Abstract. Wind observations made at Gadanki (13.5°N) by using Indian MST Radar for few days in September, October, December 1995 and January, 1996 have been analyzed to study gravity wave activity in the troposphere and lower stratosphere. Horizontal wind variances have been computed for gravity waves of period (2±6) h from the power spectral density (PSD) spectrum. Exponential curves of the form e ar have been ®tted by least squares technique to these variance values to obtain height variations of the irregular winds upto the height of about 15 km, where Z is the height in kilometers. The value of H, the scale height, as determined from curve ®tting is found to be less than the theoretical value of scale height of neutral atmosphere in this region, implying that the waves are gaining energy during their passage in the troposphere. In other words, it indicates that the sources of gravity waves are present in the troposphere. The energy densities of gravity wavē uctuations have been computed. Polynomial ®ts to the observed values show that wave energy density increases in the troposphere, its source region, and then decreases in the lower stratosphere.

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1] Mesosphere-stratosphere-troposphere radar measurements have been used to estimate momentum flux of gravity waves in a 2-6 hour period in the lower atmosphere over Gadanki (13.5°N, 79.2°E), a tropical station. Different methods have been adopted to compute momentum flux profiles, and a comparative study shows that momentum flux estimates produced by a hybrid method (Worthington and Thomas, 1996) which measures the vertical wind with a vertical beam and the horizontal wind with a pair of radial beams and those obtained by direct computation of spatial covariances (u 0 w 0 and v 0 w 0 ) show satisfactory agreement. The symmetric beam radar method of Vincent and Reid (1983) has the unique advantage since it does not require vertical beam measurement, and it is found to produce momentum flux estimates compatible with other methods except in high wind shear zones. It is observed that the result of momentum flux obtained by the symmetric beam method shows excellent matching with other methods when the average of vertical winds derived from E-W and N-S beams is used in the formula for both zonal and meridional fluxes. (2005), Comparison of gravity wave momentum fluxes estimated by different methods using mesosphere-stratosphere-troposphere radar, Radio Sci., 40, RS4009,

Abstract. Wind observations made at Gadanki (13.5°N) by using Indian MST Radar for few days in September, October, December 1995 and January, 1996 have been analyzed to study gravity wave activity in the troposphere and lower stratosphere. Horizontal wind variances have been computed for gravity waves of period (2-6) h from the power spectral density (PSD) spectrum. Exponential curves of the form eZ/H have been fitted by least squares technique to these variance values to obtain height variations of the irregular winds upto the height of about 15 km, where Z is the height in kilometers. The value of H, the scale height, as determined from curve fitting is found to be less than the theoretical value of scale height of neutral atmosphere in this region, implying that the waves are gaining energy during their passage in the troposphere. In other words, it indicates that the sources of gravity waves are present in the troposphere. The energy densities of gravity wave fluctuations have been computed. Polynomial fits to the observed values show that wave energy density increases in the troposphere, its source region, and then decreases in the lower stratosphere.Key words. Meteorology and atmospheric dynamics (middle atmosphere dynamics; turbulence; waves and tides)

[1] Diurnal cycle hourly horizontal wind measurements by VHF radar in the altitude range of 3 -20 km made at a low-latitude station, Gadanki (13.5°N, 79.2°E), are used to investigate seasonal variation of tidal parameters. The observations are compared with the recent updated version of the global scale wave model (GSWM-2000). Measured amplitudes are found to be much larger than model values, the discrepancy being larger in convective seasons, particularly for zonal winds. Observations suggest superposition of nonmigrating modes on normal migrating tides. The comparison between the observed and model is good in phase behavior, especially for meridional winds. The terdiurnal component is found to have significant amplitude. Energy densities of tidal components become maximum in the upper troposphere and get reduced in the lower stratosphere. However, the seasonal variations deserve further investigation with longer data sets and with a stress on interannual variability.