Snow-graupel collisions in clouds: a newly derived formulation for breakup of single crystals
(2022) In Student thesis series INES NGEM01 20202Dept of Physical Geography and Ecosystem Science
- Abstract
- The observed and well-known discrepancy between concentrations of ice nucleating particles in the environment and the concentrations of ice particles in clouds show that there are additional ‘secondary’ processes enhancing the concentrations of ice particles. In present-day modelling of weather and climate, such processes are mostly overlooked and thus a cause for uncertainty.
Recent modelling studies have shown that one of the secondary ice production (SIP) mechanisms can have a dominant influence in some cloud types. This mechanism is fragmentation due to collisions between ice particles in clouds. The most prolific collision type is between snow and graupel particles.
In the present project, the goal of the research was to use... (More) - The observed and well-known discrepancy between concentrations of ice nucleating particles in the environment and the concentrations of ice particles in clouds show that there are additional ‘secondary’ processes enhancing the concentrations of ice particles. In present-day modelling of weather and climate, such processes are mostly overlooked and thus a cause for uncertainty.
Recent modelling studies have shown that one of the secondary ice production (SIP) mechanisms can have a dominant influence in some cloud types. This mechanism is fragmentation due to collisions between ice particles in clouds. The most prolific collision type is between snow and graupel particles.
In the present project, the goal of the research was to use additional empirical evidence to improve the values of parameters in Phillips’ theoretical formulation, presented by Phillips et al. (2017b), when applied to collisions between crystals and graupel/hail. This formulation is the only comprehensive model of in-cloud ice-ice collisions to date. Empirical data from inspection of a past published lab study is shown here and implemented into the theoretical scheme of Phillips formulation through combination with photographic evidence of ice particle morphology from the literature.
The newly parameterised scheme can be implemented for 5 different crystal types in the temperature range of -4 to -25°C. The results imply that fragmentation in snow-graupel collision might have a larger effect on ice multiplication than is currently modelled.
In addition, an experimental set-up was developed and used to grow graupel and snow crystal particles. Recommendations for possible future experiments to observe this process of SIP are discussed. (Less) - Popular Abstract
- Ice in clouds stems from several processes, it all starts with initial freezing of small droplets. As pure water in the atmosphere can be supercooled to -40°C these droplets that freeze above this temperature are helped in their phase change by ice nucleating particles (INPs). However, the concentrations of INPs in clouds are not always predictive of the concentrations of ice in clouds. Hence, one of the secondary ice production mechanisms proposed to cover this gap was ice-ice collisions in clouds producing fragments due to breakup. The following describes the summary of how a newly derived formulation for the fragmentation in snow-graupel collision was produced for different morphologies of snow crystals.
The observed and well-known... (More) - Ice in clouds stems from several processes, it all starts with initial freezing of small droplets. As pure water in the atmosphere can be supercooled to -40°C these droplets that freeze above this temperature are helped in their phase change by ice nucleating particles (INPs). However, the concentrations of INPs in clouds are not always predictive of the concentrations of ice in clouds. Hence, one of the secondary ice production mechanisms proposed to cover this gap was ice-ice collisions in clouds producing fragments due to breakup. The following describes the summary of how a newly derived formulation for the fragmentation in snow-graupel collision was produced for different morphologies of snow crystals.
The observed and well-known discrepancy between concentrations of INPs in the environment and the concentrations of ice particles in clouds show that there are additional secondary processes enhancing the concentrations of ice particles. In present-day modelling of weather and climate, such processes are mostly overlooked and thus a cause for uncertainty.
Recent modelling studies have shown that one of the secondary ice production (SIP) mechanisms can have a dominant influence in some cloud types. This mechanism is fragmentation due to collisions between ice particles in clouds. The most prolific collision type is between snow and graupel particles.
In the present project, the goal of the research was to use additional empirical evidence to improve the values of parameters in Phillips’ theoretical formulation, presented by Phillips et al. (2017b), when applied to collisions between crystals and graupel/hail. This formulation is the only comprehensive model of in-cloud ice-ice collisions to date. Empirical data from inspection of a past published lab study is shown here and implemented into the theoretical scheme of Phillips formulation through a combination with photographic evidence of ice particle morphology and characteristics from literature.
The newly parameterised scheme can be implemented for 5 different crystal types in the temperature range of -4 to -25°C. The results imply that fragmentation in snow-graupel collision might have a larger effect on ice multiplication than is currently modelled.
In addition, an experimental set-up was developed and used to grow graupel and snow crystal particles. Recommendations for possible future experiments to observe this process of SIP are discussed. (Less)
Please use this url to cite or link to this publication:
http://lup.lub.lu.se/student-papers/record/9101602
- author
- van der Brug, Victor Craig LU
- supervisor
- organization
- course
- NGEM01 20202
- year
- 2022
- type
- H2 - Master's Degree (Two Years)
- subject
- keywords
- Physical Geography and Ecosystem Analysis, Secondary Ice Production, Ice Cloud Number Concentration, Cloud Ice, Ice-Ice Collisions, Snow Crystal, Atmospheric Science & Biogeochemical Cycles
- publication/series
- Student thesis series INES
- report number
- 581
- language
- English
- id
- 9101602
- date added to LUP
- 2022-10-11 11:20:46
- date last changed
- 2023-02-01 03:42:09
@misc{9101602,
abstract = {{The observed and well-known discrepancy between concentrations of ice nucleating particles in the environment and the concentrations of ice particles in clouds show that there are additional ‘secondary’ processes enhancing the concentrations of ice particles. In present-day modelling of weather and climate, such processes are mostly overlooked and thus a cause for uncertainty.
Recent modelling studies have shown that one of the secondary ice production (SIP) mechanisms can have a dominant influence in some cloud types. This mechanism is fragmentation due to collisions between ice particles in clouds. The most prolific collision type is between snow and graupel particles.
In the present project, the goal of the research was to use additional empirical evidence to improve the values of parameters in Phillips’ theoretical formulation, presented by Phillips et al. (2017b), when applied to collisions between crystals and graupel/hail. This formulation is the only comprehensive model of in-cloud ice-ice collisions to date. Empirical data from inspection of a past published lab study is shown here and implemented into the theoretical scheme of Phillips formulation through combination with photographic evidence of ice particle morphology from the literature.
The newly parameterised scheme can be implemented for 5 different crystal types in the temperature range of -4 to -25°C. The results imply that fragmentation in snow-graupel collision might have a larger effect on ice multiplication than is currently modelled.
In addition, an experimental set-up was developed and used to grow graupel and snow crystal particles. Recommendations for possible future experiments to observe this process of SIP are discussed.}},
author = {{van der Brug, Victor Craig}},
language = {{eng}},
note = {{Student Paper}},
series = {{Student thesis series INES}},
title = {{Snow-graupel collisions in clouds: a newly derived formulation for breakup of single crystals}},
year = {{2022}},
}