The afternoon-evening transition (AET) in the atmospheric boundary layer has been studied in an integrated approach using 3 years of tower, sodar and wind profiler measurements. Such a long-term data set has been used for the first time to understand the behavior of AET. It allowed us to study the seasonal variation. In contrast to the common belief that the transition evolves from bottom to top, the present study clearly showed that the start time of transition follows top-to-bottom evolution.

Sources and propagation characteristics of high-frequency gravity waves observed in the mesosphere using airglow emissions from Gadanki and Hyderabad, India, are investigated using reverse ray tracing. Wave amplitudes are also traced back, including both radiative and diffusive damping. Interestingly, large vertical shears in the horizontal wind are noticed near the ray terminal points (at 10-12km altitude) and are thus identified to be the source for generating the observed gravity waves.