Tropical Cumulus Interaction with and Modification of the Subcloud Region

Abstract

Nineteen cases of tropical cumulus convective activity at and below cloud base are described using simultaneous measurements at as many as six levels between the surface and 1200 m. Updrafts are traced from just above cloud base to near the ocean surface. An inventory of updrafts and downdrafts indicates that about 80% are either warm/moist (up) or cold/dry (down) relative to their immediate environments. However, the remaining 20% of the drafts are found to make significant contributions to the total cloud transports. Various degrees and types of modification of the lower PBL structure associated with cumulus activity are illustrated with before, during and after profiles. Cloud transports of mass, heat, moisture and momentum are estimated using only those drafts with a vertical velocity greater than ± 0.5 m s?1.