UKESM1

UKESM1
Name	UKESM1
Developer	Met Office Hadley Centre; Natural Environment Research Council; UK Research and Innovation
First release	2018
Latest release	2021
Programming language	Fortran; MPI; OpenMP
Platform	High-performance computing clusters; ARCHER; JASMIN
Resolution	Coupled atmosphere–ocean; typical 1.25°×1.875° atmosphere; 1° ocean
Components	Atmosphere; ocean; sea ice; land surface; biogeochemistry; aerosols; chemistry; interactive carbon cycle
Website	Met Office publications

UKESM1 is a coupled Earth system model developed primarily by the Met Office Hadley Centre in collaboration with UK research councils and universities. It couples atmosphere, ocean, sea ice, land surface, biogeochemistry and atmospheric chemistry components to simulate climate, carbon cycle feedbacks and aerosol–cloud interactions. The model is used across international intercomparison projects and informs assessments by bodies such as the Intergovernmental Panel on Climate Change, the World Climate Research Programme and national climate services.

Overview

UKESM1 was designed as the United Kingdom entry to the Coupled Model Intercomparison Project Phase 6 and integrates physical climate processes with biogeochemical cycles and atmospheric composition. The development drew on legacy code and scientific expertise from the Met Office Hadley Centre, NERC, UKRI centres and university groups including University of Oxford, University of Reading, University of Exeter and Imperial College London. UKESM1 participates in international experiments alongside models from institutions such as NOAA Geophysical Fluid Dynamics Laboratory, Max Planck Institute for Meteorology, NASA Goddard Institute for Space Studies and ECMWF.

Model Components

The atmospheric component derives from the Met Office Unified Model, sharing heritage with operational forecast systems used at Met Office and research configurations deployed at UK Met Office centres. The ocean component uses NEMO, a model developed in part by the National Oceanography Centre and French partners such as LOCEAN. Sea ice is represented by CICE, which is used by groups including Los Alamos National Laboratory and University of Washington. The land surface scheme incorporates JULES, developed by the Met Office and partners at University of Leeds, University of Edinburgh and Hadley Centre. Carbon cycle and biogeochemistry modules employ components from models developed at University of East Anglia, Plymouth Marine Laboratory, University of Bristol and Centre for Ecology & Hydrology. Atmospheric chemistry and aerosol schemes link to efforts by groups such as Leeds University, University of Cambridge and University of York.

Development and Versions

Initial development of UKESM1 built on the HadGEM family and the Unified Model lineage, integrating interactive chemistry work from projects funded by Natural Environment Research Council and European Research Council grants. Major coordinated development occurred through consortia involving Met Office Hadley Centre, University of Reading, National Centres for Atmospheric Science and the British Antarctic Survey. Versions evolved through internal testing, CMIP6 submissions and subsequent bugfix and tuning cycles, with related branches maintained for seasonal forecast and high-resolution experiments at facilities such as ARCHER2 and JASMIN.

Evaluation and Performance

UKESM1 has been evaluated against observational products from networks and missions including ARGO, TOA radiative fluxes datasets, satellite missions like MODIS, AIRS, CALIPSO and in situ networks from Rosenstiel School of Marine and Atmospheric Science collaborators. Performance assessments compare UKESM1 to CMIP6 peers such as models from GFDL, MPI-M, NCAR, CNRM, INM and IPSL. Metrics include reproducibility of historical temperature trends used by IPCC assessments, representation of aerosol forcing examined alongside work by IPCC authors and carbon cycle constraints from projects like RECCAP2. Development teams publish diagnostics in journals such as Journal of Climate, Geophysical Research Letters and Atmospheric Chemistry and Physics.

Applications and Research Use

UKESM1 is applied to attribution studies connected to events like major heatwaves assessed in IPCC AR6, to long-term projections informing UK Climate Change Committee analyses, and to process studies on aerosol–cloud interactions relevant to research by GEWEX and CLIVAR. The model supports marine biogeochemistry work linked to Oceans 2025 priorities, terrestrial carbon research used by Global Carbon Project contributors and chemistry–climate interactions investigated by SPARC researchers. Cross-disciplinary projects use UKESM1 output for impacts research involving organizations such as Met Office Hadley Centre, UKMO, DEFRA, Environment Agency, Centre for Ecology & Hydrology and international partners at NOAA, JPL and European Space Agency.

Computational Implementation

UKESM1 is implemented in Fortran and parallelized with MPI and OpenMP directives to run on UK and international supercomputers including ARCHER, UK Met Office Cray systems, HPC Wales and cloud research platforms. Model coupling is managed by the control framework used across Met Office configurations and community couplers employed by ESMF and OASIS-type interfaces. Reproducibility and data management leverage infrastructures such as JASMIN, the Earth System Grid Federation and community tools promoted by WCRP and CMIP6 data protocols.

Limitations and Future Directions

Limitations include resolution constraints compared with regional and convection-permitting models developed at University of Leeds and ETH Zurich, parameterized processes that remain under active study by teams at Imperial College London and University of Cambridge, and uncertainties in aerosol and cloud microphysics being researched by groups at NCAR and MPI-M. Future directions emphasize higher resolution experiments similar to initiatives at ECMWF, improved process representation informed by field campaigns led by British Antarctic Survey, NERC-funded observatories and satellite missions by ESA and NASA. Ongoing development seeks tighter integration with reduced-complexity models used by the IPCC scenario community and coupling to sectoral impact models applied by agencies such as UK Climate Impacts Programme and Met Office Forecasting Research.

Category:Earth system models