Diurnal variation of short-period (20-120 min) gravity waves in the equatorial Mesosphere and Lower Thermosphere and its relation to deep tropical convection

Abstract

We study short period gravity waves (20-120 min) in the equatorial Mesosphere and Lower Thermosphere (MLT) using a Medium Frequency (MF) radar at Pameungpeuk (7.4° S, 107.4° E), Indonesia. In particular, we study local time and seasonal variation of the gravity wave variance and its relation to tropical convection. The gravity wave variance at 88 km enhances between 20:00 LT and 07:00 LT, with a peak at 02:00-03:00 LT. The enhancement is mainly observed during February-April and September-October and shows inter-annual variability. Convective activity over the same location persists from 16:00-21:00 LT with a peak activity ∼18:00 LT and enhances between November-April. Time delay between the peak of convection and that of gravity wave activity ranges 1-15 h, which is consistent with theoretical calculations and previous reports based on reverse ray tracing analysis. © 2011 Author(s).