HiLLA-SAI simulations in UKESM1, CESM2-WACCM and E3SMv3

Simulations of High-latitude low-altitude (HiLLA) stratopsheric aerosol injection (SAI) under various injection strategies, carried out in three earth system models: UKESM1, CESM2-WACCM, and E3SMv3. The simulations are in support of the analysis contained in Duffey et al., 2025; The global climate response to High-Latitude Low-Altitude Stratospheric Aerosol Injection (HiLLA-SAI) (forthcoming). In each case, 12Tg SO2 per year is injected into the lower stratosphere, starting in 2035, and causing the climate state to deviate from the background SSP2-4.5 scenario. Two central injection strategies are simulated: HiLLA-13 and HiLLA-15, which have injection at 60°N/S in the local spring (March-June/September-Devember), and at 13 km and 15 km, respectively. These simulatations are 35-years in length. Nine additional 3-year sensitivy simulations vary the injection latitude, longitude, altitude and seasonality. See also the analysis code here https://github.com/alistairduffey/HiLLA_MM Data here does not include all outpus on levels (ozone, geopotential height and SO4 burdens), as these files are too large for practical storage on Zenodo. Contact Alistair Duffey ([e-mail]) for help locating them. For SO4/H2SO4 mass mixing ratios under HiLLA-13 and HiLLA-15 (case 1 and case 4): Zonal mean SO4 burdens are included for CESM2-WACCM, under "SO4 burden/"; data on several defined pressure levels is included for E3SM in "E3SM_HiLLA_Mass_so4.zip"; zonal means for UKESM are in the seperate upload "UKESM1_HiLLA_mass_H2SO4.zip". Note that mass-mixing ratio for UKESM1 includes H2SO4 by mode - nucleation ('nuc'), Aitken (ait), accumulation ('acc'), and course ('cou'). Runs are labelled as follows in file naming: UKESM1 CESM2-WACCM E3SMv3 Description u-dm204dn587 case01 01 HiLLA-13 : 35-year run with injection at 13km, 60°N/S, MAMJ/SOND, 180° longitude u-dk092 case02 02 Latitude sensitivity: 3-year run with injection at 13km, 70°N/S, MAMJ/SOND, 180° longitude u-dk163 case03 03 Latitude sensitivity: 3-year run with injection at 13km, 50°N/S, MAMJ/SOND, 180° longitude u-dn760 case04 04 HiLLA-15 : 35-year run with injection at 15km, 60°N/S, MAMJ/SOND, 180° longitude u-dk101 case05 05 Altitude sensitivity: 3-year run with injection at 15km, 70°N/S, MAMJ/SOND, 180° longitude u-dk164 case06 06 Altitude sensitivity: 3-year run with injection at 15km, 50°N/S, MAMJ/SOND, 180° longitude u-dn605 case07 07 Seasonality sensitivity: 3-year run with injection at 13km, 60°N/S, MAM/SON, 180° longitude u-dn675 case08 08 Seasonality sensitivity: 3-year run with injection at 13km, 60°N/S, MAMJJ/SONDJ, 180° longitude u-dn690 case09 09 Seasonality sensitivity: 3-year run with injection at 13km, 60°N/S, FMAMJ/ASOND, 180° longitude u-dn757 case10 10 Longitude sensitivity: 3-year run with injection at 13km, 60°N/S, MAMJ/SOND, 0° longitude u-dn758 case11 11 Longitude sensitivity: 3-year run with injection at 15km, 60°N/S, MAMJ/SOND, 0° longitude - - control SSP2-4.5 reference case - existing CMIP6 simulations are used for comparison in UKESM1 and CESM2-WACCM u-dj993 - - Additional 3-year sensitivity run with the same injection parameters as HiLLA-13 (13km, 60°N/S, MAMJ/SOND, 180° longitude). Only conducted in UKESM1. u-dk035 - - Additional 3-year sensitivity run with the same injection parameters as HiLLA-15 (15km, 60°N/S, MAMJ/SOND, 180° longitude). Only conducted in UKESM1. v1.1 added some additional SO4/H2SO4 data for UKESM1 and E3SM relative to v1.0 v1.2 added column integrated SO4 burdens for CESM2-WACCM (CESM2WACCM_TMSO4.zip). Corrected mistaken run labels in table above.