Disturbances of 1-2 Hour-Periods Observed in the Tropical Lower Troposphere during the TOGA-COARE IOP

Abstract

Mesoscale disturbances in the tropical lower troposphere having periods of 1-2 hours were detected in the wind profiler data during the intensive observing period of the Tropical Ocean-Global Atmosphere Coupled Ocean-Atmosphere Response Experiment (TOGA-COARE). Seven cases were detected with average amplitudes of the vertical velocity greater than 0.1ms^-1.
One case that was observed at Kapingamarangi (1.1°N, 154.8°E) on January 7, 1993 was examined in detail. This disturbance had a period of 60 minutes and a duration of 6 hours. Assuming that this disturbance was a gravity wave, the vertical and horizontal wavelengths were estimated as 5.4-7.6km and 24-37km, respectively. Using satellite and sounding data, it was inferred that the disturbance was excited by a mesoscale cloud line lying about 400km ESE from Kapingamarangi, and then propagated in a wave duct in the troposphere.