A parametrization of the ice water content observed in frontal and convective clouds

Bower, Keith; Moss, Sarah J.; Johnson, Doug; Choularton, T. W.; Latham, John; Brown, Philip R. A.; Blyth, Alan; Cardwell, John

doi:10.1002/qj.49712253605

Cited by 66 publications

(49 citation statements)

References 48 publications

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“…In the tropics, high skin temperature tends to trigger tropical deep convection easily. Bower et al (1996) found that the vigorous in-cloud updrafts in convective clouds do not leave enough time for supercooled droplets to transform into ice crystals, thus suppressing ice formation or pushing supercooled liquid water to a colder cloud top height. West et al (2014) concluded that the sub-grid vertical velocity enhancing leads to an increase of the liquid water path.…”

Section: Temporal Correlations Between Scfs and Meteorological Paramementioning

confidence: 99%

Effects of atmospheric dynamics and aerosols on the fraction of supercooled water clouds

Zhang

et al. 2017

Atmos. Chem. Phys.

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Abstract. Based on 8 years of (January 2008-December 2015 cloud phase information from the GCM-Oriented Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) Cloud Product (GOCCP), aerosol products from CALIPSO and meteorological parameters from the ERA-Interim products, the present study investigates the effects of atmospheric dynamics on the supercooled liquid cloud fraction (SCF) during nighttime under different aerosol loadings at global scale to better understand the conditions of supercooled liquid water gradually transforming to ice phase.Statistical results indicate that aerosols' effect on nucleation cannot fully explain all SCF changes, especially in those regions where aerosols' effect on nucleation is not a first-order influence (e.g., due to low ice nuclei aerosol frequency). By performing the temporal and spatial correlations between SCFs and different meteorological factors, this study presents specifically the relationship between SCF and different meteorological parameters under different aerosol loadings on a global scale. We find that the SCFs almost decrease with increasing of aerosol loading, and the SCF variation is closely related to the meteorological parameters but their temporal relationship is not stable and varies with the different regions, seasons and isotherm levels. Obviously negative temporal correlations between SCFs versus vertical velocity and relative humidity indicate that the higher vertical velocity and relative humidity the smaller SCFs. However, the patterns of temporal correlation for lower-tropospheric static stability, skin temperature and horizontal wind are relatively more complex than those of vertical velocity and humidity. For example, their close correlations are predominantly located in middle and high latitudes and vary with latitude or surface type. Although these statistical correlations have not been used to establish a certain causal relationship, our results may provide a unique point of view on the phase change of mixed-phase cloud and have potential implications for further improving the parameterization of the cloud phase and determining the climate feedbacks.

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Section: Temporal Correlations Between Scfs and Meteorological Paramementioning

confidence: 99%

Effects of atmospheric dynamics and aerosols on the fraction of supercooled water clouds

Zhang

et al. 2017

Atmos. Chem. Phys.

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“…The authors note that in regions of high liquid water content, the ice particle concentration may increase by a factor of 10 on the time scale of a few minutes. In a synthesis of data from frontal clouds, maritime convective clouds, and continental convective clouds, Bower et al (1996) concluded that in most instances, ice concentrations could be reconciled with either primary production or the Hallett-Mossop riming-splintering mechanism. The authors noted that in some cases, ice was found in concentrations greater than could be explained by primary nucleation, and at temperatures outside the range applicable for riming-splintering.…”

Section: Secondary Productionmentioning

confidence: 99%

Production of Ice in Tropospheric Clouds: A Review

Cantrell¹,

Heymsfield²

2005

Bull. Amer. Meteor. Soc.

414

376

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“…Table 1 in Mossop, 1978), however, this may be subject to shattering artefacts (McFarquhar et al, 2007). A common explanation is that secondary ice production by the HallettMossop process (HM) produces large numbers of additional ice particles Mossop et al, 1972;Blyth and Latham, 1993;Bower et al, 1996;Hogan et al, 2002;Huang et al, 2009;Crosier et al, 2011). This process occurs during riming at slightly supercooled temperatures (−3 • C to −8 • C) by rime splintering (Hallett and Mossop, 1974).…”

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confidence: 99%

Ice formation and development in aged, wintertime cumulus over the UK: observations and modelling

et al. 2012

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Abstract. In situ high resolution aircraft measurements of cloud microphysical properties were made in coordination with ground based remote sensing observations of a line of small cumulus clouds, using Radar and Lidar, as part of the Aerosol Properties, PRocesses And InfluenceS on the Earth's climate (APPRAISE) project. A narrow but extensive line (∼100 km long) of shallow convective clouds over the southern UK was studied. Cloud top temperatures were observed to be higher than −8 • C, but the clouds were seen to consist of supercooled droplets and varying concentrations of ice particles. No ice particles were observed to be falling into the cloud tops from above. Current parameterisations of ice nuclei (IN) numbers predict too few particles will be active as ice nuclei to account for ice particle concentrations at the observed, near cloud top, temperatures (−7.5 • C).The role of mineral dust particles, consistent with concentrations observed near the surface, acting as high temperature IN is considered important in this case. It was found that very high concentrations of ice particles (up to 100 L −1 ) could be produced by secondary ice particle production providing the observed small amount of primary ice (about 0.01 L −1 ) was present to initiate it. This emphasises the need to understand primary ice formation in slightly supercooled clouds. It is shown using simple calculations that the Hallett-Mossop process (HM) is the likely source of the secondary ice.Model simulations of the case study were performed with the Aerosol Cloud and Precipitation Interactions Model (ACPIM). These parcel model investigations confirmed the HM process to be a very important mechanism for producing the observed high ice concentrations. A key step in generating the high concentrations was the process of collision and coalescence of rain drops, which once formed fell rapidly through the cloud, collecting ice particles which caused them to freeze and form instant large riming particles. The broadening of the droplet size-distribution by collisioncoalescence was, therefore, a vital step in this process as this was required to generate the large number of ice crystals observed in the time available.Simulations were also performed with the WRF (Weather, Research and Forecasting) model. The results showed that while HM does act to increase the mass and number concentration of ice particles in these model simulations it was not found to be critical for the formation of precipitation. However, the WRF simulations produced a cloud top that was too cold and this, combined with the assumption of continual replenishing of ice nuclei removed by ice crystal formation, resulted in too many ice crystals forming by primary nucleation compared to the observations and parcel modelling.

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A parametrization of the ice water content observed in frontal and convective clouds

Cited by 66 publications

References 48 publications

Effects of atmospheric dynamics and aerosols on the fraction of supercooled water clouds

Effects of atmospheric dynamics and aerosols on the fraction of supercooled water clouds

Production of Ice in Tropospheric Clouds: A Review

Ice formation and development in aged, wintertime cumulus over the UK: observations and modelling

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