| M.A. Miller Department of Meteorology Pennsylvania State University University Park, PA 16802 814-238-8898 |
B.A. Albrecht and R.M. Peters Department of Meteorology Pennsylvania State University University Park, PA 16802 814-865-9500 |
A Cloud Observing System (COS) was deployed on the island of Santa Maria during the ASTEX. The system consisted of a laser ceilometer, a multichannel microwave radiometer, a narrow-beam infrared window radiometer, high-resolution radiosonde launches, and surface micrometeorological instrumentation. The most important component of the system is a 94 GHz Doppler radar capable of continuously monitoring cloud microphysical structure.
In addition to over 360 hours of cloud observations by the COS on Santa Maria,
observations of marine boundary-layer convective complexes were made during the
ASTEX. These structures were often characterized by a wide convective "tower"
(2-5 km in width) extending from near the surface lifting condensation level
upward to the inversion, where the cloud spread horizontally into an extensive
sheet of stratocumulus. In many cases, these structures had excessive drizzle
rates (occasionally over 2 mm/hr), overshooting cloud-tops, and long lifetimes.
Some of the structures were characterized by large equivalent potential
temperature signatures at the surface suggesting that the air had originated
higher in the boundary-layer.