Towards Understanding the Climate Response to the Historical Dust Increase in ICON-XPP

Mineral dust aerosol shapes the global climate, mainly through interactions with radiation and clouds, and especially on the regional level close to major emission sources. However, the Coupled Model Intercomparison Project, phase six (CMIP6) models with coupled dust emission parameterization schemes fail to reproduce the 55 ± 30% increase in atmospheric dust concentration since 1850 (Kok et al. 2023). In the present study, we construct the historically changing monthly 'Dust Plumes' (DuPlumes) climatology (Sudarchikova et al. in prep.) and investigate implications of changing dust aerosol for the global climate in ICON-XPP, Germany's designated model for CMIP7. DuPlumes consists of a parameterized analytical framework, originally designed for anthropogenic aerosols (Stevens et al. 2017).  To create the representation of natural desert-dust aerosols, this study utilizes reanalysis data of dust optical depth, measurement data of scattering properties, and a marine-core-based reconstruction of the historical trend. To constrain the spatial pattern of present-day optical depth by observation, we use data of four reanalysis products (CAMS, MERRA2, JAero, and NAAPS), monthly averaged for the decade around the year 2010 (2004–2015). Plume functions related to ten dust plumes globally are fitted to the data using a gradient descent algorithm. The fit achieves a spatial correlation of r=0.98 with the data, with maximum deviations in summer of 0.08, or 2% of maximum aerosol optical depth, which is smaller than the uncertainty measured across the reanalysis ensemble. Compared to the currently implemented static ICON-XPP dust climatology, the reanalysis ensemble and, subsequently, dust plumes suggest considerably higher optical depth (~0.1) in the Eastern Asian Taklamakan and Gobi Desert regions. The vertical profile is informed by the 2007–2019 climatology derived from Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) retrievals. We also include measurements of dust scattering properties from literature, including in-situ data and laboratory measurements. Ongoing work includes ICON-XPP experiments with dust optical properties represented by DuPlumes. These allow us to estimate the spatial pattern of effective radiative effects of the present-day natural dust relative to the pre-industrial levels.

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Kok, J.F., Storelvmo, T., Karydis, V.A., Adebiyi, A.A., Mahowald, N.M., Evan, A.T., He, C., Leung, D.M.: Mineral dust aerosol impacts on global climate and climate change. Nat Rev Earth Environ. 4, 71–86 (2023). https://doi.org/10.1038/s43017-022-00379-5

Stevens, B., Fiedler, S., Kinne, S., Peters, K., Rast, S., Müsse, J., Smith, S.J., Mauritsen, T.: MACv2-SP: A parameterization of anthropogenic aerosol optical properties and an associated Twomey effect for use in CMIP6. Geoscientific Model Development. 10, 433–452 (2017). https://doi.org/10.5194/gmd-10-433-2017