Sea Ice Concentration Fields for Operational Forecast Model Initialization: An R2O Success Story

Florence Fetterer (1), Ann Windnagel (2), J. Scott Stewart (2), Walt N. Meier (3)

Abstract
The first strategic goal in NOAA’s Arctic Action Plan is “Forecast sea ice”. The U.S. Navy, too, has a goal of making better short-term operational sea ice forecasts. The Naval Research Laboratory’s 1/12° Arctic Cap Nowcast/Forecast System (ACNFS) is a development platform for the operational model that runs at the Naval Oceanographic Office, producing forecasts of sea ice drift, concentration, thickness and more that are used by the National Ice Center (NIC) and by the NOAA National Weather Service. How good are predictions? One metric NRL uses to evaluate skill is to measure distance between forecast ice edge and the manually drawn ice edge given in a NIC ice edge product. To improve skill, NRL needed better ice concentration initialization fields. We developed a daily 4 km field from a blend of two other daily sea ice data products. First is ice coverage from MASIE, the Multisensor Analyzed Sea Ice Extent product, at a 4 km grid cell size. Second are ice concentrations from the Advanced Microwave Scanning Radiometer 2 (AMSR2) at a 10 km grid cell size. MASIE and AMSR2 data are blended together to take advantage of the best features of both products. MASIE is based on a NIC analysis product that uses multiple sensors and manual quality control of the data, and is more likely to be accurate in showing where ice is present than is AMSR2, while the AMSR2 sea ice concentration product gives concentration information not available from MASIE alone. NRL found that use of the methodology improved forecast skill, substantially improving the extent of Arctic sea ice in the model. Based on these results, the Naval Oceanographic Office began using the methodology in operational model runs in February 2015. We’ve made a prototype of the product, “MASAM2”, available as a contribution to the Arctic Research Consortium of the United States (ARCUS) Sea Ice Prediction Network. NOAA@NSIDC hosts the data at http://nsidc.org/data/g10005.