Global and Regional Patterns in High Ice Water Content Conditions

View More View Less
  • 1 National Center for Atmospheric Research, Boulder, CO
  • 2 University of Colorado, Boulder, CO
  • 3 Bureau of Meteorology, Melbourne, Australia
© Get Permissions
Restricted access

Abstract

High ice water content (HIWC; defined herein as at least 1.0 g m−3) conditions are often found in the anvils of convective systems and can cause engine damage and/or failure in aircraft. We use ice water content (IWC) retrievals from satellite-borne radar and lidar (CloudSat and CALIOP) to provide the first analysis of global HIWC frequency using 11 years of data (2007 to 2017). Results show HIWC is generally present in 1 to 2% of CloudSat and CALIOP IWC retrievals between flight levels 270 (27,000 ft or 8.230 km) and 420 (FL420; 42,000 ft or 12.801 km) in areas with frequent convection. Similar rates of HIWC are found over midlatitude oceans at relatively low altitudes (below FL270). Possible non-convective mechanisms for the formation of this low-level HIWC are discussed, as are the uncertainties suggesting the results at these low altitudes are an overestimation of the true threat of HIWC to aircraft engines. The satellite IWC retrievals are also used to validate a HIWC diagnostic tool which provides storm-scale statistics on HIWC over the Contiguous United States (CONUS) during the summer convective season (May through August, 2012 to 2019). Results over the CONUS suggest HIWC over the Great Plains is highest in June, when a point in the region is under HIWC conditions about 25 hours out of 30 days on average. The mean area-equivalent diameters of HIWC conditions in some areas of the Great Plains exceeds 350 km and the conditions can persist for 4 to 5 hours.

Corresponding Author: Allyson Rugg, PO Box 3000, National Center for Atmospheric Research, Boulder, CO 80307 arugg@ucar.edu

Abstract

High ice water content (HIWC; defined herein as at least 1.0 g m−3) conditions are often found in the anvils of convective systems and can cause engine damage and/or failure in aircraft. We use ice water content (IWC) retrievals from satellite-borne radar and lidar (CloudSat and CALIOP) to provide the first analysis of global HIWC frequency using 11 years of data (2007 to 2017). Results show HIWC is generally present in 1 to 2% of CloudSat and CALIOP IWC retrievals between flight levels 270 (27,000 ft or 8.230 km) and 420 (FL420; 42,000 ft or 12.801 km) in areas with frequent convection. Similar rates of HIWC are found over midlatitude oceans at relatively low altitudes (below FL270). Possible non-convective mechanisms for the formation of this low-level HIWC are discussed, as are the uncertainties suggesting the results at these low altitudes are an overestimation of the true threat of HIWC to aircraft engines. The satellite IWC retrievals are also used to validate a HIWC diagnostic tool which provides storm-scale statistics on HIWC over the Contiguous United States (CONUS) during the summer convective season (May through August, 2012 to 2019). Results over the CONUS suggest HIWC over the Great Plains is highest in June, when a point in the region is under HIWC conditions about 25 hours out of 30 days on average. The mean area-equivalent diameters of HIWC conditions in some areas of the Great Plains exceeds 350 km and the conditions can persist for 4 to 5 hours.

Corresponding Author: Allyson Rugg, PO Box 3000, National Center for Atmospheric Research, Boulder, CO 80307 arugg@ucar.edu
Save