Lidar observations of middle atmospheric gravity wave activity over a low-latitude site (Gadanki, 13.5° N, 79.2° E)

Sivakumar, Venkataraman; Rao, P. B.; Benchérif, Hassan

doi:10.5194/angeo-24-823-2006

Cited by 32 publications

(27 citation statements)

References 42 publications

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“…These values compare well with the values reported by Wilson et al (1991), where potential energies were found to be ~ 6-13 J/kg for altitudes 30-45 km and ~ 16-30 J/kg for altitudes 45-60 km for observations carried out at Haute Provence (44 o N, 6 o E) and Biscarosse (BIS) (44 o N, 1 o W). In an earlier study over Gadanki, Sivakumar et al (2006) reported the potential energy to be in the range of 0.1 -10 J/kg at 30-40 km altitudes and ~10-30 J/kg at 40-50 km altitudes, which also is in good agreement with our values, especially at the upper limits of the considered interval. It is worth mentioning here that the calculated potential energies over Gadanki are larger than Arecibo which is consistent with the observed larger variability over Gadanki compared with Arecibo.…”

Section: Resultssupporting

confidence: 81%

“…It operates with a real-time multichannel scalar (MCS) software that provides a photon count profile with a range resolution of 300 m. The signal returns are integrated over 5000 laser shots, generating photon count profiles with a time resolution of 250 s. The method of analysis adopted to determine the temperature profile closely follows that given by Hauchecorne and Chanin (1980). The accuracy of the temperature measurements varies between 0.5-1.5 K in the stratosphere and 2-3 K in the mesosphere (e.g., Sivakumar et al, 2006). Some of the results on mean thermal structure derived using the Rayleigh lidar observations have been reported elsewhere (e.g., Sharma et al, 2006) with more details about the instrument and data analysis.…”

Section: Instrument Descriptionmentioning

confidence: 99%

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Role of Tropical Convective Cells in the Observed Middle Atmospheric Gravity Wave Properties from Two Distant Low Latitude Stations

Taori¹,

Raizada²,

Ratnam³

et al. 2012

ESR

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We investigate the role of convective processes in triggering middle atmospheric gravity waves with the help of simultaneous measurements of middle atmospheric temperature variability from two tropical stations, Gadanki (13.5 o N, 79.2 o E) and Arecibo (18.3 o N, 66.7 o W). Our data reveal that some of the wave periods are similar at both locations indicating the source regions of waves to be similar at both the stations. However, the potential energies of short period gravity waves are found to be significantly higher over Gadanki compared to that at Arecibo. The most striking observation is that background wind conditions were similar and convective processes occurred very close to Gadanki compared to Arecibo. In the view absence of other wave sources during the period of observations, we suggest the strength as well as the distance of convective cells from the location of the observations is responsible for the observed differences in gravity wave spectrum and energies.

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Section: Resultssupporting

confidence: 81%

Section: Instrument Descriptionmentioning

confidence: 99%

Role of Tropical Convective Cells in the Observed Middle Atmospheric Gravity Wave Properties from Two Distant Low Latitude Stations

Taori¹,

Raizada²,

Ratnam³

et al. 2012

ESR

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“…The important aspects of these studies include: propagation characteristics of gravity waves in the realistic atmosphere (Midgley and Liemohn, 1966;Hines and Reddy, 1967;Lindzen, 1970), wave-mean flow interactions (Booker and Bretherton, 1967;Lindzen, 1973;Dunkerton, 1980;McIntyre, 1980), generation of turbulence and enhanced diffusion (Weinstock, 1976;Lindzen, 1981) and wave saturation and its effects (Fritts, 1984;Fritts and Rastogi, 1985). In recent years, the Rayleigh lidar technique has emerged as an effective means to study the gravity wave activity in the middle atmosphere over the height range of 30-70 km Hauchecorne, 1981, 1991;Wilson et al, 1990a, b;Gardner et al, 1989;Whiteway and Carswell, 1995;McDonald et al, 1998;Sivakumar et al, 2006;Ramkumar et al, 2006;Antonita et al, 2007). Further techniques provided important results, including rocketsonde measurements (Dewan et al, 1984), balloon soundings (Fritts et al, 1988;Nastrom et al, 1997).…”

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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“…During the month of May, observed differences are less as local phenomena are different during summer months. Prominent gravity wave and planetary wave activities are also equally imperative in modifying thermal structures in the low-latitude region (e.g., Sivakumar et al 2006;Kishore et al 2006). These are the plausible causes for the higher temperatures recorded during these months over both the locations.…”

Section: Discussionmentioning

confidence: 99%

Study of thermal structure differences from coordinated lidar observations over Mt. Abu (24.5° N, 72.7° E) and Gadanki (13.5° N, 79.2° E)

et al. 2015

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Rayleigh lidars at Gadanki (13.5°N, 79.2°E), a tropical site, and at Mt. Abu (24.5°N, 72.7°E), a subtropical site, in India were operated simultaneously during the months of March, April, and May 2004. Significant differences are found in the temperatures over both the locations. Higher temperature,~10-20 K, in the altitude region of 40-65 km is found during March 2004 over Mt. Abu. The mean stratopause temperature during March 2004 is found~284 K at an altitude of 48 km over Mt. Abu, which is 18 K higher than the observed stratopause temperature of~266 K over Gadanki. During April and May 2004, the temperatures over Mt. Abu are higher in the entire altitude range of 30-70 km than over Gadanki. Lidar-observed temperatures, over both the locations, are compared with the temperatures observed by SABER (Sounding of the Atmosphere using Broadband Emission Radiometry; onboard TIMED (Thermosphere Ionosphere Mesosphere Energetics and Dynamics)) and HALOE (Halogen Occultation Experiment; onboard UARS (Upper Atmosphere Research Satellite)). It is found that the lidar-observed temperatures are in qualitative agreement with the temperature observed by satellites, though quantitatively there are significant differences. Wave types of fluctuations have been noted in the upper stratosphere and in the lower mesosphere over both the locations.

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Lidar observations of middle atmospheric gravity wave activity over a low-latitude site (Gadanki, 13.5° N, 79.2° E)

Cited by 32 publications

References 42 publications

Role of Tropical Convective Cells in the Observed Middle Atmospheric Gravity Wave Properties from Two Distant Low Latitude Stations

Role of Tropical Convective Cells in the Observed Middle Atmospheric Gravity Wave Properties from Two Distant Low Latitude Stations

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

Study of thermal structure differences from coordinated lidar observations over Mt. Abu (24.5° N, 72.7° E) and Gadanki (13.5° N, 79.2° E)

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