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2nd Workshop on Cloud Organization (WCO2)

16–19 May 2022
Utrecht
Europe/Amsterdam timezone

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Contribution List

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  1. 81. Arrival and registration
    16/05/2022, 09:00
    Poster
  2. 29. Spontaneous clustering of convection in simple models, cloud resolving models and observations.
    Adrian Tompkins (ICTP)
    16/05/2022, 09:35

    This talk address convective aggregation on the mesoscale in idealized cloud resolving models, in highly simplified stochastic models and in the latest observations in the tropical western Pacific.

    Cloud resolving models run in idealized conditions of radiative convective equilibrium often show randomly distributed convection switching to a state in which the convection is highly clustered,...

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  3. 8. Links between spatial organization and plume rooting in a decentralized framework for convective transport
    Roel Neggers (University of Cologne)
    16/05/2022, 10:05

    In this study a spectral model for convective transport is coupled to a thermal population model on a horizontal microgrid. Thermals interact under simple rules, reflecting pulsating growth and environmental deformation. Long-lived thermal clusters thus form on the microgrid, exhibiting scale growth, spatial organization and memory. Size distributions of cluster number are diagnosed from the...

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  4. 33. Explaining convective self-aggregation onset with a stochastic reaction-diffusion model of the Tropics
    Giovanni Biagioli (University of Trieste)
    16/05/2022, 10:20

    In an attempt to explain some differences existing between cloud-resolving models (CRMs) about the occurrence, under certain circumstances, of states in which convection self-aggregates, a simplified, two-dimensional, stochastic model was developed. Its prognostic equation governs the evolution of column total water relative humidity in tropical free troposphere, including convective...

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  5. 38. Influence of Aerosol Perturbation Duration on the Organization of Stratocumulus: Large Eddy Simulation and Heuristic Dynamical Modeling
    Graham Feingold (NOAA)
    16/05/2022, 11:00

    Marine boundary layer stratocumulus clouds tend to occur in two distinct organizational states: the closed cell, high cloud fraction state and the open-cell, low cloud fraction state. The selection of the state is determined by the amount of precipitation, which is in turn strongly influenced by the aerosol concentration. Natural and anthropogenic aerosol perturbations have characteristic...

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  6. 4. Circling in on Convective Self-Aggregation
    Silas Boye Nissen (Niels Bohr Institute, University of Copenhagen)
    16/05/2022, 11:30

    In radiative-convective equilibrium simulations, convective self-aggregation (CSA) is the spontaneous organization into segregated cloudy and cloud-free regions. Evidence exists for how CSA is stabilized, but how it arises favorably on large domains is not settled. Using large-eddy simulations, we link the spatial organization emerging from the interaction of cold pools (CPs) to CSA. We...

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  7. 18. Cloud botany - shallow cumulus organization in an LES ensemble
    Fredrik Jansson (TU Delft)
    16/05/2022, 11:45

    Many mesoscale patterns in trade-wind cloud fields appear to result from the self-organisation of sub-mesoscale cumulus convection. To advance our understanding of these self-organising processes and the role they play in regulating radiation from the trades to space, we have run an ensemble of idealised large-eddy simulations on domains larger than 100 km using the DALES model. Each...

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  8. 21. In search of ghost cold pools and moisture rings
    Adrian Tompkins (ICTP)
    16/05/2022, 12:00

    Moisture rings at cold pool fronts have been identified as playing a key role in convective propagation in numerical simulations. However, it is not clear if these are features of real cold pools due to the uncertainties of model microphysics and representation of turbulence at the cold pool front. We therefore analyse more than a decade of station observations from two islands in the tropical...

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  9. 27. Understanding cloud systems structure and organization using a machine’s self-learning capability
    Mr Dwaipayan Chatterjee (Institute for Geophysics and Meteorology, University of Cologne)
    16/05/2022, 12:02

    Our work aims to understand the structure and organization of cloud systems by exploiting the self-learning capability of a deep neural network. The neural network utilizes deep clustering and non-parametric instance-level discrimination for decision-making at any learning stage.

    The data augmentation in the data pipeline, multi-clustering of the dense vectors, and Multilayer perceptron...

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  10. 59. Self-organized quantization and oscillations on continuous fixed-energy sandpiles
    Jan Haerter (Niels Bohr Institute, Copenhagen University)
    16/05/2022, 12:04

    Atmospheric self-organization and activator-inhibitor dynamics in biology provide examples of checkerboard-like spatio-temporal organization. We study a simple model for local activation-inhibition processes. Our model, first introduced in the context of atmospheric moisture dynamics, is a continuous-energy and non-Abelian version of the fixed-energy sandpile model. Each...

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  11. 58. Network approaches to the geometric structure of shallow cloud fields
    Franziska Glassmeier (TU Delft)
    16/05/2022, 12:06

    The cellular structure of stratocumulus clouds decks and their evolution has been modeled by describing them as cellular, nearest-neighbor networks (Glassmeier& Feingold, 2017, PNAS). We review this approach and discuss options and challenges for its generalization to shallow cumulus cloud fields.

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  12. 9. How well do stereo cameras observe shallow cumulus spatial organization? An evaluation combining atmospheric path-tracing and high-resolution Large-Eddy Simulations (LES)
    Yannick Burchart
    16/05/2022, 12:08

    Spatial organization is essential for convection parameterization in numerical weather and climate models. However, spatial organization is challenging to observe. Most ground-based measurements consist of one-dimensional profile data, often sampled by lidars or radars. A recently explored new method of obtaining multi-dimensional information is to utilize hemispheric images from networks with...

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  13. 13. Diurnal signals in flower cloud organization in the upstream Tradewind regions during EUREC4A
    Salima Ghazayel (University of Cologne)
    16/05/2022, 12:10

    Tradewind shallow cumulus clouds cover vast areas of the subtropical oceans, and are associated with various modes of mesoscale organization. During the EUREC4A field campaign in the subtropical Atlantic in early 2020, unique in-situ and remote sensing measurements were made that allow characterization of Trade wind cloud organization as well as the large-scale environment in which this...

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  14. 60. The spacing and thermodynamics of updraughts in organised shallow cumulus
    Steven Boeing (University of Leeds)
    16/05/2022, 12:12
    Mesoscale organization of shallow and deep cumulus convection
    Poster
    Poster pitches

    We consider the clouds that form in Lagrangian high-resolution and single-column model simulations based on different days of the EUREC4A/ATOMIC field campaign. These simulations are driven using ERA5 reanalysis, and contain examples of flower type and gravel type organisation. In particular, we consider the spacing and thermodynamic properties of updraughts and detrained air during different...

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  15. 52. Dependence of Cloud Radiative Effect on Cloud Organization in the Trades
    Pouriya Alinaghi (TU Delft), Franziska Glassmeier (TU Delft)
    16/05/2022, 12:14

    Shallow cumuli are the most frequent types of clouds over the subtropical oceans where they occur in several shapes and patterns. These types of clouds potentially play a major role in regulating the radiative budget of the Earth system. An important question is to what extent cloud patterns alter under climate change and how this will feedback onto a rising of temperature. In this study, we...

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  16. 14. Clear-Sky Turbulence and Shallow Convection: New Insights Combining SAR Images, Satellite Brightness Temperature and In-Situ Measurements
    Pierre-Etienne Brilouet
    16/05/2022, 12:16

    Studying the marine atmospheric boundary layer (MABL) processes at play to organize cloudiness through satellite products is challenging. Here, we propose an innovative approach to investigate the MABL dynamical structures by combining spaceborne Synthetic Aperture Radar (SAR) images, and brightness temperature measurements from the Geostationary Operational Environmental Satellite...

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  17. 16. Cloud size and cloud spacing distributions of trade-wind cumuli observed at cloud base for a range of mesoscale organizations
    Julius Mex (LMD)
    16/05/2022, 12:18

    During the EUREC4A field campaign that took place near Barbados in Jan-Feb 2020, the French ATR aircraft flew in the lower troposphere and characterized the macrophysical, microphysical and turbulent properties of trade cumuli around the cloud-base level. Using horizontal lidar-radar observations and in-situ measurements, we characterize the cloud size and cloud spacing distributions of cumuli...

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  18. 63. Momentum transport and the organization of shallow convection
    Alessandro Carlo Maria Savazzi (Delft University of Technology)
    16/05/2022, 12:20

    Simulations of a marine cold air outbreak with the mesoscale weather model HARMONIE suggest that parameterized shallow convective momentum transport acts to diminish circulations that accompany cellular cloud structures. In this study we test this hypothesis in the trade-wind region where various type of shallow cumulus cloud patterns occur using a hierarchy of model simulations of the EUREC4A...

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  19. 43. Shallow convective organization in the Trades as seen by self-learning artificial intelligence
    Sabrina Schnitt (University of Cologne)
    16/05/2022, 12:22

    The organization of shallow convection in the trades influences precipitation development, cold pool formation, clouds’ radiative effects, and, thus, climate sensitivity. Deep learning techniques, especially in computer vision and self-supervision, are suitable tools to understand cloud organization purely from a machine’s perspective. Yet, the physical interpretation of the network’s classes...

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  20. 82. A new conceptual picture of the transition layer
    Anna Lea Albright
    16/05/2022, 12:24

    In the trades, the transition layer above the mixed layer top has long been observed and simulated. Yet its origins remain little investigated. The transition layer is often associated with an about 150 m deep layer between the mixed and subcloud layer tops that acts as a barrier to overlying convection. Using extensive observations from the EUREC4A field campaign, we propose a new conceptual...

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  21. 75. Process Oriented evaluation of the oversea AROME configuration: focus on the representation of cloud organisation
    Florent Beucher (Météo-France)
    16/05/2022, 12:26

    This study evaluates the ability of the French Convection-Permitting model AROME-OM to represent shallow cumulus and their main organisations for boreal winter conditions in the North Atlantic trades.
    It uses a set of three winter seasons (January-February 2018-2020) of high-resolution (1.3 and 2.5 km) simulations over the Caribbean domain (9.7-22.9°N, 75.3°W-51.7°W).
    The model is assessed...

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  22. 67. Competition between convection of mesoscale patterns and its impacts on self-organization in idealized CRM simulations
    Wei-Ming Tsai (University of Miami)
    16/05/2022, 12:28

    This study first aims to address why mesoscale convective patterns are important and investigate the effects on both dynamics and thermodynamics using a cyclic cloud-permitting model, CM1. A set of idealized experiments to address the competition between isolated and agglomerated, organized convection using large-domain simulations with explicit representations of both convective-scale and...

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  23. 69. Factors controlling precipitation in idealised monsoon simulations over an aquapatch
    Maxime Colin (Leibniz Centre for Tropical Marine Research)
    16/05/2022, 12:30

    The traditional view of monsoons as continental sea breezes generated by land-sea contrasts was shown to have serious limitations. Therefore, it remains unclear if the surface temperature contrast matters for the monsoon precipitation, and why there is a non-linear intensification of precipitation intensity with surface temperature forcing. Here, we aim to determine if monsoon non-linearities...

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  24. 22. The Diurnal Evolution of Controls on Trade Wind Mesoscale Morphologies
    Paquita Zuidema (University of Miami, RSMAS, USA)
    16/05/2022, 12:32

    The diurnal cycle in trade-wind cloudiness is thought to be driven by the diurnal cycle in the relative occurrence frequency of mesoscale cloud morphologies (i.e., Vial et al. 2021). These morphologies can be grouped by their distinct appearance and size into four categories: Sugar, Gravel, Flowers, and Fish. The diurnal cycle in cloudiness is associated with a late afternoon maximum in the...

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  25. 26. Numerical choices in Large-Eddy Simulations influence their ability to represent length scale growth in shallow convection
    Dr Stephan de Roode (Delft University of Technology)
    16/05/2022, 15:15

    A growing body of evidence suggests that shallow circulations play a key role in organising trade-wind clouds at the mesoscales. In turn, many of these mesoscale circulations appear to emerge directly from the shallow convection itself. We infer a very simple model for explaining this feedback from Large-Eddy Simulations of a classical numerical experiment with minimal physics (BOMEX), which...

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  26. 54. Natural selection by buoyancy and the ecology of pattern in convection
    Brian Mapes (University of Miami)
    16/05/2022, 15:30

    A conceptually guided literature review will be offered, in an attempt to frame the issue of pattern formation in evolutionary terms. Gravity is omniscient about density variations, and rewards them with a conversion from potential to kinetic energy. Some of that kinetic energy can induce further density patterning, with a pattern and scale dependent efficiency, by shaping latent heat release...

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  27. 77. Monday discussion (Adrian Tompkins, Graham Feingold, Brian Mapes, Franziska Glassmeier)
    16/05/2022, 16:00
  28. 88. Ice breaker at NODA (in the library)
    16/05/2022, 17:30
  29. 47. Mesoscale organization of trade-wind clouds: lessons from EUREC4A and questions
    Sandrine Bony (LMD/IPSL, CNRS, Sorbonne University)
    17/05/2022, 09:15

    Shallow convection exhibits a large diversity of spatial organizations at the mesoscale. Over the past years, a few prominent patterns of trade-wind clouds have been identified over the tropical western Atlantic. These patterns depend on environmental conditions and exert different radiative impacts. This raises two questions: What are the physical processes underlying changes in the mesoscale...

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  30. 6. Organisation of the trade-wind flower-clouds: driving processes and sensitivity
    Thibaut Dauhut (CNRM (CNRS and Meteo France), Toulouse, France)
    17/05/2022, 09:45

    The trade-wind cumuli are a great source of uncertainty for the future climate as their net radiative effect is hardly represented in the global models. The spatial organization of these clouds, that drives their radiative effect, has been categorized into 4 major patterns: Sugar, Flower, Gravel and Fish. The processes governing their spatial organization and the relationships with the large...

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  31. 7. How well do large-eddy simulations capture the observed co-variability of trade-wind cloudiness and its environment?
    Hauke Schulz (Max Planck Institute for Meteorology)
    17/05/2022, 10:00

    Recent observations revealed that meso-scale patterns of shallow convection in the downwind trades can be connected to specific atmospheric environments whose characteristics are not solely from within the trades but have traces from tropical or mid-latitudinal origin depending on the pattern. As a consequence of this co-variability of patterns and air-mass characteristics, a different...

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  32. 62. The role of three dimensional radiation in transitions from shallow to deep convection
    Chiel van Heerwaarden
    17/05/2022, 10:15

    While radiative transfer through cloud fields is a 3D process, we generally solve this only in 1D due to the high computational costs involved. As a consequence, large-eddy simulations with 1D radiation have highly simplified shortwave heating and longwave cooling in clouds. Also, surface fields of direct radiation have cloud shadows at the wrong location and surface diffuse radiation is too...

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  33. 44. The Organization and Vertical Structure of Shallow Convection in Marine Cold-Air Outbreaks, based on Cold-Air Outbreaks in the Marine Boundary Layer Experiment (COMBLE): Developing the Framework for an Intercomparison Modeling Study
    Bart Geerts (University of Wyoming)
    17/05/2022, 11:00

    The Arctic’s complex atmospheric environment remains a large source of uncertainty for numerical models across a range of scales, especially during cold-air outbreaks (CAOs). Under CAO conditions, the convective boundary layer grows rapidly with increasing fetch and intricate cloud structures transition from narrow rolls near the ice edge to cells downstream. To study the CAO cloud regime, the...

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  34. 57. Cold pool and mesh refinement: what is gained at higher resolutions?
    Romain Fiévet (Niels Bohr Institute)
    17/05/2022, 11:15

    It is well-recognized that triggering of convective cells through cold pools is key to the organization of convection, as reviewed in Zuidema et al. (2017). Yet, numerous studies have found that both the characterization and parameterization of these effects in numerical models is cumbersome - in part due to the lack of numerical convergence (Δx→ 0) achieved in typical cloud-resolving...

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  35. 28. The ubiquity of mesoscale shallow circulation in the trades
    Geet George (Max Planck Institute for Meteorology, Hamburg, Germany)
    17/05/2022, 11:30

    From EUREC$^4$A observations, we find evidence for shallow circulations at meso-scales in the trades. Shallow circulations have been shown as one of the main drivers behind genesis and maintenance of convective aggregation. They have been studied in models, as well as been identified in moisture space. We identify similar signals for the first time in physical space. Over time-means of 3-6...

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  36. 31. On the relationship between precipitation and the spatial structure in trade wind convection
    Jule Radtke (Meteorological Institute, Center for Earth System Research and Sustainability, Universität Hamburg; Max Planck Institute for Meteorology, Hamburg, Germany )
    17/05/2022, 11:45

    When trade wind convection organises into spatial patterns, it is often in conjunction with precipitation formation, raising the question of the role of convective spatial organisation for precipitation and vice versa. We analyse measurements from the C-band radar Poldirad upstream of Barbados during the EUREC4A field campaign to investigate the spatial behaviour of precipitating shallow...

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  37. 34. In-Situ Perspectives on the Sub-Cloud Layer during EUREC4A/ATOMIC
    Gijs de Boer
    17/05/2022, 12:00

    During the ATOMIC and EUREC4A campaigns, the University of Colorado RAAVEN (CU-RAAVEN) uncrewed aircraft system (UAS) was operated in the near-shore environment from Morgan Lewis Barbados. The aircraft conducted 37 research flights, capturing detailed information on the sub-cloud layer and atmospheric boundary layer between 24 January and 15 February. In this presentation, we will provide...

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  38. 68. Interactions between aerosol, clouds and circulation in high-resolution, cloud-resolving simulations with an imposed SST gradient
    Andrew Williams (University of Oxford)
    17/05/2022, 12:15

    The coupling between clouds and circulation has long been recognised both as an essential aspect of tropical circulations as the circulations that accompany clouds are also known to play a role in their spatial organization. For example, mesoscale circulations driven by the heating contrast between convecting and non-convecting regions can drive moisture aggregation in the convecting...

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  39. 56. The role of mesoscale convective organization in the generation of extreme precipitation over Europe
    Nicolas Da Silva (Centre for Ocean and Atmospheric Sciences, School of Environmental Sciences, University of East Anglia, Norwich, Norfolk, NR4 7TJ, United Kingdom)
    17/05/2022, 12:17

    Mesoscale Convective Systems (MCS) are common over Europe during the warm season (Morel and Senesi, 2002b) and are able to produce severe weather such as extreme precipitation leading to flash floods (Fiori et al., 2014). Studies analyzing the climatological characteristics of MCS over Europe are rare and were often based on only a few years of data or were focused on a limited area of Europe....

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  40. 65. Convective organization from the interaction between cold pools and thermally induced mesoscale circulations
    Edward Engelbrecht (Jacobs University Bremen/Leibniz ZMT)
    17/05/2022, 12:19

    Land surface conditions can influence the onset and strength of convective systems. This is because sharp gradients in land surface properties result in differential latent and sensible heat fluxes, which leads to the development of mesoscale atmospheric circulations similar to the circulations present in land-sea breezes. These mesoscale circulations play an important roll in controlling the...

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  41. 3. Sensitivity of Tropical Extreme Precipitation to Surface Warming in Aquaplanet Experiments Using the ICON Model
    Alejandro uribe (Stockholm University)
    17/05/2022, 12:21

    Increases in atmospheric water vapor holding capacity with temperature (7% K−1–8% K−1, CC-rate) can lead to increasing extreme precipitation (EP). Observations show that tropical EP has increased during the last five decades with a rate higher than in the extratropics. Global climate models (GCM's) diverge in the magnitude of increase in the tropics, and cloud-resolving models (CRM's) indicate...

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  42. 10. The impact of land-sea contrasts in the aggregation of convection
    Beth Dingley (AOPP, University of Oxford)
    17/05/2022, 12:23

    Studies on the self-aggregation of convection have identified key physical mechanisms which drive and then maintain aggregation in a range of idealised radiative-convection equilibrium (RCE) models. These models are typically run without any land, rotation, variation in sea-surface temperatures (SSTs), or a diurnal cycle. Therefore, a key recurring question is how these convective processes...

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  43. 71. A high-level analysis of complex Arctic mixed-phase cloud dynamics
    Dr J. Antoon van Hooft (TU Delft)
    17/05/2022, 12:25

    Mixed-phase clouds play an important role in the Arctic climate system. However, accurate climate projections are seriously hampered due to uncertainties in representing these clouds. Understanding their dynamical behavior based on first principles is a challenging task which requires the disentanglement of mixed-phase micro-physical complexities and a multitude multitude of...

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  44. 74. MCS longevity in the transition from land to sea
    Irene Livia Kruse (NBI)
    17/05/2022, 12:27
    Mesoscale organization of shallow and deep cumulus convection
    Poster
    Poster pitches

    Mesoscale convective systems (MCSs) are organized clusters of thunderstorms spanning more than 100 km horizontally, persisting often for multiple hours. They are known to be the dominant source of rainfall in the tropics, and the longest-lived MCSs are shown to be largely responsible for tropical extreme precipitation [Roca and Fiolleau, 2020]. Globally, the most extreme storms tend to be...

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  45. 12. ​​The role of cold pools and microphysics schemes in the organization of convection
    Alejandro Casallas (Abdus Salam International Centre for Theoretical Physics)
    17/05/2022, 12:29

    It has been suggested that larger coldpool radii can delay the onset of convective self-aggregation. We demonstrate that coldpool characteristics can differ between 5 of the commonly microphysical schemes used by the WRF-model. We systematically increase/decrease coldpool size by changing the evaporation of rain to observe the impact on organization. One complication in interpreting these...

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  46. 51. Open cell convection in HARMONIE-AROME
    Wim de Rooy (researcher)
    17/05/2022, 12:31

    With a resolution of 2.5km, HARMONIE-AROME is a NWP model that roughly resolves deep convection. It is not clear if such a model should be capable of resolving open cell convection, as can be observed above sea under unstable conditions (e.g. during a cold air outbreak). However, especially the rain associated with this type of convection, can be important if it occurs with temperatures around...

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  47. 23. How does microphysical phase relate to cloud morphology transition speed within cold-air outbreaks over the northwest Atlantic?
    Paquita Zuidema (University of Miami), Dr Seethala Chellappan (University of Miami), the ACTIVATE Science Team, Simon Kirschler (DLR)
    17/05/2022, 12:33

    Cold-air outbreaks off of the eastern US seaboard provide dramatic visual examples of cloud morphological transitions from closed-cell to more open-celled circulations. Space-based lidar and radar indicate the transitions typically involve mixed-phase clouds and precipitation, but may also remain liquid-only at times. Because the air flow moves over the Gulf Stream, significant surface...

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  48. 84. Investigating extreme precipitations in tropical squall lines
    Sophie Abramian (Institut Pierre-Simon Laplace)
    17/05/2022, 12:35

    Squall lines are the consequence of the interaction of low-level shear with cold pools associated with convective downdrafts, and beyond a critical shear, squall lines tend to orient themselves. It has been shown that this orientation has the effect of reducing the incoming wind shear to the squall line and maintains equilibrium between wind shear and cold pool spreading (Abramian et al...

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  49. 76. Dependency of mesoscale organization on grid anisotropy in large-eddy simulations at Gray Zone resolutions
    Stephan de Roode (Delft University of Technology)
    17/05/2022, 12:37

    A new generation of operational atmospheric models operating at horizontal resolutions in the range 200 m up to ~ 2 km is becoming increasingly popular for operational use in numerical weather prediction and climate applications. Such grid spacings are becoming sufficiently fine to resolve a fraction of the turbulent transports. Here we analyze LES results of a convective boundary layer...

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  50. 61. Properties and transitions of mesoscale convective organisation during EUREC4A using unsupervised learning
    Leif Denby (University of Leeds)
    17/05/2022, 15:15

    The representation of shallow tradewind cumulus clouds in climate models accounts for the majority of inter-model spread in climate projections, highlighting an urgent need to understand these clouds better. In particular, their spatial organisation appears to cause a strong impact of their radiative properties and dynamical evolution. The precise mechanisms driving different forms of...

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  51. 20. Observations and simulations of stable water isotopes and their link to the mesoscale organization of shallow trade-wind clouds
    Leonie Villiger (Institute for Atmospheric and Climate Science, ETH Zurich, Zurich, Switzerland )
    17/05/2022, 15:30

    Water molecules containing a heavy hydrogen or oxygen atom have lower saturation vapor pressures and diffusivities than their light counterparts, which leads to a change in their relative abundance during phase transitions. Each process controlling the water vapor budget of shallow cumulus clouds in the trade wind region such as ocean evaporation, convective and turbulent mixing, condensation...

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  52. 66. Cloud response to higher warming conditions over the Tropical Atlantic using the COSMO model
    Dr Abraham Torres-Alavez (ETH Zürich)
    17/05/2022, 15:45

    Using the COSMO model, as part of the EUREC4A modeling project, we present a set of convection-resolving simulations of current and future climate over the EUREC4A study area. The main objectives of these simulations are: 1) to evaluate the capacity of the convection-resolving COSMO model to capture tropical-cloud characteristics from January 1 to March 1 2020; 2) to assess future changes in...

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  53. 78. Tuesday discussion (Sandrine Bony, Bjorn Stevens, Pier Siebesma)
    17/05/2022, 16:00
  54. 83. A short History of Cloud Observations in Art and Science
    Bjorn Stevens, Anna Lea Albright
    17/05/2022, 19:30

    Looking up. Our eyes are drawn to the sky. The sky can promise rain, sunshine, storms, clouds in a variety of forms ... in this talk, we trace a history of observing the sky, particularly the history of observing clouds and observing air pollution. In the 19th century, an amateur meteorologist, Luke Howard, gave clouds their names (cumulus, stratus, etc), which grew into the first...

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  55. 70. Land effects on organised convection – mechanisms and applications
    Cornelia Klein
    18/05/2022, 09:15

    Different from oceans, the land surface can dry out, creating strong gradients in surface fluxes and temperatures. 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. On larger scales, land surface...

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  56. 11. Daytime convective development over land: the role of surface forcing
    wojciech grabowski (NCAR)
    18/05/2022, 09:45

    Diurnal cycle of solar radiation over tropical and midlatitude summertime continents forces strong evolution of atmospheric convection. As surface sensible and latent heat fluxes increase after sunrise, a dry convective boundary layer develops in the early morning hours. It proceeds with the formation of shallow convective clouds as the convective boundary layer deepens and may eventually lead...

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  57. 19. Illuminating the Sub-Mesoscale Structure of Cold Pools with a Dense Station Network during FESSTVaL
    Bastian Kirsch (University of Hamburg)
    18/05/2022, 10:00

    Cold pools are crucial for understanding the organization of atmospheric convection. However, their detailed structure remains a blind spot of operational station networks. In summer 2021 the FESSTVaL field experiment aimed to address this observational gap and shed light on the structure and life cycle of cold pools on the sub-mesoscale (100 m to 10 km). The experiment took place in the rural...

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  58. 41. The Organization and Vertical Structure of Shallow Convection in Marine Cold-Air Outbreaks, based on the Cold-Air Outbreaks in the Marine Boundary Layer Experiment (COMBLE): Observations
    Bart Geerts (University of Wyoming)
    18/05/2022, 10:15

    When cold air blows off boreal continents or the Arctic ice over open water, a well-recognized cloud pattern forms with clouds streets and, further downwind, an open cellular structure. Despite the ubiquity of this cold-air outbreak (CAO) cloud regime over high-latitude oceans, we have a rather poor understanding of its properties, including its macroscale organization. In the 2019-’20 cold...

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  59. 25. Evaluation of ECMWF lightning forecast over Indian subcontinent during 2020 premonsoon months
    Dr Parthasarathi Mukhopadhyay (Indian Institute of Tropical Meteorology)
    18/05/2022, 11:00

    Convective cumulus clouds with vigorous updrafts and downdrafts form thunderstorms. Severe thunderstorms consist of multiple thunderclouds at different stages, and the storm itself has a longer lifetime than individual cells. As the convective clouds grow larger, the negative charge accumulates in their lower region, and the positive charge in the upper level forms a dipole. When the charge...

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  60. 49. A cold pool perturbation scheme to improve convective initiation in convection-permitting models
    Mirjam Hirt
    18/05/2022, 11:15

    Cold pools are essential for organizing and initiating convection. In a recent investigation, we identified several sensitivities of cold pool driven convective initiation to model resolution within hectometer simulations. In particular, a causal graph analysis has revealed that the dominant impact of model resolution on convective initiation is a direct consequence of weak...

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  61. 39. Dependency of precipitation and cloud radiative feedback on subgrid scale clouds structure; a machine learning approach
    Sara Shamekh (Columbia University)
    18/05/2022, 11:30

    The organization of convective clouds has been argued to have a significant impact on the atmospheric humidity and circulation, as well as precipitation and cloud radiative feedback, yet global models do not include a parameterization of unresolved subgrid cloud structure. In this study, we investigate the necessity of including subgrid scale cloud structure in the model and whether it...

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  62. 48. Reassessing the Cohen and Craig (2006) theory: Fluctuations in an equilibrium convective cloud ensemble at horizontal resolutions ranging from 2 km to 125 m
    Dr Julien Savre (Ludwig-Maximilians-Universität Munich)
    18/05/2022, 11:45

    About 15 years ago, Cohen and Craig (2006, CC06) proposed a general theory describing the fluctuations of the properties characterising a convective cloud ensemble developing under fixed external forcing. This theory later served as the basis of the Plant-Craig stochastic convection scheme which has been in particular implemented in the ICON model operated by the German weather service....

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  63. 30. Moisture transports and rain cell statistics in organised convection and their potential role in super Clausius-Clapeyron scaling
    Geert Lenderink (KNMI)
    18/05/2022, 12:00

    In observations of (sub)hourly precipitation, it is often found that the extremes display a dependency on (dew point) temperature exceeding the Clausius-Clapeyron (CC) relation. Such super CC behaviour is commonly explained by dynamical feedback mechanisms in convective clouds whereby enhanced latent heating (and cooling due to evaporation) could produce more vigorous, or more organised...

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  64. 15. Parametrising cold-pool effects in the Met Office Unified Model
    Gabriel Rooney (Met Office UK)
    18/05/2022, 12:15

    Cold pools formed by convective downdraughts can feed back onto the organisation and diurnal cycle of convection. This presentation describes a parametrisation of cold pools, C-POOL, recently developed within the Met Office Unified Model (UM). The parametrisation includes forcing by downdraughts, dissipation, and various pathways for influencing parametrised convection in the UM. It also...

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  65. 86. Group photo
    18/05/2022, 12:30
  66. 46. Self-aggregation of convective storms
    caroline muller (CNRS/LMD)
    18/05/2022, 15:15

    Idealized simulations of the tropical atmosphere have predicted that clouds can spontaneously clump together in space, despite perfectly homogeneous settings. This phenomenon has been called self-aggregation, and results in a state where a moist cloudy region with intense deep convective storms is surrounded by extremely dry subsiding air devoid of deep clouds. We review here the main findings...

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  67. 79. Wednesday discussion (Caroline Muller, Cornelia Klein, Jan Haerter)
    18/05/2022, 15:45
  68. 87. Boat to dinner
    18/05/2022, 17:15
  69. 73. Mesoscale organization of shallow convection: the role of rain and cold pools
    Raphaela Vogel
    19/05/2022, 09:15

    Shallow-convective organization and rain are two sides of the same coin. The mesoscale organization of shallow convection tends to increase rain rates, and rain is an important ingredient for organising shallow convection. Rain induces mesoscale organization preferentially through evaporatively-driven downdrafts, which trigger cold pools that spread out at the surface as density currents. Cold...

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  70. 50. How well can we simulate mesoscale cloud organisation as observed during EUREC4A ?
    Pier Siebesma (Delft University of Technology), Louise Nuijens (TU Delft)
    19/05/2022, 09:45

    It has become clear over the last couple of years that shallow cumulus convection over the subtropical oceans has a strong tendency to develop itself into a rich variety of spatial cloud structures. It is particular challenging to simulate these mesoscale cloud patterns. On the one hand, it requires turbulence resolving resolutions of 100 m to represent the vertical convective mixing processes...

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  71. 45. Low-level radiative cooling peaks in regimes of shallow convective organization
    Benjamin Fildier (Laboratoire de Météorologie Dynamique, ENS, Paris)
    19/05/2022, 10:00

    In models, a local maximum of clear-sky radiative cooling in the lower troposphere often appears as a necessary condition for the development and persistence of convective organization. However, no robust understanding has been provided for the emergence and disappearance of lower-tropospheric cooling in the atmosphere. Here we propose a theoretical characterization of clear-sky radiative...

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  72. 72. Wind-responsive diurnal sea skin temperature for large-eddy simulations
    Reyk Börner (University of Reading)
    19/05/2022, 10:15

    The diurnal variability of sea skin temperature (SST) is suspected to play an important role for convective organization above the tropical ocean, from driving cumulus congestus convection to triggering the active phase of the Madden-Julian Oscillation. Recent cloud-resolving simulations demonstrate how imposed diurnal SST oscillations strongly impact mesoscale convective aggregation,...

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  73. 80. Thursday discussion (Raphaela Vogel, Louise Nuijens)
    19/05/2022, 11:00
  74. 89. Final discussion
    19/05/2022, 11:45
  75. 42. Controls on organisation with CoMorph
    Alison Stirling (Met Office)

    CoMorph is a new mass-flux convection scheme, developed at the Met Office as part of the ParaCon programme. We report on the organisation that results with this scheme across a range of scales and forcings, and the key controls on the emergent structures that form.

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