Retrieval Of Air-Sea CO₂Transfer Velocity Based On Calipso Lidar Production

Cloud aerosol lidar with orthogonal polarization （CALIOP） is one of thepayloads of the Cloud Aerosol Lidar and Infrared Pathfinder Satellite Observation（CALIPSO） mission, which can produce laser pulses of532nm and1064nm.According to the theory of geometry optics, the wavelength of laser pluses is shorterthan those of the sea surface waves, so the lidar can measure mean square slope of allwavelengths. Mean square slope is more directly linked to the gas transfer velocitythan wind speed, and and it can be accurately measured from CALIPSO lidar, so thelidar data can be used to investigate the relation between air sea CO₂transfer velocityand the sea surface mean square slope.Because rain has a large effect on the gas transfer velocity, the non zero rain ratefilter criteria is added during the lidar data processing. Sea surface mean squareslope σ2derived from four months （January, April, July and October,2007） lidar datais related to air sea gas transfer velocity k660calculated by wind speed data usingWanninkhof k660U10relationship. The wind speed data is provided by collocatedAdvanced Microwave Scanning Radiometer for the Earth Observing System（AMSR E）. Finally a segmented exponential k2660σrelationship is obtained. The gastransfer velocity retrieved using the segmented exponential relationship is comparedanalyzed with that estimated from four conventional wind speed parameterizations oftransfer velocity. In low and moderate wind speed conditions, the new relationship hasa strong correlation with others.Monthly （January, April, July and October） and annual mean air sea CO₂fluxesin2007are also discussed, with the solubility of CO₂in seawater calculated byAMSR E sea surface temperature and World Ocean Atlas （WOA） salinity data and theCO₂partial pressure between surface ocean and air provided byAtlantic Oceanographic andMeteorological Laboratory（AOML）. Because of the effort of seasonal changes in watertemperatures, biological utilization of CO₂and water mixing as well as changes in wind speeds, four monthly mean global air sea CO₂fluxs show seasonal CO₂sink/source variation in mid latitude regions. The CO₂sink is located in20°⁵0°latitudes of both hemispheres and the Southern Ocean and the large CO₂source islocated in equatorial Pacific region. The distribution characteristics of air sea CO₂flux is similar to those of AOML flux results.