Abstract
One of the interesting and poorly understood features of mesosphere and lower thermosphere (MLT) region is the phenomenon of Mesospheric Inversion Layers (MILs). The poor understanding of MILs is due to limited access of their occurrence height region, however the lidars are more efficient tools which provide stratosphere and mesosphere nocturnal temperatures with high temporal and vertical resolutions. The state-of-the-art lidar system comprising Mie, Rayleigh lidars installed at National Atmospheric Research Laboratory (NARL), Gadanki (13.5°N, 79.2°E), India has provided an excellent opportunity to undertake this study. The Nd:YAG laser source with lower power (11W) has been replaced by the one with higher power (30W) in January 2007. As the laser power has been increased, the molecular back scatter signal is also increased and consequently the top height level of the temperature retrieval has been increased to ~90-95 km. In the present study, the role of dominant causative mechanisms for the occurrence of MILs has been discussed using mainly the lidar and satellite (TIMED-SABER) observations over Gadanki region.
Highlights
Mesospheric Inversion Layer (MIL) is the region of temperature gradient inversion from negative to positive in mesosphere, over several kilometers in thickness [1,2,3]
The study of MILs is essential for the comprehensive understanding of middle atmosphere/mesosphere and lower thermosphere (MLT) energy budget
Their causative mechanisms are quite complex, the MILs occur mainly due to Gravity Wave (GW) breaking, Planetary Wave (PW) critical level interaction, chemical heating and GW-Tidal interaction [2,3]
Summary
Mesospheric Inversion Layer (MIL) is the region of temperature gradient inversion from negative to positive in mesosphere, over several kilometers in thickness [1,2,3]. Alhough the MILs have been reported from several sites using lidar and space borne observations, their morphological characteristics are still unknown. Their causative mechanisms are quite complex, the MILs occur mainly due to Gravity Wave (GW) breaking, Planetary Wave (PW) critical level interaction, chemical heating and GW-Tidal interaction [2,3]. The waves deposit energy and momentum in the background when they break and influence the thermal, dynamical structures and the chemical composition. In addition to the above dynamical processes, the heating due to several exothermic reactions mainly among H, O, O2, O3, OH, HO2 enhances the background temperature which is maintained as a MIL
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