VIIRS Ice Concentration
Frequently Asked Questions about the VIIRS Ice Concentration Product
1) What is this product?
This product has three fields of interest to the forecaster. The first is Ice Cover, which simply tells the forecaster if the surface is ice, land, water, or cloudy. The second is Ice Concentration, which gives a percentage (in tens of %) of the fraction of the pixel covered by ice. The third and final field is Ice Surface Temperature, which tells the forecaster the skin temperature of the ice n Kelvin. 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.1
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. However, this product is not created if clouds are present.
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. Also, the VIIRS Ice Age and Thickness product.
6) How is this product created?
This automated algorithm detects ice cover and retrieves ice concentration. Ice cover is first determined by a group-criteria technique. Then ice concentration is retrieved based on the determined normalized reflectance/BT of pure ice and pure water through application of a tie point algorithm. Ice cover is further refined based on the retrieved ice concentration. Ice surface temperature is retrieved using brightness temperatures at split window channels at 10 and 11 um, M15 and M16 for VIIRS, and satellite sensor scan angle derived from sensor zenith angle. The equation coefficients are based on modeled radiances in the 11 and 12 um bands using Arctic and Antarctic temperature and humidity profiles, and angular emissivity models for snow. Ice cover is detected at the pixel level over water surface under clear conditions. Clear condition is determined from the input cloud mask. 1
Snow covered ice show high reflectance in the visible channels, and very low reflectance in short-wavelength infrared channels. Many ice types also have this characteristic, and most ice types have higher reflectance than open water, which typically has a very low reflectance. Ice cover has colder surface temperature than open water. And water with higher salinity usually has lower melting temperature.1
1NOAA/NESDIS/STAR. NOAA NESDIS Center for Satellite Applications and Research: Algorithm Theoretical Basis Document: Ice Surface Temperature, Ice Concentration, and Ice Cover. v1.0, December 17, 2015.