11 Nov 2022
11 Nov 2022
Status: this preprint is currently under review for the journal ACP.

Aerosol-cloud-radiation interaction during Saharan dust episodes: The dusty cirrus puzzle

Axel Seifert1, Vanessa Bachmann1, Florian Filipitsch3, Jochen Förstner1, Christian Grams4, Gholam Ali Hoshyaripour4, Julian Quinting4, Anika Rohde4, Heike Vogel4, Annette Wagner2, and Bernhard Vogel4 Axel Seifert et al.
  • 1Deutscher Wetterdienst, Offenbach, Germany
  • 2Deutscher Wetterdienst, Hohenpeißenberg, Germany
  • 3Deutscher Wetterdienst, Lindenberg, Germany
  • 4Institute of Meteorology and Climate Research (IMK-TRO), Karlsruhe Institute of Technology (KIT), Karlsruhe, Germany

Abstract. Dusty cirrus clouds are extended optically thick cirrocumulus decks that occur during strong mineral dust events. So far they have been mostly documented over Europe associated with dust-infused baroclinic storms. Since today's numerical weather prediction models neither predict mineral dust distributions nor consider the interaction of dust with cloud microphysics, they cannot simulate this phenomenon. We postulate that the dusty cirrus forms through a mixing instability of moist clean air with drier dusty air. A corresponding sub-grid parameterization is suggested and tested in the ICON-ART model. Only with help of this parameterization ICON-ART is able to simulate the formation of the dusty cirrus, which leads to substantial improvements in cloud cover and radiative fluxes compared to simulations without this parameterization. A statistical evaluation over six Saharan dust events with and without observed dusty cirrus shows robust improvements in cloud and radiation scores. The ability to simulate dusty cirrus formation removes the linear dependency on mineral dust aerosol optical depth from the bias of the radiative fluxes. This suggests that the formation of dusty cirrus clouds is the dominant aerosol-cloud-radiation effect of mineral dust over Europe.

Axel Seifert et al.

Status: open (until 23 Dec 2022)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse

Axel Seifert et al.

Axel Seifert et al.


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Short summary
We investigate how mineral dust can lead to the formation of cirrus clouds. Dusty cirrus clouds lead to a reduction in solar radiation at the surface and, hence, a reduced photovoltaic power generation. Current weather prediction systems are not able to predict this interaction of mineral dust and cirrus clouds. We have developed a new physical description of the formation of dusty cirrus clouds. Overall, we can show a considerable improvement in forecast quality of clouds and radiation.