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  • 1
    Publication Date: 2022-03-24
    Description: Volcanic ash (VA) from explosive eruptions contributes to aerosol loadings in the atmosphere. Aside from the negative impact of VA on air quality and aviation, these particles can alter the optical and microphysical properties of clouds by triggering ice formation, thereby influencing precipitation and climate. Depending on the volcano and eruption style, VA displays a wide range of different physical, chemical, and mineralogical properties. Here, we present a unique data set on the ice nucleation activity of 15 VA samples obtained from different volcanoes worldwide. The ice nucleation activities of these samples were studied in the Aerosol Interaction and Dynamics in the Atmosphere (AIDA) cloud simulation chamber as well as with the Ice Nucleation Spectrometer of the Karlsruhe Institute of Technology (INSEKT). All VA particles nucleated ice in the immersion freezing mode from 263 to 238K with ice nucleation active site (INAS) densities ranging from ∼105 to 1011 m−2, respectively. The variabilities observed among the VA samples, at any given temperature, range over 3.5 orders of magnitude. The ice‐nucleating abilities of VA samples correlate to varying degrees with their bulk pyroxene and plagioclase contents as a function of temperature. We combined our new data set with existing literature data to develop an improved ice nucleation parameterization for natural VA in the immersion freezing mode. This should be useful for modeling the impact of VA on clouds.
    Description: Plain Language Summary: Volcanic ash particles, which are generated during volcanic eruptions, can initiate ice formation in clouds. The clouds formed by these volcanic ash particles can influence precipitation, and in turn, weather and climate. In our study, we investigated the ability with which volcanic ash particles form ice in clouds. We performed our study in a state‐of‐the‐art aerosol and cloud simulation chamber and on a cold‐stage instrument. The findings show that volcanic ash particles can form ice as effectively as mineral dust particles or their components. These results will help scientists to have a better understanding of the impact of volcanic ash particles on clouds.
    Description: Key Points: The ice‐nucleating ability of natural volcanic ash particles in the immersion freezing mode can vary by 3.5 orders of magnitude. Ice‐nucleating properties of volcanic ash particles correlate to varying degrees with their pyroxene and plagioclase contents. The temperature‐dependent immersion freezing ability of volcanic ash is approximated with an exponential fit line.
    Description: Alexander von Humboldt‐Stiftung (Humboldt‐Stiftung) http://dx.doi.org/10.13039/100005156
    Description: Marie Skłodowska‐Curie Actions
    Description: ERC 2018 ADG
    Description: Deutsche Forschungsgemeinschaft (DFG) http://dx.doi.org/10.13039/501100001659
    Description: Helmholtz Association of German Research Centres
    Description: EUROCHAMP 2020 Infrastructure Activity
    Keywords: ddc:551.38 ; ddc:549 ; ddc:552.23
    Language: English
    Type: doc-type:article
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  • 2
    Publication Date: 2023-06-06
    Description: 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 global operational numerical weather prediction models neither predict mineral dust distributions nor consider the interaction of dust with cloud microphysics, they cannot simulate this phenomenon. We have performed ICON-ART limited-area simulations with 2 km grid spacing to understand and predict the formation of dusty cirrus clouds. Based on these simulations, 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 special sub-grid 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. At the IUGG we will present first simulations with the dusty cirrus parameterization in the global ICON-ART model and discuss the occurrence of dusty cirrus in Asia.
    Language: English
    Type: info:eu-repo/semantics/conferenceObject
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  • 3
    Publication Date: 2023-06-06
    Description: For efficient planning and integration of photovoltaic power plants into the power grids, better knowledge of the aerosol-cloud-radiation interaction and more accurate radiation forecasts are needed. However, most operational numerical weather prediction models rely on an aerosol climatology and ignore the spatio-temporal variability of the atmospheric aerosol. In special weather conditions like Saharan dust outbreaks or extended wildfires, this leads to significant deficiencies in the operational forecasts. At Deutscher Wetter­dienst (DWD) and Karlsruhe Institute of Technology (KIT) the project "PermaStrom" aims to improve radiation forecasts. Using the ICON-ART modeling system the emission, transport, and deposition of mineral dust, black carbon from vegetation fires, and sea salt are explicitly simulated. To achieve the project goals and to examine in detail, the effect of Saharan dust on solar radiation, accurate and extensive measurements of the Saharan dust in the atmosphere and of the ground reaching solar radiation is needed. In our presentation, we will show results for several strong dust episodes in Germany. Dust clouds transported from the Saharan region to Germany are detected and tracked using ceilometer, spectroscopic and broadband radiation measurements from several sites within the measurement network of the DWD. We will focus on the direct and indirect aerosol effects and how these affect the solar irradiance at the ground. Furthermore, we will show how the implementation of prognostic mineral dust in the ICON-ART NWP model can improve the radiation forecasts during such events.
    Language: English
    Type: info:eu-repo/semantics/conferenceObject
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