First Observations of Short-Period Eastward Propagating Planetary Waves From the Stratosphere to the Lower Thermosphere (110 km) in Winter Antarctica

Abstract

Unique Fe lidar observations in May 2014 at McMurdo, combined with Aura-Microwave Limb Sounder measurements, lead to a new discovery that the amplitudes of 4 day and 2.5 day planetary waves (PWs) grow rapidly from 1–2 K at 100 km to over 10 K at 110 km. This report is also the first observation of short-period (1–5 days) eastward propagating PWs from 30 km all the way to 110 km. The Specified Dynamics-Whole Atmosphere Community Climate Model reproduces the observed three dominant peaks of amplitudes in temperature and coherent vertical phase structures. The data-model comparison indicates a possible mechanism: After PWs originated from the stratosphere dissipate along the critical level, the surviving waves are amplified by in situ instability in the mesosphere and lower thermosphere, resulting in the second (third) peak in geopotential (temperature). This third peak in temperature explains the PW amplitude growth from 100 to 110 km.