Workshop on Spatial Organisation of Convection, Clouds and Precipitation

Session

Modelling and Parameterising Deep Convective Organisation

DEEP1

5 May 2021, 15:00

virtual

Conveners

Modelling and Parameterising Deep Convective Organisation: Interactive Session

• There are no conveners in this block

Modelling and Parameterising Deep Convective Organisation: Guiding Questions

• Douglas Parker (University of Leeds)
• Mitchell Moncrieff (Climate & Global Dynamics Laboratory, NCAR)
• Brian Mapes (University of Miami/RSMAS, Miami, FL)
• J. David Neelin (University of California, Los Angeles)
• Cathy Hohenegger (Max Planck Institute for meteorology)
• Ronald Dickman (UFMG)

Modelling and Parameterising Deep Convective Organisation: Panel Discussion

• Brian Mapes (University of Miami/RSMAS, Miami, FL)
• Douglas Parker (University of Leeds)
• Mitchell Moncrieff (Climate & Global Dynamics Laboratory, NCAR)
• J. David Neelin (University of California, Los Angeles)
• Ronald Dickman (UFMG)
• Cathy Hohenegger (Max Planck Institute for meteorology)

Modelling and Parameterising Deep Convective Organisation: Poster Pitches

• There are no conveners in this block

Modelling and Parameterising Deep Convective Organisation: Introduction

• There are no conveners in this block

47. A stochastic model for tropical precipitation clustering and connections to branching processes

Fiaz Ahmed (University of California, Los Angeles)

05/05/2021, 16:00

Modelling and Parameterising Deep Convective Organisation

Interactive presentation

Tropical convective organization in space is here addressed by examining precipitation clusters — spatially continuous regions exceeding a threshold precipitation. The probability distributions of the area and of the cluster power — the total rainfall integrated over the cluster — follow a power law (with slope ~ -1.5) bounded by a large-event cutoff. We show how a minimal stochastic model of...

43. Cold Pools and the Organization of Tropical Convection in Global Cloud-System Resolving Simulations

Steven Krueger (University of Utah)

05/05/2021, 16:00

Modelling and Parameterising Deep Convective Organisation

Interactive presentation

The DYAMOND (DYnamics of the Atmospheric general circulation Modeled On Non-hydrostatic Domains) project produced simulations of forty days, beginning 1 August 2016, using global models with a cloud-system resolving grid spacing of 5 km or less. How might we use this set of simulations to learn more about the effects of cold pools on convection?

We have developed a global (tropical ocean)...

73. Conceptualizing diurnal surface warming in the tropical ocean

Reyk Börner (Atmospheric Complexity, Niels Bohr Institute)

05/05/2021, 16:00

Modelling and Parameterising Deep Convective Organisation

Interactive presentation

Which processes cause and maintain convective organization in the tropics? Recent cloud-resolving simulations indicate that, compared to studies performed under radiative convective equilibrium, a diurnally varying boundary surface substantially changes the spatiotemporal patterns of convection. To better understand feedbacks between the atmosphere and an interactive ocean requires an accurate...

63. Defining a cold pool-resolving scale for numerical simulations of convective self-organisation

Romain Fiévet (Niels Bohr Institute)

05/05/2021, 16:00

Modelling and Parameterising Deep Convective Organisation

Interactive presentation

In state-of-the art cloud-resolving models, convective self-aggregation (CSA) finds itself consistently hampered by finer horizontal resolutions [Muller & Held (2012), Yanase et al. (2020)]. This feature was ascribed to the effect of cold pool (CP) gust fronts in opposing the positive moisture feedback underlying CSA [Jeevanjee & Romps (2013)]. Further, recent numerical experiments [Haerter et...

37. Essentially Lagrangian simulation of clouds using the Moist Parcel-In-Cell (MPIC) model

Steven Boeing (University of Leeds)

05/05/2021, 16:00

Modelling and Parameterising Deep Convective Organisation

Interactive presentation

The Moist Parcel-In-Cell (MPIC) model provides an essentially Lagrangian approach to moist convection. In this approach, parcels represent both the thermodynamic and the dynamical prognostic properties of the flow. The parcels have a finite volume and carry part of the circulation and thermodynamic attributes (liquid water potential temperature and total water content).

The representation...

20. Extreme precipitation scaling, rain cell sizes, and the role of cold pools, and their relation to climate change

Geert Lenderink (KNMI and TUD)

05/05/2021, 16:00

Modelling and Parameterising Deep Convective Organisation

Interactive presentation

Dependencies of observed (sub)hourly rainfall on near surface dew point temperature show relations exceeding the Clausius-Clapeyron relation. Those so-called super CC scaling rates can be only sustained when sufficient moisture is provided to cloud systems by dynamical feedbacks. Large eddy simulation clearly show a tendency to produce large cloud structures under warmer conditions, and cold...

68. How do families of MCSs organize in time and space?

Irene Livia Kruse (NBI)

05/05/2021, 16:00

Modelling and Parameterising Deep Convective Organisation

Interactive presentation

Mesoscale convective systems (MCSs), long-lived clusters of convective cells spanning more than 100 km in diameter, are known to be the dominant source of rainfall in the tropics, and the longest-lived clusters are shown to be largely responsible for tropical extreme precipitation. These systems are known to be organized and maintained by the atmospheric characteristics needed for deep...

86. Identification and visualization of (high-impact) vortices on different scales

Lisa Schielicke

05/05/2021, 16:00

Modelling and Parameterising Deep Convective Organisation

Interactive presentation

In this work, we will present a vortex identification method that is able to identify vortices
in different data sets of various grid spacings from global reanalysis data to convection-permitting small scale simulations. The method is based on a kinematic analysis of the flow field using the dimensionless kinematic vorticity number Wk. Wk identifies and extracts vortex areas or vortex tubes...

81. In search of ghost cold pools and moisture rings

Ms Enora Le Gall (Ecole Normale Supérieure, Paris)

05/05/2021, 16:00

RCE and Processes in Deep Convective Organization

Interactive presentation

Past work with numerical models has suggested that convectively generated cold pools can play a fundamental role in the triggering of new convection, even in situations of low wind shear, through their determination of the boundary layer moisture field (although cold pool collisions can still add a dynamic element to this thermodynamic picture). The models show cold pool spreading until they...

79. Observed land effects on characteristics of organised convection

Cornelia Klein (UK Centre for Ecology and Hydrology | University of Innsbruck, Austria)

05/05/2021, 16:00

Modelling and Parameterising Deep Convective Organisation

Interactive presentation

Characteristics of the land surface affect cloud development and growth through changes in heating and moistening of the lower troposphere, affecting convective stability and inducing mesoscale circulations in areas of differential heating. Our understanding of the degree to which the land surface may affect and spatio-temporally structure organised convection is still limited and...

29. Organized Convection Parameterization for GCMs

Mitchell Moncrieff (Senior Scientist (emeritus))

05/05/2021, 16:00

Modelling and Parameterising Deep Convective Organisation

Interactive presentation

The enormous exchange of energy during transitions between the three phases of water and the dominance of convection as a transport process are fundamental to Earth’s weather and climate. Moist convection organizes into mesoscale systems (MCSs) but, being neither parameterized nor adequately resolved, MCSs are missing from contemporary global climate models (GCMs). This long-standing...

30. Scale-free distributions in nature: an overview of self-organized criticality

Ronald Dickman (UFMG)

05/05/2021, 16:00

Modelling and Parameterising Deep Convective Organisation

Interactive presentation

Power-law distributions in nature pose a challenge for statistical physics. The paradigm of self-organized criticality (SOC), introduced by Per Bak and coworkers [1], might resolve this puzzle. SOC shows how scale-free event-size and duration distributions can arise in the apparent absence of tuning parameters, in a system of many interacting entities, each having a threshold for relaxation,...

41. Self-Aggregation from Cold Pool Interaction and Global Energy Constraints

Jan Haerter (Niels Bohr Institute, Copenhagen University)

05/05/2021, 16:00

Modelling and Parameterising Deep Convective Organisation

Interactive presentation

Typical explanations for convective self-aggregation invoke radiative convective equilibrium and free tropospheric feedbacks of circulation and radiation, caused by horizontal moisture inhomogeneities. We here show, that these feedbacks would not be needed when considering that cold pools interact. Building a simple model for this interaction, where the probability for new convective cells is...

65. Subcloud layer circulation of isolated moist convection cells

Christopher Moseley (Department of Atmospheric Sciences, National Taiwan University, Taipei 10617, Taiwan)

05/05/2021, 16:00

Modelling and Parameterising Deep Convective Organisation

Interactive presentation

We analyze a single diurnal cycle simulated by the two large eddy simulation (LES) models UCLA-LES and the vector vorticity model VVM in an idealized setup, which show precipitating deep convection in the course of the afternoon. Both models use the same initial conditions, horizontal and vertical grid, but show significant differences in the total amount of precipitation, and in the size of...

26. The diurnal path to persistent convective self-aggregation

Gorm Gruner Jensen (Atmospheric Complexity, NBI, Uni. Copenhagen)

05/05/2021, 16:00

Modelling and Parameterising Deep Convective Organisation

Interactive presentation

Convective self-aggregation (CSA) has attracted a lot of attention as a possible explanation for large scale tropiccal weather phenomena such as the Madden-Julian oscillation and cyclo-genesis. However, CSA is hampered in the realistic limit of fine model resolution when cold pools---dense air masses beneath thunderstorm clouds---are well-resolved.

Here we mimic the diurnal cycle in...

77. The Effects of the Unified Parameterization in the CWBGFS: the Diurnal Cycle of Precipitation over Land in the Maritime Continent

Mr Chun-Yian Su (Department of Atmospheric Sciences, National Taiwan University)

05/05/2021, 16:00

Modelling and Parameterising Deep Convective Organisation

Interactive presentation

The unified parameterization (UP) is a framework that physically adjusts the precipitation partition between the parameterized convection and the grid-scale processes based on the convective updraft fraction. This study investigates the effects of the UP on the diurnal cycle of precipitation over land in the Maritime Continent using an atmospheric general circulation model at the spatial...

66. The fractal nature of clouds in global convection-resolving simulations and satellite data

Hannah Christensen (University of Oxford)

05/05/2021, 16:00

Modelling and Parameterising Deep Convective Organisation

Interactive presentation

Recent years have seen an increase in the production of global convection-resolving (or at least convection-permitting) atmospheric simulations. These simulations are very realistic when compared to observations. A good example of this can be seen in images of simulated cloud condensate fields, rendered in such a way that they can be directly compared to satellite images of the Earth (e.g. Fig...

46. Theory of precipitation probability distributions

Prof. J. David Neelin (University of California, Los Angeles)

05/05/2021, 16:00

Modelling and Parameterising Deep Convective Organisation

Interactive presentation

Relatively simple mathematical models derived from climate model equations can yield insight into how the characteristic form of probability distributions arise for different measures of precipitation, including event accumulations, time averaged intensities and spatial clusters. Stochastic differential equations for moisture and energy equations under reasonable approximations yield...

58. Treating Deep Convective Updrafts in the Tropical Atlantic like Interacting Particles?

Fabian Senf (Leibniz Institute for Tropospheric Research)

05/05/2021, 16:00

Modelling and Parameterising Deep Convective Organisation

Interactive presentation

Understanding the spatial correlations and interactions between tropical clouds remains a challenge for climate research. Here, we develop and apply an analysis that treats deep convective updrafts in the Tropical Atlantic like interacting particles. We discuss how far we can reproduce our findings with simplified equilibrium statistics and which possible routes towards open, non-equilibrium...

34. Understanding the Triggering of Nor’westers over West Bengal, India

Rituparna Sarkar (Indian Institute of Tropical Meteorology)

05/05/2021, 16:00

Modelling and Parameterising Deep Convective Organisation

Interactive presentation

Every year during premonsoon season, the eastern parts of the Indian subcontinent experiences severe thunderstorms. These mesoscale convective storms are locally known as ‘Kalbaishakhi’ or ‘nor’westers’. To forecast these organized storms with sufficient lead time it is important to know the convective initiation processes responsible for triggering these organized cloud formations. ARW-WRF...

11. How is convective organization promoted by stochastic shallow convection?

Mirjana Sakradzija (Max Planck Institute for Meteorology)

Organisation in Shallow Convection

Interactive presentation

The focus of my talk will be on the interaction between parameterized shallow convection and resolved deep convection in convection-permitting simulations. The shallow convection is parameterized by a stochastic approach that uses a uniform spatial distribution of clouds, so no convective organization is represented at the subgrid scales. Nevertheless, such stochastic shallow convection...