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Instrument: CLS : Cloud Lidar System
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The Cloud Lidar System (CLS), which was operated from the left ER2 superpod, measured the backscatter cross-sections of cloud and aerosol particles at 1.064 and 0.532 microns. It was used in the TOGA/COARE experiment primarily to profile clouds below the flight level of the aircraft which was typically 18.0-20.5 km. In cases where the cloud optical thicknesses were small, boundary layer aerosol backscatter signals were detectable. The 0.532 micron lidar return was split into signals that were parallel and perpendicular to the outgoing laser radiation, thereby providing polarization sensitive data principally for cloud particle phase state detection. The cloud lidar provided information on the internal vertical structure of optically thin clouds which aids in the determination of the overall influence of such clouds on the radiative balance in both the shortwave and longwave portions of the spectrum. Another principal application that was planned for the ER2 CLS was the study of radiative heating and cooling rates for tropical cirrus. The CLS provided a detailed picture of internal cloud structure which aided in the interpretation of visible, infrared, and microwave radiometric data when they are applied to the determination of radiative fluxes and forcing. The lidar signal was useful up to a maximum optical thickness of 3 to 4. It provided the locations of cloud layer boundaries, both vertically and horizontally, which was useful in most types of cloud studies. The CLS can provide information on cloud particle characteristics. Depolarization of the laser pulses detected at the green wavelenghts can reveal water phase state of the particles. CLS backscatter information, when combined with multispectral radiometric observations, can be used in the determination particle size and concentration within the clouds. The lidar also gathered data on boundary layer heights and aerosol backscatter cross-sections. From the distribution of cloud base heights in and around the marine boundary layer, an estimate of the LCL (lifting condensation level) can be obtained. When combined with the sea surface temperature this could provide a measure of the moisture content. From the intensity of the lidar return, estimates of cloud liquid water are possible.

[Summary provided by NASA]