The Structure of Super Cloud Clusters Observed in 1-20 June 1986 and their Relationship to Easterly Waves

Abstract

The structural features of the eastward-propagating super cloud clusters and their westwardpropagating internal structures observed over the Pacific Ocean are described based on the GMS IR fundamental histogram data and the Global Objective Analysis (GANAL) Data. The analysis period is 1∼20 June 1986 during which four organized groups of cloud clusters (super cloud clusters) with a longitudinal scale of about 3000 km successively propagated eastward over the equatorial western Pacific Ocean.
The main results are as follows. (1) The hierarchical structure of the super cloud clusters observed in 1∼20 June 1986 was associated with the equatorial eastward-propagating Kelvin wave-type mode and several degrees off equatorial westward-propagating "easterly waves" . (2) The equatorial eastwardpropagating mode was dominant between 10°N and 10°S, mainly in the zonal wind component. The phase relation between the wind and the height anomaly showed this mode had a Kelvin wave-type structure, although the propagation speed was as slow as 10°∼12°/day. The vertical structure indicated the downward energy propagation. The conversion from the convectively constructed potential energy to kinetic energy was not distinct, while the energy flux input from the southern hemisphere was indicated in the upper troposphere. (3) The structure of the westward mode associated with the westward-traveling cloud clusters corresponded to the "easterly waves" . To the rear of the lower convergence of the eastward mode (in SCC region), the upper level structure of the "easterly waves" was more firmly formed with the enhanced cloud activity producing the energy conversion from the available potential to the kinetic energy of the "easterly waves". Its amplitude in the lower troposphere was not significantly influenced by the eastward mode.