Observations of the diurnal tide during seven intensive radiosonde campaigns in Australia and Indonesia

Abstract

Seven intensive radiosonde campaigns of between five days and one month duration were conducted in northern Australia and the Indonesian region between 2001 and 2006. These data were used to study the diurnal tide below 30 km altitude. Inter‐campaign comparisons were made at Darwin (12°S, 131°E) and Koto Tabang (0°S, 100°E). The amplitudes of the diurnal tide did not depend upon the strength of tropospheric convection at Koto Tabang or whether there were monsoon conditions at Darwin. However, the amplitude of the zonal wind component at Koto Tabang during the different campaigns was influenced by the background QBO zonal wind structure. Stratospheric amplitudes exceeded 2.0 m s−1 at 16–17 km and 24–26 km, where the zonal wind shear was greater than 15 m s−1 km−1 during November–December 2005, but were 0.3 m s−1 when the wind shear was close to zero above 25 km during April–May 2004. The local time phase structures at Darwin and Koto Tabang were similar between campaigns and also similar to previous observations in the region, suggesting a uniform regional scale heating source. Vertical wavelengths of the stratospheric diurnal tide were generally 5–20 km. This, together with the tidal interaction with the background wind shear, suggests the presence of non‐migrating components.