Impact of gas‐phase HNO<sub>3</sub> and NH<sub>3</sub> on microphysical processes in atmospheric clouds

Hegg, D́ean A.

doi:10.1029/1999gl011252

Cited by 28 publications

(25 citation statements)

References 19 publications

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“…Several modelling studies have shown that acidic gases, like nitric acid and hydrochloric acid, may increase the amount of solute in the liquid aerosol particles prior to cloud droplet formation and thus enhance their ability to form cloud droplets (Kulmala et al, 1993;Nenes et al, 2002;Xue and Feingold, 2004;Romakkaniemi et al, 2005). This effect is further enhanced by the presence of a gaseous base, like ammonia, that neutralizes the liquid solutions, allowing the uptake of both acid and base at a lower relative humidity (Hegg, 2000;Kokkola et al, 2003a;Romakkaniemi et al, 2005). In addition to the condensation, semivolatile gases can also evaporate from the particles, which would decrease their CCN activity.…”

Section: Introductionmentioning

confidence: 99%

Ammonium nitrate evaporation and nitric acid condensation in DMT CCN counters

et al. 2014

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Abstract. The effect of inorganic semivolatile aerosol compounds on the cloud condensation nucleus (CCN) activity of aerosol particles was studied by using a computational model for a DMT-CCN counter, a cloud parcel model for condensation kinetics and experiments to quantify the modelled results. Concentrations of water vapour and semivolatiles as well as aerosol trajectories in the CCN column were calculated by a computational fluid dynamics model. These trajectories and vapour concentrations were then used as an input for the cloud parcel model to simulate mass transfer kinetics of water and semivolatiles between aerosol particles and the gas phase.Two different questions were studied: (1) how big a fraction of semivolatiles is evaporated from particles after entering but before particle activation in the DMT-CCN counter? (2) How much can the CCN activity be increased due to condensation of semivolatiles prior to the maximum water supersaturation in the case of high semivolatile concentration in the gas phase?Both experimental and modelling results show that the evaporation of ammonia and nitric acid from ammonium nitrate particles causes a 10 to 15 nm decrease to the critical particle size in supersaturations between 0.1 % and 0.7 %. On the other hand, the modelling results also show that condensation of nitric acid or similar vapour can increase the CCN activity of nonvolatile aerosol particles, but a very high gas phase concentration (as compared to typical ambient conditions) would be needed. Overall, it is more likely that the CCN activity of semivolatile aerosol is underestimated than overestimated in the measurements conducted in ambient conditions.

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Section: Introductionmentioning

confidence: 99%

Ammonium nitrate evaporation and nitric acid condensation in DMT CCN counters

et al. 2014

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“…The strength of the HNO 3 effect depends on the acidity of aerosol particles (Hegg, 2000). To take this into account, we have included the variable B c into parameterization.…”

Section: Comparison Of Parameterization With Parcel Modelmentioning

confidence: 99%

“…Previous cloud model studies have shown that water-soluble trace gases such as nitric acid (HNO 3 ) and ammonia (NH 3 ) can increase the cloud droplet number concentration (CDNC) significantly (Kulmala et al, 1993;Korhonen et al, 1996;Hegg, 2000). The increase in the cloud droplet number concentration will reduce the mean cloud droplet size which in turn increases cloud albedo (Twomey, 1974).…”

Section: Introductionmentioning

confidence: 99%

Parameterization of the nitric acid effect on CCN activation

2005

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Abstract. In this paper we present a parameterization of the nitric acid effect on cloud droplet formation. The new parameterization is intended to be used in large scale models in order to obtain regional and global estimates of the effect of nitric acid on cloud drop concentrations and the radiative balance. The parameterization is based on numerical air parcel model simulations and can be applied for unimodal and bimodal lognormal aerosol particle size distributions in a large variety of different conditions. In addition to the aerosol particle distribution and gas-phase HNO 3 concentration, the parameterization requires temperature, total pressure, updraft velocity, and the number concentration of cloud droplets formed at zero nitric acid concentration, as input parameters. The parameterization is also suitable for describing the effect of hydrochloric acid on the cloud drop concentrations, and in practice, the HNO 3 and HCl concentrations can be summed up to yield the total effect. The comparison between the parameterization and the results from numerical air parcel model simulations show good consistency.

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“…Recent model calculations have shown that also NH 3 has a substantial effect on cloud droplet formation Hegg, 2000). The simultaneous dissolution of NH 3 and HNO 3 and/or HCl in the droplets can significantly inCorrespondence to: H. Kokkola (harri.kokkola@uku.fi) crease the hygroscopicity of aerosol droplets and decrease the critical supersaturation at the droplet surface.…”

Section: Introductionmentioning

confidence: 99%

On the formation of radiation fogs under heavily polluted conditions

2003

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Abstract.We have studied the effect of gaseous pollutants on fog droplet growth in heavily polluted air using a model that describes time-dependent sulfate production in the liquid phase and thermodynamical equilibrium between the droplets and the gas phase. Our research indicates that the oxidation of SO 2 to sulfate has a significant effect on fog droplet growth especially when hygroscopic trace gases, for example HNO 3 and NH 3 are present. The increased sulfate production by dissolution of hygroscopic gases results from increased pH (caused by absorption of ammonia) and from the increased size of the fog/smog droplets. Our results indicate that unactivated fogs may become optically very thick when the droplet concentrations are on the order of several thousand per cubic centimeter of air.

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Impact of gas‐phase HNO₃ and NH₃ on microphysical processes in atmospheric clouds

Abstract: Abstract. Model calculations are presented for the impact of trace gas absorption on aerosol activation and precipitation formation in clouds. In contrast to previous studies, acidic aerosols are examined. The results suggest a significant impact, primarily associated with NH 3.

Cited by 28 publications

References 19 publications

Ammonium nitrate evaporation and nitric acid condensation in DMT CCN counters

Ammonium nitrate evaporation and nitric acid condensation in DMT CCN counters

Parameterization of the nitric acid effect on CCN activation

On the formation of radiation fogs under heavily polluted conditions

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Impact of gas‐phase HNO3 and NH3 on microphysical processes in atmospheric clouds

Abstract: Abstract. Model calculations are presented for the impact of trace gas absorption on aerosol activation and precipitation formation in clouds. In contrast to previous studies, acidic aerosols are examined. The results suggest a significant impact, primarily associated with NH 3.

Cited by 28 publications

References 19 publications

Ammonium nitrate evaporation and nitric acid condensation in DMT CCN counters

Ammonium nitrate evaporation and nitric acid condensation in DMT CCN counters

Parameterization of the nitric acid effect on CCN activation

On the formation of radiation fogs under heavily polluted conditions

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Impact of gas‐phase HNO₃ and NH₃ on microphysical processes in atmospheric clouds