Preliminary Results on the Aggregation of Ice Crystals

Hallgren, R. E.; Hosler, Charles L.

doi:10.1029/gm005p0257

Cited by 9 publications

(6 citation statements)

References 5 publications

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“…Although not directly part of SIP, ice aggregation is another process that impacts N i and may therefore be important in affecting high IWC. There are several different approaches to parameterize the ice collection efficiency, which is a key parameter in the aggregation parameterization (Hallgren and Hosler, 1960;Lin et al 1983;Cotton et al, 1986;Ferrier et al, 1994Ferrier et al, , 1995Milbrandt and Yau, 2005a, b;Seifert and Beheng, 2006). Khain and Pinsky (2018) showed that the collection efficiencies in these parameterizations vary by more than 2 orders of magnitude for any given temperature between −40 and 0 • C. Sensitivity simulations conducted in the framework of this current study showed a high sensitivity of the modelled IWC and N i to the collection efficiency of ice.…”

Section: Ice Collection Efficiencymentioning

confidence: 99%

The impacts of secondary ice production on microphysics and dynamics in tropical convection

Korolev

Milbrandt

et al. 2022

Atmos. Chem. Phys.

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Abstract. Secondary ice production (SIP) is an important physical phenomenon that results in an increase in the ice particle concentration and can therefore have a significant impact on the evolution of clouds. In this study, idealized simulations of a mesoscale convective system (MCS) were conducted using a high-resolution (250 m horizontal grid spacing) mesoscale model and a detailed bulk microphysics scheme in order to examine the impacts of SIP on the microphysics and dynamics of a simulated tropical MCS. The simulations were compared to airborne in situ and remote sensing observations collected during the “High Altitude Ice Crystals – High Ice Water Content” (HAIC-HIWC) field campaign in 2015. It was found that the observed high ice number concentration can only be simulated by models that include SIP processes. The inclusion of SIP processes in the microphysics scheme is crucial for the production and maintenance of the high ice water content observed in tropical convection. It was shown that SIP can enhance the strength of the existing convective updrafts and result in the initiation of new updrafts above the melting layer. Agreement between the simulations and observations highlights the impacts of SIP on the maintenance of tropical MCSs in nature and the importance of including SIP parameterizations in models.

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Section: Ice Collection Efficiencymentioning

confidence: 99%

The impacts of secondary ice production on microphysics and dynamics in tropical convection

Korolev

Milbrandt

et al. 2022

Atmos. Chem. Phys.

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“…The significantly larger values of aggregation number in the D12 case compared to the other cases ( Fig. 8a-d) is a result of the greater number concentration of ice crystals forming at warmer temperatures where particle "sticking" efficiency is higher (Hallgren and Hosler, 1960). While aggregation is the primary precipitation process in the stratiform regime, the aggregation numbers in this regime are smaller than in the convective regime.…”

Section: Effects On Convective Psds and Collection Processesmentioning

confidence: 83%

Investigating the impacts of Saharan dust on tropical deep convection using spectral bin microphysics

Gibbons¹,

Min²,

Fan³

2018

Atmos. Chem. Phys.

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Abstract. To better understand the impacts of dust aerosols on deep convective cloud (DCC) systems reported by previous observational studies, a case study in the tropical eastern Atlantic was investigated using the Weather Research and Forecasting (WRF) model coupled with a spectral bin microphysics (SBM) model. A detailed set of ice nucleation parameterizations linking ice formation with aerosol particles has been implemented in the SBM. Increasing ice nuclei (IN) concentration in the dust cases results in the formation of more numerous small ice particles in the heterogeneous nucleation regime (between − 5 and −38 • C) compared to the background ("Clean") case. Convective updrafts are invigorated by increased latent heat release due to depositional growth and riming of these more numerous particles, which results in increased overshooting and higher convective core top heights. Competition between the more numerous particles for available water vapor during diffusional growth and available smaller crystals and/or drops during collection reduces particle growth rates and shifts precipitation formation to higher altitudes in the heterogeneous nucleation regime. A greater number of large snow particles form in the dust cases, which are transported from the core into the stratiform regime and sediment out quickly. Together with reduced homogeneous ice formation, the stratiform and/or anvil cloud occurrence shifts frequency to warmer temperatures and reduces anvil cloud extents. Total surface precipitation accumulation is reduced proportionally as IN concentration is increased; though the stratiform precipitation accumulation is increased due to greater snow formation and growth, it does not counteract the reduced convective accumulation due to less efficient graupel formation. Radar reflectivity values are increased in the dust cases at temperatures below 0 • C in both the convective and stratiform regimes due to more large snow particles, and reduced in the convective core near the surface due to melt of small ice or graupel particles, consistent with case study observations.

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“…Earlier observations also provide some evidence of collection efficiency. Laboratory study conducted by Hallgren and Hosler (1960) unveiled a peak aggregation efficiency of 0.1∼0.2 at 15℃, and progressively declined to 0.06∼0.03 across 5∼-25℃. Results from an ice cloud chamber used in Connolly et al (2012) indicated a maximum collection efficiency of 0.2∼0.6 at 15℃ with a gradual reduction on either side of this temperature.…”

Section: Parameterizations Of Collection Efficiencymentioning

confidence: 98%

Evaluating Ice Phase Microphysics in the Simulation of a Snowstorm Over Northern China

Zhang,

Ouyang,

Wang

et al. 2024

JGR Atmospheres

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The complexity of ice particles in the atmosphere makes it difficult to model microphysical growth processes accurately. In this study, we simulated a snowfall case over Northern China Plain using two different microphysics schemes, that is, Thompson and Morrison schemes, in the Advanced Research WRF (Weather Research and Forecasting) model. Both schemes are able to reproduce the event, albeit with a slightly weaker precipitation compared with the surface observation. However, the radar reflectivity factor in Morrison simulation is higher than the radar observation to ∼10 dBZ. Further analysis reveals that such stronger radar reflectivity in the Morrison simulation might be caused by larger collection efficiency, which would lead to more active self‐aggregation process in prediction of snow number concentration and then larger snow particle size. Sensitivity tests show that using an alternative formula of collection efficiency produces smaller radar reflectivity that is in better agreement with observations. This study highlights the accurate representation of self‐aggregation process and underscores the needs of further improvement of ice microphysics schemes for the better snowfall simulations.

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Preliminary Results on the Aggregation of Ice Crystals

Cited by 9 publications

References 5 publications

The impacts of secondary ice production on microphysics and dynamics in tropical convection

The impacts of secondary ice production on microphysics and dynamics in tropical convection

Investigating the impacts of Saharan dust on tropical deep convection using spectral bin microphysics

Evaluating Ice Phase Microphysics in the Simulation of a Snowstorm Over Northern China

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