57th EASTERN SNOW CONFERENCE 

Syracuse, New York, USA, 2000 

Prospects for the Interactive 

Multisensor Snow and Ice Mapping System (IMS)

BRUCE H. RAMSAY1

ABSTRACT 

The National Oceanic and Atmospheric Administration’s National Environmental Satellite, 

Data, and Information Service (NOAA/NESDIS) operationally implemented the daily Interactive 

Multisensor Snow and Ice Mapping System (IMS) in 1997. This geographic information system 

replaced the manual Northern Hemispheric weekly snow mapping process in 1999, and its 

products are used as input to the National Weather Service’s Eta model. Preliminary validation of 

the daily product was completed in 1998. A more rigorous validation of the daily product with 

respect to its use in the continuance of the climatologies produced from the weekly snow and ice 

maps is underway. Output from an experimental automated snow and ice mapping algorithm for 

North America, using visible and infrared imagery from NOAA’s Geostationary Operational 

Environmental Satellite Imager and microwave data from the Defense Meteorological Satellite 

Program’s Special Sensor Microwave/Imager, is under evaluation by operational meteorologists in 

NOAA/NESDIS for potential use as a first guess in IMS. In addition, 1.6 Φm imagery from the 

NOAA-15 satellite’s Advanced Very High Resolution Radiometer/3, and snow and ice products 

from the National Aeronautics and Space Administration’s Moderate Resolution Imaging 

Spectroradiometer, aboard the Earth Observing System Terra satellite, are under evaluation for 

potential inclusion in IMS. This paper presents a brief overview of the current IMS and its near 

future prospects. 

Key Words: Mapping, Remote sensing, Snow cover 

 

1

 Land Scientist, NOAA/NESDIS/Office of Research and Applications (E/RA11), Room 712-T, NOAA 

Science Center, 5200 Auth Road, Camp Springs, Maryland 20746-4304, USA 

email: bramsay@nesdis.noaa.gov 
INTRODUCTION

 NOAA/NESDIS prepares a daily snow and ice chart of the Northern Hemisphere (NH). Chart 

preparation is performed by a meteorologist through the inspection of visible imagery from 

sensors on-board geostationary satellites including the Geostationary Operational Environmental 

Satellite (GOES), the Meteorological Satellite (METEOSAT), and the Geostationary 

Meteorological Satellite (GMS), polar orbiting satellites including the Polar-orbiting Operational 

Environmental Satellite (POES), and imagery from the Defense Meteorological Satellite 

Program=s (DMSP) Special Sensor Microwave/Imager (SSM/I), as well as sea ice charts from the 

National Ice Center and ground weather observations. The areal coverage of snow and ice is 

charted on a map with a polar stereographic projection centered on the North Pole (Ramsay 1998). 

Weekly charts, made largely by hand, were produced from 1966 to 1999. Figure 1 shows a hand 

drawn snow and ice chart of the NH for the week of 09-15 November 1998 (Office of Research 

and Applications 1998). NOAA/NESDIS meteorologists have created daily charts through the use 

of the Interactive Multisensor Snow and Ice Mapping System (IMS) since 1997. The two year 

overlap period from 1997 to 1999 provided a data set of manual weekly and IMS daily charts for 

comparison and validation of the IMS daily maps. NOAA’s National Weather Service (NWS) has 

used the IMS daily maps in a regional Numerical Weather Prediction (NWP) model since June 

1998. The complete 34 year satellite-derived snow and ice chart data set is used in climate analysis 

(Robinson 2000; Robinson et al. 1993). The purpose of this paper is to outline likely near-term 

future enhancements to IMS. 

DISCUSSION 

The Interactive Multisensor Snow and Ice Mapping System

IMS, a geographic information system, was developed to permit meteorologists to interactively 

prepare daily NH snow and ice maps and to take advantage of additional remotely sensed imagery 

such as that based on DMSP passive microwave data from SSM/I. The previously used manual 

method in production of the weekly chart took eight to ten hours depending upon the season. 

Meteorologists using IMS routinely produce daily maps in under 90 minutes. IMS provides the 

opportunity for meteorologists to compare imagery and other snow and ice maps in the same scale 

and format to produce a more accurate product at higher spatial and temporal resolution than with 

the manual production of snow and ice maps. The spatial resolution of IMS charts are 23 

kilometers (km) while the weekly charts were prepared at 190 km. Figure 2 is an IMS snow and 

ice chart of North America for 12 March 2000 (Satellite Services Division 2000). The enhanced 

spatial and temporal resolution provided through IMS was sought by the NWS to improve NWP 

model output over North America. 

A preliminary analysis of the 1997 to 1998 NH snow season daily and weekly snow chart data 

sets indicated the daily IMS product was superior to the weekly product in accuracy as well as in 

its spatial and temporal resolution. Map accuracy was determined by resampling the higher 

resolution IMS daily maps produced on Mondays to the lower resolution of the weekly snow 

maps, also produced on Mondays, and then comparing both low resolution data sets to weather 

station reports. Additional validation of the data sets over the two year period is being continued. 

The integration of data from the daily snow maps into the Eta Data Assimilation System used by 

the NWS National Centers for Environmental Prediction over North America began on 03 June 

1998 (Environmental Modeling Center 1998). Figure 3 shows three Eta model horizontal grid 

domains over North America and extended areas at 48, 29, and 32 km resolution (Rogers et al. 

1999). Eta-32 is the most recent of the three grids implemented. The primary difference between 

the grids is their vertical resolution (not shown). 

Experimental Automated Snow Mapping System

NOAA/NESDIS developed an automated snow mapping system based on a decision tree 

algorithm. This system began experimental production in 1999. The algorithm uses GOES visible 
Figure 1. Northern Hemisphere Snow and Ice Boundary Chart for the week of 09–15 November 1998. 

and infrared imagery and SSM/I data. The experimental product currently provides coverage of 

North America and will be evaluated by NOAA/NESDIS operational meteorologists during the 

forthcoming 2000-2001 NH snow and ice season. One of the objectives is to evaluate this product 

as a potential first guess in IMS over North America. Figure 4 is a snow map from this system for 

12 March 2000 (Office of Research and Applications 2000). The most recent snow map from the 

automated snow mapping system may be viewed at (http://orbit-net.nesdis.noaa.gov/crad/sat/surf/ 

snow/HTML/snow.htm). Snow maps from August 1999 to the present, plus a new experimental 

snow fraction product for use in the Eta model, from March 2000 to the present, may also be 

accessed at this site. 
Figure 2. Snow and ice chart for North America from NOAA’s Interactive Multisensor Snow and Ice 

Mapping System for 12 March 2000. Snow is white, ice is light grey, land is medium grey, and water is dark 

grey. 

The NWS has a requirement for snow and ice products over the Southern Hemisphere (SH). 

Additional data sets and applicable methods of analysis are being considered to expand the 

algorithm to provide global coverage. Experimental regional products for areas over South 

America are planned for production this year. These products will also be evaluated for potential 

inclusion into IMS. 

Advanced Very High Resolution Radiometer/3 Channel 3A

NOAA’s newest addition to POES is NOAA-15. The NOAA-KLM satellite series has an 

upgraded Advanced Very High Resolution Radiometer (AVHRR) sensor, AVHRR/3. NOAA-K 

became NOAA-15 on its successful launch on 13 May 1998, and is in a morning orbit. Among 

other improvements to AVHRR/3, Channel 3 was split so that data may be collected at a new 

spectral range centered on 1.6 micrometers Φm), noted as Channel 3A , or in the previously 

configured 3.7 Φm spectral band, now designated as Channel 3B. Channel 3A was explicitly 

designed for use in the discrimination between snow cover and clouds. The albedo of clouds is 

higher than that of snow at 1.6 μm (Hall et al. 1998; Dozier 1989). The switch for Channel 3A and 

3B may only turn on one or the other channel, but not both simultaneously. The decision was 
Figure 4. Snow map of North America from NOAA’s Experimental Automated Snow Mapping System for 12 

March 2000. Snow is white, land is medium grey, water is dark grey. 

made to collect Channel 3A imagery for evaluation during part of the 1998-1999 NH snow and ice 

season but to leave Channel 3B turned on and in operational mode the rest of the time. NOAA-L is 

scheduled for launch in August 2000 in an afternoon orbit (Kidwell 1999). 

Two NOAA-15 AVHRR images taken at the same time of snow and ice cover over the U.S., 

from Ohio to New York, are displayed in Figure 5. They provide the opportunity for a visual 

comparison of imagery from Channel 1 and Channel 3A. The shortwave infrared image on the left 

Figure innumeric Interactive operationally the National 3.designations Shown Multisensor implemented Centers are theindicate for Snow threeEnvironmental in the horizontal and theEta horizontal IceData Mapping domains PredictionÕs Assimilation gridSystem, resolution of the originally Eta 48, System Eta inanalysis kilometers. Eta 29, onmapped 03andJune andforecasting Snow at1998 Eta 32 23 kilometer cover grids system. dataforresolution, fromNorth TheNOAAÕ EtaAmerica gridsÕ wa used
Figure 5. Images of snow and ice cover from the NOAA-15 Advanced Very High Resolution Radiometer for 

12 March 1999. The shortwave infrared image on the left is from Channel 3A (1.6:m) and the visible image 

on the right is from Channel 1 (0.63:m). Snow and clouds cover the area over south-central New York, 

central Pennsylvania, and soutern Ohio. It is difficult to differentiate snow cover from clouds in the Channel 

1 image (right); however, the clouds are much easier to identify as the bright white areas in the Channel 3A 

image (left). 

is from Channel 3A, and the visible image on the right is from Channel 1 (0.63 Φm). Clouds are 

not easily distinguished from the snow cover on the ground in the visible image on the right. 

However, the clouds can be seen as the bright white areas over southern Ohio, central 

Pennsylvania, and south-central New York, and can are readily differentiated from the snow cover 

in the image on the left (Operational Significant Event Imagery Team 1999). 

Initial evaluation of imagery from Channel 3A indicates a high potential value for use in 

creating new satellite-derived products, including snow maps, through channel differencing 

techniques (National Operational Hydrologic Remote Sensing Center, 2000; Hillger 1999). Plans 

have been implemented to develop an automated system to produce an AVHRR/3 experimental 

global snow and ice product based in part on the 1.6 m channel and to take advantage of the 

launch of NOAA-L during the 2000-2001 NH snow and ice season. NOAA-L will have Channel 

3A turned on in operational mode for the collection of imagery over areas north of 30 degrees 

latitude. Channel 3B will be turned on in operational mode the remainder of the time over areas 

not impacted by seasonal snow cover. The images used in Figure 5 may be viewed in an enlarged 

format at (http://www.osei.noaa.gov/Events/Snow/). This site also provides other images of snow 

and ice over the Southern Hemisphere, as well as the NH, from 1996 to the present. 

Moderate Resolution Imaging Spectroradiometer

The National Aeronautics and Space Administration (NASA) successfully launched the polar 

orbiting Earth Observation System (EOS) Terra satellite (formerly EOS AM-1) on 18 December 

1999. On-board is the Moderate Resolution Imaging Spectroradiometer (MODIS). MODIS has 36 

channels providing spectral coverage from the visible to thermal infrared which includes a 1.6 m 

band, Band 6. The MODIS global product suite includes daily maps of snow cover, sea ice, and 

lake ice at either 500 meter (m) or 1 km resolution as well as 8-day and monthly composites at 

smaller scale for use in climate modeling and analysis (Riggs et al. 2000; Hall et al. 1998). 

NOAA and NASA implemented a joint program in which a portion of the entire MODIS data 

stream transmitted, stored and processed by NASA, has been directed to a NOAA/NESDIS 

computer at NASA’s Goddard Space Flight Center in Greenbelt, Maryland. Near real-time 

imagery and data are being processed and will be sent to NOAA/NESDIS for evaluation and use 

by NOAA atmospheric, oceanic, and terrestrial operational and research communities in the near 
Figure 6. Snow and ice map of North America from NASA’s Moderate Resolution Imaging Spectroradiometer showing the maximum snow cover over an eight-day period from 05 March to 12 March 2000. 

Snow is white, clouds are light grey, land is medium grey, and water is dark grey. 

future. NOAA/NESDIS operational meteorologists will evaluate MODIS snow and ice imagery 

and products for potential use in IMS. 

The NASA-provided map derived from MODIS imagery in Figure 6 shows snow and ice cover 

over North America composited overan eight-day period from 05 to 12 March 2000 (Hall 2000). 

Although a composite map, a comparison by visual observation with the daily operational IMS 

snow and ice chart in Figure 2, and the daily experimental automated snow map in Figure 4 shows 

generally good agreement among the three products. This and other snow and ice products from 

MODIS may be viewed at (http://snowmelt.gsfc.nasa.gov/MODIS_Snow/modis.html). 

Initial Joint Polar System and the Meteorological Operational Satellite Program

The European Organisation for the Exploitation of Meteorological Satellites (EUMETSAT) and 

the U.S. entered an agreement on 19 November 1998 to provide a mutually supported polar 

orbiting operational satellite system called the Initial Joint Polar System (IJPS) starting in 2003. 

EUMETSAT will launch and maintain the Meteorological Satellite (METOP) in a morning orbit 

(European Organisation for the Exploitation of Meteorological Satellites, 1999). The U.S. will 

continue the NOAA polar orbiting satellite series in the afternoon orbit. Both satellites will carry a 
core set of sensors, including AVHRR/3 among others, to maintain the continuity of operational 

data and meteorological observations, such as those of snow and ice (Office of Systems 

Development 2000; European Space Agency 1999). Additional information on the background 

and implementation of the IJPS and METOP may be obtained at (http://discovery.osd.noaa. 

gov/IJPS/),(http://www.eumetsat.de/en/index.html?area=left2.html&body=/en/area2/cgms/ap9-12.

htm&a=284&b=2&c’280&d=200&e=0, or (http://www.esrin.esa.it/htdocs/esa/progs/METOP. 

html). 

National Polar-Orbiting Operational Environmental Satellite System

The future of the DMSP, operated by the Department of Defense (DOD) through the U.S. Air 

Force, and the POES program, run by the Department of Commerce (DOC) through NOAA, is in 

the merger of these two programs into the National Polar-orbiting Operational Environmental 

Satellite System (NPOESS). The Integrated Program Office (IPO) was established to oversee the 

successful convergence of these U.S. military and civilian polar orbiting satellite programs. The 

IPO is composed of representatives of the DOD, DOC, and NASA. The first NPOESS launch is 

schedule for 2008, after the current suite of POES and DMSP satellites have been placed in orbit. 

NASA is providing support for the development of new satellite and remote sensing technologies 

(NOAA Office of Public and Constituent Affairs 2000; Clinton 1994). Information on the IPO 

may be accessed at (http://www.ipo.noaa.gov/). The NPOESS Electronic Library may be viewed 

at (http://npoesslib.ipo.noaa.gov/). 

Visible/Infrared Imager/Radiometer Suite

One of the sensors to be flown on NPOESS is the Visible/Infrared Imager/Radiometer Suite 

(VIIRS). VIIRS will provide imagery on the areal extent of snow and ice cover at 500 m 

resolution (the requirement is subject to review at this time), as well as a binary map indicating 

snow or no snow, and a fractional measure of snow cover in each grid cell. The number and 

spectral range of channels have yet to be determined (Associate Directorate for Acquisition 2000). 

Details on the VIIRS instrument and requirement specifications may be accessed at 

(http://npoesslib.ipo.noaa.gov/S_viirs.htm). 

CONCLUSION

The development and operational implementation of IMS was predicated on specific 

requirements of the NWS and other customers for an accurate NH snow and ice cover product at 

higher spatial and temporal resolution then previously available. IMS has successfully met those 

needs over its brief three-year period of operation. However, it is necessary to enhance IMS based 

on new requirements, new satellite sensors, and new methods for mapping snow and ice cover. 

The NOAA/NESDIS experimental automated snow mapping system, the AVHRR/3 experimental 

global snow and ice mapping system, and imagery and automated maps from NASA’s MODIS 

instrument will all provide opportunities to enhance IMS products and expand IMS coverage 

beyond the NH this year. These new requirements, sensors, and methods represent a link to the 

future of global snow and ice mapping for IMS in IJPS/METOP and NPOESS/VIIRS, among 

others. The plan is to take advantage of these new products to enhance IMS now and also use them 

to prepare for the future. 

ACKNOWLEDGMENTS 

Acknowledgment is given to Peter Romanov (Peter.Romanov@nesdis.noaa.gov), 

NOAA/NESDIS, for information on the NOAA/NESDIS experimental automated snow mapping 

system, George Stephens (George.Stephens@noaa.gov) from the NOAA/NESDIS Operational 

Significant Event Imagery Team for processing of the AVHRR/3 Channel 3A imagery, and to 
Dorothy Hall (dhall@glacier.gsfc.nasa.gov), NASA/GSFC, for information on MODIS snow and 

ice map products. 

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