Secondary ice production : An empirical formulation and organization of mechanisms among simulated cloud-types
(2023)- Abstract
- Clouds are essential elements within Earth's atmosphere, posing a challenge for cloud-resolving models in understanding the creation of new cloud ice particles from existing ice and liquid phases. Such ice initiation determines cloud microphysical and radiative properties, influencing cloud phase, precipitation and cloud extent/properties. To address this challenge effectively, it proves beneficial to differentiate the fundamental microphysical properties of various cloud types, considering their basic classifications.
A few historical experimental studies a few decades ago delved into how sublimation of ice crystals causes the emission of fragments. These fragments subsequently grow into crystals, and in some cases, may evolve into... (More) - Clouds are essential elements within Earth's atmosphere, posing a challenge for cloud-resolving models in understanding the creation of new cloud ice particles from existing ice and liquid phases. Such ice initiation determines cloud microphysical and radiative properties, influencing cloud phase, precipitation and cloud extent/properties. To address this challenge effectively, it proves beneficial to differentiate the fundamental microphysical properties of various cloud types, considering their basic classifications.
A few historical experimental studies a few decades ago delved into how sublimation of ice crystals causes the emission of fragments. These fragments subsequently grow into crystals, and in some cases, may evolve into snow or graupel. This sublimational breakup represents a form of secondary ice production, capable of causing ice multiplication in natural clouds. The origins of the high ice concentrations observed in clouds are becoming better understood, but still have some uncertainty.
In this study, an empirical numerical formulation for sublimation breakup in cloud models is introduced. This formulation is based on comprehensive laboratory data gathered from previous studies. By analyzing experiments that measured the number of ice fragments generated through sublimation, considering factors such as relative humidity and initial ice particle size, we derived essential parameters for a sublimation breakup scheme. The research findings highlight the prevalence of size dependency in smaller particles, while larger particles exhibit comparable dependencies.
Ice initiation in clouds has primarily focused on specific cloud systems, revealing that the majority of ice particles in the mixed-phase region result from secondary ice production mechanisms. However, these studies have been limited to individual cloud types. The objective of this thesis is to broaden the understanding of each secondary ice production mechanism's contribution across various fundamental cloud types with a more all-inclusive approach. To achieve this, numerical simulations are conducted utilizing our ‘Aerosol-Cloud model’ for different cloud categories. These simulations are then validated against in-situ cloud observations obtained from four distinct cloud observational campaigns, each representing a different cloud type for comprehensive analysis.
In this study, the roles of various secondary ice production processes, including the HM process, ice-ice collisional breakup, raindrop-freezing fragmentation, and sublimational breakup were meticulously examined. These analyses are conducted through controlled simulations for different fundamental cloud types. Within warm cloud convective clouds, the HM process is particularly notable near the freezing level, making contributions within specific temperature ranges. Ice-ice collisional breakup emerges as the predominant secondary ice production mechanism across all cloud types, being the only one with appreciable activity in cold-based convection. Additionally, in slightly warm-based convective clouds, the breakup resulting from ice-ice collision takes precedence within the convective updrafts. (Less)
Please use this url to cite or link to this publication:
https://lup.lub.lu.se/record/5d9dd925-6ecf-421e-98ef-64d694bb1ea1
- author
- Deshmukh, Akash LU
- supervisor
- opponent
-
- Professor Kuhn, Thomas, Luleå University of Technology (LTU), Dept. of Computer Science, Electrical and Space Engineering.
- organization
- publishing date
- 2023-10-20
- type
- Thesis
- publication status
- published
- subject
- keywords
- ice, collision, ice production, ice enhancement, secondary ice, sublimation, fragmentation
- pages
- 297 pages
- publisher
- Lund
- defense location
- Världen (Sal F111), Geocentrum I, Sölvegatan 10
- defense date
- 2023-12-07 10:15:00
- ISBN
- 978-91-89187-30-6
- 978-91-89187-29-0
- project
- Secondary ice production: An empirical formulation and organization of mechanisms among simulated cloud-types
- language
- English
- LU publication?
- yes
- id
- 5d9dd925-6ecf-421e-98ef-64d694bb1ea1
- date added to LUP
- 2023-11-07 14:57:34
- date last changed
- 2023-11-16 11:38:19
@phdthesis{5d9dd925-6ecf-421e-98ef-64d694bb1ea1,
abstract = {{Clouds are essential elements within Earth's atmosphere, posing a challenge for cloud-resolving models in understanding the creation of new cloud ice particles from existing ice and liquid phases. Such ice initiation determines cloud microphysical and radiative properties, influencing cloud phase, precipitation and cloud extent/properties. To address this challenge effectively, it proves beneficial to differentiate the fundamental microphysical properties of various cloud types, considering their basic classifications.<br/>A few historical experimental studies a few decades ago delved into how sublimation of ice crystals causes the emission of fragments. These fragments subsequently grow into crystals, and in some cases, may evolve into snow or graupel. This sublimational breakup represents a form of secondary ice production, capable of causing ice multiplication in natural clouds. The origins of the high ice concentrations observed in clouds are becoming better understood, but still have some uncertainty.<br/>In this study, an empirical numerical formulation for sublimation breakup in cloud models is introduced. This formulation is based on comprehensive laboratory data gathered from previous studies. By analyzing experiments that measured the number of ice fragments generated through sublimation, considering factors such as relative humidity and initial ice particle size, we derived essential parameters for a sublimation breakup scheme. The research findings highlight the prevalence of size dependency in smaller particles, while larger particles exhibit comparable dependencies.<br/>Ice initiation in clouds has primarily focused on specific cloud systems, revealing that the majority of ice particles in the mixed-phase region result from secondary ice production mechanisms. However, these studies have been limited to individual cloud types. The objective of this thesis is to broaden the understanding of each secondary ice production mechanism's contribution across various fundamental cloud types with a more all-inclusive approach. To achieve this, numerical simulations are conducted utilizing our ‘Aerosol-Cloud model’ for different cloud categories. These simulations are then validated against in-situ cloud observations obtained from four distinct cloud observational campaigns, each representing a different cloud type for comprehensive analysis.<br/>In this study, the roles of various secondary ice production processes, including the HM process, ice-ice collisional breakup, raindrop-freezing fragmentation, and sublimational breakup were meticulously examined. These analyses are conducted through controlled simulations for different fundamental cloud types. Within warm cloud convective clouds, the HM process is particularly notable near the freezing level, making contributions within specific temperature ranges. Ice-ice collisional breakup emerges as the predominant secondary ice production mechanism across all cloud types, being the only one with appreciable activity in cold-based convection. Additionally, in slightly warm-based convective clouds, the breakup resulting from ice-ice collision takes precedence within the convective updrafts.}},
author = {{Deshmukh, Akash}},
isbn = {{978-91-89187-30-6}},
keywords = {{ice; collision; ice production; ice enhancement; secondary ice; sublimation; fragmentation}},
language = {{eng}},
month = {{10}},
publisher = {{Lund}},
school = {{Lund University}},
title = {{Secondary ice production : An empirical formulation and organization of mechanisms among simulated cloud-types}},
url = {{https://lup.lub.lu.se/search/files/164508847/Thesis_Akash_Deshmukh.pdf}},
year = {{2023}},
}