The multi-party 4D-Atlantic Dust & Ocean Modelling & Observing Study (DOMOS), funded by the European Space Agency (ESA), ran over two years from September 2021 to 2023 and delivered unique datasets and studies related to the dust cycle and its connections with atmospheric processes as well as ocean biogeochemistry. Desert dust is one of the most abundant aerosol types. As such, it is an important weather and climate forcer via its impact on solar-reflected radiation and Earth’s emitted thermal radiation. Dust radiative processes can also affect the static stability of the atmosphere and might play a role in the development of cyclonic circulation. In addition, dust is the primary source of soluble iron. This is a necessary nutrient to produce tiny phytoplankton organisms, thought to be responsible for the absorption of atmospheric CO2 connected to anthropogenic activity into the ocean.
The DOMOS consortium was formed by six partners: the Barcelona Supercomputing Center (BSC), the National Observatory of Athens (NOA), the Norwegian Meteorological Institute (MetNo), the University of Cologne, the Royal Netherlands Institute for Sea Research (NIOZ), and ECMWF (the coordinator).
Dust, dust everywhere...
The project delivered a new satellite-based dataset of dust optical depth and dust deposition over the Atlantic basin for the period 2007–2020 (see the first illustration), which has been evaluated against existing deposition datasets. The product is based on the LIVAS (LIdar climatology of Vertical Aerosol Structures) pure dust dataset, which provides profiles of dust concentrations derived from CALIPSO lidar measurements. The DOMOS-LIVAS deposition dataset shows an overestimation compared to ground-based, sparse measurements. This is possibly the result of assumptions that are made on particle size and dust scattering properties. More observations, such as the Aeolus and upcoming EarthCARE lidar observations, are needed to extend the product in time and to improve its accuracy. The project also showed the need for independent observations for the evaluation of satellite-derived products. Moored buoys and ship observations in open ocean areas are key to this calibration and evaluation activity, as they are deployed in areas where ground-based reference measurements are scarce.
Dust reanalyses, utilising state-of-the-art assimilation systems and novel observations for dust assimilation, were also produced for two case studies. These showed the benefits of synergistic observations in the form of profiles and column-integrated quantities. An analysis using Infrared Atmospheric Sounding Interferometer (IASI) dust optical depth for September 2021 was the main scientific contribution from ECMWF. It showed the benefits of using infrared information for dust aerosols within the Integrated Forecasting System (IFS) in composition configuration. The dust interacts with strong meteorological features, such as hurricanes, and deposition is higher where precipitation occurs. This implies a dependency of the dust aerosol distribution on both transport and precipitation processes. There could also be an impact of dust aerosols on precipitation through radiative processes in pre-hurricane conditions (see the example plots for Hurricane Larry).
Model reconstructions of dust and iron deposition from the EC‑Earth3‑Iron model were also produced by BSC for the period 1991–2020. An evaluation and comparison with the DOMOS-LIVAS dataset, using the Aeroval platform (https://aeroval.met.no/) developed by MetNo, was also performed for dust optical depths and dust deposition fields. This was done using the EC-Earth3 model run as well as the Copernicus Atmosphere Monitoring Service (CAMS) reanalysis, showing strengths and weaknesses of the models in reproducing the seasonality of dust fields.
More dust and iron but not phytoplankton
The EC‑Earth3‑Iron datasets enabled the study of the ocean response to changes in iron sources. Dust remains the most important iron source, with fossil fuel becoming more important over the years, particularly in winter, as well as biomass burning. The use of new dust and iron deposition datasets in an ocean biogeochemistry model showed that the phytoplankton primary production is not increased where the deposition is higher, contrary to what was expected. However, there is an overall increase in iron storage within the ocean, which could affect the seasonality of the phytoplankton primary production and therefore modify the climate feedback from the ocean.
Written on behalf of the ESA DOMOS project consortium, Contract Nr. 4000135024/21/I-NB.