DOI: 10.5281/zenodo.1300980
title: Regional So2 Removal Simulations With Hadgem3-Ga4

description: This dataset contains time-averaged model output from simulations performed with the UK Met Office HadGEM3-GA4 (UM Version 8.2) climate model, investigating the climate response to regional reductions in anthropogenic sulfur dioxide (SO<sub>2</sub>) emissions.

The model configuration and experimental setup are described in: Kasoar, M., Shawki D. & Voulgarakis, A. (2018), Similar spatial patterns of global climate response to aerosols from different regions, <em>npj Climate and Atmospheric Science</em>, 1(1), doi:10.1038/s41612-018-0022-z<em>.</em>  An overview of the experimental setup, experiment identifiers and file naming convention for this dataset, is given below.

Simulations were performed as 200-year long coupled atmosphere-ocean simulations.  The model was run with repeating year-2000 values for aerosol emissions and greenhouse gas concentrations throughout the simulation.  The first 50 years were discarded as spin-up, and 150-year annual and seasonal averages calculated over the remaining simulation period.  Data is provided as NetCDF files, containing the 150-year means of all the diagnostics that were output from these model runs.

Additionally, 26-year long atmosphere-only simulations with prescribed year-2000 sea surface temperatures (SST) and sea ice concentrations were also performed.  For these fixed-SST simulations, the first year was discarded as spin-up and the remaining 25 years averaged over.

Six 200-year atmosphere-ocean control simulations were carried out to assess internal variability, with different initial atmospheric states but otherwise identical inputs.  Only one 26-year fixed-SST control simulation was performed.  For both atmosphere-ocean and fixed-SST setups, a series of perturbation experiments were then carried out in which SO<sub>2</sub> emissions were set up zero over a particular region of the world, while being kept the same as in the control runs elsewhere.  Each SO<sub>2</sub> removal experiment was run with one simulation for atmosphere-ocean and fixed-SST setups.

File naming convention: [JOBID]_[number of years averaged][season]_avg.nc

JOBID is a five-letter run identification number (see below).  Number of years averaged over is either 150 (atmosphere-ocean simulations) or 25 (fixed-SST simulations).  Season is either 'year' for annual means, or 'djf', 'mam', 'jja', 'son', for December-January-February, March-April-May, June-July-August, or September-October-November seasonal averages, respectively.

Experiment identifiers and descriptions are as follows:

<strong>Atmosphere-ocean simulations:</strong>

xizko: Base control run (year-2000 aerosol emissions and greenhouse gas concentrations everywhere)

xizka: Alternative control simulation with different initial atmospheric state (i.e. perturbed initial conditions).  Emissions/GHG concentrations unchanged.

xizkp: Alternative control simulation with different initial atmospheric state

xkhqb: Alternative control simulation with different initial atmospheric state

xkhqc: Alternative control simulation with different initial atmospheric state

xkhqd: Alternative control simulation with different initial atmospheric state

xizkm: No SO<sub>2</sub> emissions from the northern hemisphere mid-latitudes (30°N-60°N).  Outside this region, emissions kept the same as in the control simulations.

xizks: No SO<sub>2</sub> emissions from East Asia (105°E-145°E, 20°N-45°N)

xizkv: SO<sub>2</sub> emissions removed from North America (235°E-290°E, 30°N-50°N).  *For North America, SO<sub>2</sub> emissions were not completely reduced to zero as in the other regions.  Instead, emissions were set to zero from the following major emission sectors: energy production, industry, transport, domestic use, and waste.  In practice though, this corresponds to a 97% removal of SO<sub>2</sub> emissions over this domain.

xizkw: No SO<sub>2</sub> emissions from Europe.  For Europe, instead of a latitude-longitude box, the domain was defined following the HTAP Phase II European region definition (described at: http://iek8wikis.iek.fz-juelich.de/HTAPWiki/WP2.1) which follows country borders.

xkhqa: No SO<sub>2</sub> emissions from South Asia (70°E-90°E, 10°N-30°N)

<strong>Fixed-SST simulations:</strong>

xjnda: Atmosphere-only control run (year-2000 aerosol emissions and greenhouse gas concentrations everywhere, prescribed year-2000 sea surface temperatures and sea-ice concentrations)

xjnde: Atmosphere-only; no SO<sub>2</sub> emissions from the northern hemisphere mid-latitudes (30°N-60°N)

xjndh: Atmosphere-only; no SO<sub>2</sub> emissions from East Asia (105°E-145°E, 20°N-45°N)

xjndp: Atmosphere-only; SO<sub>2</sub> emissions removed from North America (235°E-290°E, 30°N-50°N).  *For North America, SO<sub>2</sub> emissions were not completely reduced to zero as in the other regions.  Instead, emissions were set to zero from the following major emission sectors: energy production, industry, transport, domestic use, and waste.  In practice though, this corresponds to a 97% removal of SO<sub>2</sub> emissions over this domain.

xjndq: Atmosphere-only; no SO<sub>2</sub> emissions from Europe.  For Europe, instead of a latitude-longitude box, the domain was defined following the HTAP Phase II European region definition (described at: http://iek8wikis.iek.fz-juelich.de/HTAPWiki/WP2.1) which follows country borders.

xjndr: Atmosphere-only; no SO<sub>2</sub> emissions from South Asia (70°E-90°E, 10°N-30°N)
description: Simulations with HadGEM3-GA4 were performed using the MONSooN system, a collaborative facility supplied under the Joint Weather and Climate Research Programme, which is a strategic partnership between the Met Office and the Natural Environment Research Council.  The authors were funded by the Natural Environment Research Council under grant NE/K500872/1, and by the Grantham Institute for Climate Change and the Environment.