16-day wave observed in the meteor winds at low latitudes in the southern hemisphere

Horizontal winds obtained from meteor radar over Cachoeira Paulista, Brazil (22.7 degrees S, 45.0 degrees W), between April 1999 and April 2004 have been used to investigate the planetary-scale 16-day wave. Spectral analysis shows the presence of bursts in the 12- to 20-day period range, mainly in the zonal component, with enhancements observed during all seasons. The 16-day wave exhibits year-to-year variability, but did not exhibit a clear seasonal behavior. This study reveals that the 16-day wave at 22.7 degrees S was strongest during austral autumn-winter seasons for the years 2002 and 2003, whilst for 1999-2000, 2000-2001 and 2002-2003 16-day wave was strongest during spring-summer seasons. The 16-day wave activity was observed during both winter and summer months over Cachoeira Paulista, and the enhancements seen for summer seasons reinforce the interpretation of inter-hemispheric penetration. During the most intense events in the zonal component, the vertical structure revealed maximum amplitudes of about 14 m/s at 90 km and above and, the vertical phase structure showed descending phase with vertical wavelengths of about 51 +/- 11 km. (c) 2006 COSPAR. Published by Elsevier Ltd. All rights reserved.