Ice Cover Duration Metadata ================================= File dur_ice.txt covers the 105 winters 1898-2002 and it contains ----------------------------------------------------------------- 1. modeled data for winters 1898-1972 (Assel 1990) 2. Canadian Ice Service data for winters 1973-1988 (Assel 2003) 3. National Ice Center data for winters 1996-2002 (Assel 2003) 4. An average of CIS and NIC data, based on daily data, for winters 1989-1995 ----------------------------------------------------------------- If the user wants the original cis and nice files for winters 1989-1995 they are available as well in cis-dur.txt and nic-dur.txt. -------------------------- Record Format:(i5,4i4) -------------------------- Information in each record -------------------------- field 1. year of the winter season, e.g. winter of 1897-1898 is give as 1898 field 2. lake spatial averaged ice duration field 3. west basin spatial averaged ice duration field 4. center basin spatial averaged ice duration field 5. east basin spatial averaged ice duration -------------------------------- File Name Number of records -------------------------------- Dur_ice.txt 105 cis-dur.txt 7 nic-dur.txt 7 -------------------------- Definition of Ice Duration -------------------------- the duration of ice cover (days) is the difference between date of first ice concentration is greater than 10% and date of last ice concentration is greater or equal to 10%. If the first and last reported date of ice occurred on the same date the duration of ice cover is set to 1. If no ice cover was present for a given basin on a given winter, the duration is set to 0. Zero duration occurred on the following basins and years: Center Basin: 1953 and 1998; East Basin: 1932, 1933, 1949, and 1953. A code of "0" was entered for the duration for these basins and years. Note ------------------------------------------------------------------------------------ Modeled data are based on information abstracted from Assel (1990). Observed data were calculated from data on daily ice cover grids given in Assel (2003). Assel, R.A., 1990. An ice-cover climatology for Lake Erie and Lake Superior for the winter seasons 1897-98 to 1982-83, International Journal of Climatology, 10:731-748. Assel, R.A., 2003. NOAA Atlas, An Electronic Atlas of Great Lakes Ice Cover winters 1972-2003. NOAA Great Lakes Environmental Research Laboratory, Ann Arbor, Michigan 48105. Data Set Created December 2003 ------------------------------ Raymond Assel NOAA/GLERL 4840 S. State Rd. Ann Arbor, MI email: Ray.Assel@noaa.gov