Observation of an ultraslow 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 TOGA-COARE (Tropical Ocean-Global Atmosphere and Coupled Ocean-Atmosphere Response Experiment). Evidence is found for a wave near the tropopause with periods similar to 30-40 days and with very slow (similar to 3 m s(-1)) eastward propagation. This oscillation appears quite coherent across the region considered (a 37 degrees longitude spread). The oscillation has a short vertical wavelength (similar to 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.