A lidar and backscatter sonde measurement campaign at Table Mountain during February-March 1997: Observations of cirrus clouds

Results from a measurement campaign performed at Table Mountain Facility/Je t Propulsion Laboratory/California Institute of Technology (34.38 degreesN, 117.68 degreesW, 2280 m ASL) are presented. Between 19 February and 18 Mar ch 1997 more than 400 h worth of lidar data were acquired and four backscat ter sondes were launched. About 50% of the observations show the presence o f cirrus clouds at altitudes close to and below the tropopause. Of these cl ouds 80% are characterized as subvisual with optical depths below 0.03 at a wavelength of 532 nm. Simple geometrical considerations lead to cloud spat ial scales of 0.31 km vertically and 7.5 km horizontally, respectively. Dev iations from color ratio values derived on the basis of geometrical optics are interpreted as small particle signatures. Comparing backscatter ratio p rofiles observed concurrently by three aerosol lidars, mean deviations of a bout 10% are found.