Introduction

The National Ice Center (NIC), a tri-agency operational center, operated by the National Oceanic and Atmospheric Administration (NOAA), the United States Navy, and the United States Coast Guard, prepares a daily Northern Hemisphere Snow and Ice chart. This chart, prepared on a polar stereographic projection is centered on the North Pole with a 60 degree latitude of true scale, provides information on the areal coverage of the snow and ice. The visible and Near-infrared imagery of the polar orbiting satellites (POES) and geostationary orbiting environmental satellites (GOES) are the primary tools for the analysis of this snow and ice cover. Low resolution visible data are augmented whenever possible by the visible high resolution imagery and visible GOES, GMS, MTSAT, and METEOSAT data. In addition, ground weather observations, synthetic aperture radar (SAR), microwave scatterometer returns, numerical weather prediction, sea ice models, buoys, reconnaissance flights, and various DMSP visible and microwave products are incorporated into the daily Snow and Ice chart.

Philosophy and Purpose

Polar orbiting satellites are the only source of a complete look at the polar areas of the earth, since their orbits cross near the poles approximately every two hours with 12 to 13 orbits a day of useful visible data. This visible imagery can then be analyzed to detect the snow and ice fields and the difference in reflectivity of the snow and ice. By analyzing these areas each day, areas of cloud cover over a particular area of snow and ice can be kept to a minimum to allow a cloud free look at these regions. This chart can then be useful as a measure of the extent of snow and ice for any day during the year and it can also be compared to previous year for climatic studies.