title: Atmospheric CO(2) column measurements in cloudy conditions using intensity-modulated continuous-wave lidar at 1.57 micron.
abstract: This study evaluates the capability of atmospheric CO2column measurements under cloudy conditions using an airborne intensity-modulated continuous-wave integrated-path-differential-absorption lidar operating in the 1.57-μm CO2absorption band. The atmospheric CO2column amounts from the aircraft to the tops of optically thick cumulus clouds and to the surface in the presence of optically thin clouds are retrieved from lidar data obtained during the summer 2011 and spring 2013 flight campaigns, respectively. For the case of intervening thin cirrus clouds with an average cloud optical depth of about 0.16 over an arid/semi-arid area, the CO2column measurements from 12.2 km altitude were found to be consistent with the cloud free conditions with a lower precision due to the additional optical attenuation of the thin clouds. The clear sky precision for this flight campaign case was about 0.72% for a 0.1-s integration, which was close to previously reported flight campaign results. For a vegetated area and lidar path lengths of 8 to 12 km, the precision of the measured differential absorption optical depths to the surface was 1.3 - 2.2% for 0.1-s integration. The precision of the CO2column measurements to thick clouds with reflectance about 1/10 of that of the surface was about a factor of 2 to 3 lower than that to the surface owing to weaker lidar returns from clouds and a smaller CO2differential absorption optical depth compared to that for the entire column.
authors.forename: Bing
authors.initials: B
authors.lastname: Lin
authors.forename: Amin R
authors.initials: AR
authors.lastname: Nehrir
authors.forename: F Wallace
authors.initials: FW
authors.lastname: Harrison
authors.forename: Edward V
authors.initials: EV
authors.lastname: Browell
authors.forename: Syed
authors.initials: S
authors.lastname: Ismail
authors.forename: Michael D
authors.initials: MD
authors.lastname: Obland
authors.forename: Joel
authors.initials: J
authors.lastname: Campbell
authors.forename: Jeremy
authors.initials: J
authors.lastname: Dobler
authors.forename: Byron
authors.initials: B
authors.lastname: Meadows
authors.forename: Tai-Fang
authors.initials: TF
authors.lastname: Fan
authors.forename: Susan
authors.initials: S
authors.lastname: Kooi