Difference between 1 degree and 2 degree NorESM3 and NorESM2

[oyvindseland]

I have compared NorESM2-MM and LM piControl with a recent version of 1 and 2 degree in NorESM3. In this first write-up I will mainly on natural aerosols
NorESM2 MM vs LM: https://ns2345k.web.sigma2.no/datalake/diagnostics/ADF/plots/N1850frc2_f09_tn14_20190913_1051_1080_vs_N1850_f19_tn14_20190621_1771_1800/website/index.html

NorESM3: 2 degreee vs 1 degree: https://ns2345k.web.sigma2.no/datalake/diagnostics/ADF/plots/n1850.ne30_tn14.noresm3_0_beta03b-run2_yr001.20251023_31_60_vs_n1850.ne16pg3_tn14.noresm3_0_beta03b.CPLHIST.2025-10-29_291_320/website/index.html
( NorESMhub/noresm3_dev_simulations#254 and NorESMhub/noresm3_dev_simulations#259)

The 2 degree NorESM3 is a bit out of balance but I do not think that will impact the results very much.

The difference in 2 meter temperature is larger in NorESM3 than NorESM2 but not by much (-0.87 vs -0.77 K) The difference itself is quite substantial though.

The difference in SWCF is larger in NorESM3, 2.8 W m-2 vs 1.2 W m-2. Note that these are values are positive, so the SW cooling for cloud is smaller in 1 degree.
LWCF is also lower in 1 degree NorESM3 (-0.71 vs -0.15 W m-2) The overall LWCF is very close for the 2 degree versions although a good portion of chance is involved here. (NorESM3-2 degree: 25.20 W m-2; NorESM2-LM 25.19 W m-2)
Net solar surface radiation is higher for the 1 degree version in both NorESM2 and NorESM3.
There is a strong decrease in net clear sky solar radiation, but it is at least partly caused by a large increase in sea-ice in addition to the increase in aerosols.

Emissions (Tg y-1) and burdens (Tg) :
(NorESM3 1 degree; difference in % compared to 2 degree ; NorESM2-MM ; difference in % compared to 2 degree)
Sea-salt emis(4962 ; 6 % ; 3906 ; 7 %)
Sea-salt column burden (15.0 ; 8 % ; 10.3 ; 5%)
Dust emissions( 2830; 23 % ; 1873 ; 11% )
Dust column burden (22.8 ; 30 % ; 9.4 ; 11 %)
DMS emissions (48.61 ; 5 % ; 41.13 ; 8 %)
DMS concentrations (0.174; 1% ; 0.135 ; 4 %)
monoterpene emssions (91.5 ; 14 % ; 105.9 ; -5 %)
isoprene emisssions (388.5 ; 20 % ; 467.0 ; -4% )

--> Stronger increase in both emissions and lifetime of mineral dust in NorESM3
--> Same sensitivity for sea-salt emissions, Increase in life-time although less impact compared to dust
--> Similar change in DMS
-->Opposite sign for BVOC emissions

Comparison NorESM3 vs NorESM2 1 degree
https://ns2345k.web.sigma2.no/datalake/diagnostics/ADF/plots/n1850.ne30_tn14.noresm3_0_beta03b-run2_yr001.20251023_31_60_vs_N1850frc2_f09_tn14_20190913_1051_1080/website/index.html

[oyvindseland]

NorESM3 vs NorESM2 degree PI control : https://ns2345k.web.sigma2.no/datalake/diagnostics/ADF/plots/n1850.ne16pg3_tn14.noresm3_0_beta03b.CPLHIST.2025-10-29_291_320_vs_N1850_f19_tn14_20190621_1771_1800/website/index.html