Measurements of heterogeneous ice nuclei in the western United States in springtime and their relation to aerosol characteristics

Richardson, M.; DeMott, Paul J.; Kreidenweis, Sonia M.; Cziczo, D. J.; Dunlea, E. J.; Jimenez, José L.; Thomson, D. S.; Ashbaugh, Lowell L.; Borys, Randolph D.; Westphal, Douglas L.; Casuccio, Gary; Lersch, Traci L.

doi:10.1029/2006jd007500

Cited by 183 publications

(196 citation statements)

References 67 publications

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“…The apparent relation of ice nuclei number concentrations to the number concentrations of certain subsets of the atmospheric aerosol has been recognized for more than 40 years (20,(22)(23)(24). All of these studies noted either linear or power law relations between ice nuclei and aerosol number concentrations within restricted size ranges, generally those particles larger than 0.3-μm diameter.…”

Section: Discussionmentioning

confidence: 99%

Predicting global atmospheric ice nuclei distributions and their impacts on climate

DeMott

Prenni²,

Liu³

et al. 2010

Proc. Natl. Acad. Sci. U.S.A.

1,128

1,218

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Knowledge of cloud and precipitation formation processes remains incomplete, yet global precipitation is predominantly produced by clouds containing the ice phase. Ice first forms in clouds warmer than −36°C on particles termed ice nuclei. We combine observations from field studies over a 14-year period, from a variety of locations around the globe, to show that the concentrations of ice nuclei active in mixed-phase cloud conditions can be related to temperature and the number concentrations of particles larger than 0.5 μm in diameter. This new relationship reduces unexplained variability in ice nuclei concentrations at a given temperature from ∼10 3 to less than a factor of 10, with the remaining variability apparently due to variations in aerosol chemical composition or other factors. When implemented in a global climate model, the new parameterization strongly alters cloud liquid and ice water distributions compared to the simple, temperature-only parameterizations currently widely used. The revised treatment indicates a global net cloud radiative forcing increase of ∼1 W m −2 for each order of magnitude increase in ice nuclei concentrations, demonstrating the strong sensitivity of climate simulations to assumptions regarding the initiation of cloud glaciation.aerosol indirect effects | climate forcing | ice nucleation T he formation of ice in clouds is of vital importance to life on Earth, as ice formation is one of the key processes initiating precipitation. In addition, since ice nucleation is tied to the action of specific aerosol particles, natural and human impacts on ice nucleation in the atmosphere can lead to alteration of the energy and hydrological cycles (1). Ice nucleation in clouds occurs via two primary pathways: homogeneous freezing of liquid particles below about −36°C and heterogeneous ice nucleation, triggered by "ice nuclei" that possess surface properties favorable to lowering the energy barrier to crystallization. Once ice is formed, some circumstances may favor generation of ice from preexisting ice particles, or secondary ice formation (2). Heterogeneous ice nucleation remains an enigmatic topic involving multiple mechanistic processes (3) that sometimes defy ready investigation or description. Despite the lack of a complete understanding of heterogeneous ice formation processes, a variety of techniques have been developed and used to detect the presence of and quantify the number concentrations of atmospheric ice nuclei as a function of temperature (4). These measurements show that, although generally representing only 1 in 10 5 of ambient particles in the free troposphere (5), ice nuclei (IN) can nevertheless exert an influence on cold cloud microphysical processes that is disproportionate to their low number concentrations. For example, the concentrations of IN needed to explain observed precipitation rates range from as small as 10 −3 per standard liter at −10°C (6) to more typical estimates of a few IN per standard liter at −20°C (7).The sensitivity of precipitation initiation fro...

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Section: Discussionmentioning

confidence: 99%

Predicting global atmospheric ice nuclei distributions and their impacts on climate

DeMott

Prenni²,

Liu³

et al. 2010

Proc. Natl. Acad. Sci. U.S.A.

1,128

1,218

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“…More recently, single particle mass spectrometry has shown that mineral dusts and metallic particles are substantially enhanced in the fraction of aerosol that nucleate ice heterogeneously, relative to the background aerosol (DeMott et al, 2003a, b;Richardson et al, 2007;Mertes et al, 2007;Pratt et al, 2009). Richardson et al (2007) demonstrated that mineral dust represented only a few percent of the total background aerosol, but represented ∼1/3 of the particles that served as ice nuclei in mixed phase clouds. showed that, in the Amazon region where ice nucleation is dominated by biogenic material above 248 K, ice nucleation on mineral dust becomes increasingly important below 246 K.…”

Section: Introductionmentioning

confidence: 99%

“…Early studies where residues of snowflakes were analysed by electron microscopy demonstrated that clay minerals were present inside 28 to 88% of snowflakes, depending on location (Pruppacher and Klett, 1997). More recently, single particle mass spectrometry has shown that mineral dusts and metallic particles are substantially enhanced in the fraction of aerosol that nucleate ice heterogeneously, relative to the background aerosol (DeMott et al, 2003a, b;Richardson et al, 2007;Mertes et al, 2007;Pratt et al, 2009). Richardson et al (2007) demonstrated that mineral dust represented only a few percent of the total background aerosol, but represented ∼1/3 of the particles that served as ice nuclei in mixed phase clouds.…”

Section: Introductionmentioning

confidence: 99%

Heterogeneous freezing of water droplets containing kaolinite particles

et al. 2011

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Abstract. Clouds composed of both ice particles and supercooled liquid water droplets exist at temperatures above ∼236 K. These mixed phase clouds, which strongly impact climate, are very sensitive to the presence of solid particles that can catalyse freezing. In this paper we describe experiments to determine the conditions at which the clay mineral kaolinite nucleates ice when immersed within water droplets. These are the first immersion mode experiments in which the ice nucleating ability of kaolinite has been determined as a function of clay surface area, cooling rate and also at constant temperatures. Water droplets containing a known amount of clay mineral were supported on a hydrophobic surface and cooled at rates of between 0.8 and 10 K min −1 or held at constant sub-zero temperatures. The time and temperature at which individual 10-50 µm diameter droplets froze were determined by optical microscopy. For a cooling rate of 10 K min −1 , the median nucleation temperature of 10-40 µm diameter droplets increased from close to the homogeneous nucleation limit (236 K) to 240.8 ± 0.6 K as the concentration of kaolinite in the droplets was increased from 0.005 wt% to 1 wt%. This data shows that the probability of freezing scales with surface area of the kaolinite inclusions. We also show that at a constant temperature the number of liquid droplets decreases exponentially as they freeze over time. The constant cooling rate experiments are consistent with the stochastic, singular and modified singular descriptions of heterogeneous nucleation; however, freezing during cooling and at constant temperature can be reconciled best with the stochastic approach. We report temperature dependent nucleation rate coefficients (nucleation events per unit Correspondence to: B. J. Murray (b.j.murray@leeds.ac.uk) time per unit area) for kaolinite and present a general parameterisation for immersion nucleation which may be suitable for cloud modelling once nucleation by other important ice nucleating species is quantified in the future.

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“…This is corroborated by the analysis of Borys et al (2000) who found substantial sulfate and nitrate mass in cloud water samples collected at SPL during the winter. Richardson et al (2007) used an aerosol mass spectrometer and other methods to measure aerosol composition at SPL during April and May of 2004. They also found high proportions of inorganic compounds that dominated the total aerosol mass except during dust events.…”

Section: Ccn Closure Attemptmentioning

confidence: 99%

Cold and transition season cloud condensation nuclei measurements in western Colorado

Ward

Cotton

2011

Atmos. Chem. Phys.

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Abstract.Recent studies have shown that orographic precipitation and the water resources that depend on it in the Colorado Rocky Mountains are sensitive to the variability of the region's aerosols, whether emitted locally or from distant sources. However, observations of cloud droplet nucleating aerosols in western Colorado, climatologically upwind of the Colorado Rocky Mountains, have been limited to a few studies at a single, northern site. To address this knowledge gap, atmospheric aerosols were sampled at a ground site in southwestern Colorado and in low-level north to south transects of the Colorado Western Slope as part of the Inhibition of Snowfall by Pollution Aerosols (ISPA-III) field campaign. Total particle and cloud condensation nuclei (CCN) number concentrations were measured for a 24-day period in Mesa Verde National Park, in September and October 2009. Regression analysis showed a positive relationship between mid-troposphere atmospheric pressure to the west of the site and the total particle count at the ground site, but no similar statistically significant relationship was found for the observed CCN. These data were supplemented with particle and CCN number concentration, as well as particle size distribution measurements collected aboard the King Air platform during December 2009. A CCN closure attempt was performed and suggested that the sampled aerosol may have had a low hygroscopicity that changed little with the largescale wind direction. Together, the sampled aerosols from these field programs were characteristic of a rural continental environment with CCN number concentrations that varied slowly in time, and little in space along the Western Slope.

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Measurements of heterogeneous ice nuclei in the western United States in springtime and their relation to aerosol characteristics

Cited by 183 publications

References 67 publications

Predicting global atmospheric ice nuclei distributions and their impacts on climate

Predicting global atmospheric ice nuclei distributions and their impacts on climate

Heterogeneous freezing of water droplets containing kaolinite particles

Cold and transition season cloud condensation nuclei measurements in western Colorado

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