Circle-A: Parametrizing Convection in the Hard Grey Zone: Modelling the Interaction of Turbulent Cloud processes with Explicit Cloud Dynamics.

Lead Research Organisation: University of Reading
Department Name: Meteorology

Abstract

"Anarchy is the mother of Order", claimed Proudhon, referring to the Anarchist movement. Many might question whether this is true of human behaviour, but it certainly is of the atmosphere. Some of the most extreme weather on earth is associated with deep convective rain storms driven by the heat released and buoyancy generated when water vapour turns into liquid cloud water or ice. These storms start out as small turbulent eddies which grow into violent thunderstorms, the most severe of which preserve their existence by a process of continual regeneration. In the right conditions, storms can organise into much larger structures such as squall lines covering hundreds of kilometres and lasting many hours. The most extreme, violent and beautiful example of organised convection is the tropical cyclone.
This ever-larger scale organisation nevertheless remains, in part, controlled by processes occurring at the smallest turbulent scales. If we represent these processes poorly in models used to predict weather and climate, we severely compromise the accuracy of their predictions. Ever-increasing computer power has given us the ability to run higher resolution models that are beginning to represent individual clouds with some realism, but we are far from directly resolving those processes that control the size, intensity, number etc. of clouds. This project is aimed at substantially improving the way we represent the effect of these processes on cloud growth and dissipation in practicable weather forecast models and climate models.
We can get so far by theoretical derivation from the fundamental equations of physics, but doing so raises more unanswered questions, such as how can we predict the distribution of water in a cloud, which is highly sensitive to motions within turbulent eddies, given only limited information of average properties over larger scales (e.g. a few km)? We can 'close' the problem by forming hypotheses about dependencies based upon arguments such as scaling and symmetry, but these need testing and calibrating. As part of the project we plan to run a number of ambitious reference simulations of controlled, idealized, convective flows, to provide data to test these hypotheses. We also propose developing a hierarchy of simplified representations of the turbulent flow directed specifically at cost effective modelling of deep convection. In particular, we plan to implement three schemes:
1. A 'Rolls-Royce' scheme, with as little approximation as possible.
2. A highly simplified scheme similar to those commonly used but and with a fresh analysis of key parameters.
3. A new scheme traceable from 1 but based on a simplification of 1 directed specifically at the representation of deep convective clouds, focussing on vertical motion and resulting condensation separately from horizontal motion.
The high resolution data will be analysed much the same way that observational data would be if available, but we also plan to make use of high-resolution models is a way which could never be achieved through observation; we plan to provide information about the 'truth' directly to lower resolution simulations as they run, either turbulent fluxes or mean variables. This can be done in a number of ways to learn about which terms are most important in driving the resolved flow. One exciting and novel way is to use techniques recently developed in the Data Assimilation Research Centre to use 'observations' (in our case, reference high-resolution simulations) to determine objectively which parametrizations best represent the 'missing' terms in a model, the omission of which lead the model to diverge from the observations.

Planned Impact

Society and the General Public
The primary impact of this project will be directly on the accuracy and utility of Met Office weather forecasts and climate predictions via improved prediction and simulation of convection in the Met Office's Unified Model. Impacts will occur through other centres; directly through Met Office Partners in MetUM development and indirectly to other centres through promulgation of the methodology and reference data it is based on. This will have impact on end-users, from government, industry and the public, through significant improvements to their products and advice. The Met Office, in common with operational prediction centres worldwide, considers this to be a major priority, made more essential by ongoing efforts to improve the dynamical cores of models to allow best use of increased parallel computing power and, hence, higher spatial resolution, such as the Gung-Ho project in the UK (now LFRic) and the ICON project in Germany.
Weather and flood forecasting: This project will improve forecasts, certainly in regional weather forecast models and hopefully also in coarser-resolution global models. Convection is responsible for the intense rainfall that generates flash floods. The Pitt Review, written after the 2007 UK floods, stressed the need for better prediction heavy precipitation. Short-range MetUM-forecasts are now being produced in the Met Office with grid-spacing of a few km. The Environment Agency/Met Office Flood Forecasting Centre now provides a national severe rainfall and flood warning service that relies on NWP forecasts. The reliability of these forecasts is compromised by deficiencies in the representation of intense rainfall from convective systems, and a more reliable parametrization will have an immediate impact on forecast quality. The importance of parametrization of turbulence and convection cannot be understated; at present, the only remedy for deficiencies in performance is higher-resolution, which is extremely expensive. Improved parametrization will facilitate larger-domains, larger ensembles to quantify forecast uncertainty, and improved data assimilation.
Climate predictions, climate-change impact assessments: The hard grey-zone parametrizion scheme will contribute to correcting major biases in the MetUM, Recent work using the MetUM at convection-permitting resolution has shown that the climate change signal for extreme rainfall cannot be relied upon from models using current convection parametrizations. A different signal emerges from 'convection-permitting' models, but these clearly, at present, have their own significant biases.
The importance of convection goes far beyond precipitation, however. "Realistic parametrizations of cloud processes are a prerequisite for reliable current and future climate simulation" and "differences in cloud response are the primary source of inter-model differences in climate sensitivity" (IPCC, Ch. 8). The representation of convection has a number of impacts on earth-system models. Wash-out by convective rain is a primary uncertainty in the global aerosol cycle, the representation of convection is more important for the summertime Sahara dust than the land surface and rainfall changes control the future of tropical forests, such as the Amazon, where some models predict a die-back with decreased rainfall, coupling convection with the carbon cycle (IPCC, 2007, Ch. 11.6.3.2).
Academic Impact
This project will deliver new understanding of atmospheric convection that will have wide impact in the academic community, as well as improved climate and earth-system models which form the basis of further academic study. It will also deliver valuable database of high-resolution reference simulations that will be used for years to come by the UK and WGNE communities: these will likely have many uses beyond those described in this proposal, as has been found, e.g., in the NERC Cascade consortium

Publications

10 25 50

Studentship Projects

Project Reference Relationship Related To Start End Student Name
NE/N013735/1 01/08/2016 30/09/2020
1787146 Studentship NE/N013735/1 01/10/2016 30/09/2019 William McIntyre
1936702 Studentship NE/N013735/1 18/09/2017 18/09/2020 Daniel Shipley
 
Description We have developed a new turbulence scheme within the Met Office/NERC Cloud model (MONC); this is partially implemented, so main results will follow later in this year, but we can show that the scheme impacts convection at intermediate scales in a useful way in that it corrects systematic errors in in-cloud turbulence intensity that have been found comparing radar-derived observations with models. These findings have yet to be published.
Exploitation Route We intend to take this closer to operational implementation (for use in convection-permitting weather and climate models) during Phase II of ParaCon.
Sectors Environment

 
Description Collaboration with Met Office 
Organisation Meteorological Office UK
Country United Kingdom 
Sector Public 
PI Contribution We have worked closely with the the Met Office a) developing and testing a new turbulence scheme in the Unified Model and b) Adding functionality to the new Met Office/NERC cloud model (MONC).
Collaborator Contribution One Met Office member of staff has worked very closely with me developing the new turbulence scheme in the Unified Model for approx one year.
Impact New diagnostic functionality in MONC model.
Start Year 2017
 
Title Conditional averaging support in AtmosFOAM 
Description AtmosFOAM is a set of tool for atmospheric modelling research on arbitrary grids using the OpenFOAM library. Conditional averaging techniques are being developed in the Circle-A project for representing buoyant convection. Conditional averaging support has been added to AtmosFOAM 
Type Of Technology Software 
Year Produced 2018 
Open Source License? Yes  
Impact Co I Weller and student Dan Shipway are able to make progress with research on the project with this software. 
URL http://www.github.com/AtmosFOAM
 
Title New diagnostic tools in Met Office/NERC cloud model (MONC) 
Description We have added a substantial set of process rate diagnostics and diagnostics related to the TKE budget. This work is ongoing. 
Type Of Technology Software 
Year Produced 2018 
Open Source License? Yes  
Impact None yet. 
 
Title New technique for calculating mixed online/offline trajectories in MONC 
Description We have implemented a new technique for calculating trajectories which is much more accurate and efficient than traditional techniques. This has yet to be committed to the trunk but is available as a branch. Code to post-process the output is under development using python. 
Type Of Technology Software 
Year Produced 2019 
Open Source License? Yes  
Impact Work in progress to apply this tool to derive improved estimates of entrainment and detrainment rates. 
URL https://puma.nerc.ac.uk/trac/UM_TOOLS/wiki/MONC
 
Title TKE-based Turbulence scheme in MONC 
Description We have added a Mellor-Yamada level 2.5 and level 3 turbulence scheme including Deardorff-like cloud condensation to the Met Office/NERC cloud model (MONC). This has yet to be committed to the trunk but is available as a branch. 
Type Of Technology Software 
Year Produced 2019 
Open Source License? Yes  
Impact This is an important potential enhancement of the model which we anticipate will improve results at lower than well-resolved LES scales, and also a step towards a grey-zone scheme. 
 
Description ECMWF physics-dynamics coupling workshop 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact Talk at the ECMWF physics-dynamics coupling workshop
Year(s) Of Engagement Activity 2018
URL https://www.ecmwf.int/en/learning/workshops/3rd-workshop-physics-dynamics-coupling-pdc18
 
Description Participation by Todd Jones in CASIM Science Meeting, UK Met Office, to discuss RCE in MONC and the Idealised UM 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Professional Practitioners
Results and Impact CASIM is the new, flexible cloud microphysics scheme in the Met Office's Unified Model (MetUM) and the Met Office/NERC Cloud Model (MONC); Todd Jones participated in a CASIM science meeting to report on the scheme's performance in radiative-convective equilibrium and to coordinate with other groups planning to contribute to RCEMIP
Year(s) Of Engagement Activity 2018
 
Description Poster advertising Circle-A project at The Future of Cumulus Parametrization workshop, 10-14 July 2017, Delft 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact This poster was intended to draw the attention of international experts in the field to the planned activities in Circle-A.
Year(s) Of Engagement Activity 2017
URL http://users.monash.edu.au/~cjakob/future_of_cu.html
 
Description Presentation by Todd Jones at 6th ParaCon Plenary Meeting, UK Met Office on Numerical Convergence in RCE 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Professional Practitioners
Results and Impact Presentation of the convergence properties of the MetUM is radiative-convective equilibrium. This pertains to what resolutions of model are required to 'resolve' deep convection in a well-defined way and hence on requirements for parametrization of deep convection in climate models.
Year(s) Of Engagement Activity 2018
 
Description Presentation by Todd Jones at AGU Fall Meeting, Washington, D.C. on Radiative-Convective Equilibrium Across the Gray Zone 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact Presentation at international conference on the performance of the Met Office's Unified Model at resolutions that span the so-called 'gray-zone' of convection. This pertains to the likely systematic error caused by inadequate resolution in convection permitting weather and climate models.
Year(s) Of Engagement Activity 2018
URL https://agu.confex.com/agu/fm18/meetingapp.cgi/Paper/438499
 
Description Presentation by Tom Webb at ParaCon Plenary meeting, Reading, on implementation of TKE budget diagnostics in the MONC 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Professional Practitioners
Results and Impact Presentation by Tom Webb at ParaCon Plenary meeting, Reading, on implementation of TKE budget diagnostics in the Met Office / NERC cloud model (MONC); this is a new model and lacks some of the functionality essential for such a model. This talk reported work by Webb and Clark on implementing a complete horizontally-averaged TKE budget, and issues arrising. This facilitated work by other using the model.
Year(s) Of Engagement Activity 2018
 
Description RCE and RCEMIP Talk by Todd Jones at biennial plenary meeting. 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Professional Practitioners
Results and Impact Presentation on the character of radiative-convective equilibrium in the Met Office's Unified Model, and the planned international Model Intercomparison Project, for which Todd Jones is representin gCircle-A.
Year(s) Of Engagement Activity 2018
URL http://myweb.fsu.edu/awing/rcemip.html
 
Description Talk by Peter Clark at ParaCon Plenary meeting, Reading, on the organisation of convection. 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Professional Practitioners
Results and Impact This talk reviewed some of the physical mechanisms behind the self-organisation of convection, and the problems that models with parametrized convection often have representing these mechanisms, often leading to very poor performance.
Year(s) Of Engagement Activity 2018
 
Description Talk by Peter Clark at The Future of Cumulus Parametrization workshop, July 2017, Delft, on stachastic parametrization of the boundary-layer. 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact This talk described the theory behind a new stochastic parametrization implemented in the Met Office's Unified Model and its impact on the triggering and growth of deep convection in the Met Office's UKV forecast model.
Year(s) Of Engagement Activity 2017
URL http://users.monash.edu.au/~cjakob/future_of_cu.html
 
Description Talk by Peter Clark at the ParaCon Plenary Meeting, Met Office, on progress with modified NNMY turbulence scheme in the MetUM 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Professional Practitioners
Results and Impact This talk reported on progress with a collaborative activity with the Met Office modifying the existing Nakanishi-Nino/Mellor Yamada 1D TKE-based boundary layer scheme in the Met Office's Unified Model to act as a 3D, scale-aware turbulence scheme.
Year(s) Of Engagement Activity 2018
 
Description Talk by Tom Webb at ParaCon plenary meeting at Met Office on level 3.0 turbulence scheme. 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Professional Practitioners
Results and Impact The Circle-A project is implementing a flexible prognostic turbulence scheme within the Met Office/NERC cloud model (MONC) to study and hopefully improve performance in so-collaed convection-permitting configurations of models. In the long run we hope to improve the performance of weather and climate models run at 'convection-permitting' resolution. This talk reported progress towards this goal: the implementation of a 'Level 3' scheme with 4 prognostic variables.
Year(s) Of Engagement Activity 2018
 
Description Talk on Circle-A at UM Convection Workshop, Singapore, Feb 2017 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact Talk outlining plans for the Circle-A project and broader ParaCon project to international workshop on convection, primarily Met Office MetUM partners (i.e. a number of National Weather Services).
Year(s) Of Engagement Activity 2017
URL https://www.metoffice.gov.uk/research/collaboration/um-partnership