MIPAS observations of longitudinal oscillations in the mesosphere and the lower thermosphere: Part 1. Climatology of odd-parity daily frequency modes.

MIPAS global sun-synchronous observations are almost locked in local time. Subtraction of the descending and ascending node measurements at each longitude only contain the longitudinal oscillations with odd daily frequencies nodd from a solar perspective at 10A.M. Contributions of the background atmosphere, persistent (on a daily basis) longitudinal oscillations and tidal modes with even daily frequencies vanish. We have determined MIPAS temperature longitudinal oscillations with nodd and wavenumber k=0-4 from 20 to 150 km from April 2007 to March 2012. To our knowledge, 5 this is the first time temperature zonal oscillations are derived in this altitude range globally from a single instrument. The major findings are the detection of: 1) migrating tides at Northern and Southern high latitudes; 2) significant k = 1 activity at extra-tropical and highlatitudes, particularly in the SH; 3) k = 3 and k = 4 eastward propagating waves that penetrate in the lower thermosphere with a significantly larger vertical wavelength than in the mesosphere; 4) a quasi-biennial oscillation of the migrating tide mainly originated in the stratosphere and propagated to the MLT. MIPAS global measurements of longitudinal oscillations are useful for testing tide modeling in the MLT region and as a lower boundary of models extending higher up in the atmosphere. [ABSTRACT FROM AUTHOR]