Stratospheric Quasi Biennial Oscillation Modulations of Migrating Diurnal Tide in the Mesosphere and Lower Thermosphere Over the Low and Equatorial Latitudes

Abstract

AbstractHorizontal wind measurements using meteor radars located at Thumba (8.5°N, 77°E; 2006–2015) Kototabang (0.2°S, 100.3°E; 2002–2017) and Tirupati (13.63°N, 79.4°E; 2013–2017) in the mesosphere‐lower thermosphere (MLT) and Specified Dynamics Whole Atmosphere Community Climate Model (SD‐WACCM) simulations are employed for investigating the diurnal tide variability at quasi‐biennial scales. The model simulations are evaluated using the meteor radar observations at three tropical locations. WACCM simulations could reproduce the seasonal evolution of diurnal tides very well over Thumba and Tirupati but there are small discrepancies over Kototabang. In order to investigate the modulation of the diurnal tide amplitudes in the MLT region by the stratospheric quasi‐biennial oscillation (SQBO), deseasonalized perturbations of diurnal tides and stratospheric winds are analyzed. A very good correspondence is found between meridional diurnal tide perturbation amplitudes and the SQBO with positive tidal perturbations during the eastward phase of SQBO and negative perturbations during the westward phase over Thumba and Tirupati. SQBO modulations of diurnal tides at global scales exhibits a positive correlation between the meridional diurnal tide perturbation with SQBO winds at 20 hPa and a negative correlation with SQBO winds at 70 hPa within ±40° latitude, except over the equator. It is also noted that the equatorial electrojet strength, is modulated by the SQBO over the Thumba, which is a dip equatorial location. The significance of present study lies in evaluating WACCM simulations at tropical locations using meteor radar measurements and in investigating the SQBO modulations of diurnal tides at global scales.