Improving Arctic sea ice edge forecasts by assimilating high horizontal resolution sea ice concentration data into the US Navy's ice forecast systems

摘要

This study presents the improvement in ice edge error within the US Navy'soperational sea ice forecast systems gained by assimilating high horizontalresolution satellite-derived ice concentration products. Since the late1980's, the ice forecast systems have assimilated near real-time sea iceconcentration derived from the Defense Meteorological Satellite Program(DMSP) Special Sensor Microwave/Imager (SSMI and then SSMIS). The resolutionof the satellite-derived product was approximately the same as the previousoperational ice forecast system (25 km). As the sea ice forecast modelresolution increased over time, the need for higher horizontal resolutionobservational data grew. In 2013, a new Navy sea ice forecast system (ArcticCap Nowcast/Forecast System – ACNFS) went into operations with a horizontalresolution of ~ 3.5 km at the North Pole. A method of blendingice concentration observations from the Advanced Microwave ScanningRadiometer (AMSR2) along with a sea ice mask produced by the National IceCenter (NIC) has been developed, resulting in an ice concentration productwith very high spatial resolution. In this study, ACNFS was initialized withthis newly developed high resolution blended ice concentration product. Thedaily ice edge locations from model hindcast simulations were comparedagainst independent observed ice edge locations. ACNFS initialized using thehigh resolution blended ice concentration data product decreased predictedice edge location error compared to the operational system that onlyassimilated SSMIS data. A second evaluation assimilating the new blended seaice concentration product into the pre-operational Navy Global OceanForecast System 3.1 also showed a substantial improvement in ice edgelocation over a system using the SSMIS sea ice concentration product alone.This paper describes the technique used to create the blended sea iceconcentration product and the significant improvements in ice edgeforecasting in both of the Navy's sea ice forecasting systems.