VIIRS Ice Age / Thickness
Frequently Asked Questions about the VIIRS Ice Age / Thickness Product
1) What is this product?
This product has two outputs of interest to the forecaster. The first is the Ice Thickness, which is defined as the total vertical length of the ice under and above the water surface. The range of values to be expected is from 0 to 3.0 meters.
The second is the Ice Age, which has eight possible outputs.:
1) "New"is defined as recently formed ice which includes frazil ice, grease ice, slush and shuga. These types of ice are composed of ice crystals which are only weakly frozen together (if at all) and have a definite form only while they are afloat, usually less than 2 cm.
2) "Nilas" is defined a thin elastic crust of ice, easily bending on waves and swell and under pressure growing in a pattern of interlocking “fingers” (finger rafting). Nilas has a matte surface and is
up to 10 cm in thickness and may be subdivided into dark nilas and light nilas.
3) "Grey" is defined as your ice 10-15 cm thick. Less elastic than nilas and breaks on swell. Usually rafts under pressure.
4) "Grey-White" is defined as young ice 15-30 cm thick. Under pressure it is more likely to ridge than to raft.
5) "First-Year Thin" is defined as first-year ice of not more than one winter's growth, 30-70 cm thick.
6) "First-Year Medium" is defined as first-year ice 70-120 cm thick.
7) "First-Year Thick" is defined as first year ice 120-180 cm thick.
8) "Older Ice" is defined as sea ice which has survived at least one summer's melt. Topographic features generally are smoother than first-year ice, and more than 180 cm thick.
This product is useful when looking as shipping routes through sea ice because the type of ice can dictate whether or not a ship can successfully navigate the area. Seasonal ice-melt/ice-growth monitoring can also be performed using this product.
2) How often do I receive this data?
The S-NPP satellite is part of the Afternoon Train (A-Train) of satellites. It crosses your area at ~1:30am and ~1:30pm local time every day.
3) How do I display this product in AWIPS-II?
4) How do I interpret the color maps associated with this product?
5) What should I use in conjunction with this product to produce a better forecast?
Ice flow forecast models and other independent ice analyses.
6) How is this product created?
Physical and statistical approaches are employed to estimate sea and lake ice thickness and age. One-dimensional Thermodynamic Ice Model (OTIM) based on the surface energy budget, containing all components of the surface energy budget has been developed to estimate sea and lake ice thickness. Then based on the knowledge of ice thickness, ice is classified into open water, new/fresh ice, grey ice, grey-white ice, thin first year ice, medium first year ice, thick first year ice, and multi-year or older ice. It inevitably involves parameterizations and/or assumptions of the sea and lake ice and associated snow characteristics, such as ice and snow conductivities, densities, and transmittances. 1
The difficult task for any ice thickness and age estimation based on the thermodynamic theory is to exploit not only ice and snow micro-physical properties which are closely related to ice and snow types and contents but also its environmental conditions such as humidity, air temperature, wind, cloud cover, water salinity and current. 1
1NOAA/NESDIS/STAR. NOAA NESDIS Center for Satellite Applications and Research: Algorithm Theoretical Basis Document: ABI and VIIRS Ice Thickness and AGE. v1.0, December 17, 2015.