ERror Growth in Operational Data Initialised Coupled Systems (ERGODICS)

Coupled initialisation of climate models is a challenging new area requiring the application of sophisticated data assimilation methods, while at the same time practically managing complex interacting physics and dynamics of the coupled system, particularly at the air-sea interface and boundary layers. This proposal focuses on understanding and then reducing coupled hindcast bias errors at a range of lead times. It will exploit hindcast sets already performed or planned at ECMWF and the Met Office, making modifications to the assimilation increments or bias schemes. Full-field hindcasts will be used where the model is forced as close to the observations as possible. The lead-time dependent climate drift contains potentially important information about the model process errors. This proposal will develop and test several methods to analyse and reduce this lead-time dependent drift, including matching initial condition drift to perturbed physics drifts, matching atmosphere-ocean initialization increments to coupled model covariances, modifying covariances to focus on longer lead time predictions, and modifying already used bias schemes within operational systems. This diversity of approaches, focused on reducing coupled bias, is a strength of the proposal allowing promising results to be developed more fully. This approach, the experience of the team, and the focus on modifications to already existing operational coupled systems will also allow this project to operate effectively as an integrating project for the whole NGWCP program, allowing promising results from other funded projects to be brought through and tested within operational model environments.

The main impact of this work will be in the testing of new methods to reduce bias in coupled models used in operational forecasting at the Met Office and at ECMWF. This project will also act as a coordinating project for the NGWCP program and as such will seek to facilitate and arrange for the testing of useful new methods emerging from the whole research program within an operational environment.
It will do this by organising program meetings inviting ECMWF and MetOffice coupled model development representation. It will also offer to represent the work of the NERC program at coupled modelling meetings both at the met office and internaitonally where appropriate.
The interests of this program is strongly aligned with the interests of both the NCAS and NCEO programs