Quasi-10-day wave in the atmosphere

Abstract

In the classical theory of oscillations on a spherical-rotating Earth, the quasi-10-day wave (Q10DW) exists as a westward propagating “free” or “unforced” normal mode oscillation with zonal wave number s = 1. In the present study, we employ Thermosphere Ionosphere Mesosphere Energetics and Dynamics/Sounding of the Atmosphere using Broadband Emission Radiometry temperature measurements between 20 and 100 km and ±50° latitude, and extending from 2002 to 2013, to provide a comprehensive perspective on the Q10DW as it actually exists in the atmosphere. Climatological seasonal-latitudinal structures are presented which demonstrate that the Q10DW is weakest during summer months and equatorward of ±50° latitude but otherwise has amplitudes ranging from 1.0 K at ∼45 kmto ∼5 K at 100 km. Seasonal asymmetries and significant interannual variability also exist. The mean period of the Q10DW is 9.8 days with a standard deviation of about 0.4 day. On average the Q10DW conforms reasonably well with theoretical expectations for a normal mode subject to the effects of dissipation and mean winds, at least below 80 km. Above 80 km this conformity often breaks down. Several factors potentially contributing to this nonconformity are discussed.