Satellites reveal Earth's seasonally shifting dust emission sources

Authors: CHAPPELL, ADRIAN - Cardiff University; Webb, Nicholas - Nick; HENNEN, MARK - Cardiff University; SCHEPANSKI, KERSTIN - Freie University; CIAIS, PHILIPPE - Laboratoire Des Sciences Du Climat Et De L'Environnement (LSCE); BALKANSKI, YVES - Laboratoire Des Sciences Du Climat Et De L'Environnement (LSCE); ZENDER, CHARLES - University Of California Irvine; TEGEN, INA - Leibniz Institute Of Freshwater Ecology And Inland Fisheries; ZENG, ZHENZHONG - Central South University; TONG, DANIEL - George Mason University; BAKER, BARRY - George Mason University; ECKSTROM, MARIE - Cardiff University; BADDOCK, MATTHEW - Loughborough University; ECKARDT, FRANK - University Of Cape Town; KANDAKI, TAREK - Yale University; LEE, JEFFREY - Texas Tech University; NOBAKHT, MOHAMMED - University Of Bedfordshire; VON HOLDT, JOHANNA - University Of Cape Town; LEYS, JOHN - The Australian National University

Submitted to: Science of the Total Environment
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/25/2023
Publication Date: 5/4/2023
Citation: Chappell, A., Webb, N.P., Hennen, M., Schepanski, K., Ciais, P., Balkanski, Y., Zender, C., Tegen, I., Zeng, Z., Tong, D., Baker, B., Eckstrom, M., Baddock, M., Eckardt, F., Kandaki, T., Lee, J., Nobakht, M., Von Holdt, J., Leys, J. 2023. Satellites reveal Earth's seasonally shifting dust emission sources. Science of the Total Environment. 883. Article 163452. https://doi.org/10.1016/j.scitotenv.2023.163452.
DOI: https://doi.org/10.1016/j.scitotenv.2023.163452

Interpretive Summary: Accurately modeling the location, timing, and amount of dust emission from different landscapes is important for quantifying effects of dust on air quality and climate. This study uses satellite observations of dust sources to calibrate a new dust emission model, then applies the model to describe the timing of dust source activity around the world. The calibrated model reveals that the amount and timing of dust emissions around the world are different to the patterns established by dust models that are tuned to the amount of dust in the atmosphere. This is because different soil, vegetation, and weather factors determine dust emission as opposed to how much dust is suspended in the atmosphere at a given location. Our results show Earth’s largest dust emissions proceed seasonally from East Asian deserts in boreal spring, to Middle Eastern and North African deserts in boreal summer and then Australian shrublands in boreal autumn-winter. This new analysis of dust emissions, from global sources, have far-reaching implications for current and future interactions between dust and climate. Our findings suggest the need to re-evaluate dust cycle modelling assumptions, modifying atmospheric dust residency, deposition tuning and using dynamic models for more reliable coupled representation of dust-climate projections.

Technical Abstract: Establishing mineral dust impacts on Earth’s systems requires numerical models of the dust cycle. Differences between dust optical depth (DOD) measurements and dust cycle model simulations indicate large model uncertainty due partially to unrealistic model assumptions about dust emission frequency. Calibrating dust cycle models to DOD measurements typically in North Africa, are routinely used to reduce dust model magnitude. This calibration forces modelled dust emissions to match atmospheric DOD, but may hide the correct magnitude and frequency of dust emission events at source compensating biases in other modelled processes of the dust cycle. Therefore, it is essential to improve physically-based dust emission modules. Here we use a global collation of satellite observations from previous studies of dust emission point source (DPS) dichotomous frequency data. We show that these DPS data have little-to-no relation with MODIS DOD frequency. We then calibrate the albedo-based dust emission model using the frequency distribution of those DPS data. The global dust emission uncertainty constrained by DPS data (±3.8 kg m-2 y-1) provides a benchmark for dust emission model development. Our calibrated model results reveal much less global dust emission (29.1±14.9 Tg y-1) than previous estimates, and show seasonally shifting dust emission predominance within and between hemispheres, opposite to a persistent North African dust emission primacy widely interpreted from DOD measurements. Earth’s largest dust emissions, proceed seasonally from East Asian deserts in boreal spring, to Middle Eastern and North African deserts in boreal summer and then Australian shrublands in boreal autumn-winter. This new analysis of dust emissions, from global sources of varying geochemical properties, have far-reaching implications for current and future dust-climate effects. Our findings suggest the need to re-evaluate dust cycle modelling assumptions, modifying atmospheric dust residency, deposition tuning and using the albedo-based parameterization for more reliable coupled representation of dust-climate projections.