Inter-annual and Seasonal Variation of UT/LS Cloud Ice Water Content in the Asian Monsoon as Observed by CALIPSO

The Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) project has recently included a new cloud ice water content product in the V3.01 data release. CALIPSO ice water content (IWC) is parameterized from Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) cloud extinction measurements. The parameterization is derived from in-situ cloud probe measurements from a variety of aircraft field campaigns. CALIOP extinction retrievals are most accurate in the highest level of bright clouds where the backscatter signal to noise ratio is largest. Therefore, CALIPSO is ideally suited for characterization of cloud IWC in the climate-sensitive upper troposphere/lower stratosphere (UT/LS) between 10-18 km, including the Tropical Tropopause layer (TTL). The CALIOP lidar has been operational since June, 2006, providing 4 years of global UT/LS IWC measurements. The straightforward nature of the extinction-based CALIPSO IWC parameterization is ideal for assessing regional distributions and temporal variability in UT/LS cirrus cloud ice water content. Currently much scientific interest is focused on the TTL in the Asian Monsoon and Western Pacific as a major global source of energy, water and anthropogenic particles and gases to the lowermost stratosphere. Two major upcoming NASA aircraft field missions will study this region - the Earth Venture Airborne Tropical Tropopause Experiment (ATTREX) and the Southeast Asia Composition, Cloud, Climate Coupling Regional Study (SEAC4RS). CALIPSO IWC measurements in the UT/LS over the past 4 years can inform the planning of these missions, and provide a context for understanding the seasonal and inter-annual variation in cirrus clouds associated with the monsoon cycle and related deep convection. In this paper we present both maps and statistics of the regional distribution and seasonal cycle of ice water content in the UT/LS as measured by CALIPSO in the Asian Monsoon and Pacific region from August 2006 - August 2010. In addition to presenting IWC and its associated uncertainties measured by CALIOP, we also compare our measurements with other IWC observations and estimate the IWC accuracy.