Seasonal variation of short‐period (&lt;2 h) gravity wave activity over Gadanki, India (13.5°N, 79.2°E)

Dutta, Gopa; Tsuda, Toshitaka; Kumar, P. Vinay; Kumar, Mukesh; Alexander, Simon P.; Kozu, Toshiaki

doi:10.1029/2007jd009178

Cited by 7 publications

(6 citation statements)

References 69 publications

(95 reference statements)

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“…Observations were made by the radar using six beam positions (east, west, zenith x , zenith y , north, and south) with 16 μ s coded pulse and 1 ms interpulse period. Data collected by the radar between 3.75 and 22 km have been processed both online and off‐line [ Dutta et al , 2008] to obtain wind profiles with a height resolution of 150 m and a time resolution of ∼3.5 min. A manual fitting was made to individual spectrum data to estimate clear air motions, avoiding the contamination of rain echo in the lower troposphere following Rao et al [1999].…”

Section: Databasementioning

confidence: 99%

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

Dutta

Kumar

et al. 2009

J. Geophys. Res.

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[1] High-frequency gravity waves generated by tropical deep convection play a major role in shaping the general circulation of the middle atmosphere. Special experiments were conducted to capture two convective events on 16 May and 5 June 2006 using VHF radar located at Gadanki (13.5°N, 79.2°E), a tropical Indian station. Control day observations were also made for necessary comparisons. Background wind and temperature information was obtained by GPS radiosonde flights launched from the same site. This work has utilized these valuable data sets to delineate characteristics of convectively generated gravity waves. A superposition of gravity waves is observed with different scales after the deep convective events. Vertical wave number spectra of radial velocities show steeper slopes and higher power spectral densities during convection which slowly reduce to their normal values. The present case studies suggest the mechanical oscillator mechanism to be a major source of convective gravity wave generation in the tropics. Estimates of vertical wind variances and momentum fluxes of short-period (<2 h) wind fluctuations show large enhancements on convective days in comparison to control days. The momentum flux frequency spectra revealed a higher contribution of 30-65 min wave periods to the mean profile in the lower stratosphere. The wavelet transform momentum flux spectra displayed the temporal variability and discretization of the gravity wave momentum fluxes in frequency and time.

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Section: Databasementioning

confidence: 99%

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

Dutta

Kumar

et al. 2009

J. Geophys. Res.

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“…Gravity wave parameterizations determine the momentum forcing of the waves on the atmosphere. These parameterizations need to be constrained by observations of momentum flux, which have been made from instruments including satellites (Ern et al 2004;Alexander et al 2008;Wright et al 2013), superpressure balloons (Vincent et al 2007;Hertzog et al 2008;Plougonven et al 2013), radars (Vincent and Reid 1983;Sato 1993;Murayama et al 1994;Sato 1994;Alexander et al 2008c;Dutta et al 2008;Sato et al 2014), and radiosondes (Sato and Dunkerton 1997;Gong et al 2008;Murphy et al 2014), although in each case the instruments can only measure part of the gravity wave spectrum. A parameterization of OGWs was sufficient for GCMs including only the troposphere and lower stratosphere.…”

Section: Introductionmentioning

confidence: 99%

Southern Hemisphere Extratropical Gravity Wave Sources and Intermittency Revealed by a Middle-Atmosphere General Circulation Model

Alexander

Sato

Watanabe

et al. 2016

Journal of the Atmospheric Sciences

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Southern Hemisphere extratropical gravity wave activity is examined using simulations from a free-running middle-atmosphere general circulation model called Kanto that contains no gravity wave parameterizations. The total absolute gravity wave momentum flux (MF) and its intermittency, diagnosed by the Gini coefficient, are examined during January and July. The MF and intermittency results calculated from the Kanto model agree well with results from satellite limb and superpressure balloon observations. The analysis of the Kanto model simulations indicates the following results. Nonorographic gravity waves are generated in Kanto in the frontal regions of extratropical depressions and around tropopause-level jets. Regions with lower (higher) intermittency in the July midstratosphere become more (less) intermittent by the mesosphere as a result of lower-level wave removal. The gravity wave intermittency is low and nearly homogeneous throughout the SH middle atmosphere during January. This indicates that nonorographic waves dominate at this time of year, with sources including continental convection as well as oceanic depressions. Most of the zonal-mean MF at 408-658S in January and July is due to gravity waves located above the oceans. The zonal-mean MF at lower latitudes in both months has a larger contribution from the land regions but the fraction above the oceans remains larger.

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“…Using VHF radar measurements, Vincent et al [2004] presented GW variability with period in the range of 8–180 min in the lower troposphere in the vicinity of intense deep convective storms over Tiwi Islands (11.4°S, 130.5°E) in Northern Australia, and attributed convectively generated GWs to be the cause for the enhancements in the wave energy. Furthermore, results from four years of continuous wind observations made with VHF radar at Gadanki (13.5°N, 79.2°E) [ Dutta et al , 2008] also suggest deep tropical convection to be the main source of short‐period (<2 h) GW activity in the troposphere and lower stratosphere. More recently, Tsuda et al [2009] found that the spatial and seasonal variations of potential energy, E p , to be closely related with the convective wave generation in the tropics.…”

Section: Discussionmentioning

confidence: 99%

High-frequency gravity waves observed in the low-latitude mesosphere-lower thermosphere (MLT) region and their possible relationship to lower-atmospheric convection

Kovalam

Tsuda

Gurubaran³

2011

J. Geophys. Res.

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[1] Observations of Medium Frequency (MF) radar winds made at Pameungpeuk (7.5°S, 107.5°E) and Tirunelveli (8.7°N, 78°E) between February and March 2010 are used to study gravity wave activity in the equatorial mesosphere and lower thermosphere (80-100 km). Gravity wave variances in the 20-120 min period band and their spectra are computed. Daily values of gravity wave variances show modulations on time scales ranging from diurnal to planetary waves. Spectra of wave variances display peaks at tidal periods and show evidence of gravity wave modulation at 24, 12, and 8 h periods. Statistical investigation of waves, made using Stokes parameter technique, indicates that the directionality of the mesospheric wave field is highly anisotropic. The role of lower-atmospheric sources on the MLT gravity wave variability is also examined. Spatial distribution of cloud top temperature and rainfall rates are used. GW activity at mesosphere-lower thermosphere (MLT) heights shows clear anticorrelation with the cloud top temperature and positive correlation with rainfall rates suggesting a possible link between observed gravity wave variability and the variations in the deep tropical convection.Citation: Kovalam, S., T. Tsuda, and S. Gurubaran (2011), High-frequency gravity waves observed in the low-latitude mesosphere-lower thermosphere (MLT) region and their possible relationship to lower-atmospheric convection,

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Seasonal variation of short‐period (<2 h) gravity wave activity over Gadanki, India (13.5°N, 79.2°E)

Cited by 7 publications

References 69 publications

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

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

Southern Hemisphere Extratropical Gravity Wave Sources and Intermittency Revealed by a Middle-Atmosphere General Circulation Model

High-frequency gravity waves observed in the low-latitude mesosphere-lower thermosphere (MLT) region and their possible relationship to lower-atmospheric convection

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