Characterization of In-Flight Icing Conditions on the SOCRATES Mission Using Airborne Radar and Lidar Data in Conjunction with In Situ Cloud Measurements

The Southern Ocean Cloud, Radiation, and Aerosol Transport Experimental Study (SOCRATES) project used the NSF/NCAR Gulfstream V aircraft to take measurements in the data sparse Southern Ocean region between Australia and Antarctica. The aircraft payload included sensors for observing the full range of cloud and precipitation particles. Observations often included supercooled liquid water (SLW) conditions. SLW is known to be responsible for hazardous aircraft icing conditions. Supercooled large drop (SLD) icing is especially dangerous. SLD icing conditions were deemed present if the maximum drop size diameter (Dmax) from the liquid drop size distribution was greater than 100 μm.

Particle types were retrieved from HIAPER Cloud Radar (HCR) and High Spectral Resolution Lidar (HSRL) measurements. The retrieval technique uses a fuzzy-logic algorithm (Vivekanandan et al., 1999). The HCR and HSRL measurement boundaries for identifying various types of precipitation particles were based on results presented in Shupe (2007). By using this scheme, locations of SLW and SLD above and below the aircraft can be identified. By comparing areas where icing conditions were observed in situ, the performance of the HCR/HSRL retrieval for diagnosing icing conditions and distinguishing between SLW and SLD can be assessed.

In this study, a comprehensive picture of icing conditions in SOCRATES will be created using HCR and HSRL particle identification in conjunction with in-situ observations collected from the aircraft. This effort will expand the utility of the SOCRATES data set for evaluating satellite icing products (Smith et al., 2019) and Significant Meteorological Advisories (SIGMETs) by identifying icing conditions while the aircraft operated above, below or within clouds.

Shupe, M. D., 2007: A ground-based multisensor cloud phase classifier. JGR, VOL. 34, L22809, doi:10.1029/2007GL031008.

Smith, W.L., C. Wang, D. Spangenberg, S. Bedka, and P. Minnis, 2019: Exploring GOES-16 Data to Improve Aircraft Icing Diagnoses. 2019 Joint Satellite Conference, American Meteorol. Soc., 30 Sept - 1 Oct 2019, Boston, MA.

Vivekanandan, J., D. S. Zrnic, S. M. Ellis, R. Oye, A. V. Ryzhkov, and J. Straka, 1999: Cloud microphysics retrieval using S-band dual-polarization radar measurements. Bull. Amer. Meteor. Soc., 80, 381-388.