NOAA KLM User's Guide

Section 9.6.2

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9.6.2 Interactive Multisensor Snow and Ice Mapping System: 1999 - present

The Interactive Multisensor Snow and Ice Mapping System (IMS) was designed and built to improve the previously produced weekly snow and ice map by producing a more accurate, timely product. Clear sky imagery from both the NOAA POES and GOES show the snow line very well. The problem is that current visible and infrared analysis techniques suffer from persistent cloud cover near the snow boundary. This makes daily observations difficult and infrequent. Microwave snow products are generally independent of cloud cover. However, snow and ice analyses based on visible, infrared, or microwave satellite imagery have varying accuracies under certain environmental conditions or over specific types of terrain. It's therefore advantageous to allow a meteorologist to assess satellite imagery and derived snow maps from multiple remote sensing instruments and data sources, and from them interactively produce a composite that is more accurate than the individual snow cover maps.

IMS is a UNIX-based workstation application. It provides the capability for an analyst to create, save, edit, and distribute maps showing the extent of snow and ice cover over the Earth's Northern Hemisphere with a resolution of 23 kilometers. Snow and ice mapping is performed daily in approximately one to two hours. New data sources available on the workstation, in addition to the data sets used in producing the former weekly snow and ice map (see Section 9.6.1 ), include the Special Sensor Microwave/Imager (SSM/I) snow map from Defense Meteorological Satellite Program (DMSP) satellites, daily snow maps from the NWS National Operational Hydrologic Remote Sensing Center (NOHRSC), and NOAA-15's Advanced Microwave Sounding Unit (AMSU) snowcover map. Imagery from the AVHRR/3 1.6 micron channel, selected for its ability to discriminate snow cover from clouds, will be provided by NOAA-16. Data overlays of elevation contours, coastlines and rivers, and geopolitical boundaries are also available. IMS editing features allow toggling between two or more snow maps and other mapped data sets, such as land cover maps. The software produces a final snow map with appropriate header information and with an ancillary map containing information about data sources and quality flags.

The IMS workstation's graphical user interface (GUI) is able to display an entire Northern Hemisphere daily snow and ice map or portions thereof. The snow and ice map depicts snow in white, ice in yellow, land in beige, and water in dark blue. The GUI provides pull down menus in the upper left corner of the screen for file retrieval and storage, access to editing tools, image display, annotation of images, and access to help text. A tool palette of draw and edit icons is located on the upper right side of the screen. These icons provide the means for map rotation in 90 degree units, undoing the last action taken, the exclusive drawing and erasure of snow and ice, zooming in on a given area, reversion from zoom mode to a normal view (a 1024x1024 pixel matrix), clearing the screen of snow or ice, and fine detail addition or deletion of snow or ice in non-contiguous snow or ice areas. Static overlay buttons provide data layers consisting of coastlines, elevation at 500 meter intervals, land use, latitude-longitude grid, international boundaries, U.S. state and Canadian provincial political boundaries, rivers and lakes, climatological snow maps and vegetation indices. Other available functions include the option to clear the overlays or imagery from the screen as well as toggling between two images or maps. The command line of buttons at the bottom of the GUI provides access to a variety of imagery and derived products including visible imagery from AVHRR, GOES, GMS, and METEOSAT, microwave products derived from SSM/I and AMSU data, snow and ice maps from NOHRSC, NIC, and USAF daily snow analyses, as well as surface observations from manual and automated weather stations. Production of a daily Northern Hemisphere experimental product began in February 1997. Operational implementation of IMS was completed in November 1997 and formally replaced the weekly product in June 1999. The current daily digital product is in ASCII format and archived at the National Snow and Ice Data Center (NSIDC: http://nsidc.org/index.html). A 15 month validation, funded by NOAA's Office of Global Programs, was conducted over two snow seasons in which the weekly and daily products were produced in parallel. A digital weekly snow and ice map will be derived from the daily digital products for comparison with the current weekly product and for continuation into the future of the satellite derived weekly snow and ice map climatological record begun in 1966. The results of the validation will be published. Feedback from the snow and ice community on the IMS daily product is welcome and encouraged. It is routinely posted on the NOAA/NESDIS Office of Satellite Data Processing and Distribution's (OSDPD) home page (http://psbsgi1.nesdis.noaa.gov:8080/OSDPD/OSDPD2.html) and on the NOAA/NESDIS/OSDPD Satellite Services Division's home page at (http://www.ssd.noaa.gov/SSD/ML/realtime.html#SNOWSec).

In summary, digital snow and ice map products archived at NSIDC ( http://nsidc.org/NSIDC/CATALOG/ENTRIES/nsi-0046.html) consist or will consist of the following:


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