Assessment of one-dimensional icing forecast model applied to stratiform clouds

Aircraft icing can seriously impair aircraft performance. In this paper we assess a one-dimensiona l icing forecast model (presently residing at the U.S. Army Atmospheric Sciences Laboratory) by using recent airborne collected microphysics data. Our prime interest was the variation of potential aircraft icing in stratiform clouds. We discuss the icing model microphysics, including algorithms used to determine icing severity indices, temperature, liquid water content (LWC), and median volume diameter (MVD) of supercooled water droplets. Output from the one-dimensional model suggests that the icing potential in stratiform clouds does not exceed light. The model more often forecasts trace icing for both fixed-wing aircraft and helicopters. The model does not compute a value for LWC great enough to allow for more serious icing events. We therefore conclude that a method must be established to obtain better estimates of drop-size characteristics and LWC (for stratus clouds) to forecast the full range of potential icing for Army aircraft. Otherwise when using the one-dimensional model as currently structured, one would not expect any more than light icing when stratus clouds are observed.