Two-year statistics of columnar-ice production in stratiform clouds over Hyytiälä, Finland: environmental conditions and the relevance to secondary ice production

Li, Haoran; Möhler, Ottmar; Petäj̈ä, Tuukka; Moisseev, Dmitri

doi:10.5194/acp-21-14671-2021

Cited by 14 publications

(11 citation statements)

References 105 publications

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“…-In most SIP processes, small ice splinters are created that could then start growing in favorable cloud conditions. This small ice would create a small but sharp peak at small velocities in the Doppler velocity spectrum (see e.g., Figure 1c in Li et al, 2021). In the ICNC retrieval, the entire Doppler velocity spectrum is fit to an unimodal distribution for an assumed ice crystal shape (Bühl et al, 2019).…”

Section: Uncertainties and Caveats Of The Proposed Methodologymentioning

confidence: 99%

Retrieving ice nucleating particle concentration and ice multiplication factors using active remote sensing validated by in situ observations

Wieder

Ihn

Mignani

et al. 2022

Preprint

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Abstract. Understanding the evolution of the ice phase within mixed-phase clouds (MPCs) is necessary to reduce uncertainties related to the cloud radiative feedback in climate projections and precipitation initiation. Both primary ice formation via ice nucleating particles (INPs) and secondary ice production (SIP) within MPCs are unconstrained, not least because of the lack of atmospheric observations. In the past decades, advanced remote sensing methods have emerged which provide high resolution data of aerosol and cloud properties and could be key in understanding microphysical processes on a global scale. In this study, we retrieved INP concentrations, and ice multiplication factors (IMFs) in wintertime orographic clouds using active remote sensing and in situ observations obtained during the RACLETS campaign in the Swiss Alps. INP concentrations in air masses dominated by Saharan dust and continental aerosol were retrieved from a polarization Raman lidar and validated with aerosol and INP in situ observations on a mountaintop. A calibration factor of 0.0204 for the global INP parameterization by DeMott et al. (2010) is derived by comparing in situ aerosol and INP measurements improving the INP concentration retrieval for continental aerosols. Based on combined lidar and radar measurements, the ice crystal number concentration and ice water content were retrieved and validated with balloon-borne in situ observations, which agreed with the balloon-borne in situ observations within an order of magnitude. For seven cloud cases the ice multiplication factors (IMFs), defined as the quotient of the ice crystal number concentration to the INP concentration, were calculated. The median IMF was around 80 and SIP was active (defined as IMFs > 1) nearly 85 % of the time. SIP was found to be active at all observed temperatures (−30 °C to −5 °C) with highest IMFs between −20 °C and −5 °C. The introduced methodology could be extended to larger datasets to better understand the impact of SIP not only over the Alps but also at other locations and for other cloud types.

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Section: Uncertainties and Caveats Of The Proposed Methodologymentioning

confidence: 99%

Retrieving ice nucleating particle concentration and ice multiplication factors using active remote sensing validated by in situ observations

Wieder

Ihn

Mignani

et al. 2022

Preprint

View full text Add to dashboard Cite

show abstract

“…However, when the concentration of small ice crystals exceeds that of ambient INPs, SIP processes must have contributed to the ICNC. As such, several studies compare INPC with total ICNC to infer the occurrence of SIP (e.g., Ladino et al, 2017;Li et al, 2021;Wieder et al, 2022a). The cloud microphysical properties can additionally be used to identify the mechanism potentially responsible for SIP.…”

Section: Introductionmentioning

confidence: 99%

Conditions favorable for secondary ice production in Arctic mixed-phase clouds

Pasquier¹,

Henneberger²,

Ramelli³

et al. 2022

Atmos. Chem. Phys.

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Abstract. The Arctic is very susceptible to climate change and thus is warming much faster than the rest of the world. Clouds influence terrestrial and solar radiative fluxes and thereby impact the amplified Arctic warming. The partitioning of thermodynamic phases (i.e., ice crystals and water droplets) within mixed-phase clouds (MPCs) especially influences their radiative properties. However, the processes responsible for ice crystal formation remain only partially characterized. In particular, so-called secondary ice production (SIP) processes, which create supplementary ice crystals from primary ice crystals and the environmental conditions that they occur in, are poorly understood. The microphysical properties of Arctic MPCs were measured during the Ny-Ålesund AeroSol Cloud ExperimENT (NASCENT) campaign to obtain a better understanding of the atmospheric conditions favorable for the occurrence of SIP processes. To this aim, the in situ cloud microphysical properties retrieved by a holographic cloud imager mounted on a tethered balloon system were complemented by ground-based remote sensing and ice-nucleating particle measurements. During the 6 d investigated in this study, SIP occurred during about 40 % of the in-cloud measurements, and high SIP events with number concentrations larger than 10 L−1 of small pristine ice crystals occurred in 4 % of the in-cloud measurements. This demonstrates the role of SIP for Arctic MPCs. The highest concentrations of small pristine ice crystals were produced at temperatures between −5 and −3 ∘C and were related to the occurrence of supercooled large droplets freezing upon collision with ice crystals. This suggests that a large fraction of ice crystals in Arctic MPCs are produced via the droplet-shattering mechanism. From evaluating the ice crystal images, we could identify ice–ice collision as a second SIP mechanism that dominated when fragile ice crystals were observed. Moreover, SIP occurred over a large temperature range and was observed in up to 80 % of the measurements down to −24 ∘C due to the occurrence of ice–ice collisions. This emphasizes the importance of SIP at temperatures below −8 ∘C, which are currently not accounted for in most numerical weather models. Although ice-nucleating particles may be necessary for the initial freezing of water droplets, the ice crystal number concentration is frequently determined by secondary production mechanisms.

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“…This small ice would create a small but sharp peak at small velocities in the Doppler velocity spectrum (see e.g., Fig. 1c in Li et al, 2021). In the ICNC retrieval, the entire Doppler velocity spectrum is fit to a unimodal distribution for an assumed ice crystal shape (Bühl et al, 2019).…”

Section: Uncertainties and Caveats Of The Proposed Methodologymentioning

confidence: 99%

“…For measurements close to the melting layer, a temperature of −0.5 • C was used for plotting. IMFs fromPasquier et al (2022) were provided by personal communication Li et al (2021). do not provide correlated data of ICNC, INP concentration, and temperature.…”

mentioning

confidence: 99%

Retrieving ice-nucleating particle concentration and ice multiplication factors using active remote sensing validated by in situ observations

Wieder

Ihn²,

Mignani³

et al. 2022

Atmos. Chem. Phys.

View full text Add to dashboard Cite

Abstract. Understanding the evolution of the ice phase within mixed-phase clouds (MPCs) is necessary to reduce uncertainties related to the cloud radiative feedback in climate projections and precipitation initiation. Both primary ice formation via ice-nucleating particles (INPs) and secondary ice production (SIP) within MPCs are unconstrained, not least because of the lack of atmospheric observations. In the past decades, advanced remote sensing methods have emerged which provide high-resolution data of aerosol and cloud properties and could be key in understanding microphysical processes on a global scale. In this study, we retrieved INP concentrations and ice multiplication factors (IMFs) in wintertime orographic clouds using active remote sensing and in situ observations obtained during the RACLETS campaign in the Swiss Alps. INP concentrations in air masses dominated by Saharan dust and continental aerosol were retrieved from a polarization Raman lidar and validated with aerosol and INP in situ observations on a mountaintop. A calibration factor of 0.0204 for the global INP parameterization by DeMott et al. (2010) is derived by comparing in situ aerosol and INP measurements, improving the INP concentration retrieval for continental aerosols. Based on combined lidar and radar measurements, the ice crystal number concentration and ice water content were retrieved and validated with balloon-borne in situ observations, which agreed with the balloon-borne in situ observations within an order of magnitude. For seven cloud cases the ice multiplication factors (IMFs), defined as the quotient of the ice crystal number concentration to the INP concentration, were calculated. The median IMF was around 80, and SIP was active (defined as IMFs > 1) nearly 85 % of the time. SIP was found to be active at all observed temperatures (−30 to −5 ∘C), with the highest IMFs between −20 and −5 ∘C. The introduced methodology could be extended to larger datasets to better understand the impact of SIP not only over the Alps but also at other locations and for other cloud types.

show abstract

Two-year statistics of columnar-ice production in stratiform clouds over Hyytiälä, Finland: environmental conditions and the relevance to secondary ice production

Cited by 14 publications

References 105 publications

Retrieving ice nucleating particle concentration and ice multiplication factors using active remote sensing validated by in situ observations

Retrieving ice nucleating particle concentration and ice multiplication factors using active remote sensing validated by in situ observations

Conditions favorable for secondary ice production in Arctic mixed-phase clouds

Retrieving ice-nucleating particle concentration and ice multiplication factors using active remote sensing validated by in situ observations

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