10th International Aerosol Conference September 2 - September 7, 2018 America's Center Convention Complex St. Louis, Missouri, USA
Abstract View
The Influence of Dust Mineralogy on Its Aerosol Suspension Freezing Behavior
KRISTINA HÖHLER, Romy Ullrich, Thea Schiebel, Nadine Schittko, Barbara Dietel, Peter G. Weidler, Konrad Kandler, Ottmar Möhler, Thomas Leisner, Karlsruhe Institute of Technology
Abstract Number: 322 Working Group: Unraveling the Many Facets of Ice Nucleating Particles and Their Interactions with Clouds
Abstract In mixed phase clouds, the freezing of individual cloud droplets is triggered by the presence of so-called ice nucleating particles (INPs). As this first ice formation usually is followed by a chain reaction of secondary ice multiplication processes, the abundance of these very rare aerosol species is critically for the initialization of precipitation and for cloud radiative properties.
Because of its high global atmospheric abundance, soil dust from arid regions is known to contribute significantly to INP concentrations, especially for freezing temperatures below -15°C. In past studies it was suggested that the immersion freezing behavior of this predominantly mineral dust can be described by a single parameterization disregarding the dust origin (Ullrich et al., 2017). On the other hand, some laboratory studies on suspension freezing behavior suggest that single mineralogical components, especially K-Feldspar, control the ice nucleating potential of the aerosols (Atkinson et al., 2013). This might imply the need for understanding the global distribution of aerosols with various compositions and the use of individual parameterizations for specific minerals in weather and cloud models.
In the INUIT09 campaign, organized at the AIDA (Aerosol Interaction and Dynamics in the Atmosphere) facility at KIT in Germany in July 2017, mineral dusts of different origin were carefully characterized according mineralogical composition and ice nucleation activity. Amongst other techniques, the new Ice Nucleation Spectrometer of the Karlsruhe Institute of Technology (INSEKT) was used to investigate the immersion freezing behavior of aerosol that was dry dispersed into a large vessel, sampled on filters and washed off. The construction of INSEKT was inspired by the design of the Colorado State University Ice Spectrometer developed by Hill et al. (2016), which enables the investigation of 50µl samples in 96-well PCR plates inserted in a temperature controlled aluminum block. INSEKT works with automated optical freezing detection during defined cooling ramps and can be used to study freezing events to temperatures as low as -27°C.
We will show first results on the immersion freezing behavior of eleven samples from different arid regions and discuss correlations with particle mineral compositions.