Studies on refractivity structure constant, eddy dissipation rate, and momentum flux at a tropical latitude

Rao, D. Narayana; Kishore, P.; Rao, T. Narayana; Rao, S. Vijaya Bhaskara; Reddy, K. Krishna; Yarraiah, M.; Hareesh, M.

doi:10.1029/97rs00251

Cited by 40 publications

(24 citation statements)

References 25 publications

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“…In general, the momentum flux pattern and its general characteristics observed in the present work are similar to that of the observations mentioned above. The estimation of momentum flux magnitude at the Indian MST radar site by Rao et al (1997Rao et al ( , 1998 and Sasi et al (1998) are also in agreement with the present results. The momentum flux values and its pattern observed in the present work compared to the results of others mentioned above are due to the differences in the wind conditions.…”

Section: Resultssupporting

confidence: 82%

Momentum flux associated with gravity waves in the low-latitude troposphere

Nayar

Sreeletha

2003

Ann. Geophys.

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Abstract. The vertical fluxes of horizontal momentum at tropospheric heights are calculated for four days, 25-28 August 1999. The mean zonal wind during these days show the presence of strong westward wind at the upper troposphere. Both the symmetric beam radar method and the power spectral method of evaluation of vertical flux of zonal and meridional momentum shows nearly the same result for quiet conditions. The temporal evolution of the momentum flux is estimated for a day with strong zonal shear and convection. These results indicate that on 28 August 1999, the strong downward vertical wind in the lower altitude range is associated with upward vertical flux of zonal momentum, and strong upward vertical wind is associated with downward vertical flux. Similarly, the strong shear in zonal wind is associated with the increase in negative values in vertical flux in the upper troposphere. Analysis of the role of wave periods in the transport of momentum flux indicates that the vertical momentum flux magnitude is not evenly distributed in all wave periods, but instead it peaks at certain wave periods in the range 10 to 100 min.

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Section: Resultssupporting

confidence: 82%

Momentum flux associated with gravity waves in the low-latitude troposphere

Nayar

Sreeletha

2003

Ann. Geophys.

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“…Chang et al (1997) used ST radar data from Christmas Island to study tropospheric gravity waves, and they found a broad range of frequency associated with gravity wave activity in the troposphere. The derived flux values agree well with the values obtained from MU radar and by Rao et al (1997), Dhaka et al (2001). This paper is organized as follows.…”

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

confidence: 70%

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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“…Hocking (1988) measured the turbulence parameters in the upper mesosphere and lower thermosphere with a 2-MHz narrow beam radar for about two years over Adelaide, Australia. In the tropics, detailed studies of turbulence parameters are sparse, except a few by Rao et al (1997) using a small data set and Rao et al (2001) using three years of radar data. But in both the studies, results are confined only to troposphere and lower stratosphere.…”

Section: Introductionmentioning

confidence: 99%

Seasonal variation of vertical eddy diffusivity in the troposphere, lower stratosphere and mesosphere over a tropical station

et al. 2001

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Abstract. Long-term VHF radar (53 MHz with 3 • beamwidth) observations at Gadanki (13.5 • N, 79.2 • E), India, during the period from September 1995 to August 1999 are used to study monthly, seasonal and annual medians of vertical eddy diffusivity, K in the troposphere, lower stratosphere and mesosphere. First, the spectral width contribution due to non-turbulent effects has been removed for further analysis and the monthly, seasonal medians of K are calculated. The monthly median of K in the troposphere shows maximum and minimum in June-July and November-December, respectively. In general, large values of K are seen up to 10 km and then decrease with height. Larger values of K are observed during monsoon and post-monsoon than in winter and summer. In general, the maximum and minimum values of the annual median of K (in logarithmic values) in the troposphere are found to be 0.25 and −1.3 m 2 s −1 respectively. In the mesosphere, the monthly median of K shows maximum and minimum during June-July and November-December, respectively, similar to the lower atmosphere. The value of K in the mesosphere becomes larger and it increases with height up to 75 km and again decreases above that height.The maximum values are seen during the summer, followed by equinoxes and a minimum during the winter. In general, the maximum and minimum values of K (in logarithmic values) are found to be 0.7 and 0.3 m 2 s −1 , respectively, in the mesosphere. A comparison of Doppler spectral parameters in different beam directions shows anisotropy in both signalto-noise ratio (SNR) and spectral widths in the mesosphere, whereas it shows isotropy in SNR and anisotropy in the spectral widths in troposphere and lower stratosphere.

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Studies on refractivity structure constant, eddy dissipation rate, and momentum flux at a tropical latitude

Cited by 40 publications

References 25 publications

Momentum flux associated with gravity waves in the low-latitude troposphere

Momentum flux associated with gravity waves in the low-latitude troposphere

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

Seasonal variation of vertical eddy diffusivity in the troposphere, lower stratosphere and mesosphere over a tropical station

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