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Collection/Aggregation in a Lagrangian cloud microphysical model: Insights from column model applications

Unterstraßer, Simon and Hoffmann, Fabian and Lerch, Marion (2020) Collection/Aggregation in a Lagrangian cloud microphysical model: Insights from column model applications. EGU General Assembly, 2020-05-04 - 2020-05-08, Wien (online). doi: 10.5194/egusphere-egu2020-1997.

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Official URL: https://meetingorganizer.copernicus.org/EGU2020/EGU2020-1997.html


Lagrangian cloud models (LCMs) are considered the future of cloud microphysical modeling. However, LCMs are computationally expensive due to the typically high number of simulation particles (SIPs) necessary to represent microphysical processes such as collection/aggregation successfully. In this study, the representation of collection/aggregation is explored in one-dimensional column simulations, allowing for the explicit consideration of sedimentation, complementing the authors' previous study on zero-dimensional collection in a single grid box. Two variants of the Lagrangian probabilistic all-or-nothing (AON) collection algorithm are tested that mainly differ in the assumed spatial distribution of the droplet ensemble: The first variant assumes the droplet ensemble to be well-mixed in a predefined three-dimensional grid box (WM3D), while the second variant considers explicitly the vertical coordinate of the SIPs, reducing the well-mixed assumption to a two-dimensional, horizontal plane (WM2D). Both variants are compared to established Eulerian bin model solutions. Generally, all methods approach the same solutions, and agree well if the methods are applied with sufficiently high accuracy (foremost the number of SIPs, timestep, vertical grid spacing). However, it is found that the rate of convergence depends on the applied model variant. Most importantly, the study highlights that results generally require a smaller number of SIPs per grid box for convergence than previous box simulations indicated. The reason is the ability of sedimenting SIPs to interact with an effectively larger ensemble of particles when they are not restricted to a single grid box. Since sedimentation is considered in most commonly applied three-dimensional models, the results indicate smaller computational requirements for successful simulations than previously assumed, encouraging a wider use of LCMs in the future.

Item URL in elib:https://elib.dlr.de/134922/
Document Type:Conference or Workshop Item (Speech)
Title:Collection/Aggregation in a Lagrangian cloud microphysical model: Insights from column model applications
AuthorsInstitution or Email of AuthorsAuthor's ORCID iDORCID Put Code
Unterstraßer, SimonDLR, IPAhttps://orcid.org/0000-0003-3772-3678UNSPECIFIED
Hoffmann, FabianNOAA, Boulder, CO, USAhttps://orcid.org/0000-0001-5136-0653UNSPECIFIED
Date:2 May 2020
Refereed publication:No
Open Access:Yes
Gold Open Access:No
In ISI Web of Science:No
Keywords:Collisional growth, aggregation, collection, Smoluchowksi, column model, Lagrangian microphysics, particle-based microphysics, population balance equation
Event Title:EGU General Assembly
Event Location:Wien (online)
Event Type:international Conference
Event Start Date:4 May 2020
Event End Date:8 May 2020
HGF - Research field:Aeronautics, Space and Transport
HGF - Program:Aeronautics
HGF - Program Themes:air traffic management and operations
DLR - Research area:Aeronautics
DLR - Program:L AO - Air Traffic Management and Operation
DLR - Research theme (Project):L - Climate, Weather and Environment (old)
Location: Oberpfaffenhofen
Institutes and Institutions:Institute of Atmospheric Physics > Transport Meteorology
Deposited By: Unterstraßer, Dr. Simon
Deposited On:15 May 2020 18:08
Last Modified:24 Apr 2024 20:37

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