RP 6: From lab to field - examining immersion freezing of atmospheric relevant ice nucleating particles
Dr. Heike Wex
Leibniz-Institute for Tropospheric Research, Leipzig
Assistance: Dr. Susan Hartmann, Sarah Grawe (PhD student), Thomas Conrath (technician), Stefanie Augustin (PhD student)
During phase 1 of this project, immersion freezing measurements were done using the Leipzig Aerosol Cloud Interaction Simulator (LACIS, Hartmann et al., 2011) in RP6. Many cooperations took place, including both INUIT partners and partners form outside of INUIT. The following results have been obtained:
- measurements of coated and uncoated different mineral dusts (two kaolinite samples, illite-NX and a feldspar sample) corroborated that K-feldspar is an important mineral dust for ice nucleation in general and the most ice active mineral dust studied so far (Wex et al., 2014; Augustin-Bauditz et al., 2015) - see Figure 1
- LACIS and CFDC measurements of immersion freezing for kaolinite samples were in good agreement with each other (Wex et al., 2014)
- based on measurements of coated kaolinite particles with LACIS and CFDC, we claim that there are only three basically different freezing processes, enabling a joint description of immersion freezing and condensation freezing (Wex et al., 2014) - see Figure 2
- immersion freezing was observed to scale well with particle surface area for kaolinite particles (Hartmann et al., 2015), stressing the importance to account for multiply charged particles when using size-segregated particles
- of two instrumental inter-comparisons done during INUIT-1, one was led by RP6, where it was found that all instruments included were in good agreement when measuring immersion freezing induced by Snomax (Wex et al., 2015) - see Fig. 3
- Illite-NX was examined in the second inter-comparison led by RP7, including also LACIS and 16 additional instruments (Hiranuma et al., 2015)
- parameterizations were developed for nucleation rates of single ice nucleation active macromolecules (INM) from P. syringae bacteria and Birch pollen (Hartmann et al., 2013, Augustin et al., 2013) - see Figure 4
- a new, computationally efficient version of the Soccer Ball Model was developed contributing to modeling in RP5, together with contact angle distributions derived from LACIS for a suite of different INP (Niedermeier et al., 2014, Niedermeier et al., 2015)
- LACIS measurements were done for particles consisting of mixtures of a mineral dust together with biologic INM from pollen (Augustin-Bauditz et al., 2015) and for particles containing INM from fungal spores (Pummer et al., 2015)
During phase 1, mineral dust particles and biological particles were mostly examined separately. The main goals of phase 2 are on one hand grouped around fundamentally understanding the workings of heterogeneous ice nucleation in general. On the other hand, we will also put an additional stronger focus on the examination of including atmospherically more relevant samples such as mixed biological-mineral particles, soil dusts and others as ashes and particles from the marine surface layer, including the samples suggested for inter-comparison measurements within INUIT Phase 2. Topics aimed at are:
Topics aimed at are:
- examination, quantification and parameterization of the immersion freezing behavior of various INP, including biological (fungal) and especially mixed biological-mineral INP, particularly more atmospherically relevant materials (e.g., soil dusts) and INUIT-2 test samples;
- examination of the influences of surface treatments (e.g., coatings) on the ice nucleation behavior of biological, mixed biological-mineral and soil dust INP in order to gain information on the INP’s chemical and mineralogical nature and possible effects of aging, adding to our understanding what it is that makes a particle an effective INP;
- deriving and inter-comparing different parameterizations (both time dependent and time independent ones) and making them available for implementation in e.g., cloud resolving and/or larger scale models; deepening the understanding of the importance of time dependence for the description of the ice nucleation process;
- extending our investigations towards the identification of the heterogeneous freezing mechanism below water saturation, i.e., towards immersion freezing in highly concentrated solutions and deposition ice nucleation.
Augustin et al. (2013), Immersion freezing of birch pollen washing water, Aerosol Chem. Phys., 13, 10989–11003.
Augustin-Bauditz et al. (2014), The immersion mode ice nucleation behavior of mineral dusts: A comparison of different pure and surface modifed dust, Geophys. Res. Lett., 41, doi:10.1002/2014GL061317.
Augustin-Bauditz et al. (2015), The immersion freezing behavior of mineral dust particles mixed with biological substances, Atmos. Chem. Phys. Discuss., 15, 29639-29671.
Hartmann et al. (2011), Homogeneous and heterogeneous ice nucleation at LACIS: Operating principle and theoretical studies, Atmos. Chem. Phys., 11, 1753–1767.
Hartmann et al. (2013), Immersion freezing of ice nucleating active protein complexes, Atmos. Chem. Phys., 13, 5751-5766.
Hartmann et al. (2015), Immersion freezing of kaolinite - scaling with particle surface area, J. Atmos. Sci., 10.1175/JAS-D-15-0057.1.
Hiranuma et al. (2015), A comprehensive laboratory study on the immersion freezing behavior of illite NX particles: a comparison of seventeen ice nucleation measurement techniques, Atmos. Chem. Phys., 15, 2489–2518, doi:10.5194/acp-15-2489-2015.
Niedermeier et al. (2014), A computationally efficient description of heterogeneous freezing: A simplified version of the Soccer ball model, Geophys. Res. Lett., 41, doi:10.1002/2013GL058684. Niedermeier et al. (2015), Can we define an asymptotic value for the ice active surface site density for heterogeneous ice nucleation?, J. Geophys. Res., doi:10.1002/2014JD022814.
Pummer et al. (2015), Ice nucleation by water-soluble macromolecules, Atmos. Chem. Phys., 15, 4077–4091, doi:10.5194/acp-15-4077-2015.
Wex et al. (2014), Kaolinite particles as ice nuclei: learning from the use of different kaolinite samples and different coatings, Atmos. Chem. Phys., 14, doi:10.5194/acp-14-5529-2014.
Wex et al. (2015), Intercomparing different devices for the investigation of ice nucleating particles using Snomax as test substance, Atmos. Chem. Phys., 15, 1463–1485, doi:10.5194/acp-15-1463-2015.