HIGH-RESOLUTION PROPERTIES OF THE EQUATORIAL PACIFIC MARINE ATMOSPHERIC BOUNDARY-LAYER FROM LIDAR AND RADIOSONDE OBSERVATIONS

A ''thermostat'' mechanism for cooling the Equatorial Pacific is being tested with data collected during the Central Equatorial Pacific Expe riment. The Los Alamos National Laboratory participated by fielding tw o shipboard lidars that collected nearly continuous data over the Paci fic from 10 to 21 March 1993 as the ship sailed from Guadalcanal to Ch ristmas Island. A Raman lidar measured water vapor mixing ratio in the lower troposphere, especially in the marine atmospheric boundary laye r (ABL), and an aerosol backscatter lidar measured height and thicknes s of clouds to an altitude of 20 km. The data collected from these two lidars were used to determine ocean-atmosphere phenomenology, which i n turn, affects the climatology of the Central Pacific. Agreement betw een coincident radiosonde and the Raman water vapor lidar measurements was typically within +/-0.25 g kg(-1) of water. Divergence between th e two instruments occurred at transitions between distinct layers in t he lower marine atmosphere. Reasons for this divergence will be discus sed. Above the ABL the lidar and radiosonde are in excellent agreement . A wealth of detail is apparent in the lidar-derived profiles. For ex ample, there are large variations in water vapor mixing ratio-the expr ession of the inherent low-frequency, intermittent, atmospheric turbul ence that produces spatially discrete features such as convective plum es. These features define the structure and extent of the ABL. Using t he ABL structural characteristics, an analysis of the relationship bet ween entrainment zone (EZ) height and observed sea surface temperature (SST) revealed counterintuitive behavior-that the height of the EZ de creases as SST increases in the range between 27 degrees and 30 degree s C.