VHF radar observations of gravity waves at a low latitude

[摘要] Wind observations made at Gadanki (13.5°N)by using Indian MST Radar for few days in September, October, December 1995 andJanuary, 1996 have been analyzed to study gravity wave activity in thetroposphere and lower stratosphere. Horizontal wind variances have been computedfor gravity waves of period (2-6) h from the power spectral density (PSD)spectrum. Exponential curves of the form e^Z/Hhave been fitted by least squares technique to these variance values to obtainheight variations of the irregular winds upto the height of about 15 km, where Zis the height in kilometers. The value of H, the scale height, asdetermined from curve fitting is found to be less than the theoretical value ofscale height of neutral atmosphere in this region, implying that the waves aregaining energy during their passage in the troposphere. In other words, itindicates that the sources of gravity waves are present in the troposphere. Theenergy densities of gravity wave fluctuations have been computed. Polynomialfits to the observed values show that wave energy density increases in thetroposphere, its source region, and then decreases in the lower stratosphere.

Key words. Meteorology and atmospheric dynamics (middleatmosphere dynamics; turbulence; waves and tides)

[学科分类] 地球科学(综合)