GATE phase III Mean Synoptic-Scale Radiative Convergence Profiles

Abstract

Tropospheric radiative convergence profiles are derived for an easterly wave composite during Phase III of the GATE. The easterly waves observed during this period were generally well developed. The profiles also represent the magnitudes and the spatial distribution of atmospheric radiative convergence of the Intertropical Convergence Zone in the GATE area. The 12 h mean daytime and nighttime profiles are presented. Cloud-top pressure distributions as a function of wave position are also presented. The results of this research indicate three possible radiative induced mechanisms which contribute to the observed diurnal cycle in large-scale mass convergence: 1) radiative convergence differences between the ITCZ and the surrounding regions; 2) mesoscale radiative convergence differences between clear and cluster regions, and 3) a nighttime upper level tropospheric cooling maximum that is centered one-half a wavelength from the region of maximum convective activity.