Studies on the Competition Between Homogeneous and Heterogeneous Ice Nucleation in Cirrus Formation

Kärcher, B.; DeMott, Paul J.; Jensen, E. J.; Harrington, Jerry Y.

doi:10.1029/2021jd035805

Cited by 24 publications

(22 citation statements)

References 77 publications

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“…In principle, the successful simplifications could mean that these processes are unimportant in the atmosphere. However, both are usually believed to be important processes for ICNC (Kanji et al., 2017; Kärcher et al., 2022; Korolev & Leisner, 2020; Qu et al., 2022; Villanueva et al., 2021) and thus the model behavior seems faulty. The insensitivity of ECHAM‐HAM to heterogeneous freezing (formulations) has been documented before (Dietlicher, 2018; Dietlicher et al., 2019; Hoose, Lohmann, Erdin, & Tegen, 2008; Ickes et al., 2022; Villanueva et al., 2021) but never as clearly as in the present study.…”

Section: Resultsmentioning

confidence: 99%

Addressing Complexity in Global Aerosol Climate Model Cloud Microphysics

Proske

Ferrachat

Klampt

et al. 2023

J Adv Model Earth Syst

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In climate modeling, our task is to represent an immensely complex system which we wish to understand and learn about. Model development inherently faces tradeoffs between epistemic values like tractability, interpretability, validation potential, and specificity (Beucler et al., 2021;Larsen et al., 2016;Undorf et al., 2022), which manifest themselves in the ever present question of where to draw the line for details. Understanding nature requires a simplification of the mechanisms at play, but wanting to be precise calls for more details that increase complexity (Tapiador et al., 2019). For the term "model complexity" we here follow the "loose definition" mentioned in García-Callejas and Araújo (2016) that a model becomes more complex the more difficult to comprehend its computations are and the more processes/computations there are (Baartman et al. (2020) andRandall et al. (2003)).Climate modeling has followed the mirror view (Parker, 2022), meaning that it wants to mirror the Earth system in the model representation. Different modeling approaches would be following for example, the predictive or

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Section: Resultsmentioning

confidence: 99%

Addressing Complexity in Global Aerosol Climate Model Cloud Microphysics

Proske

Ferrachat

Klampt

et al. 2023

J Adv Model Earth Syst

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“…In all simulation cases, homogeneous freezing takes place on monodisperse liquid solution droplets that are characterized by a total number concentration of 500 cm −3 and a mean wet radius of 0.25 μm (Kärcher, DeMott et al., 2022). No sensitivity simulations were performed here, as the susceptibility of homogeneously nucleated ICNCs to liquid solution droplet number concentration and size is weak (Hoyle et al., 2005; Kärcher & Lohmann, 2002; Kay & Wood, 2008).…”

Section: Methodsmentioning

confidence: 99%

The Role of Mineral Dust Aerosol Particles in Aviation Soot‐Cirrus Interactions

Kärcher¹,

Marcolli

Mahrt

2023

JGR Atmospheres

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Predicting cirrus cloud properties with confidence requires a sound understanding of the relative roles of homogeneous and heterogeneous ice formation. This study explores the effect of mineral dust and contrail‐processed aviation soot particles as ice‐nucleating particles (INPs) competing with liquid solution droplets in cirrus formation. We study aerosol‐cirrus interactions by accounting for atmospheric variability in updraft speeds and INP number concentrations. Our results confirm the dominant role of mineral dust in ice nucleation events in cirrus clouds. In addition, we show that pre‐existing thin cirrus may suppress ice formation when updraft speeds are low. We find that homogeneous freezing of liquid solution droplets dominates clear‐sky aerosol‐cirrus interaction above a threshold updraft speed determined by total number concentrations and ice nucleation abilities of INPs. When mineral dust particles exceed number concentrations of 10 L−1, they reduce homogeneously nucleated ice crystal numbers significantly and even prevent homogeneous freezing for frequently observed local updraft speeds between 10 and 20 cm s−1. When both mineral dust and aviation soot particles coexist with solution droplets, dust typically prevents ice nucleation by aviation soot. Aviation soot exerts a notable impact on cirrus ice numbers only if updrafts are weak, large soot particles are present in number concentrations that are considerably higher than typically observed in emission measurements, and/or number concentrations of mineral dust and other INPs are low. Overall, our results elucidate the role of aviation soot‐cirrus interactions in the presence of other INP types.

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“…Competing ice nucleation between solution droplets and INPs in cirrus has recently been studied on the process level with the help of numerical simulations (Kärcher et al., 2022) (hereafter K22), based on substantial progress that has been made in characterizing ice nucleation abilities of INPs (Kanji et al., 2017), mainly in laboratory settings. Progress has also been made in characterizing the magnitude of, and variability in, vertical wind speeds at cirrus altitudes, through quasi‐Lagrangian in situ measurements (Podglajen et al., 2016).…”

Section: Introductionmentioning

confidence: 99%

A Parameterization of Cirrus Cloud Formation: Revisiting Competing Ice Nucleation

Kärcher¹

2022

JGR Atmospheres

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This study develops an advanced physically‐based parameterization of heterogeneous ice nucleation in cirrus clouds that includes an updated parameterization of stochastic homogeneous freezing of supercooled solution droplets. Both components are formulated based on the same methodology and level of approximation, without numerical integration of the underlying ice supersaturation equation. The new scheme includes measured ice nucleation spectra describing deterministic ice activation from an arbitrary number of types of ice‐nucleating particles (INPs), tracks the competition for available water vapor between the different ice nucleation modes, and allows for new ice formation and growth within pre‐existing cirrus clouds. The computationally efficient scheme works with a minimal set of physical input parameters and predicts total nucleated ice crystal number concentrations (ICNCs) along with the maximum ice supersaturation attained during cirrus formation events. Aspects of its implementation into host models are discussed, including the provision of suitably parameterized vertical wind speeds. The parameterization is validated by comparisons to numerical simulations. First off‐line applications to mineral dust and aviation soot particles are presented, including ICNC ensemble statistics resulting from the coupling with statistics of updraft speed variability.

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Studies on the Competition Between Homogeneous and Heterogeneous Ice Nucleation in Cirrus Formation

Cited by 24 publications

References 77 publications

Addressing Complexity in Global Aerosol Climate Model Cloud Microphysics

Addressing Complexity in Global Aerosol Climate Model Cloud Microphysics

The Role of Mineral Dust Aerosol Particles in Aviation Soot‐Cirrus Interactions

A Parameterization of Cirrus Cloud Formation: Revisiting Competing Ice Nucleation

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