The Interactive Multisensor Snow and Ice Mapping System (IMS) is an operational software package for analyzing snow nd ice coverage. This software enables qualified analysts to look at various satellite imagery and derived products (from GOES, Himawari, METEOSAT, JPSS, POES, EOS, DMSP), radar, models and ground station data in order to make an informed decision as to snow and ice cover over the Northern Hemisphere at 1-km resolution. The National Centers for Environmental Prediction (NCEP) relies on IMS for snow cover and lake cover initialization for its multiple models. The twice daily analysis also serves as a data source supporting NOAA’s hydro-meteorological and climate programs, as well as numerous university and private institutional studies.
The Polar and Geostationary Operational Environmental Satellite programs (POES/GOES) operated by NESDIS provide invaluable visible and infrared spectral data in support of these efforts. Clear-sky imagery from both the POES and the GOES sensors show snow/ice boundaries very well; however, the visible and infrared techniques may suffer from persistent cloud cover near the snowline, making observations difficult (Ramsay, 1995). Microwave products (DMSP and AMSR-E) are unobstructed by clouds and thus can be used as another observational platform in most regions. Synthetic Aperture Radar (SAR) imagery also provides all-weather, near daily capacities to discriminate between sea and lake ice. With several other derived and modeled snow/ice products of varying accuracy, such as those from the National Centers for Environmental Prediction (NCEP), the Center for Satellite Applications and Research (STAR), and the The National Operational Hydrologic Remote Sensing Center (NOHRSC), it is highly desirable for analysts to be able to interactively compare and contrast the products so that a more accurate composite map can be produced.
The Satellite Analysis Branch (SAB) of NESDIS first began generating Northern Hemisphere Weekly Snow and Ice Cover analysis charts derived from the visible satellite imagery in November, 1966. The spatial and temporal resolutions of the analysis (190 km and 7 days, respectively) remained unchanged for the product's 33-year lifespan. However, these resolutions and other shortcomings had been shown to cause errors in the National Meteorological Center's Numerical Weather Prediction (NWP) models (Mitchell, 1993). The weekly update often missed changes in snow cover which occurred on a daily basis. Further, erroneous snowcover in the NWP models contributed to significant errors in low-level air temperatures forecasts, leading to inaccurate predictions of rainfall versus snowfall (Murphy, 1993).
As a result of increasing customer needs and expectations, it was decided that an efficient, interactive workstation application should be constructed which would enable analysts to produce snow/ice analyses at a higher resolution and on a daily basis (~24 km / 1024 x 1024 grid and once per day) using a consolidated array of new as well as existing satellite and surface imagery products. The Daily Northern Hemisphere Snow and Ice Cover chart began to be produced in February, 1997 by SAB meteorologists on the newly created Interactive Multisensor Snow and Ice Mapping System (IMS).
Another large resolution improvement began in early 2004, when improved technology allows analysts to begin creation of a daily ~4 km (6144x6144) grid.
In March 2008, the product was migrated from SAB to the USNIC. The production system and methodology was preserved during the migration. Since migrating to the USNIC, the IMS has seen improvements in the number and quality of satellite resources available to analysts with several multi-spectral satellite composites being created, an increase in the amount of SAR data being made available, and the addition of additional data sources such as AMSR-2.
Since the IMS migrated to the NIC, several other major upgrades have improved the quality of the analysis. While the IMS is still updated daily for the entire northern hemisphere, North America and the surrounding waters are updated twice daily - valid at 18Z and 0Z. Additionally, the IMS analysis has been produced on a 1 km (24,576 x 24,576) grid, in addition to the 4 and 24 km resolutions, since 2014. The 1 and 4 km resolution analysis are also available in GRIB2 and GeoTIFF formats.
The sea-ice and snow analyses produced at the U.S. National Ice Center (USNIC) have long been recognized by many in the scientific community as valuable for applications such as validating remote sensing algorithms, planning field experiments, and for process studies where accurate information about ice conditions on a local or regional scale is required. The National Snow and Ice Data Center (NSIDC) has archived and documented a selection of USNIC products, beginning in the 1970s with analog (paper) charts from what was then called the Joint Ice Center. This archive can be accessed at https://nsidc.org/data/g02156.
"The Interactive Multisensor Snow and Ice Mapping System" by Bruce H. Ramsay (Adobe PDF 1.2MB)
"Prospects for the Interactive Multisensor Snow and Ice Mapping System (IMS)" by Bruce H. Ramsay (Adobe PDF 565KB)
"Enhancements to, and forthcoming developments in the Interactive Multisensor Snow and Ice Mapping System (IMS)" by Sean R. Helfrich (Adobe PDF 805KB)