19 Jul 2021

19 Jul 2021

Review status: this preprint is currently under review for the journal ACP.

Quantification of the dust optical depth across spatiotemporal scales with the MIDAS global dataset (2003–2017)

Antonis Gkikas1, Emmanouil Proestakis1, Vassilis Amiridis1, Stelios Kazadzis2,3, Enza Di Tomaso4, Eleni Marinou1,5, Nikos Hatzianastassiou6, Jasper F. Kok7, and Carlos Pérez García-Pando4,8 Antonis Gkikas et al.
  • 1Institute for Astronomy, Astrophysics, Space Applications and Remote Sensing, National Observatory of Athens, Athens, 15236, Greece
  • 2Physikalisch-Meteorologisches Observatorium Davos, World Radiation Center, Switzerland
  • 3Institute of Environmental Research and Sustainable Development, National Observatory of Athens, Greece
  • 4Barcelona Supercomputing Center, Barcelona, Spain
  • 5Deutsches Zentrum für Luft- und Raumfahrt (DLR), Institut für Physik der Atmosphäre, Oberpfaffenhofen, Germany
  • 6Laboratory of Meteorology, Department of Physics, University of Ioannina, Ioannina, Greece
  • 7Department of Atmospheric and Oceanic Sciences, University of California, Los Angeles, CA 90095, USA
  • 8ICREA, Catalan Institution for Research and Advanced Studies, Barcelona, Spain

Abstract. Quantifying the dust optical depth (DOD) and its uncertainty across spatiotemporal scales is key to understanding and constraining the dust cycle and its interactions with the Earth System. This study quantifies the DOD along with its monthly and year-to-year variability between 2003 and 2017 at global and regional levels based on the MIDAS (ModIs Dust AeroSol) dataset, which combines MODIS-Aqua retrievals and MERRA-2 reanalysis products. We also describe the annual and seasonal geographical distributions of DOD across the main dust source regions and transport pathways. MIDAS provides columnar mid-visible (550 nm) DOD at fine spatial resolution (0.1° × 0.1°), expanding the current observational capabilities for monitoring the highly variable spatiotemporal features of the dust burden. We obtain a global DOD of 0.032 ± 0.003 – approximately a quarter (23.4 % ± 2.4 %) of the global AOD – with about one order of magnitude more DOD in the northern hemisphere (0.056 ± 0.004; 31.8 % ± 2.7 %) than in the southern hemisphere (0.008 ± 0.001; 8.2 % ± 1.1 %) and about 3.5 times more DOD over land (0.070 ± 0.005) than over ocean (0.019 ± 0.002). The northern hemisphere monthly DOD is highly correlated with the corresponding monthly AOD (R2 = 0.94) and contributes 20 % to 48 % of it, both indicating a dominant dust contribution. In contrast, the contribution of dust to the monthly AOD does not exceed 17 % in the southern hemisphere, although the uncertainty in this region is larger. Among the major dust sources of the planet, the maximum DODs (~1.2) are recorded in the Bodélé Depression of the northern Lake Chad Basin, whereas moderate-to-high intensities are encountered in the Western Sahara (boreal summer), along the eastern parts of the Middle East (boreal summer) and in the Taklamakan Desert (spring). Over oceans, major long-range dust transport is observed primarily along the Tropical Atlantic (intensified during boreal summer) and secondarily in the North Pacific (intensified during boreal spring). Our calculated global and regional averages and associated uncertainties are consistent with some but not all recent observationally based studies. Our work provides a simple, yet flexible method to estimate consistent uncertainties across spatiotemporal scales, which will enhance the use of the MIDAS dataset in future studies.

Antonis Gkikas et al.

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on acp-2021-572', Anonymous Referee #1, 03 Aug 2021
  • RC2: 'Comment on acp-2021-572', Anonymous Referee #2, 05 Aug 2021

Antonis Gkikas et al.

Data sets

ModIs Dust AeroSol (MIDAS) Antonis Gkikas, Emmanouil Proestakis, Vassilis Amiridis, Stelios Kazadzis, Enza Di Tomaso, Alexandra Tsekeri, Eleni Marinou, Nikos Hatzianastassiou, and Carlos Pérez García-Pando

Antonis Gkikas et al.


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Short summary
We present a comprehensive climatological analysis of dust optical depth (DOD) relying on the MIDAS dataset. MIDAS provides columnar mid-visible (550 nm) DOD at fine spatial resolution (0.1 × 0.1) over a 15-year period (2003–2017). In the current study, the analysis is performed at various spatial (from regional to global) and temporal (from months to years) scales. More specifically, focus is given on specific regions hosting the major dust sources as well as downwind areas of the planet.