Heterogeneous freezing of droplets with immersed mineral dust particles – measurements and parameterization

Niedermeier, D.; Hartmann, S.; Shaw, Raymond A.; Covert, David S.; Mentel, T. F.; Schneider, Johannes; Poulain, Laurent; Reitz, P.; Spindler, C.; Clauß, T.; Kiselev, Alexei; Hallbauer, E.; Wex, Heike; Mildenberger, K.; Stratmann, Frank

doi:10.5194/acpd-9-15827-2009

Cited by 26 publications

(53 citation statements)

References 39 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Thereby, the mineralogical composition of soil particles acting as CCN respective IN, the particles shape and surface structure, and their microphysical properties are relevant for its successful action in cloud formation processes. The role of mineral dust particles in cloud formation processes is observed during several measurement campaigns (e.g., [138]) and confirmed by laboratory studies (e.g., [139]). Modeling studies implementing observed dust-cloud interaction processes provide insights into regional and global implications as well as they enable the community to assess the relevance of dust-cloud interactions for the atmospheric energy budget, the hydrological cycle and thus the Earth climate.…”

Section: Cloudssupporting

confidence: 57%

Transport of Mineral Dust and Its Impact on Climate

Schepanski

2018

Geosciences

152

View full text Add to dashboard Cite

Mineral dust plays a pivotal role in the Earth's system. Dust modulates the global energy budget directly via its interactions with radiation and indirectly via its influence on cloud and precipitation formation processes. Dust is a micro-nutrient and fertilizer for ecosystems due to its mineralogical composition and thus impacts on the global carbon cycle. Hence, dust aerosol is an essential part of weather and climate. Dust suspended in the air is determined by the atmospheric dust cycle: Dust sources and emission processes define the amount of dust entrained into the atmosphere. Atmospheric mixing and circulation carry plumes of dust to remote places. Ultimately, dust particles are removed from the atmosphere by deposition processes such as gravitational settling and rain wash out. During its residence time, dust interacts with and thus modulates the atmosphere resulting into changes such as in surface temperature, wind, clouds, and precipitation rates. There are still uncertainties regarding individual dust interactions and their relevance. Dust modulates key processes that are inevitably influencing the Earth energy budget. Dust transport allows for these interactions and at the same time, the intermittency of dust transport introduces additional fluctuations into a complex and challenging system.

show abstract

Section: Cloudssupporting

confidence: 57%

Transport of Mineral Dust and Its Impact on Climate

Schepanski

2018

Geosciences

152

View full text Add to dashboard Cite

show abstract

“…Figure 3 shows an example of the image frame being filled with droplets and highlights the maximum number of droplets that could be analysed per experiment based on the optics used, a number that could be increased if needed by either generating smaller droplets, using lower-magnification optics, or by using a CCD camera with a wider field of view. The fraction of droplets frozen, f ice ( T ), by temperature T for a range of atmospherically relevant INP was calculated (Vali 1971 , 1994 ; Connolly et al 2009 ; Niedermeier et al 2010 ; Niemand et al 2012 ): where n ice ( T ) is the total number of frozen droplets at temperature T and n tot is the total number of droplets. In order to avoid contact freezing, i.e.…”

Section: Resultsmentioning

confidence: 99%

The study of atmospheric ice-nucleating particles via microfluidically generated droplets

Tarn

Sikora

Porter

et al. 2018

Microfluid Nanofluid

View full text Add to dashboard Cite

Ice-nucleating particles (INPs) play a significant role in the climate and hydrological cycle by triggering ice formation in supercooled clouds, thereby causing precipitation and affecting cloud lifetimes and their radiative properties. However, despite their importance, INP often comprise only 1 in 103–106 ambient particles, making it difficult to ascertain and predict their type, source, and concentration. The typical techniques for quantifying INP concentrations tend to be highly labour-intensive, suffer from poor time resolution, or are limited in sensitivity to low concentrations. Here, we present the application of microfluidic devices to the study of atmospheric INPs via the simple and rapid production of monodisperse droplets and their subsequent freezing on a cold stage. This device offers the potential for the testing of INP concentrations in aqueous samples with high sensitivity and high counting statistics. Various INPs were tested for validation of the platform, including mineral dust and biological species, with results compared to literature values. We also describe a methodology for sampling atmospheric aerosol in a manner that minimises sampling biases and which is compatible with the microfluidic device. We present results for INP concentrations in air sampled during two field campaigns: (1) from a rural location in the UK and (2) during the UK’s annual Bonfire Night festival. These initial results will provide a route for deployment of the microfluidic platform for the study and quantification of INPs in upcoming field campaigns around the globe, while providing a benchmark for future lab-on-a-chip-based INP studies.Electronic supplementary materialThe online version of this article (10.1007/s10404-018-2069-x) contains supplementary material, which is available to authorized users.

show abstract

“…The influence of stochastic fluctuations of the ice germ size in a supercooled droplet on the freezing temperature of the droplet is less clear and has been the subject of recent research [Vali, 2008]. Formulations on the basis of both singular hypotheses [e.g., Connolly et al, 2009] and stochastic hypotheses [e.g., Niedermeier et al, 2009] have been used to describe droplet freezing rates in recent studies.…”

mentioning

confidence: 99%

Experimental study on the ice nucleation ability of size‐selected kaolinite particles in the immersion mode

et al. 2010

View full text Add to dashboard Cite

[1] The recently developed immersion mode cooling chamber has been used as an extension of the Zurich ice nucleation chamber (ZINC) in order to measure the ice nucleation efficiency of size-selected kaolinite particles in the immersion mode. Particles with selected diameters of 200, 400, and 800 nm have been activated as cloud condensation nuclei in order to obtain water droplets with single immersed particles. After continuous cooling of the droplets to the experimental temperature in ZINC, the frozen fraction of the droplets was measured with a recently developed depolarization detector, the ice optical detector (IODE). Temperatures below −30°C were necessary to freeze 50% of the droplets throughout the investigated size range. Although not very strong, a size dependence of the freezing efficiency has been observed. The median freezing temperature increases from −35°C for 200 nm kaolinite particles to −33°C for 800 nm particles. An experiment with 200 nm ammonium sulfate particles in the same temperature range resulted in no significant frozen fraction of the droplets. This suggests that the ice crystals observed in experiments with kaolinite particles nucleated heterogeneously. The temperature-dependent frozen fraction of water droplets has been fitted with different theoretical models. Comparison of the resulting fit curves with the data suggests that including the concept of active sites in the description of the ice nucleus surface is more appropriate than the approximation of a constant contact angle.Citation: Lüönd, F., O. Stetzer, A. Welti, and U. Lohmann (2010), Experimental study on the ice nucleation ability of size-selected kaolinite particles in the immersion mode,

show abstract

Heterogeneous freezing of droplets with immersed mineral dust particles – measurements and parameterization

Cited by 26 publications

References 39 publications

Transport of Mineral Dust and Its Impact on Climate

Transport of Mineral Dust and Its Impact on Climate

The study of atmospheric ice-nucleating particles via microfluidically generated droplets

Experimental study on the ice nucleation ability of size‐selected kaolinite particles in the immersion mode

Contact Info

Product

Resources

About