Atmospheric Chemistry and Physics www.atmos-chem-phys.net 1680-7316 1680-7324 4 7 2004 10.5194/acp-4-1989-2004 http://www.atmos-chem-phys.net/4/1989/2004/ http://www.atmos-chem-phys.net/4/1989/2004/acp-4-1989-2004.html http://www.atmos-chem-phys.net/4/1989/2004/acp-4-1989-2004.pdf 1989 1996 2004-10-01 Rayleigh lidar observation of a warm stratopause over a tropical site, Gadanki (13.5° N; 79.2° E) V. Sivakumar B. Morel H. Bencherif J. L. Baray S. Baldy A. Hauchecorne P. B. Rao Laboratoire de Physique de l’Atmosphère CNRS–UMR 8105, Université de La Réunion, 15 Av. René Cassin, BP 7151, 97715 Saint-Denis Messag. Cedex 9, La Réunion, France Institut Pierre Simon Laplace (IPSL), Observatoire de Physique de l’Atmosphère de la Réunion (OPAR), La Réunion, France Service d’Aéronomie CNRS-UMR 7620, France National Remote Sensing Agency, Bala Nagar, Hyderabad – 500 037, India The first Rayleigh lidar observation of a stratopause warming over a tropical site, Gadanki (13.5° N; 79.2° E), is presented in this paper. The warming event was observed on 22-23 February 2001, and found to occur in the stratopause region (~45km). The magnitude of the warming was found to be ~18K with respect to the winter-mean temperature profile derived from the lidar data collected over March 1998 to July 2001. The event observed by the lidar has also been seen in data from the Halogen Occultation Experiment (HALOE) on board the UARS satellite. The zonal-mean temperature at 80° N and the zonal-mean zonal wind at 60° N from the National Centre for Environmental Prediction (NCEP) reanalysis and the European Centre for Medium-Range Weather Forecasts (ECMWF) analysis indicate that a major warming episode took place in the northern polar hemisphere a week before the day of the observation over Gadanki. Eliassen-Palm (E-P) flux calculations from ECMWF analysis show evidence of propagation of planetary-wave activity from high and mid- to low latitudes subsequent to the major warming episode over the pole. Our results support the view that the most likely source mechanism for the observed stratopause warming is the increase in planetary-wave activity.