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NOAA Atlas
An Electronic Atlas of Great Lakes Ice Cover
Winters: 1973 - 2002
Raymond A. Assel
National Oceanic and Atmospheric Administration
Great Lakes Environmental Research Laboratory
Ann Arbor, Michigan 48105
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Introduction
Synoptic ice chart observations for the Great Lakes began in 1960. A synoptic
ice chart usually covers only a portion of one or more of the Great Lakes.
Synoptic ice charts for a 20-winter base period (1960 to 1979) were digitized
(Assel, 1983), and a multi-winter statistical analysis of ice concentration
patterns over nine half-month periods (Dec. 16-31 to April 16-30) was
published as a National Oceanic and Atmospheric Administration (NOAA)
Great Lakes Ice Atlas (Assel et al., 1983) 20-years ago. Composite ice
charts, a blend of observations from different data sources (ships, shore,
air craft, and satellite) that cover the entire area of the Great Lakes
for a given date, and which may contain some estimated ice cover data,
were produced starting in the 1970s. A 30-winter (1973-2002) set of composite
ice charts was digitized, and a multi-winter statistical analysis of the
climatology of the ice cover concentration was completed.
The results of this analysis are published here as an electronic NOAA
Great Lakes Ice Atlas. Detailed documentation and description of analysis
methods, and a discussion of the resulting products, will supplement this
atlas as a series of reports. The first report in that series (Assel,
Norton, and Cronk, 2002) describes the original data set and is included
here. Other reports will be added as they become available. Please cite
this atlas (Assel, 2003) and those reports when using these data.
This Atlas contains approximately 1.4-gigabytes of data, much of which
is in compressed files (about 4-gigabytes when uncompressed). Because
of its large size it is not practical to download the entire atlas from
the Internet. Therefore, it is also being made available on CD-ROM and
DVD formats. To request a copy of the atlas on CD-ROM or DVD send an email
to iceatlas.glerl@noaa.gov.
Data and Analysis Products
Original Ice Charts. The original
ice chart data set consists of over 1200 digitized ice charts. These ice
charts display observed ice cover over each Great Lake throughout every
winter season from 1973 to 2002. Ice chart data is available as Arc/Info
Export, ASCII grids, and graphic files.
Analysis Products. There are three analysis
products. The first product includes ice charts of the following: dates
of the first reported ice, dates of the last reported ice, and ice duration
for each winter, as well as, the maximum, minimum and average ice cover
concentrations.
The second product is the 30-year annual daily ice cover time series.
The daily time series was used to create: 1) computer animations of spatial
patterns of ice cover for each winter, 2) line plots of lake averaged
ice cover for each lake over the 30 winters.
The third product is weekly statistics. There are weekly ice charts and
grids of: maximum, 3rd quartile, median, 1st quartile, and minimum ice
cover concentrations for the 30-winter base period. The weekly statistics
are based on the original ice chart data set and not on the daily time
series.
Links for each product noted above contain an introductory section with
pertinent information on file names, structure, and data. Secondary documentation
links provide additional details in some cases. General background
on the overall NOAA Great Lakes Ice Atlas is provided in the
Read Me file. It is
highly recommended that users read this background information prior to
accessing the data.
Concluding Remarks
The NOAA Great Lakes Ice Atlas is a national resource for those seeking
information on Great Lakes ice cover climatology. It provides a benchmark
of ice cover and ice cover variation of the Great Lakes during the last
quarter of the 20th century and early years of the 21st Century. The NOAA
National Ice Center and the Canadian Ice Service use information from
this atlas in making operational analysis products of Great Lakes ice
cover. Portions of these data have also been used by other federal and
state government agencies, academia, and the private sector for research,
educational, operational, and engineering applications. This atlas and
dataset will be archived at the National Snow and Ice Data Center (http://nsidc.org).
The Great Lakes Environmental Research Laboratory (GLERL) will maintain
the Internet version of the atlas, http://www.glerl.noaa.gov/data/ice/atlas/,
for several years to come and will still continue to supply CD-ROM and
DVD versions of the atlas after that.
Acknowledgments
This work was funded in part by NOAA’s Earth System and Data Information
Management program. The NIC and the CIS provided the historic ice charts.
Mr. David Norton's (GLERL) contributions during the data reduction and
quality control phases of this project were critical for its successful
completion. University of Michigan’s Cooperative Institute for Limnology
and Ecosystems Research (CILER) staff; D. Meyers, B.A. Hibner, N. Morse,
P.J. Trimble, K. Cronk, and M. Rubens and GLERL staff; Ms. Deborah Lee,
provided invaluable contributions to this project. Ms. Janet Szczesny
(CILER), Ms. Cathy Darnell (GLERL), and Mr. Gregory Lang (GLERL) were
instrumental in the development of the GUI. This is GLERL Contribution
Number 1266.
Reference
Assel, R.A. 2003. Great
Lakes Ice Cover, First Ice, Last Ice, and Ice Duration: Winters 1973-2002.
NOAA TM GLERL-125. Great Lakes Environmental Research Laboratory, Ann
Arbor, MI.
Assel, R.A. 2003. An Electronic Atlas of Great Lakes Ice Cover. NOAA Great
Lakes Ice Atlas, Great Lakes Environmental Research Laboratory, Ann Arbor,
Michigan 48105.
Assel, R.A., D. C. Norton, and K. C. Cronk. 2002. A
Great Lakes Digital Ice Cover Data Base for Winters 1973_2000. NOAA
Technical Memorandum GLERL_121, Great Lakes Environmental Research Laboratory,
Ann Arbor, MI.
Assel, R.A., F.H. Quinn, G.A. Leshkevich, and S.J. Bolsenga, 1983. Great
Lakes Ice Atlas. NOAA Atlas No. 4. Great Lakes Environmental Research
Laboratory, Ann Arbor, MI.
Assel, R.A., 1983. A
Computerized Ice Concentration Data Base for the Great Lakes. NOAA
DR ERL GLERL-24. Great Lakes Environmental Research Laboratory, Ann Arbor,
MI.
Technical Notes
- To view PDF files: download a free copy of Adobe
Acrobat Reader from the Adobe website.
- To open .zip files: Many compression utilities, such as WINZIP (http://www.winzip.com/),
PKZIP (http://www.pkware.com/),
or Stuffit Expander (http://www.stuffit.com/),
can be used. Note: these files were originally created and compressed
on a Windows platform. Please be aware that formatting errors may occur
if uncompressed using a non-Windows platform.
- To view .AVI animation files: any software capable of playing ".avi",
such as Microsoft Windows Media Player may be used. Windows
Media Player may be downloaded from the Microsoft website.
- To view .FLC animation files: any software capable of playing ".flc",
such as QuickTime, may be used. QuickTime
may be downloaded from the Apple website.
Disclaimers
The NOAA Great Lakes Ice Atlas is maintained by the National Oceanic and
Atmospheric Administration's Great Lakes Environmental Research Laboratory
(GLERL). NOAA makes no warranty regarding these data, expressed or implied,
nor does the fact of distribution constitute such a warranty. NOAA and
GLERL cannot assume liability for any damages caused by any errors or
omissions in these data, nor as a result of the failure of these data
to function on a particular system.
Specific products and manufacturers are mentioned throughout the NOAA
Ice Atlas. Mention of these products or manufacturers does not constitute
an endorsement by GLERL, NOAA, or the Department of Commerce.
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