An enhancement of the lunar tide in the MLT region observed in the Brazilian sector during 2006 SSW

Meteor radar observations at São João do Cariri (7.4°S, 36.5°W), Cachoeira Paulista (23°S, 45°W) and Santa Maria (29.7°S, 53.7°W) have permitted estimates to be made of winds and temperature in the mesosphere and lower thermosphere (MLT). Using horizontal winds the lunar semidiurnal tide was determined from January 2005 to December 2008 for these three sites. In January 2006 an unusual enhancement was observed in the lunar tide amplitude at these stations, for meridional and zonal components. During this period, sudden stratospheric warming (SSW) events were observed in the northern hemisphere. Meridional and zonal winds observed in Brazil showed evidence of SSW effects in the MLT region. Moreover, the mesospheric temperatures at Cachoeira Paulista and Santa Maria presented cooling and a semimonthly oscillation, which followed the new–full–new moon phases. These results suggest that the enhancement of the lunar tide could be a response for the SSW in the MLT.

► Meteor radar measurements were used to study the lunar tide at three Brazilian sites.
► An enhancement of the lunar tide amplitudes was observed at all sites during the 2006 sudden stratospheric warming (SSW).
► The meridional and zonal winds showed evidences of 2006 SSW effects in the southern MLT region.
► A semimonthly oscillation was observed in the mesospheric temperatures.