NOAA News || NOAA Home Page

June 29, 1999 — The hand-drawn Weekly Snow and Ice Chart of the Northern Hemisphere—NOAA's longest-running operational satellite product—has given way to more modern interactive computer techniques to improve product quality.

The Satellite Analysis Branch of NOAA's National Environmental Satellite, Data, and Information Service (NESDIS) first began generating Northern Hemisphere Weekly Snow and Ice Cover analysis charts derived from NOAA's GOES and POES visible satellite imagery in November 1966. By measuring the fluctuations in snow and ice patterns during the year and comparing with other periods, the product initially provided valuable data for climatic research.

The spatial and temporal resolutions of the analyzed weekly chart, 190 km and seven days, respectively, have remained unchanged for more than 30 years. However, shortcomings, such as partially obstructed observations caused by persistent cloud cover near snow boundaries, caused errors in numerical weather prediction models. The weekly product update also often missed subtle, but important, changes in daily snowcover. Accuracy is critical, as erroneous snowcover in the models could contribute to significant errors in low-level air temperature forecasts and subsequently lead to inaccurate predictions of rainfall versus snowfall.

As a result of increasing customer needs and expectations, NOAA decided to design and implement an efficient, interactive workstation application. The hand-drawn chart required six to nine hours of production time per week; the new Interactive Multi-sensor System allows daily production in only 70-80 minutes of analysis time. Transferring the computer system also enables the Satellite Analysis Branch to produce snow and ice analyses at a higher spatial resolution (~25km) each day by employing a variety of satellite data, including surface imagery products.

A commemoration was held on May 27 to observe the end of the Weekly Northern Hemisphere Snow and Ice Chart. Satellite Analysis Branch employee Thomas Baldwin remarked, "We will miss it, but not too much we like the interactive computer age!"

An example of the new snow and ice chart can be found at:
http://www.ssd.noaa.gov/SSD/ML/realtime.html

Photos of the celebration can be found at:
http://www.ssd.noaa.gov/whatsnew1/index.html