Heating Distribution by Cloud Systems Derived from Doppler Radar Observation in TOGA-COARE

Abstract

Dual Doppler radar observations were carried out from November 1992 to January 1993 during the TOGA-COARE IOP (Tropical Ocean and Global Atmosphere-Coupled Ocean Atmosphere Response Experiment, Intensive Observation Phase) at Manus Island in Papua New Guinea. The heating profiles of six stratiform and eight convective cloud systems were calculated using three-dimensional wind field and hydrometeor distribution in a same way as Roux and Sun (1990). Relations between the heating profiles and the thermodynamic properties of environment were studied. Convective and stratiform cloud systems both showed structures consistent with past studies. The heating level varied significantly with environmental conditions that had been linked to the phase of Madden Julian Oscillation (MJO). Specifically, at the beginning of the active phase of MJO, convective cloud systems dominated and the heating level was high (7 km). These cloud systems heated and moistened the middle to upper troposphere and stabilized the atmosphere. In the middle of the active phase of MJO, stratiform cloud systems dominated and the heating level lowered (5 km). At the end of the active phase of the MJO, convective cloud systems again dominated. A composite profile for the entire observation period was calculated using the representative profiles and satellite data, and was compared with that derived by Lin and Johnson (1996) using radiosonde observation. The derived maximum heating rate coincided with their results, however, the heating rates of lower and upper troposphere were smaller and the level of maximum heating (5 km) was slightly lower.