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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

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.

Additional information available at

[Summary provided by NASA]