The impact of Secondary Ice Production on Arctic Stratocumulus

Sotiropoulou, Georgia; Sullivan, Sylvia; Savre, Julien; Lloyd, Gary; Lachlan-Cope, Tom; Ekman, Annica M. L.; Nenes, Athanasios

doi:10.5194/acp-2019-804

Cited by 4 publications

(9 citation statements)

References 22 publications

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“…Another SIP mechanism, identified in recent laboratory studies (Leisner et al, 2014;75 Lauber et al, 2018), is the generation of ice fragments from shattering of relatively large frozen drops. This process however, while it is very efficient in convective clouds (Korolev et al, 2019), it has been found ineffective in polar regions (Fu et al, 2019;Sotiropoulou et al, 2020). This is in agreement with Lawson et al (2017) and Sullivan et al (2018a) who have shown that drop-shattering occurs in clouds with a relatively warm cloud base.…”

supporting

confidence: 64%

“…(Mossop and Hallett, 1974;Choularton et al, 1980). However, recent studies have shown that H-M cannot sufficiently explain the enhanced ICNCs observed in both Arctic (Sotiropoulou et al, 2020) and Antarctic (Young et 70 al., 2019) clouds. While some Antarctic studies (Vergara-Temprado et al, 2018;Young et al, 2019) suggest that the underestimation of ice multiplication in models might be related to uncertainties in the description of the H-M process, we argue that this is likely driven by the fact that almost no models include other SIP mechanisms.…”

mentioning

confidence: 99%

“…Mechanical break-up (BR) of ice particles that collide with each other is another process that results in ice multiplication (Vardiman, 1978;Takahashi et al, 1995) and it operates over a wide temperature range with maximum efficiency around -15•C. Limited knowledge of the BR mechanism comes from few laboratory experiments (Vardiman, 1978;Takahashi et al, 1995) and small-scale modeling (Fridlind et al, 2007;Phillips, 85 2011, 2016;Phillips et al, 2017a,b;Sullivan et al 2018a;Sotiropoulou et al, 2020). To the authors knowledge only two attempts have been made to incorporate this process in mesoscale models (Sullivan et al, 2018b;Hoarau et al, 2018).…”

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confidence: 99%

“…, which is a function of collisional kinetic energy and accounts for the effect of the colliding particles' size and rimed fraction (Ψ). While being more advanced than any other parameterization proposed for BR, this 95 scheme has never been implemented in mesoscale models before; it has only been tested in small-scale models for convective (Phillips et al, 2017b;Qu et al, 2020) and Arctic (Sotiropoulou et al, 2020) cloud conditions. Sotiropoulou et al (2020) recently showed that the observed ICNCs in Arctic clouds within the H-M temperature zone can be explained only by the combination of BR with the 100 H-M process, which results in a 10 to 20-fold enhancement of the primary ice crystals.…”

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confidence: 99%

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Secondary ice production in summer clouds over the Antarctic coast: an underappreciated process in atmospheric models

Sotiropoulou¹,

Vignon²,

Young³

et al. 2020

Preprint

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Abstract. The correct representation of Antarctic clouds in atmospheric models is crucial for accurate projections of the future Antarctic climate. This is particularly true for summer clouds which play a critical role in the surface melting of the ice-shelf in the vicinity of Weddell Sea. However these clouds are often poorly represented, as ice crystal number concentrations (ICNCs) are undepredicted by atmospheric models, even when primary ice formation is constrained with aerosol measurements. Rime-splintering, thought to be the dominant secondary ice production (SIP) mechanism at temperatures between −8 and −3 °C, is also very weak in summer Antarctic conditions. Including a parameterization for SIP due to break-up (BR) from collisions between ice particles in the Weather and Research Forecasting model bridges the gap between observations and simulations, suggesting that BR could account for the enhanced ICNCs in the pristine Antarctic atmosphere. These results are insensitive to uncertainties in primary ice production. The BR mechanism is currently not represented in most weather prediction and climate models; including this process can have a significant impact on the Antarctic radiation budget and thus in projections of the future regional climate.

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confidence: 64%

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confidence: 99%

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confidence: 99%

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confidence: 99%

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Secondary ice production in summer clouds over the Antarctic coast: an underappreciated process in atmospheric models

Sotiropoulou¹,

Vignon²,

Young³

et al. 2020

Preprint

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“…be reinforced at temperatures favorable for secondary ice formation (Sotiropoulou et al, 2019), where even higher ice crystal concentrations than simulated in HighINP may further increase precipitation and induce a more rapid stratocumulus breakup (Abel et al, 2017). Nevertheless, open questions remain.…”

Section: Discussionmentioning

confidence: 99%

Cloud Ice Processes Enhance Spatial Scales of Organization in Arctic Stratocumulus

Eirund

Lohmann

Possner

2019

Geophysical Research Letters

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Stratocumulus clouds around the globe tend to organize into cellular patterns, a phenomenon that has been primarily studied for the subtropical trade wind region. However, stratocumulus are also prevalent in high latitudes, where they often occur as mixed-phase clouds. Yet little research has been conducted regarding mechanisms of cloud organization in the mixed-phase regime. In cloud-resolving model simulations we investigate the processes driving organization in open-cell mixed-phase stratocumuli. Similar to warm-phase clouds, mixed-phase clouds develop a subcloud circulation of evaporated/sublimated precipitation, cold pool formation, and consecutive updrafts driving new convective cells. For a larger ice to liquid water ratio, we find locally stronger precipitation and larger cloud cells. Hence, a higher concentration of ice nucleating particles can induce a breakup of the stratocumulus organization, with implications for the radiative balance at the surface. A decrease in cloud condensation nuclei concentration is also found to intensify precipitation and impact cloud organization.Plain Language Summary Low-lying clouds have been found to organize into honeycomb-like spatial patterns. This has been primarily studied for liquid clouds in the subtropical regions but has remained unexplored in the high latitudes. Previous studies focusing on precipitating open-cell clouds have found that below cloud base a continuous cycle of evaporation and subsequent latent cooling, sinking, and lateral spreading of the air mass can be observed. Colliding air masses push the air upward which leads to localized updrafts and new cloud formation. In this study, we explore the organization of open-cell polar clouds, which consist of both liquid cloud droplets and ice crystals (so-called mixed-phase clouds).We show that open-cell mixed-phase clouds also form honeycomb-like spatial patterns following the same mechanism as liquid clouds. However, the spatial extent of cloud patterns changes with the amount of cloud ice. Clouds that contain ice produce precipitation earlier and more intensively. As a result, the cooling below cloud base is strengthened and the cloud cells grow larger. This has implications for the radiative balance at the surface. The stronger growth of ice-containing clouds leads to a breakup of the organized structures, which increases the amount of outgoing radiation.

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Global Importance of Secondary Ice Production

Zhao

Liu

2021

Geophysical Research Letters

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It has been frequently reported that measured ice crystal number concentrations (Ni) are often orders of magnitude higher than number concentrations of ice nucleating particles (INPs). Previous studies interpreted this observed discrepancy as evidence of secondary ice production (SIP) in clouds (Field et al., 2016;Korolev et al., 2020;Mossop, 1985). SIP is referred to as the ice production processes from preexisting ice crystals. Ice nucleation (or primary ice production, hereafter referred to as PIP), is the ice production processes involving aerosol particles via droplet freezing or deposition nucleation (Vali et al., 2015). Currently, there are several proposed SIP mechanisms: rime splintering (also known as the Hallett and Mossop (HM) process), ice-ice collision fragmentation (IIC), droplet shattering during freezing (FR), fragmentation during the sublimation of ice bridge, ice fragmentation during thermal shock, and activation of INPs in a transient supersaturation (Field et al., 2016;Korolev & Leisner, 2020).Observational studies have provided strong evidence of SIP in different types of clouds and in different geographic regions. By analyzing the aircraft data, Hobbs and Rangno (1985, 1990, 1998 attributed the occurrence of high Ni in maritime cumulus clouds off the Washington coast to SIP and suggested the importance of other SIP mechanisms in addition to the HM. Based on in-situ measurements of the Arctic stratus clouds, Rangno and Hobbs (2001) revealed that IIC and FR are the two important SIP mechanisms besides the HM. Based on in-situ measurements by particle imaging probes, Lawson et al. (2015) and Heymsfield and Willis (2014) found that FR contributed significantly to the high Ni in cumulus clouds in the Caribbean and Africa. Similar results were reported by Taylor et al. (2016) in maritime cumulus over the southwest peninsula of the United Kingdom. Using radar and aircraft measurements of convection in a warm-frontal mixed-phase cloud, Hogan et al. (2002) attributed the formation of column ice crystals in the convection to the SIP. Evidence of SIP was also reported by Crosier et al. (2014) in their study of convection in a strong cold front.

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The impact of Secondary Ice Production on Arctic Stratocumulus

Cited by 4 publications

References 22 publications

Secondary ice production in summer clouds over the Antarctic coast: an underappreciated process in atmospheric models

Secondary ice production in summer clouds over the Antarctic coast: an underappreciated process in atmospheric models

Cloud Ice Processes Enhance Spatial Scales of Organization in Arctic Stratocumulus

Global Importance of Secondary Ice Production

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