Observable signatures of a convectively generated wave field over the tropics using Indian MST radar at Gadanki (13.5°N, 79.2°E)

Dhaka, S. K.; Choudhary, R. K.; Malik, Shahzad A.; Shibagaki, Yoshiaki; Yamanaka, Manabu D.; Fukao, S.

doi:10.1029/2002gl014745

Cited by 49 publications

(49 citation statements)

References 12 publications

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“…Few references exist over the tropical ocean where convection is the major GW source (Beres et al, 2002). For instance, recent radar observations revealed the characteristics of highly convective zone in regard to induced GW in the UTLS in the vicinity of Bay of Bengal region and Indonesian region (Dhaka et al, 2002(Dhaka et al, , 2005. GW activity in the LS was recently explored with radiosondes in the tropical Pacific in November to December 2001 (Sato et al, 2003), above the South-East Indian Ocean at Cocos Islands (12 • S, 97 • E) between September 1992 and June 1998 (Vincent and Alexander, 2000) and above Darwin area in October to December 2001 (Tsuda et al, 2004 …”

Section: Introductionmentioning

confidence: 99%

Latitudinal and seasonal variability of gravity-wave energy in the South-West Indian Ocean

2007

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Abstract. Vertical temperature profiles obtained by radiosonde and Raman lidar measurements are used to investigate a climatology of total energy density of gravity waves (GW) in the Upper Troposphere (UT) and the Lower Stratosphere (LS) from 1992 to 2004 above Mahé (4 • S, 55 • E), Tromelin (15 • S, 54 • E) and La Réunion (21 • S, 55 • E) located in the tropical South-West Indian Ocean. The commonly used spectral index value (p≈5/3) of the intrinsic frequency spectrum is used for calculating estimated total energy density in the UT and LS. Estimated total energy density provides good estimation of total energy density in the LS but underestimates total energy density by one half in the UT above Mahé and Tromelin probably due to the activity of near-inertial frequency waves. Estimated total energy density reveals a strong seasonal variability as a function of latitude and convection as an evident active source of GW activity in the LS in austral summer. Above La Réunion, a semi-annual GW activity is observed in the LS with the signature of the subtropical barrier in the UT. Moreover, radiosondes and Raman lidar provide consistent GW surveys in the UT/LS at heights<23 km above La Réunion.

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Section: Introductionmentioning

confidence: 99%

Latitudinal and seasonal variability of gravity-wave energy in the South-West Indian Ocean

2007

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“…Gravity wave studies have been carried out in the past using the Indian MST radar observations over this latitude (Dutta et al, 1999;Dhaka et al, 2001Dhaka et al, , 2002Reddy et al, 2005;Kumar, 2006Kumar, , 2007Ratnam et al, 2008). Most of these studies aimed to explore the frequency spectra of gravity waves during various atmospheric conditions.…”

Section: Introductionmentioning

confidence: 99%

Long-term MST radar observations of vertical wave number spectra of gravity waves in the tropical troposphere over Gadanki (13.5° N, 79.2° E): comparison with model spectra

Babu

Kumar

et al. 2008

Ann. Geophys.

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Abstract. The potential utility of Mesosphere-StratosphereTroposphere (MST) radar measurements of zonal, meridional and vertical winds for divulging the gravity wave vertical wave number spectra is discussed. The data collected during the years 1995-2004 are used to obtain the mean vertical wave number spectra of gravity wave kinetic energy in the tropical troposphere over Gadanki (13.5 • N, 79.2 • E). First, the climatology of 3-dimensional wind components is developed using ten years of radar observations, for the first time, over this latitude. This climatology brought out the salient features of background tropospheric winds over Gadanki. Further, using the second order polynomial fit as background, the day-to-day wind anomalies are estimated. These wind anomalies in the 4-14 km height regions are used to estimate the profiles of zonal, meridional and vertical kinetic energy per unit mass, which are then used to estimate the height profile of total kinetic energy. Finally, the height profiles of total kinetic energy are subjected to Fourier analysis to obtain the monthly mean vertical wave number spectra of gravity wave kinetic energy. The monthly mean vertical wave number spectra are then compared with a saturation spectrum predicted by gravity wave saturation theory. A slope of 5/3 is used for the model gravity wave spectrum estimation. In general, the agreement is good during all the months. However, it is noticed that the model spectrum overestimates the PSD at lower vertical wave numbers and underestimates it at higher vertical wave numbers, which is consistently observed during all the months. The observed discrepancies are Correspondence to: A. Narendra Babu (narendraalur@gmail.com) attributed to the differences in the slopes of theoretical and observed gravity wave spectra. The slopes of the observed vertical wave number spectra are estimated and compared with the model spectrum slope, which are in good agreement. The estimated slopes of the observed monthly vertical wave number spectra are in the range of −2 to −2.8. The significance of the present study lies in using the ten years of data to estimate the monthly mean vertical wave number spectra of gravity waves, which will find their application in representing the realistic gravity wave characteristics in atmospheric models.

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“…Tsuda et al (1994a) reported that in the equatorial region, gravity wave generation was typically associated with deep convection. Dhaka et al (2001Dhaka et al ( , 2002 showed gravity wave activity associated with convection over a tropical region by using Indian MST Radar. These waves have typically periods of a few tens of minutes.…”

Section: V Subba Reddy Et Al: Studies On Atmospheric Gravity Wavmentioning

confidence: 99%

Studies on atmospheric gravity wave activity in the troposphere and lower stratosphere over a tropical station at Gadanki

Reddy

Rao²,

Babu

et al. 2005

Ann. Geophys.

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Abstract. MST radars are powerful tools to study the mesosphere, stratosphere and troposphere and have made considerable contributions to the studies of the dynamics of the upper, middle and lower atmosphere. Atmospheric gravity waves play a significant role in controlling middle and upper atmospheric dynamics. To date, frontal systems, convection, wind shear and topography have been thought to be the sources of gravity waves in the troposphere. All these studies pointed out that it is very essential to understand the generation, propagation and climatology of gravity waves. In this regard, several campaigns using Indian MST Radar observations have been carried out to explore the gravity wave activity over Gadanki in the troposphere and the lower stratosphere. The signatures of the gravity waves in the wind fields have been studied in four seasons viz., summer, monsoon, post-monsoon and winter. The large wind fluctuations were more prominent above 10 km during the summer and monsoon seasons. The wave periods are ranging from 10 min-175 min. The power spectral densities of gravity waves are found to be maximum in the stratospheric region. The vertical wavelength and the propagation direction of gravity waves were determined using hodograph analysis. The results show both down ward and upward propagating waves with a maximum vertical wave length of 3.3 km. The gravity wave associated momentum fluxes show that long period gravity waves carry more momentum flux than the short period waves and this is presented.

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Observable signatures of a convectively generated wave field over the tropics using Indian MST radar at Gadanki (13.5°N, 79.2°E)

Cited by 49 publications

References 12 publications

Latitudinal and seasonal variability of gravity-wave energy in the South-West Indian Ocean

Latitudinal and seasonal variability of gravity-wave energy in the South-West Indian Ocean

Long-term MST radar observations of vertical wave number spectra of gravity waves in the tropical troposphere over Gadanki (13.5° N, 79.2° E): comparison with model spectra

Studies on atmospheric gravity wave activity in the troposphere and lower stratosphere over a tropical station at Gadanki

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