Kelvin wave variability near the equatorial tropopause observed in GPS radio occultation measurements

Abstract

Temperature fields in the equatorial upper troposphere and lower stratosphere, derived from GPS radio occultation measurements for 2001-2002, show evidence for planetary-scale Kelvin waves. These waves have a characteristic eastward phase tilt with height and typical vertical wavelengths of ∼4-8 km. The Kelvin waves exhibit coherent vertical structure over ∼12-25 km, with maximum amplitudes near the tropical tropopause (∼17 km). The waves are often quasi-stationary near the tropopause but exhibit regular eastward propagation in the lower stratosphere (with periods near 20 days). The quasi-stationary waves modulate the climatological cold tropopause over Indonesia. The transient lower stratospheric waves show enhanced amplitudes coincident with the descending westerly shear phase of the quasi-biennial oscillation (QBO). Correlations with outgoing long-wave radiation (OLR) data show that global temperature patterns over ∼12-17 km (with characteristic Kelvin wave structure) vary coherently with transient deep convection over Indonesia. Copyright 2005 by the American Geophysical Union.