120-day variability in migrating tides from CMAM30 winds

Abstract

Migrating tides and their variability are investigated using Canadian Middle Atmosphere Model (CMAM30) zonal and meridional wind data from 1979 to 2010. Migrating diurnal (DW1) and semi-diurnal (SW2) tides show strong annual and semi-annual variations. The former is stronger in the Southern Hemisphere and the latter is significant over sub-tropical latitudes in the mesosphere. Wavelet analysis in the mesopause region shows a 120-day variability in SW2 tide over equator and ∼±20∘ with no apparent connection with solar activity. A close inspection shows that the 120-day variation is not due to variations in solar energy inputs.