Integration of observations for detection of aircraft icing conditions during AIRS2: Comparisons of microphysical parameters

Alliance Icing Research Study II (AIRS2) data have been used to better understand aircraft icing processes and the retrieval of microphysical parameters from satellite observations. AIRS2 was conducted in the southern Ontario-Quebec region in the winter of 2003-2004. Aircraft in-situ measurements were compared with retrievals obtained from GOES satellite observations and with observations obtained from ground-based platforms, including a microwave radiometer and an X-band vertical pointing Doppler radar. The in-situ data include liquid and ice particle number concentration, water content, particle effective size, temperature, icing-rate, and reflectivity from an airborne K-band radar. The case studies used in this work include (I) data from February 5,6, and 7, representing a cold front that generated mixed phase cloud conditions over a large area covering the Ohio region to NE of the Great lakes area and (II) data from the November 19 case that was also related to a cold front in the same region. The NRC Convair-580 flights used in this study are: 1) a flight over SW Lake Erie area, 2) a flight over Mirabel on Feb. 6, 3) a flight over Mirabel on Feb. 7, and 4) a flight over eastern Lake Ontario and Mirabel on Nov.19. The maximum LWC during Feb. 5-7 was measured at about 0.5 g m-3 at –13°C and 0.3 g m-3 at –20°C. The LWC also reached 0.5 g m-3 on Nov. 19 but cloud tops were glaciated based on the GOES retrievals. Supercooled large drops and drizzle were measured on all these flights. The pilots characterized these cases as having severe icing conditions. The NASA GOES icing scheme indicated icing for the Feb. 5-7 case but not for the Nov. 19 case. The McGill vertically pointing radar observations also indicated that icing was consistent with the in-situ data for all cases. The preliminary results indicated that observations should be integrated in order to better understand remote sensing retrievals and icing environments.