Preprints
https://doi.org/10.5194/acp-2022-94
https://doi.org/10.5194/acp-2022-94
 
07 Apr 2022
07 Apr 2022
Status: this preprint is currently under review for the journal ACP.

Modelling coarse and giant desert dust particles

Eleni Drakaki1,2, Vassilis Amiridis1, Alexandra Tsekeri1, Antonis Gkikas1, Emmanouil Proestakis1, Sotirios Mallios1, Stavros Solomos3, Christos Spyrou1, Eleni Marinou1,4, Claire Ryder5, Demetri Bouris6, and Petros Katsafados2 Eleni Drakaki et al.
  • 1IAASARS, National Observatory of Athens, Athens GR-15236, Greece
  • 2Harokopion University of Athens (HUA), Department of Geography, Athens GR-17671, Greece
  • 3Academy of Athens, Research Centre for Atmospheric Physics and Climatology, Athens GR-10679, Greece
  • 4Institut für Physik der Atmosphäre, Deutsches Zentrum für Luft- und Raumfahrt, Oberpfaffenhofen, Germany
  • 5University of Reading, Department of Meteorology, Reading, RG6 6BB, UK
  • 6National Technical University of Athens, School of Mechanical Engineering, Athens, GR-15780, Greece

Abstract. Dust particles larger than 20 µm in diameter (0.2 μm < D < 100 µm) have been regularly observed to remain airborne during long-range transport. In this work we extend the parameterization of mineral dust cycle in the GOCART-AFWA dust scheme of WRFV4.2.1, to include also such coarse and giant particles. The initial particle size distribution in our parameterization is based on observations over desert dust sources and the Stokes’ drag coefficient has also been updated to account for dust particles of all sizes (Re < 105). The new code is applied to simulate dust transport over Cape Verde during the August 2015 AER -D campaign. Model results are evaluated using both airborne dust measurements and the CALIPSO-LIVAS pure dust product. The results show that the modeled lifetimes of the coarser particles are shorter than those observed. Various processes are proposed to explain such inaccuracies, such as the electric field inside dust plumes and non-spherical aerodynamics. Additional sensitivity runs are performed by artificially reducing the settling velocities of the particles to compensate for such underrepresented processes in the model. Our simulations show that particles with diameters of 5–17 μm and 40–100 μm are better represented assuming 80 % reduction in settling velocity (UR80) while particles at the range 17–40 μm are better represented in the UR60 scenario. The overall statistical analysis shows that the UR80 experiment presents the closest agreement with the airborne in situ measurements both in Cape Verde and over the sources. The UR80 experiment improves also the vertical distribution of dust in the model, as compared to the CALIPSO-LIVAS pure dust product. Further research is requested in order to understand the physical processes behind the reduction of settling velocity.

Eleni Drakaki 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-2022-94', Anonymous Referee #1, 28 Apr 2022
  • RC2: 'Comment on acp-2022-94', Anonymous Referee #3, 30 Apr 2022
  • RC3: 'Comment on acp-2022-94', Anonymous Referee #2, 09 May 2022

Eleni Drakaki et al.

Eleni Drakaki et al.

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Short summary
State-of-the-art atmospheric dust models have limitations in accounting for a realistic dust size distribution (emission, transport). We improve the parameterization of the mineral dust cycle by including particles with diameter > 20 μm, as indicated by observations over deserts. Moreover, we investigate the effects of reduced settling velocities of dust particles. Model results are evaluated using airborne and spaceborne dust measurements above Cape Verde.
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