Medium frequency gravity wave characteristics obtained using Weather Research and Forecasting (WRF) model simulations

Abstract

Many studies have reported the characteristics of wide spectrum of Gravity Wave (GW) using radiosonde, MST Radar, Lidar and other observations. In this study, we made an attempt to obtain the characteristics of medium frequency GWs over a tropical station Gadanki (13.5°N and 79.2°E) using the Weather Research and Forecasting (WRF) model simulations for the period 2006–2017. Prior to GWs analysis, we have validated the model outputs with radiosonde measurements over Gadanki to check the performance of the model in capturing the realistic features as seen in the observations. Profiles of horizontal winds and temperature are validated and the results of statistical analysis indicate that there is a good correspondence between the WRF model simulations and the radiosonde measurements. The FFT and wavelet analysis on the winds revealed the spectrum of waves. The band pass filtered wind perturbations showed clear downward phase propagation with the dominant periods 2–5 h. The observed vertical and horizontal wave lengths are in the range of 6–8 km (3–8 km) and 100–200 km (100–500 km) in the troposphere (stratosphere), respectively. These characteristics match well with those reported from the same location using MST radar and radiosonde observations. Further, the long-term features like semi-annual oscillation, annual oscillation and quasi-biannual oscillations are also simulated very well in the WRF outputs. These results show the model's ability to simulate near realistic features as seen the observations and can also be used to supplement the missing observations with errors limits as its uncertainty.