Mesospheric inversion layer (MIL) is a layer of enhanced temperature with several kilometers vertical thickness that is superimposed upon the characteristically decreasing mesospheric thermal structure. Although MILs have been known for decades through all sorts of available techniques, their study is still of significant relevance for understanding of the energy and momentum budget of mesosphere and lower thermosphere (MLT) region. The suggested causative mechanisms for the occurrence of MILs are: gravity wave (GW) breaking, planetary wave (PW) critical level interaction, GW-tidal interaction and chemical heating. A large MIL has been observed at ~79-84 km (amplitude ~50 K and thickness ~4.5 km) using Rayleigh lidar temperatures on the night of 24^th January 2007 over a tropical site, Gadanki (13.5°N, 79.2°E). It is observed that a dominant GW (T~33 min, λ_z~6.4 km) propagates vertically and attains convective instability in the MIL region. The horizontal wave parameters are derived from the GW dispersion relation using rocketsonde and MF (medium frequency) radar winds over SHAR (13.7°N,80.2°E) and Tirunelveli (8.7°N,77.8°E) respectively. Further it is evident that the wave amplitude gets saturated at ~80 km and the eddy diffusion coefficient (D_eddy) increases drastically in the inversion region (~80-85 km). The heating/cooling rates (~10 K/hr) observed at the bottom/top levels of the MIL further elucidates the inversion layer occurred mainly due to the turbulence generated by the gravity wave breaking. However the TIMED-SABER total chemical heating by seven major exothermic reactions among H, O, O₃, OH, HO₂ plays minor role during this MIL event. On contrary, it is also evident that chemistry dominates dynamics during a few large MIL events observed in January-February 2011 over Gadanki region.