New “Young Research Talents” project led by NERSC started in October: CoRea!

CoRea stands for “Coupled reanalysis of the climate back to 1850”. This project is led by Yiguo Wang from the Climate Dynamics and Prediction group. It is his first time leading a research project himself: Congratulations, Yiguo!

 

On Thursday the 15th of October, the CoRea members met in Bergen – and online – to kick off the project. CoRea will run over the course of three years, and it has national and international partners.

While Yiguo Wang (NERSC) is the project leader, other researchers from NERSC, the Geophysical Institute at the University of Bergen (GFI/UiB), and the Norwegian Research Centre (NORCE) are collaborating in this project, together with researchers from École des Ponts ParisTech (ENPC) in France and from the European Centre for Medium-Range Weather Forecasts (ECMWF) in Great Britain. Some of the Norway-based researchers are also affiliated with the Bjerknes Climate Prediction Unit at the Bjerknes Centre for Climate Research.

CoRea is a “Young Research Talents” project and is funded by the FRIPRO scheme by the Research Council of Norway. 

The CoRea project aims to provide an innovative approach to climate reanalysis. To understand what the project members set out to do, one first needs to understand what “reanalysis” means.

Kick-off meeting partially digital. Project participants personally present (from left to right): Mao-Lin Shen (GFI/UiB), Yiguo Wang (project leader and WP3 leader, NERSC), Ingo Bethke (GFI/UiB), Patrick Raanes (WP2 leader, NORCE), François Counillon (NERSC), Lea Svendsen (WP1 leader, GFI/UiB), Ping-Gin Chiu (GFI/UiB). Digitally present on-screen: Patrick Laloyaux (ECMWF) and Marc Bocquet (ENPC). Not in photo: Yongqi Gao, Noel Keenlyside: Photo: Shuo Wang (GFI/UiB)Kick-off meeting partially digital. Project participants personally present (from left to right): Mao-Lin Shen (GFI/UiB), Yiguo Wang (project leader and WP3 leader, NERSC), Ingo Bethke (GFI/UiB), Patrick Raanes (WP2 leader, NORCE), François Counillon (NERSC), Lea Svendsen (WP1 leader, GFI/UiB), Ping-Gin Chiu (GFI/UiB). Digitally present on-screen: Patrick Laloyaux (ECMWF) and Marc Bocquet (ENPC). Not in photo: Yongqi Gao, Noel Keenlyside: Photo: Shuo Wang (GFI/UiB)

What is “climate reanalysis”?

A reanalysis is the reconstruction of past climate produced by combining observational data and modelling. These are combined using a method called data assimilation. This look back in time is important for climate scientists for several reasons, such as to investigate and better understand climate change and its impacts.

The observational data that can be included in a reanalysis are – for example – atmospheric data such as air temperature and pressure, or oceanic data such as water temperature and salinity.

 

What different types exist?

Different types of climate reanalyses exist. Many reanalyses are produced with so-called uncoupled simulation systems. In these, the focus is either on reanalysing the atmosphere (e.g. ERA-5 by ECWMF), or the ocean (e.g. ORAS5 by ECWMF). However, the climate is governed by such complex and dynamic processes, that this type of reanalysis is not optimal when wanting to understand how ocean and atmosphere dynamically interact with each other over time.

To circumvent this problem, coupled reanalyses have been developed. By being coupled, the different components of the Earth system model (atmosphere and ocean) can dynamically influence one another. Most coupled reanalyses include both atmospheric and oceanic data into the assimilation process, and they allow us to look back in time and better understand how variable the climate was in the past, compared to uncoupled reanalyses. These coupled reanalyses are great, but they do have one drawback: When trying to understand how ocean and atmosphere interact, and how they influence climate variability, the typical coupled reanalyses cannot give a fully satisfying answer. To fully understand the role of the ocean in the climate system, CoRea will take a different approach than the typical reanalyses

 

What is CoRea planning to do?

The CoRea project wants to solve exactly this problem and provide a solution to better understand the role of the ocean in the climate system. The project members are planning to produce the first coupled climate reanalysis from 1850 to the present, and plan to only include oceanic data in the assimilation process. This project is the first of its’ kind to cover such a large time span while only including ocean data in the assimilation process.

This new high-quality dataset will be of great importance for climate researchers.

 

What are the tools Yiguo Wang and his project partners are going to use?

The Norwegian Climate Prediction Model (NorCPM), developed by the Bjerknes Climate Prediction Unit, will play a big role in this project. It performs well for long-term reanalyses and will be improved further during the next three years with input from CoRea.

Yiguo Wang and his team will develop a new data assimilation technique based on the Ensemble Kalman Smoother (EnKS) partly developed by a NERSC researcher, that will be included in NorCPM.

 

Aside from the science, what makes this project special?

Yiguo Wang and the other two work package leaders, Lea Svendsen and Patrick Raanes, as well as some of the other project members, are early career researchers. They bring valuable knowledge and experience to the table and will be supported by senior researchers and software engineers. Also, the fact that NorCPM will be further developed in the frame of the CoRea project is beneficial for future work with climate prediction and reanalysis.

A coupled reanalysis, only assimilating oceanic data, has never been done to this extent, reaching as far back as 1850. The results of this project will have far-reaching impacts on the quality of understanding climate change, climate variability, and the role the ocean plays in all of it.

 

 

Detailed information on the CoRea project can be found here: https://www.nersc.no/project/corea