CALIOP Version 4 Observations of Global Cirrus Cloud Visible Extinction and Ice Mass Distribution in the Tropical TTL

Using the newly released Version 4, Level 2 Cloud and Aerosol LIdar with Orthogonal Polarization (CALIOP) data set, we show the ten-year climatology and inter-annual variability in the distribution of cloud fraction, convective cloud fraction, and cloud ice water content in the global tropical tropopause layer (TTL).  The Version 4 CALIOP calibration has improved the accuracy and detection limit of backscatter coefficients from thin cloud layers in the TTL.  The space-based lidar is rarely fully attenuated at altitudes above 14 km, and detects a bi-modal distribution of layer-integrated backscatter from cirrus clouds.  The distribution is dominated by sub-visible cirrus preferentially occurring near the cold point tropopause, but also shows a second mode of convective clouds that extend into the TTL.  We will evaluate the standard Version 4 extinction and ice water content using in situ measurements of ice particle size and area distributions from the SPEC, Inc. fast forward-scattering and 2D-S cloud probes, as well as direct ice water content measurements from the NOAA total water instruments during recent aircraft field missions.