A ground-based remote icing detection system (GRIDS) perspective on the November 11, 2003 SLD case during AIRS2

On 11 November 2003, the Ground-based Remote Icing Detection System (GRIDS), captured a marked transition in cloud composition that moved across the AIRS II field program suite of instruments, based at Montreal's Mirabel Airport. Glaciated clouds, which presented little, if any icing threat, gave way to warm-topped, stably-stratified, water dominated cloud at subfreezing temperatures. As documented by in-situ aircraft sampling, these clouds featured significant water contents and supercooled large drops (SLD) with diameters exceeding 300 microns, resulting in moderate and even moderate-to-severe icing conditions. Most telling of the transition from the GRIDS' perspective, was a significant change in the depolarization ratio, from that indicative of ice to that of liquid droplets.