Marine Boundary Layer Cloud Characteristics Defined From Surface-Based Remote Sensors

A suite of remote sensors was located on the island of Santa Maria in the Azores during the Atlantic Stratocumulus Transition Experiment (ASTEX). Various types and amounts of boundary layer clouds were observed during the one-month period (June 1992) of intensive observations. Cloud statistics and characteristics for this period are obtained from data collected with a 94 Hz radar, a laser ceilometer, a microwave radiometer, and a narrow-beam IR radiometer operating at 9.5-11.5 microns. The cloud radar is used to define cloud top and the occurrence of drizzle. The laser ceilometer is used to define cloud-base height and statistics on cloud cover. Statistics on cloud depth are obtained by combining cloud top heights from the radar and cloud base height from the ceilometer. The microwave radiometer gives cloud liquid water path and the IR radiometer provides cloud-base radiance. The percentage of time that clouds can be detected with each of these instruments will be compared. These comparisons will be made for thin, broken, and solid cloud conditions. Diurnal variations in cloud characteristics will be defined.