Nucleation studies in the Martian atmosphere

Määttänen, Anni; Vehkamäki, Hanna; Lauri, Antti; Merikallio, S.; Kauhanen, Janne; Savijärvi, Hannu; Kulmala, Markku

doi:10.1029/2004je002308

Cited by 90 publications

(78 citation statements)

References 40 publications

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“…We modify the original expression used in Hoose et al (2010) concerning J het (the rate of heterogeneous nucleation per aerosol particle and per second) with the form factor (f ) raised to the −1/2 power instead of 1/2 (see Eq. 1); this is done due to the unphysical behavior of the original expression which implies that J het →0 when f →0 (i.e., the ice nucleation rate will become smaller on more easily wettable materials) (Määttänen et al, 2005;Barahona, 2012).…”

Section: Single-contact-angle (α) Modelmentioning

confidence: 99%

Different contact angle distributions for heterogeneous ice nucleation in the Community Atmospheric Model version 5

et al. 2014

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Abstract. In order to investigate the impact of different treatments for the contact angle (α) in heterogeneous ice nucleating properties of natural dust and black carbon (BC) particles, we implement the classical-nucleation-theory-based parameterization of heterogeneous ice nucleation (Hoose et al., 2010) in the Community Atmospheric Model version 5 (CAM5) and then improve it by replacing the original singlecontact-angle model with the probability-density-functionof-α (α-PDF) model to better represent the ice nucleation behavior of natural dust found in observations. We refit the classical nucleation theory (CNT) to constrain the uncertain parameters (i.e., onset α and activation energy in the single-α model; mean contact angle and standard deviation in the α-PDF model) using recent observation data sets for Saharan natural dust and BC (soot). We investigate the impact of the time dependence of droplet freezing on mixed-phase clouds and climate in CAM5 as well as the roles of natural dust and soot in different nucleation mechanisms. Our results show that, when compared with observations, the potential ice nuclei (IN) calculated by the α-PDF model show better agreement than those calculated by the single-α model at warm temperatures (T ; T > −20 • C). More ice crystals can form at low altitudes (with warm temperatures) simulated by the α-PDF model than compared to the single-α model in CAM5. All of these can be attributed to different ice nucleation efficiencies among aerosol particles, with some particles having smaller contact angles (higher efficiencies) in the α-PDF model. In the sensitivity tests with the α-PDF model, we find that the change in mean contact angle has a larger impact on the active fraction at a given temperature than a change in standard deviation, even though the change in standard deviation can lead to a change in freezing behavior. Both the single-α and the α-PDF model indicate that the immersion freezing of natural dust plays a more important role in the heterogeneous nucleation than that of soot in mixed-phase clouds. The new parameterizations implemented in CAM5 induce more significant aerosol indirect effects than the default parameterization.

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Section: Single-contact-angle (α) Modelmentioning

confidence: 99%

Different contact angle distributions for heterogeneous ice nucleation in the Community Atmospheric Model version 5

et al. 2014

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“…In our previous article on one-component nucleation in the Martian atmosphere published in Journal of Geophysical Research -Planets (Määttänen et al, 2005) we derived a form of the one-component Zeldovich factor only applicable for a planar pre-existing condensation nucleus (CN) surface. Pruppacher and Klett (Pruppacher and Klett, 1997, pp.202) state that the Zeldovich factor can be expressed as…”

Section: Theorymentioning

confidence: 99%

“…ϕ is the formation energy of the cluster, * stands for the critical cluster, T is the temperature and k is the Boltzmann constant. Equation (11) in our paper Määttänen et al (2005) is based on equation…”

Section: Theorymentioning

confidence: 99%

“…results on its effect on nucleation. It should be noted that the formulation presented in Määttänen et al (2005) is well applicable for large pre-existing particles acting as CN, and thus the approximation does not affect the results of paper Määttänen et al (2005), but for small CN the differences may be large. The Zeldovich factor is by definition…”

Section: Theorymentioning

confidence: 99%

“…The paper Määttänen et al (2005) included also two other approximations. The cluster circumference was approximated in the nucleation rate expressions (8) and (12) Määttänen et al (2005) as πr sin ϑ, which is again an approximation for a planar pre-existing surface. The correct form for a spherical pre-existing particle is 2πR p sin φ, where sin φ can be calculated with the help of Eq.…”

Section: Theorymentioning

confidence: 99%

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Technical Note: The heterogeneous Zeldovich factor

et al. 2007

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Abstract. In this technical note we present the exact form of the Zeldovich factor for heterogeneous nucleation on spherical pre-existing particles. We study the error caused by planar pre-existing surface approximations, which have been used in our earlier heterogeneous nucleation model and elsewhere in the literature. We also test the significance of widely used approximations for cluster surface area and circumference. We conclude that the approximations do not affect the predicted onset saturation. Especially for small pre-existing particles the nucleation rates calculated with the exact and approximative models differ significantly.

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Global climate modeling of the Martian water cycle with improved microphysics and radiatively active water ice clouds

Navarro

Madeleine

Forget

et al. 2014

J. Geophys. Res. Planets

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206

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Water ice clouds play a key role in the radiative transfer of the Martian atmosphere, impacting its thermal structure, its circulation, and, in turn, the water cycle. Recent studies including the radiative effects of clouds in global climate models (GCMs) have found that the corresponding feedbacks amplify the model defaults. In particular, it prevents models with simple microphysics from reproducing even the basic characteristics of the water cycle. Within that context, we propose a new implementation of the water cycle in GCMs, including a detailed cloud microphysics taking into account nucleation on dust particles, ice particle growth, and scavenging of dust particles due to the condensation of ice. We implement these new methods in the Laboratoire de Météorologie Dynamique GCM and find satisfying agreement with the Thermal Emission Spectrometer observations of both water vapor and cloud opacities, with a significant improvement when compared to GCMs taking into account radiative effects of water ice clouds without this implementation. However, a lack of water vapor in the tropics after Ls = 180° is persistent in simulations compared to observations, as a consequence of aphelion cloud radiative effects strengthening the Hadley cell. Our improvements also allow us to explore questions raised by recent observations of the Martian atmosphere. Supersaturation above the hygropause is predicted in line with Spectroscopy for Investigation of Characteristics of the Atmosphere of Mars observations. The model also suggests for the first time that the scavenging of dust by water ice clouds alone fails to fully account for the detached dust layers observed by the Mars Climate Sounder.

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Nucleation studies in the Martian atmosphere

Cited by 90 publications

References 40 publications

Different contact angle distributions for heterogeneous ice nucleation in the Community Atmospheric Model version 5

Different contact angle distributions for heterogeneous ice nucleation in the Community Atmospheric Model version 5

Technical Note: The heterogeneous Zeldovich factor

Global climate modeling of the Martian water cycle with improved microphysics and radiatively active water ice clouds

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