NorESM model

 

NorESM2 is a global earth system model mainly intended for use in the Norwegian and Nordic research community. See e.g. https://www.climateurope.eu/earth-system-modeling-a-definition/  for a definition of Earth System Models. NorESM is to a large extent built on the the community model originating from the National Center for Atmospheric Research (NCAR) in USA but with different component models for ocean, biogeochemistry, as well as modifications done in other component models.  A previous version of the model, NorESM1 contributed to the modelling intercomparison project for climate models, CMIP5. The latest version of the model, NorESM2 includes updates of NorESM specific components and parameterisation as well as an update to the latest version of the community model, CESM2.  (http://www.cesm.ucar.edu/models/cesm2/)

CAM6-Oslo is the atmosphere component of NorESM2, and its aerosol module is OsloAero6.0. OsloAero6.0 is an updated version of OlsoAero5.3, used in CAM5.3-Oslo / NorESM1.2 (Kirkevåg et al., 2018; Karset et al., 2018), which has been developed from the predecessor versions CAM4-Oslo / NorESM1 over the course of the last 5 years. The most important changes consist of new treatments of aerosol emissions and aerosol growth, as well as coupling of aerosols with clouds through updated cloud schemes in the host model (CAM6).

Emissions and oxidant fields from CMIP5 have been replaced with CMIP6 emissions, to prepare for the CMIP6 simulations (contributing to the upcoming 6’th assessment report from IPCC). Some natural emissions of aerosols and precursors that are calculated interactively in the model have also been modified. Mineral dust emissions have been reduced to giver better comparison with observed surface concentrations and aerosol optical properties. Sea-salt emissions have been increased and become more sensitive to surface wind speed (Salter et al., 2015) to obtain a better radiative balance at top of the atmosphere for use in the CMIP6 simulations. Optical properties are now calculated assuming humidity growth of aerosols based on clear-sky relative humidity instead of the grid averaged humidity, The formulation used for emissions of DMS from the ocean surface layer has been harmonized, now being the same whether the model is run with prescribed sea surface temperatures and sea-ice or with a fully interactive ocean and sea-ice model (with DMS concentrations from HAMOCC). Finally, the treatment of nucleation and growth of sulfate and secondary organic aerosol particles has been modified to better take into account the sink of freshly nucleated particles due to coagulation with other aerosols in the model. All these updates from CAM5.3-Oslo to CAM6-Oslo will be documented and published as part of the NorESM2 model documentation for CMIP6 and IPCC AR6.

 

References for publications with eSTICC acknowledgent:

Kirkevåg, A., Grini, A., Olivié, D., Seland, Ø., Alterskjær, K., Hummel, M., Karset, I. H. H., Lewinchal, A., Liu, X., Makkonen, R., Bethke, I., Griesfeller, J., Schulz, M., and Iversen, T.: A production-tagged aerosol module for Earth system models, OsloAero5.3 – extensions and updates for CAM5.3-Oslo, Geosci. Model Dev., 11, 3945-3982, https://doi.org/10.5194/gmd-11-3945-2018, 2018.

Salter, M. E., Zieger, P., Acosta Navarro, J. C., Grythe, H., Kirkevåg, A., Rosati, B., Riipinen, I., and Nilsson, E. D.: An empirically derived inorganic sea spray source function incorporatingsea surface temperature, Atmos. Chem. Phys., 15, 11047–11066, https://doi.org/10.5194/acp-15-11047-2015, 2015.

Other references:

Karset, I. H. H., Berntsen, T. K., Storelvmo, T., Alterskjær, K., Grini, A., Olivié, D., Kirkevåg, A., Seland, Ø., Iversen, T., and Schulz, M.: Strong impacts on aerosol indirect effects from historical oxidant changes, Atmos. Chem. Phys., 18, 7669–7690, https://doi.org/10.5194/acp-18-7669-2018, 2018.