Abstract
Abstract. Mineral dust impacts key processes in the Earth system, including the radiation budget, clouds, and nutrient cycles. We evaluate dust aerosols in 16 models participating in the sixth phase of the Coupled Model Intercomparison Project (CMIP6) against multiple reanalyses and observations. We note that both the reanalyses and observations used here have their limitations and particularly that dust emission and deposition in reanalyses are poorly constrained. Most models, and particularly the multi-model ensemble mean (MEM), capture the spatial patterns and seasonal cycles of global dust processes well. However, large uncertainties and inter-model diversity are found. For example, global dust emissions, primarily driven by model-simulated surface winds, vary by a factor of 5 across models, while the MEM estimate is double the amount in reanalyses. The ranges of CMIP6 model-simulated global dust emission, deposition, burden, and optical depth (DOD) are larger than previous generations of models. Models present considerable disagreement in dust seasonal cycles over North China and North America. Here, DOD values are overestimated by most CMIP6 models, with the MEM estimate 1.2–1.7 times larger compared to satellite and reanalysis datasets. Such overestimates can reach up to a factor of 5 in individual models. Models also fail to reproduce some key features of the regional dust distribution, such as dust accumulation along the southern edge of the Himalayas. Overall, there are still large uncertainties in CMIP6 models' simulated dust processes, which feature inconsistent biases throughout the dust life cycle between models, particularly in the relationship connecting dust mass to DOD. Our results imply that modelled dust processes are becoming more uncertain as models become more sophisticated. More detailed output and dust size-resolved variables in particular, relating to the dust cycle in future intercomparison projects, are needed to enable better constraints of global dust cycles and enable the potential identification of observationally constrained links between dust cycles and optical properties.
Highlights
Mineral dust, a key component of the Earth system, has important impacts on the global climate and environment through a number of pathways (Mahowald et al, 2010; Gassó et al, 2010; Knippertz and Stuut, 2014; Shao et al, 2011; Mahowald et al, 2014; Kok et al, 2018; Jin et al, 2021)
We look at the drivers of dust emissions in each individual model and Copernicus Atmosphere Monitoring Service (CAMS) reanalysis at the global scale (Fig. 5), and we demonstrate the relative importance of each driver in different seasons at regional scales (Fig. 6 for model ensemble mean (MEM) and Fig. S2 in the Supplement for CAMS)
We examine dust aerosols in 16 state-of-theart Earth system models participating in the CMIP6 Atmospheric Model Intercomparison Project (AMIP)
Summary
A key component of the Earth system, has important impacts on the global climate and environment through a number of pathways (Mahowald et al, 2010; Gassó et al, 2010; Knippertz and Stuut, 2014; Shao et al, 2011; Mahowald et al, 2014; Kok et al, 2018; Jin et al, 2021). Given the large uncertainties in previous generations of climate models discussed above, it is important to evaluate the performance of the CMIP6 models – in particular, how well do these models simulate dust processes compared to each other and compared to observations and previous generations of models. Such understanding would serve as a benchmark for the dust-modelling community to interpret a variety of processes related to dust in climate models, while helping climate model centres to develop their models into the phase, and help target future observations directed towards constraining model processes.
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