Observation of an Ultra-Slow Large-Scale Wave Near the Tropical Tropopause

An analysis is made of very high resolution radiosonde data taken at seven western Pacific island stations during the TOGA-COARE experiment. Evidence is found for a wave near the tropopause with periods ~30-40 days and with very slow (~3 m-s-1) eastward propagation. This oscillation appears quite coherent across the region considered (a 37o longitude spread). The oscillation has a short vertical wavelength (~3 km) and is strongly attenuated above the tropopause, and thus would be very hard to observe in either satellite data or conventional meteorological analyses.