Email j.m.weber@reading.ac.uk
The United Kingdom Earth System Model (UKESM) is a global chemistry-climate model which simulates all aspects of the Earth System including the atmosphere, the land surface, the ocean and the cryosphere and the interactions between these components. UKESM was one of the major climate models which contributed to the 6th Coupled Model Intercomparison project (CMIP6) which contributed to the evidence base of the IPCC 6th Assessment Report in 2021 (AR6). UKESM development is a collaborative effort by the Met Office and scientists working at other institutions contributions in a wide range of disciplines. A detailed description of UKESM can be found here.
I have extensive experience setting up and running a wide range of simulations in UKESM on the MONSOON and ARCHER2 supercomputers for my own work and for colleagues. My experience includes:
Free-running atmosphere-only experiments such as those in AerChemMIP (Collins et al; 2017).
Land use/cover change experiments. This has involved modifying land surface input files in UKESM’s atmosphere-only mode (e.g. increasing or decreasing forest cover) including converting and regridding land surface input files from CESM to work in UKESM.
Fully coupled simulations where all components of the climate (atmosphere, land surface, oceans and cryosphere) can interact.
Nudged atmosphere-only experiments with high frequency output for comparison against surface, aircraft and satellite observational data.
I have also acted as a demonstrator for the 2021 and 2022 UKCA training courses (link here) run by Dr N. Luke Abraham. UKCA (United Kingdom Chemistry and Aerosol) is the component of UKESM which simulates atmospheric chemistry and aerosol processes. This demonstrating role involved helping students with the course’s exercises and explaining aspects of the model.
Model development is an ongoing process informed by advances in the understanding of important Earth system processes, for example the chemical reactions of the most important BVOCs. I view model development as the responsibility of all researchers who use the model and I have been fortunate to collaborate with colleagues at the Met Office and the Universities of Leeds and Cambridge to make four substantial improvements to UKESM such that I am now a co-author on the technical documentation (link here - requires MOSRS access). All of these updates are available for use by the UKESM community. I have also served as a Science Reviewer and Code Reviewer during the lodging of model updates developed by other researchers.
As an atmospheric chemist I am primarily interested in processes which determine atmospheric composition. These are simulated in UKCA, the atmospheric chemistry and aerosol part of UKESM. During my PhD I led work to add and evaluate an improved chemistry mechanism called CRI-Strat 2 (CS2), building on extensive prior work done by Dr Scott Archer-Nicholls, in UKCA which features some of the most recent advances in the understanding of isoprene oxidation chemistry with knock-on effects for oxidant concentrations and aerosol (paper here). CS2 is now a selectable option in UKESM.
During my PhD I improved the coupling between BVOCs and aerosol by updating the aerosol code in UKESM to allow for production of secondary organic aerosol (SOA) from isoprene in addition to its default production from monoterpenes. This significantly improves the faithfulness of SOA production, particularly in its spatial variation given that monoterpenes are emitted to a greater extent by mid and high latitude forests while isoprene emissions occurs to a much greater extent in the tropics. Working with Dr Colin Johnson at the Met Office, SOA production from isoprene will be a selectable option in UKESM from vn13.3 and this update also makes addition of SOA from other species such as anthropgenic pollutants (e.g. benzene and toluene) much easier to implement.
Working with Dr Cat Scott (Leeds), Dr Scott Archer-Nicholls (Cambridge) and Dr Hamish Gordan (Carneige-Mellon), I helped implement a bugfix to correct the concentration of secondary organic material able to participate in nucleation.
UKESM simulates isoprene and monoterpene emissions interactively, combining parameterisations for the effect of temperature, CO2 concentration, photosynthetic activity and the propensity of different types of vegetation (grasses, evergreen trees, deciduous trees etc.) to emit these species. The latter is described by each type of vegetation’s emission factor and I am currently working on developing a new set of emission factors which will improve the simulation of BVOC emissions. This will be particularly important for modelling future climate scenarios as changes to the land use and land cover (e.g. deforesation for agriculuture or afforestation to remove CO2) are likely to have significant impacts on BVOC emissions. This update was published in Geoscientific Model Development (link [here] (https://gmd.copernicus.org/articles/16/3083/2023/)).