About the NIC IMS Products

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Interactive Multisensor Snow and Ice Mapping System (IMS)

IMS Daily Northern Hemisphere Snow & Ice Analysis

Introduction

The National Oceanic and Atmospheric Administration / National Environmental Satellite, Data, and Information Service (NOAA/NESDIS) has an extensive history of monitoring snow and ice coverage. Accurate monitoring of global snow/ice cover is a key component in the study of climate and global change as well as daily weather forecasting.

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). The 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 sea and lake ice. With several other derived snow/ice products of varying accuracy, such as those from NCEP and the NWS 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 snowcover 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 SAB to produce snow/ice analyses at a higher resolution and on a daily basis (~25 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 has been produced since February, 1997 by SAB meteorologists on the IMS.

Another large resolution improvement began in early 2004, when improved technology allowed the SAB to begin creation of a daily ~4 km (6144x6144) grid. At this time, both the ~4 km and ~24 km products are available from NSIDC with a slight delay. Near real-time gridded data is available in ASCII format by request.
In March 2008, the product was migrated from SAB to the National Ice Center (NIC) of NESDIS. The production system and methodology was preserved during the migration. Improved access to DMSP, SAR, and modeled data sources is expected as a short-term from the migration, with longer term plans of twice daily production, GRIB2 output format, a Southern Hemisphere analysis, and an expanded suite of integrated snow and ice variable on horizon.

For information on requesting this data, please contact the NIC IMS Manager or the NIC Liaison

II. Purpose

The purpose of the Interactive Multisensor Snow and Ice Mapping System (IMS) is to provide SAB analysts with the ability to interactively create, save, and distribute highly accurate maps depicting the extent of daily hemispheric snow and ice coverage. In order to assist the user in making snow/ice determinations, the IMS incorporates a wide variety of satellite imagery (AVHRR, GOES, SSMI, etc.) as well as derived mapped products (USAF Snow/Ice Analysis, AMSU, AMSR-E, NCEP models, etc.) and surface observations. The product is presently used as an operational input into several NWS computer weather prediction models as well as several other governmental agencies.