Meteor radar estimation of Gravity Wave Variances and Momentum Fluxes in the mesosphere lower thermosphere: Evaluation of different methods using simulations and observations over three tropical locations

Meteor Radar is widely used to study Gravity wave (GW) variances and their Momentum Fluxes (MFs) at mesospheric altitudes. However, the accuracy of meteor radar observations of GWMF should be evaluated before they can be used for research applications. In this regard, the present study evaluates the meteor radar observations of GWMF obtained from Thumba [8.5 degrees N, 77 degrees E (2006-2015)], Kototabang [0.2 degrees S, 100.3 degrees E (2002-2017)] and Tirupati [13.63 degrees N, 79.4 degrees E (2013-2018)]. These radars provide hourly zonal and meridional wind observations round the clock in 80-100 km height domain known as mesosphere lower thermosphere region. Three methods are employed to evaluate the meteor radar performance in estimating the simulated GWMFs, Viz., 1) Day by day analysis, which is traditional Hocking method 2) Composite day analysis and 3) Modified Composite day analysis. After evaluating these methods by employing GW simulations, it is found that modified composite day analysis shows good agreement and the same is used for constructing the GWMF climatologies over the observational locations. The significance of the present study lies in evaluating the three different methods for estimating GWMF by employing GW simulations and meteor radar observations.