A Prototype Method for Diagnosing High Ice Water Content Probability Using Satellite Imager Data

Recent studies have found that flight through deep convective storms and ingestion of high mass concentrations of ice crystals, also known as high ice water content (HIWC), into aircraft engines can adversely impact aircraft engine performance. These aircraft engine icing events caused by HIWC have been documented during flight in weak reflectivity regions near convective updraft regions that do not appear threatening in onboard weather radar data. Three airborne field campaigns were conducted in 2014 and 2015 to better understand how HIWC is distributed in deep convection, both as a function of altitude and proximity to convective updraft regions, and to facilitate development of new methods for detecting HIWC conditions, in addition to many other research and regulatory goals. This paper describes a prototype method for detecting HIWC conditions using geostationary (GEO) satellite imager data coupled with in-situ total water content (TWC) observations collected during the flight campaigns. Three satellite-derived parameters were determined to be most useful for determining HIWC probability: 1) the horizontal proximity of the aircraft to the nearest overshooting convective updraft or textured anvil cloud, 2) tropopause-relative infrared brightness temperature, and 3) daytime-only cloud optical depth. Statistical fits between collocated TWC and GEO satellite parameters determine the membership functions for the fuzzy logic derivation of HIWC probability. The products are demonstrated using data from several campaign flights and validated using a subset of the satellite-aircraft collocation database. We found that the daytime HIWC probability agrees quite well with TWC time trends and identifies extreme TWC events with high probability. Discrimination of HIWC is more challenging at night with IR-only information. The products show the greatest capability for discriminating TWC ³ 0.5 g m^-3, the 65^th percentile of TWC observed during the 50 flights across three campaigns. Product validation remains challenging due to vertical TWC uncertainties and the typically coarse spatio-temporal resolution of the GEO data.