NCEP's Hybrid-GODAS: A Path towards an Operational "Strongly Coupled" Ocean/Ice/Wave Data Assimilation System

The pursuit of "strongly coupled" data assimilation, by which observations in one Earth system domain are allowed to directly impact the analysis of another domain, is an active topic. Experiments with the CFSv2 show that positive impacts can be made by using strongly coupled ocean-atmosphere DA, but it is difficult to do so with real observations and the current model due to large diurnal biases and low vertical resolution at the domain interface. A more likely place to see the advancement of strongly coupled DA with operational models is with the ocean/ice/wave domains.

NCEP is developing ensemble DA systems based around the Local Ensemble Transform Kalman Filter (LETKF) for each of these domains, with the ocean Hybrid-GODAS planned for operational deployment in 2019. Development on these systems can proceed independently, but by utilizing a common LETKF framework, and with design decisions made in the development of the Hybrid-GODAS, a feasible path to strongly coupled ocean/ice/wave data assimilation is now available.