Rayleigh lidar observations of mesospheric inversion layers over Gadanki (13.5[degrees]N, 79.2[degrees]E) and their relationship with gravity wave activity

Fifteen nights of Rayleigh lidar temperature profiles over Gadanki (13.5[degrees]N, 79.2[degrees]E) for the period January - February 1999 show the presence of mesospheric inversion layers (MILs) on ten nights indicating their frequent occurrences over low latitudes. The role of gravity waves in causing the MILs has been investigated using the temperature profiles derived from the half an hour integrated photon counts. The temperature deviations from the nightly mean temperature are inferred as due to gravity waves and potential energy per unit mass due to these waves; and their spectra are examined separating MIL nights and non-MIL nights. The spectra of potential energy per unit mass (E sub(p)) computed from the temperature fluctuations attain broad band convective instability limit at mesospheric heights on MIL nights, whereas the spectra just tend to attain the limit on non-MIL nights at longer wavelengths. These results indicate that enhanced gravity wave growth and breaking due to convective instability may be the potential mechanism for the occurrence of these MILs.