The South Pole Atmospheric Radiation and Cloud Lidar Experiment (SPARCLE)

Longwave radiation spectra emitted by clouds, greenhouse gases, and the snow surface are being measured at South Pole Station using the Polar Atmospheric Emitted Radiance Interferometer (PAERI). This experiment is currently underway from November 2000 to November 2001. The PAERI spectra are being used to improve atmospheric radiation models of the water-vapor greenhouse effect, and to quantify the contributions of water vapor, carbon dioxide, ozone, and clouds to the longwave energy budget of the Antarctic Plateau. The spectra are also being used for groundbased remote sensing of cloud base heights, cloud optical depths, and sizes of cloud ice crystals and water droplets. The interferometer can be configured as a transmissometer to measure absorption of water vapor along a horizontal path near the surface. The vertical distribution of backscattering by ice crystals in clouds is measured by a micropulse lidar. Ice crystals in clouds, as well in diamond dust and blowing snow, are sampled by a hydrometeor videosonde (HYVIS) flying on a tethered balloon, and are also collected at the surface as they fall, for photomicroscopy. The balloon also carries a frost-point hygrometer to measure humidity in the lowest kilometer of the atmosphere, for use in explaining the ice crystal shapes observed and to constrain the radiation modeling.