Ice fog (pogonip) and frost in Arctic: application to aviation

Ice fog and frost occurs very often in the northern latitudes and Arctic regions during winter; ice fog occurs about 20% of time at temperatures (T)<-20C. Ice fog is strongly related to frost formation, a major reason for aircraft deicing that is considered more dangerous than snow because frost has greater tendency than snow particles to adhere to aircraft surfaces. The goals of this work are to better understand 1) physical processes for ice fog formation, 2) the relation of ice fog to frost occurrence, 3) the importance of ice fog for aviation, and to develop 4) skills for ice fog nowcasting using remote sensing and surface observations and model forecasts. At the low temperatures, snow/ice crystal water equivalent (SWE) can be very low e.g. 2-3%, and it can be swept by very low wind speed (e.g. 1 m/s). Therefore, motivation for deicing chemicals use in the north is likely related to frost and ice fog conditions. During Fog Remote Sensing and Modeling (FRAM)-ICE project, approximately 40 different sensors were used to observe various visibility, precipitation, and ice particle spectra; Profiling MicroWave Radiometer (PMWR) based vapor mixing ratio, T, and liquid water content; and satellite based fog coverage. During the 2 month project, snow precipitation rarely exceeded 6 cm per day and the total snow amount was about 20 cm with SWE about 3-5% usually. Clear skies were dominant approximately 60% of the time and an inversion layer existed almost everyday between surface and 1 km height. Ice fog during the project was not predicted by the any forecast. Project results and related challenges in the northern latitudes will be presented.