SPACE-TIME INTEGRITY OF IMPROVED STRATOSPHERIC AND MESOSPHERIC SOUNDER AND MICROWAVE LIMB SOUNDER TEMPERATURE-FIELDS AT KELVIN WAVE SCALES

Space-time analyses, which are sensitive to details of retrieval and g ridding processes not seen in zonal and time means, are used to invest igate the integrity of version 8 gridded retrieved temperatures from t he improved stratospheric and mesospheric sounder (ISAMS) on the upper atmosphere research satellite (UARS). This note presents results of s uch analyses applied to ISAMS tropical data. Comparisons are made with microwave limb sounder (MLS), also on UARS, temperatures. Prominent z onal wave number 1 features are observed with characteristics similar to those expected for Kelvin waves. Time versus longitude plots reveal quasi-regular eastward phase progression from November 1991 to mid-Ja nuary 1992. The perturbations extend throughout the upper stratosphere and lower mesosphere (altitudes of 32-64 km), exhibiting peak-to-peak amplitudes of up to 2 degrees-3 degrees it and periods from similar t o 2 weeks in midstratosphere to similar to 1 week at higher altitudes. Faster Kelvin waves with periods of 3-5 days are also found in the lo wer mesosphere. Height versus time plots reveal downward phase and upw ard group velocities, consistent with forcing from below. Vertical wav elengths are similar to 20 km for the slower mode and about twice this scale for the faster 3 to 5-day mode. The features are trapped within +/-10 degrees-15 degrees bf the equator. Kelvin wave signatures in IS AMS and MLS temperatures are compared at 10 and 1 hPa. Good agreement is found, illustrating the internal consistency and ability of both IS AMS and MLS temperature grids to capture relatively small amplitude fe atures with space-time scales of fast, zonally asymmetric equatorial m odes.