Details

Autor(en) / Beteiligte

• Heymsfield, Andrew J.
• Miloshevich, Larry M.
• Slingo, Anthony
• Sassen, Kenneth
• Starr, David O'C.

Titel

An observational and theoretical study of highly supercooled altocumulus

Ist Teil von

• Journal of the atmospheric sciences, 1991-04, Vol.48 (7), p.923-945

Ort / Verlag

Legacy CDMS: American Meteorological Society

Erscheinungsjahr

1991

Quelle

EZB Free E-Journals

Beschreibungen/Notizen

• The microphysics of two altocumulus clouds sampled at a temperature of about -30 C through the NCAR King Air aircraft and coincident lidar has been characterized. The clouds are structurally similar to stratocumulus and have extensive cloudtop entrainment, a capping temperature inversion, and a dry layer above. Microphysical and radiative properties of both clouds have been modeled numerically. When entrainment effects are incorporated in the model, calculations of droplet concentration and mean diameter profiles compare favorably with the measurements. Radiative transfer calculations indicate that radiative cooling causes sufficient negative buoyancy in cloudtop parcels for producing convective instability and reproducing the observed downdraft velocities. It is shown that entrainment of warmer, drier air near a cloudtop counteracts the radiatively induced negative buoyancy in the downdrafts.