Item

Abstract

Characteristics of tropospheric low‐frequency gravity waves are diagnosed in radiosonde soundings from the Tropical Warm Pool‐International Cloud Experiment (TWP‐ICE) near Darwin, Australia. The waves have typical vertical wavelengths of about 4 km, horizontal wavelengths of about 600 km and intrinsic periods of about 12 hours. These scales match those of the vertical, horizontal and temporal variability found in area‐averaged horizontal wind divergence over the same domain. Vertical profiles of divergence show wave‐like structures with variability of the order of 2× 10‐5s‐1 in the free troposphere. The results for Darwin are similar to previously reported observed mesoscale patterns of divergence/convergence over the tropical Atlantic. The findings imply that tropical divergence on spatial scales of a few hundred kilometers, which is known to influence the organization of convection, may be forced by gravity waves.