Scattering, Clouds & Climate: A Short Workshop of Exploration

Mathematical Institute, University of Oxford

24th - 25th March 2014


Summary: A two-day workshop bringing together mathematicians and atmospheric physicists working on problems related to scattering of electromagnetic radiation by atmospheric ice crystals. The aim is to identify areas where advances in mathematical methods, such as high frequency asymptotics, homogenisation, and numerical schemes, may be useful in climate modelling, and, in so doing, nucleate future collaborative efforts.


***NEW*** Programme and book of talk abstracts: Click here.


***NEW*** Post-workshop report: Click here.


***NEW*** Slides from presentations: See individual links in “Programme” section below.





David Abrahams (Manchester)

Evelyn Hesse (Hertfordshire)

David Allwright (Oxford)

David Hewett (Oxford)

Anthony Baran (Met Office)

Robin Hogan (Reading)

David Bebbington (Essex)

Stephen Langdon (Reading)

Timo Betcke (UCL)

John Ockendon (Oxford)

Simon Chandler-Wilde (Reading)

Juliet Pickering (Imperial)

Jon Chapman (Oxford)

Caroline Poulsen (Rutherford Appleton Laboratory)

Paul Connolly (Manchester)

Tony Rawlins (Brunel)

Steven Dobbie (Leeds)

Helen Smith (Manchester)

Cathryn Fox (Imperial)

Valery Smyshlyaev (UCL)

Andrew Gibbs (Reading)

Thorwald Stein (Reading)

Ivan Graham (Bath)

Joseph Ulanowski (Hertfordshire)

Samuel Groth (Reading/Leuven)

Chris Westbrook (Reading)

John Hannay (Bristol)

John Wettlaufer (Oxford)


Background: The accurate prediction of the Earth’s radiation balance requires an understanding of the way that electromagnetic radiation is scattered by ice crystals in clouds. Accurately modelling this scattering is challenging because of the multiscale nature of the problem, and because of the complexity and variation in the size, shape and distribution of ice crystals within clouds. Current climate models cannot produce cloud covers that accurately agree with (a) observations and (b) other climate models. The principal methods to probe the microphysics of clouds are remote-sensing retrievals, either active (radar, lidar) or passive (radiometry/imaging), and in-situ measurements by aircraft. A central feature of the cloud components of climate models involves the interpretation of such measurements, ranging from basic scattering physics (for example the investigation of ice crystal size and distribution) to the implementation of algorithms and instrument corrections.


Focus of workshop: The key goals of the workshop are:

1. To identify the basic scattering questions that currently limit the quantitative interpretation of remotely sensed and in situ data;

2. To identify model scattering problems that are relevant to the meteorological community and involve interesting mathematical challenges.


For example, possible topics for discussion may include:

- How does polarization figure into retrieval schemes?

- Which is more important: ice crystal size distribution or shape variation?

- How useful are two-dimensional approximations?


Outcomes: Currently, advances in mathematical scattering theory and in remote sensing appear to be progressing in parallel, but given the richness of the former and the increasing importance of the latter it is hoped that a principle consequence of this workshop will be the formation of new collaborations and research proposals based on a mutually beneficial union of both.


Format: 1.5 day workshop for up to 25 invited participants, comprising talks, structured discussion sessions and informal networking. Lunches and tea/coffee will be provided and there will be a workshop dinner in college.


Date: Monday 24th - Tuesday 25th March 2014. The workshop will start at lunchtime on 24th and close at around 4.30pm on 25th. See below for a provisional programme.


Venue: Mathematical Institute, University of Oxford, Radcliffe Observatory Quarter, Woodstock Road, Oxford, OX2 6GG, UK. Dinner and overnight accommodation on Monday 24th will be provided at Somerville College. The Mathematical Institute is a short (10-15 minute) walk from the Oxford rail station. For a map showing the location of the Mathematical Institute and Somerville College click here.


Registration, lunches, and tea/coffee breaks will take place under the North Crystal on the Mezzanine. Talks will take place in lecture room L4 (again under the North Crystal on the Mezzanine).




Mon 24th



Lunch and registration


Welcome and introduction – David Hewett (Oxford) and Chris Westbrook (Reading)


Anthony Baran (Met Office) – “A unified approach to cirrus microphysics, remote sensing and climate prediction, and its impact in a climate model”


Helen Smith (Manchester) – “Laboratory measurements and modelling of the scattering properties of hollow and solid ice crystals”




David Bebbington (Essex) – “Advances in polarimetric radar scattering - modelling and analysis”


Cathryn Fox (Imperial) - "CIRCCREX: A new cirrus dataset for model evaluation"




Free time (opportunity to check in at Somerville College)


Reception and dinner at Somerville College


Tues 25th



Steven Dobbie (Leeds) – “An estimate of the optical significance of trigonal ice particles”


Joseph Ulanowski (Hertfordshire) – “Non-idealized ice crystal geometries”




Robin Hogan (Reading) – “Coherent backscattering effects for single particles and distributions of particles”


Ivan Graham (Bath) – “On shifted Laplace and related preconditioners for finite element approximations of the Helmholtz equation”




Timo Betcke (UCL) – “The BEM++ boundary element library and applications”


David Hewett (Oxford) – “Hybrid numerical-asymptotic methods for high frequency scattering”








Acknowledgements: The organisers are grateful to the Oxford Centre for Collaborative Applied Mathematics and the Oxford Mathematical Institute for funding this workshop, and to Anthony Baran (Met Office) for supplying the image of the ice crystal rosette at the top of the page.


Organisers: Dr David Hewett, Prof. John Ockendon and Prof. John Wettlaufer