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Temperature Anomalies Associated with Sudden Stratospheric Warming, Observed Above the Tropical Site of Gadanki (13.5°N, 79.2°E) with a Rayleigh Lidar

U. Jaya Prakash Raju*, P. Keckhut, M. Krishnaiah and Y. Bhavani Kumar

A quasi continuous Rayleigh lidar measurements of middle atmospheric temperature (30-70km region) have been carried out from Gadanki (13.5 N, 79.2 E), India between June, 1998 and April, 1999. Summer temperature showed a smooth and regular variation with altitudes and reasonably good agreement with MSISE-90 model atmosphere. By, contrast winter temperatures are perturbed continuously by planetary waves, as long as prevailing winds are westerlies, from October to March. Pronounced stratospheric cooling and a minor stratospheric warming events were observed during this winter period. The stratopause height and temperature vary considerably during the evolution of this phenomenon. Spectral analysis of the data reveals the presence of a 16-day wave interpreted as a free Rossby wave, another wave with large perturbations having periods of 23 to 35 days. Amplitude and Phases of theses waves exhibits a peculiar structure “quiet atmospheric layer” corresponds to the regions of minimum variability of Quasi-Stationary planetary wave no. 2 of the CIRA-86 model. The thermal structure of tropical stratosphere of northern hemisphere seems to be influenced by the dynamics of the winter time stratospheric warmings at the mid/high-latitudes. The stratospheric warming event over Gadanki appeared to be linked to warming event over the mid-latitude region. Our analysis partially strengthens the point of “propagation of 16-day planetary waves over equatorial stratosphere invades the mid-latitudes from the tropics during the evolution of Stratospheric Sudden Warming”.