Development of global ocean data assimilation system for weak coupling to the KIAPS atmospheric data assimilation system

KIAPS (Korea Institute of Atmospheric Prediction Systems) leads the development of NWP systems for the Korea Meteorological Administration (KMA), and developed the global atmosphere-surface NWP system that was made operational at KMA in April 2020. The system is based on a new atmospheric model called KIM (Korean Integrated Model), and incorporates a hybrid-4DEnVar system for deterministic analyses, and an LETKF for updating perturbations in the 50-member ensemble. During the next 4 years, KIAPS is aiming to develop this atmosphere-surface system into a full Earth system NWP system, to support skillful forecasts out to 30 days. 
KIM has been coupled with NEMO to provide the ocean component. Here, we report on our progress developing an ocean-only data assimilation for NEMO, configured for eventual use in a weakly-coupled atmosphere-ocean DA system. We focus on two aspects: (1) the impact of changing the surface forcing model from the Met Office Unified Model to KIM, and (2) the impact of reducing the ocean DA window from 24 to 6 hours, to match the atmospheric DA windows. This study will be preliminary results for the development of the coupled DA system.