README -- Describes contents of HEMCO/MULTI_ICE/v2021-07 directory
8 July 2021
Lyatt Jaegle
jaegle@uw.edu


Overview:
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Multi-year sea ice (MYI) fraction,  which is sea ice that has survived at least
one melt season. This is used in the HEMCO blowing snow sea salt emissions as
the salinity of first year sea ice (FYI) and MYI is different. Overs the Arctic 
Ocean, the MERRA-2 sea ice fraction is partitioned into MYI and FYI by using the
EASE-Grid Sea Ice Age, Version 4 from the National Snow & Ice Data Center 
(https://nsidc.org/data/NSIDC-0611/versions/4). This dataset provides Arctic
sea ice age since 1984 and is described in Tschudi et al. (2020).

For years prior to 1984 in the Arctic and for the Antarctic (all years), the MYI 
extent is based on the minimum sea ice extent in the MERRA-2 at the
end of summer of the previous year.


Files:
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multiyearice.merra2.05x0625.YYYY.nc

     Resolution  : 0.5 x 0.625 grid (361 x 576 boxes)
     Units       : unitless
     Timestamps  : Daily, 1980 through 2020
     Compression : Level 1 (nccopy -d1)
     Chunking    : nccopy -c lon/576,lat/361,time/1

References:
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NSIDC: https://nsidc.org/data/NSIDC-0611/versions/4

Tschudi, M. A., Meier, W. N., and Stewart, J. S.: An enhancement to sea ice motion 
and age products at the National Snow and Ice Data Center (NSIDC), The Cryosphere, 
14, 1519–1536, https://doi.org/10.5194/tc-14-1519-2020, 2020.