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The large temperature variability of nightly mean temperatures in 30 to 80 km altitude range is investigated using 15 years of lidar data from the year 1998 to 2012 over a low latitude station Gadanki, India (13.5o N, 79.2o E). The monthly mean values are compared with the coincident SABER temperature data obtained in a grid encompassing latitudes 08-18°N and longitudes 74-84°E during years 2002-2012 (i.e., 11 years). The comparison between the lidar and SABER measurements reveals a reasonable agreement with the standard deviation of the temperature difference ~1.5 K at 50 km and ~3 K at 70 km altitudes. To understand the physics of variability noted in the temperature data, abest-fit analysis is used. This reveals the presence of Semi-Annual Oscillation (SAO), Annual Oscillation (AO), Quasi-Biennial Oscillation (QBO), El Niño Southern Oscillation (ENSO), Solar Cycle Influence, and a residual secular trend. The residual trend shows a warming at 30-40 km altitudes and cooling between 40 and 80 km. The underlying physics of these oscillations are explained with the present knowledge of atmospheric forcings. [ABSTRACT FROM AUTHOR]

Abstract: We summarize two years of Mesosphere Lower Thermosphere Photometer (MLTP) operation of mesospheric OH and O2 emission monitoring. The deduced mesospheric OH and O2 temperatures show large variability. Nightly temperature variations over Gadanki (13.5°N, 79.2°E) are dominated by the short period wave features, while tidal amplitudes are relatively small. Our measurements are the first to report a long period seasonal variation at two upper mesospheric altitudes simultaneously over the Indian sector. Our observations reveal the presence of a dominant semi-annual oscillation (∼6months periodicity) together with a shorter period (∼2.5 months periodicity) oscillation in both OH and O2 data. [Copyright &y& Elsevier]

The vertical temperature profiles in a typical Rayleigh lidar system depends on the backscatter photon counts and the CIRA-86 model inputs. For the first time, we show that, by making simultaneous measurements of Rayleigh lidar and upper mesospheric O2 temperatures, the lidar capability can be enhanced to obtain mesospheric temperature profile up to about 95 km altitudes. The obtained results are compared with instantaneous space-borne SABER measurements for a validation. [ABSTRACT FROM AUTHOR]