Temperature‐dependent nucleation rate constants and freezing behavior of submicron nitric acid dihydrate aerosol particles under stratospheric conditions

Bertram, Allan K.; Sloan, J. J.

doi:10.1029/97jd02967

Cited by 51 publications

(106 citation statements)

References 33 publications

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“…The literature data sets also shown in Fig. 1 are taken from the nucleation rate measurements of (1) small droplets in an aerosol settling chamber (Disselkamp et al, 1996;Prenni et al, 1998) and an aerosol flow tube system (Bertram and Sloan, 1998a;Bertram et al, 2000), both with FITR detection for the transition from the liquid to the solid phase, and of (2) larger droplets deposited on cooled substrates with freezing detection by optical microscopy (Salcedo et al, 2000(Salcedo et al, , 2001 and Raman microscopy (Knopf et al, 2002). G act,v is plotted as function of the NAD saturation ratios, S NAD , which were, if not explicitly mentioned in the respective literature, calculated from the known composition of the nitric acid solutions and the temperature using the AIM thermodynamic model Clegg et al, 1998).…”

Section: Resultsmentioning

confidence: 99%

“…While recent field studies give direct evidence that NAT exists in PSCs (Voigt et al, 2000;Fahey et al, 2001;Brooks et al, 2003;Deshler et al, 2003;Voigt et al, 2005), laboratory investigations revealed the metastable NAD to nucleate in STS and binary water/nitric acid droplets at stratospheric temperatures (Disselkamp et al, 1996;Prenni et al, 1998;Bertram and Sloan, 1998a;Bertram et al, 2000;Salcedo et al, 2000Salcedo et al, , 2001Knopf et al, 2002;Stetzer et al, 2006). Tizek et al (2002) identified two metastable forms of the dihydrate, α-NAD and β-NAD, after annealing amorphous nitric acid samples of variable molar composition.…”

Section: Introductionmentioning

confidence: 99%

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Homogeneous nucleation rates of nitric acid dihydrate (NAD) at simulated stratospheric conditions – Part II: Modelling

2006

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Abstract. Activation energies G act for the nucleation of nitric acid dihydrate (NAD) in supercooled binary HNO 3 /H 2 O solution droplets were calculated from volume-based nucleation rate measurements using the AIDA (Aerosol, Interactions, and Dynamics in the Atmosphere) aerosol chamber of Forschungszentrum Karlsruhe. The experimental conditions covered temperatures T between 192 and 197 K, NAD saturation ratios S NAD between 7 and 10, and nitric acid molar fractions of the nucleating sub-micron sized droplets between 0.26 and 0.28. Based on classical nucleation theory, a new parameterisation for G act =A×(T ln S NAD ) −2 +B is fitted to the experimental data with A=2.5×10 6 kcal K 2 mol −1 and B=11.2−0.1(T −192) kcal mol −1 . A and B were chosen to also achieve good agreement with literature data of G act . The parameter A implies, for the temperature and composition range of our analysis, a mean interface tension σ sl =51 cal mol −1 cm −2 between the growing NAD germ and the supercooled solution. A slight temperature dependence of the diffusion activation energy is represented by the parameter B. Investigations with a detailed microphysical process model showed that literature formulations of volume-based (Salcedo et al., 2001) and surface-based (Tabazadeh et al., 2002) nucleation rates significantly overestimate NAD formation rates when applied to the conditions of our experiments.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Homogeneous nucleation rates of nitric acid dihydrate (NAD) at simulated stratospheric conditions – Part II: Modelling

2006

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“…: 64 wt% HNO 3 (Bertram and Sloan, 1998a); : binary HNO 3 /H 2 O aerosol of varying composition (Bertram et al, 2000). (b) : 54 wt% HNO 3 (Salcedo et al, 2001); : 54 wt% HNO 3 (Bertram and Sloan, 1998b).…”

Section: Resultsmentioning

confidence: 99%

“…All data points were derived from experiments with droplets consisting of binary aqueous nitric acid solutions of varying composition. (a) : 57 wt%, 60 wt%, and 64 wt% HNO 3 (Salcedo et al, 2001); : 64 wt% HNO 3 (Bertram and Sloan, 1998a). (b) : 54 wt% HNO 3 (Salcedo et al, 2001); : 54 wt% HNO 3 (Bertram and Sloan, 1998b).…”

Section: Introductionmentioning

confidence: 99%

Homogeneous nucleation of NAD and NAT in liquid stratospheric aerosols: insufficient to explain denitrification

et al. 2002

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Abstract.The nucleation of NAD and NAT from HNO 3 /H 2 O and HNO 3 /H 2 SO 4 /H 2 O solution droplets is investigated both theoretically and experimentally with respect to the formation of polar stratospheric clouds (PSCs). Our analysis shows that homogeneous NAD and NAT nucleation from liquid aerosols is insufficient to explain the number densities of large nitric acid containing particles recently observed in the Arctic stratosphere. This conclusion is based on new droplet freezing experiments employing optical microscopy combined with Raman spectroscopy. The homogeneous nucleation rate coefficients of NAD and NAT in liquid aerosols under polar stratospheric conditions derived from the experiments are < 2 × 10 −5 cm −3 s −1 and < 8 × 10 −2 cm −3 s −1 , respectively. These nucleation rate coefficients are smaller by orders of magnitude than the value of ∼ 10 3 cm −3 s −1 used in a recent denitrification modelling study that is based on a linear extrapolation of laboratory nucleation data to stratospheric conditions (Tabazadeh et al., Science, 291, 2591-2594). We show that this linear extrapolation is in disagreement with thermodynamics and with experimental data and, therefore, must not be used in microphysical models of PSCs. Our analysis of the experimental data yields maximum hourly production rates of nitric acid hydrate particles per cm 3 of air of about 3 × 10 −10 cm −3 (air) h −1 under polar stratospheric conditions. Assuming PSC particle production to proceed at this rate for two months we arrive at particle number densities of < 5 × 10 −7 cm −3 , much smaller than the value of ∼ 10 −4 cm −3 reported in recent field observations. In addition, the nitric acid hydrate production rate inferred from our data is much smaller than that required to reproduce the observed denitrification in the modelling study mentioned above. This clearly shows that homogeneous nucleation of NAD and NAT from liquid supercooled ternary solution Correspondence to: D. A. Knopf (Daniel.Knopf@atmos.umnw.ethz.ch) aerosols cannot explain the observed polar denitrification.

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“…Using Powell's multidimensional optimisation method (Press et al, 1988(Press et al, , 1992, the aerosol number density N as well as the count median diameter CMD and the mode width σ g of the log-normal size distribution were retrieved by minimising the summed squared residuals between experimental and calculated spectra. As discussed in numerous publications (Bertram and Sloan, 1998;Disselkamp et al, 1996;Echle et al, 1998;Eldering et al, 2001), the fit becomes insensitive to the parameters CMD and σ g when the particle radii are small compared to the wavelength of the incident radiation, i.e. approach the Rayleigh limit of Mie theory.…”

Section: Ftir Measurements and Retrieval Of Aerosol Parametersmentioning

confidence: 96%

A quantitative test of infrared optical constants for supercooled sulphuric and nitric acid droplet aerosols

Wagner¹,

Mangold

Möhler³

et al. 2003

Atmos. Chem. Phys.

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Abstract. In situ Fourier transform infrared (FTIR) extinction spectra of supercooled H 2 SO 4 /H 2 O and HNO 3 /H 2 O solution droplets were recorded in the large coolable aerosol chamber AIDA (Aerosol Interactions and Dynamics in the Atmosphere) of Forschungszentrum Karlsruhe for a range of aerosol compositions and at temperatures extending down to 192 K. The measured spectra were quantitatively analysed in terms of aerosol composition and mass concentration by using Mie theory in combination with published refractive index data as input parameters. Simultaneously, total sulphuric acid and nitric acid mass concentrations from filter analysis and total water concentrations measured with the Lyman-α hygrometer of Forschungszentrum Jülich were used to calculate the aerosol composition at thermodynamic equilibrium inside the aerosol chamber. By comparing these measured aerosol parameters with those retrieved from the analysis of the FTIR spectra, the accuracy of the literature data sets of refractive indices could be assessed. In summary, four data sets were tested in the H 2 SO 4 /H 2 O system as well as two data sets in the HNO 3 /H 2 O system, partly revealing significant discrepancies in the retrieved aerosol properties. Potential explanations for these differences are discussed in this paper.

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Temperature‐dependent nucleation rate constants and freezing behavior of submicron nitric acid dihydrate aerosol particles under stratospheric conditions

Cited by 51 publications

References 33 publications

Homogeneous nucleation rates of nitric acid dihydrate (NAD) at simulated stratospheric conditions – Part II: Modelling

Homogeneous nucleation rates of nitric acid dihydrate (NAD) at simulated stratospheric conditions – Part II: Modelling

Homogeneous nucleation of NAD and NAT in liquid stratospheric aerosols: insufficient to explain denitrification

A quantitative test of infrared optical constants for supercooled sulphuric and nitric acid droplet aerosols

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