropospheric wind shear excitation of high-phase-speed gravity waves reaching the mesosphere using the ray-tracing technique

et al. 2015

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Abstract. Sources and propagation characteristics of highfrequency gravity waves observed in the mesosphere using airglow emissions from Gadanki (13.5 • N, 79.2 • E) and Hyderabad (17.5 • N, 78.5 • E) are investigated using reverse ray tracing. Wave amplitudes are also traced back, including both radiative and diffusive damping. The ray tracing is performed using background temperature and wind data obtained from the MSISE-90 and HWM-07 models, respectively. For the Gadanki region, the suitability of these models is tested. Further, a climatological model of the background atmosphere for the Gadanki region has been developed using nearly 30 years of observations available from a variety of groundbased (MST radar, radiosondes, MF radar) and rocket-and satellite-borne measurements. ERA-Interim products are utilized for constructing background parameters corresponding to the meteorological conditions of the observations. With the reverse ray-tracing method, the source locations for nine wave events could be identified to be in the upper troposphere, whereas for five other events the waves terminated in the mesosphere itself. Uncertainty in locating the terminal points of wave events in the horizontal direction is estimated to be within 50-100 km and 150-300 km for Gadanki and Hyderabad wave events, respectively. This uncertainty arises mainly due to non-consideration of the day-to-day variability in the tidal amplitudes. Prevailing conditions at the terminal points for each of the 14 events are provided. As no convection in and around the terminal points is noticed, convection is unlikely to be the source. Interestingly, large (∼ 9 m s −1 km −1 ) vertical shears in the horizontal wind are noticed near the ray terminal points (at 10-12 km altitude) and are thus identified to be the source for generating the observed highphase-speed, high-frequency gravity waves.

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Section: Introductionmentioning

confidence: 99%

Evidence for tropospheric wind shear excitation of high-phase-speed gravity waves reaching the mesosphere using the ray-tracing technique

et al. 2015

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“…Therefore, the traditional hodograph analysis in fact can only be applied to study low-frequency GWs. Observational studies on lower-atmospheric medium-and high-frequency GWs (MHGWs) are mainly from only radiosonde at a tropical station (Leena et al, 2012b) and few radar observations at several limited sites (Dutta et al, 2009;Kuo et al, 2009, Leena et al, 2012b. Then, considering the long-term accumulations and extensive land distribution of radiosonde observations, in order to further understand the MHGWs in the lower atmosphere we need a feasible method to extract MHGW parameters from more radiosonde observations.…”

Section: S D Zhang Et Al: Spatial and Seasonal Variability Of Medimentioning

confidence: 99%

Spatial and seasonal variability of medium- and high-frequency gravity waves in the lower atmosphere revealed by US radiosonde data

Zhang

Huang

et al. 2014

Ann. Geophys.

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Abstract. We extended the broad spectral method proposed by Zhang et al. (2013) for the extraction of medium-and high-frequency gravity waves (MHGWs). This method was applied to 11 years (1998)(1999)(2000)(2001)(2002)(2003)(2004)(2005)(2006)(2007)(2008) of radiosonde data from 92 stations in the Northern Hemisphere to investigate latitudinal, continuous vertical and seasonal variability of MHGW parameters in the lower atmosphere (2-25 km). The latitudinal and vertical distributions of the wave energy density and horizontal momentum fluxes as well as their seasonal variations exhibit considerable consistency with those of inertial gravity waves. Despite the consistency, the MHGWs have much larger energy density, horizontal momentum fluxes and wave force, indicating the more important role of MHGWs in energy and momentum transportation and acceleration of the background. For the observed MHGWs, the vertical wavelengths are usually larger than 8 km; the horizontal wavelengths peak in the middle troposphere at middle-high latitudes. These characteristics are obviously different from inertial gravity waves. The energy density and horizontal momentum fluxes have similar latitude-dependent seasonality: both of them are dominated by a semiannual variation at low latitudes and an annual variation at middle latitudes; however at high latitudes, they often exhibit more than two peaks per year in the troposphere. Compared with the inertial GWs, the derived intrinsic frequencies are more sensitive to the spatiotemporal variation of the buoyancy frequency, and at all latitudinal regions they are higher in summer. The wavelengths have a weaker seasonal variation; an evident annual cycle can be observed only at middle latitudes.

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“…Alexander (1995) simulated squall lines, observing harmonics with a period of around 23-28 min in the troposphere and 12.8-7.8 min in the stratosphere, attributing them to the mechanical oscillator effect. Dutta et al (2009), have found significant periodicities between 8-15 min, 20-60 min, and 60-80 min in the troposphere between 5-10 and 10-15 km and 12.5-15 min, 15-18 min and 20-70 min bands in the lower stratosphere (LS) between 17-22 km. Numerical simulations performed by Beres et al (2004), showed that periods between 10 min and 100 min are observed.…”

Section: Introductionmentioning

confidence: 99%

“…Convective instability creates oscillatory displacements in the isentropic/isobaric surfaces and generates GWs that propagate vertically as a harmonic oscillator (Clark et al, 1986;Fovell et al, 1992;Alexander, 1995;Alexander and Holton, 1997;Lane and Reeder, 2001;Dhaka et al, 2002Dhaka et al, , 2003Kumar, 2006Kumar, , 2007Dutta et al, 2009). Based on two different convective events, Kumar (2007) studied the nonlinear interaction of GWs, finding periods of 28-12 min (35-15 min) in the troposphere and 21-8.4 min (26 min) in the lower stratosphere.…”

Section: Introductionmentioning

confidence: 99%

Investigation of convectively generated gravity wave characteristics and generation mechanisms during the passage of thunderstorm and squall line over Gadanki (13.5° N, 79.2° E)

2014

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Abstract. This study illustrates the convectively generated gravity wave generation mechanisms during the passage of thunderstorms and squall line using Indian MST radar. For the first time, it has been shown that all three generation mechanisms have been involved in the generation of gravity waves during the passage of squall line event. It is observed that the periodicities in the range of 8-80 min in the tropospheric and 8-32 min in the lower stratospheric regions and vertical wavelengths in the range of 3.2-4.8 km in the tropospheric and 1.2-1.92 km in the lower stratospheric regions are found to be dominant in the present study and are distinctly different during initial, mature and dissipative phases of convection. Amplitude of vertical wind has been weakened (from ∼ 4-6 m s −1 to ∼ 1 m s −1 ) considerably after 10-30 min of a convection event. It appears that the wind shear associated with the convective clouds acted like an obstacle to the mean background flow during the squall line passage generated gravity waves. The phase profiles corresponding to the dominant period show both downward and upward propagation of waves. The vertical extent of heating is found to be deeper during squall line event compared with thunderstorm event. From the phase profiles, during 27 September 2004, two peaks of constant phase region are observed. One is due to convective elements and the other is due to strong background wind shear; however, only one peak is observed on 29 September 2004, which is only due to convective processes.

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Characteristics of high‐frequency gravity waves generated by tropical deep convection: Case studies

Cited by 38 publications

References 64 publications

Evidence for tropospheric wind shear excitation of high-phase-speed gravity waves reaching the mesosphere using the ray-tracing technique

Evidence for tropospheric wind shear excitation of high-phase-speed gravity waves reaching the mesosphere using the ray-tracing technique

Spatial and seasonal variability of medium- and high-frequency gravity waves in the lower atmosphere revealed by US radiosonde data

Investigation of convectively generated gravity wave characteristics and generation mechanisms during the passage of thunderstorm and squall line over Gadanki (13.5° N, 79.2° E)

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