The interactive multisensor snow and ice mapping system

The interactive multisensor snow and ice mapping system (IMS) was developed to give snow and ice analysts the tools, on one platform, to inspect visually the imagery and mapped data from various sensor sources to determine the presence of snow and ice and to depict snow- and ice-covered areas on a map on a daily basis, in one hour or less. Snow and ice analysts in the National Environmental Satellite, Data, and Information Service have been creating weekly maps showing the extent of snow cover for the Northern Hemisphere since 1966 using visible imagery from polar-orbiting and geostationary satellites and surface observations as data sources. The current process is mostly manual and time-consuming, taking up to 10 hours to produce a map during the snow season. Where cloud cover precludes an unobstructed view of an area during the entire week, the analysis from the previous week is carried forward. Each week the analyst draws a new map by hand, then digitizes the extent of snow and ice cover using an 89×89 line grid overlaid on a stereographic map of the Northern Hemisphere. The hand-drawn map is photocopied and distributed and the digitized map is saved to a file for use in National Weather Service numerical models and for archival storage. IMS was designed and built to replace and improve this process by producing a more accurate and timely product. © 1998 John Wiley & Sons, Ltd.