Recently, two types of ice clouds (TICs) properties have been characterized using the Indirect and SemiDirect Aerosol Campaign (ISDAC) airborne measurements (Alaska, April 2008). TIC-2B were characterized by fewer (< 10 L−1) and larger (> 110 μm) ice crystals, and a larger ice supersaturation (> 15 %) compared to TIC-1/2A. It has been hypothesized that emissions of SO2 may reduce the ice nuclea...