Diurnal variation of lower tropospheric winds (0-3 km) over Thumba during 18-20 August 1976

Abstract

The wind data from seventeen balloon ascents conducted at Thumba during 18-20 August 1976 for providing meteorological support to the Indo-Soviet M-100 rocket diurnal launching series, have been subjected to isopleth analysis, land-sea breeze study, wind shear analysis and harmonic analysis. The lower tropospheric winds (0-3 km) are northwesterly with wind speeds increasing upto 1 to 1.5 km and then decreasing to almost half this speed above that altitude. Maximum intensity of the sea breeze (Approx. 10 m/s) is around 1530 1ST at altitudes 200 to 600 m. The land breeze effect is maximum around 0300 1ST (Approx. 10 m/s) at the altitude around 0.4 km. The wind shear values are of the order of 30 × 10^-4 per second and is maximum in the first 100 metres above ground level. The diurnal oscillation of zonal and meridional winds is strongest at 0.5 km with almost equal amplitudes of 2.62 m/s and 2.52 m/s respectively and accounts for 60 percent of the total variation while for the semidiurnal oscillation, accounting for the remaining 40 per cent the zonal wind oscillation is strongest (amplitude 1.90 m/s) at 1.0 km and the meridional oscillation is strongest (amplitude 1.35 m/s) at 3.0 km.