UARS MLS observations of gravity waves associated with the Arctic Winter Stratospheric Vortex

Abstract

Passive satellite microwave limb radiances were used to study interactions between gravity waves and stratospheric winds in mid‐ to high latitude winter. We found that the radiance variances depend significantly on the instrument line‐of‐sight (LOS) and the background wind. The radiance variances are outstanding at two viewing angles where the LOS is about 30° or 90° from the wind vector. Waves propagating in preferred directions likely cause the two optimal angles observed. The variances at the 90° angle, located inside the polar vortex, seem produced by the gravity waves propagating nearly parallel to the wind direction. The variances at the 30° angle, located near the edge of the vortex, are likely associated with perturbations propagating almost perpendicularly to the wind direction. The variance of both modes increases with the background wind speed, but saturation is observed for the waves inside the vortex as wind speed exceeds about 60m/s. Interestingly, we also found that the temperature co‐located with the variance inside the vortex is warmer by 20K at background wind speeds >60m/s, which might be correlated with the wave breaking in the vortex.