Aerosol-Cloud Coupling And Climate Interactions in the Arctic

Lead Research Organisation: University of East Anglia
Department Name: Environmental Sciences


The climate of the Arctic is changing faster than that almost anywhere else on Earth, warming at a rate of twice the global average. This warming is accompanied by a rapid melting of the sea ice - 2007 saw a record minimum in summer ice extent, and the years since have seen the 2nd and 3rd lowest summer ice extents on record - and a thinning of the ice that remains from year to year. The strong warming in the Arctic is due to several positive feedback processes, including a sea-ice albedo feedback (warmer conditions melt ice, lowering the average reflectivity of the mixed ice/ocean surface and thus absorbing more solar radiation, leading to increased ice melt and further lowering of the albedo) and several cloud feedbacks. Over most of the globe low clouds act to cool the surface since they reflect sunlight; over the arctic the highly reflective ice surface reduces the significance of cloud reflectivity, and the absorption of infrared radiation by cloud water droplets becomes the dominant effect - this acts to trap heat below cloud, warming the surface.
Although climate models generally show a strong greenhouse warming effect in the Arctic, they also disagree with each other more in the Arctic than anywhere else, producing a wider range of possible future climate conditions. The models also tend not to be able to reproduce current Arctic climate conditions very accurately. This large uncertainty in models of the Arctic climate results primarily from poor representation of physical processes within the models, and some unique and particularly challenging conditions. The largest single source of uncertainty is the representation of clouds. The models use simple representations of cloud properties that were developed from observations in mid latitude or tropical cloud systems - very different conditions from those that exist in the Arctic.

This project will make airborne in situ measurements of cloud microphysical properties, the vertical structure of the boundary layer and aerosol properties, and the fluxes of solar and infra red radiation above, below, and within cloud. It will also measure the production rates and properties of aerosol at the surface and their variability with season and extent of sea ice cover. These measurements will be used, along with a range of numerical models of aerosol and cloud processes, and atmospheric dynamics to evaluate the interactions between sea ice extent, aerosol production and cloud properties. New and improved descriptions of these processes suitable for use within climate models will be developed, tested, and implemented within the MetOffice climate model HadGEM. The ability of the current MetOffice models to reproduce the observed Arctic cloud and boundary layer properties will be tested, and the impact of the new parameterization schemes evaluated.
Finally we will undertake a series of climate simulations to examine how future climate will evolve, and the feedbacks between warming of the Arctic, melting of sea ice, production of aerosol, and the properties of clouds evaluated.

Planned Impact

This study has potentially wide impacts throughout the climate modelling community, both within academia and government agencies. Our collaboration with the Met Office guarantees both that all our results will be available directly to the Met Office and Hadley Centre, and that the necessary expertise with the UM is available to this study. A primary goal of the project is the development and implementation of new/improved parameterizations of aerosol, cloud, and boundary layer processes within the UM.

Improvements to parameterization schemes for boundary layer turbulent processes, low level cloud representation, and cloud radiative properties for large scale models will:

- Improve fidelity of climate predictions - this is essential if an accurate assessment of future climate change is to be achieved. This need is particularly pressing for the Arctic regions due to the rapid rate of observed change, and the expected continuation (perhaps acceleration) of this change, but also impacts on predicted climate for the rest of the world.

- Improved performance of numerical weather prediction for mid-to-high latitude regions (including the UK). The Arctic can seem remote, but there are direct influences on UK weather through advection of Arctic air masses, and indirect influence through changes in the tracks of North Atlantic storms associated with changes to surface pressure field in a warmer Arctic.

Improvements to predictive capabilities in the Arctic have impacts for climate prediction around the world. Reducing uncertainty in climate prediction is essential if policy makers are to be able to implement effective plans for limiting the human impacts of climate change.


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Moore G (2013) Greenland plateau jets in Tellus A: Dynamic Meteorology and Oceanography

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Renfrew I (2018) Modification of Polar Low Development by Orography and Sea Ice in Monthly Weather Review

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Renfrew I (2019) Atmospheric sensitivity to marginal-ice-zone drag: Local and global responses in Quarterly Journal of the Royal Meteorological Society

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Sergeev D (2017) Structure of a shear-line polar low Structure of a Shear-line Polar Low in Quarterly Journal of the Royal Meteorological Society

Description Determined a relationship between surface drag in the atmosphere and sea-ice concentration. This is essential for being able to understand and parameterize the transfer of momentum between the atmosphere and sea ice in models

Now determined the impact of this new parameterisation on the atmosphere. It is significant and beneficial.
See Renfrew et al. (2019) for details.
Exploitation Route The developed parameteriation is being made available to national weather forecasting agencies and climate prediction centres. It has now been implemented by the Met Office and used as validation by the European Centre for Medium-range Weather Forecasts. The scheme is in GL8 version of Met Office model and operational from September 2018.
Sectors Environment

Description Providing parameterization recommendations to the Met Office and ECMWF. Now included in Met Office Unified Model. Parameterisation now adopted by UK Met Office (in GL8). After comprehensive testing during 2017 and 2018, became part of GL8 release for climate and became part of PS41. So became part of operational forecasting suite from September 2018.
First Year Of Impact 2014
Sector Aerospace, Defence and Marine,Environment
Impact Types Societal,Economic,Policy & public services

Description Evidence for House of Lords
Geographic Reach Multiple continents/international 
Policy Influence Type Gave evidence to a government review
Description FAAM strategy committee
Geographic Reach National 
Policy Influence Type Participation in a advisory committee
Impact Helped improve accessibility and transparenecy of the NERC/Met Office Facility for Airborne Atmospheric Measurement
Description Met Office Science Advisory Committee
Geographic Reach National 
Policy Influence Type Participation in a advisory committee
Impact Advice to Met Office on continuing development of their models and services
Description Knowledge Exchange Bid - Arctic Research Programme
Amount £10,882 (GBP)
Funding ID NE/I028297/1 
Organisation Natural Environment Research Council 
Sector Public
Country United Kingdom
Start 07/2015 
End 10/2015
Description NCAS Weather Observations
Amount £35,000 (GBP)
Organisation National Centre for Atmospheric Science (NCAS) 
Sector Charity/Non Profit
Country United Kingdom
Start 03/2013 
End 04/2013
Description NCAS Weather Studentship
Amount £60,000 (GBP)
Funding ID R14756 
Organisation National Centre for Atmospheric Science (NCAS) 
Sector Charity/Non Profit
Country United Kingdom
Start 11/2011 
End 11/2014
Description Sparking Impact: UEA distribution of NERC Impact Accelerator Awards
Amount £10,500 (GBP)
Funding ID O12406 
Organisation University of East Anglia 
Department School of Environmental Sciences UEA
Sector Academic/University
Country United Kingdom
Start 04/2014 
End 06/2014
Title ACCACIA air-sea-ice fluxes database 
Description Turbulent fluxes data base from the ACCACIA field campaign 
Type Of Material Database/Collection of data 
Year Produced 2016 
Provided To Others? Yes  
Impact Validation and development of a numerical model parameterization 
Title Parameterisation of surface exchange over sea ice for weather and climate models 
Description A parameterisation based on our science has been developed and implemented in the Met Office's weather and climate models. The parameterisation is of surface exchange over sea ice. It is documented in Unified Model documentation 24, v10.5 (published in 2016). 
Type Of Technology Software 
Year Produced 2016 
Impact The parameterisation will become part of Operational weather forecasts during 2017 or 2018. It is set for 'GA8'. 
Description High-latitude dynamics workshop, Rosendahl, Norway 
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 I have co-organised a major international workshop this year on the Dynamics of Atmosphere-Ice-Ocean Interactions in the High-Latitudes, which will take place in March 2015 in Rosendal, near Bergen in Norway. I selected presentations, co-organised the programme and logistics, and helped obtain funding for around 40 invited speakers and early career scientists. I am also an invited speaker myself. A workshop report is being written. The workshop itself sparked much discussion and engagement
Year(s) Of Engagement Activity 2015
Description Presentation at a YOPP Scientific Steering Group meeting, National Marine Environment Forecasting Centre, Beijing, China 
Form Of Engagement Activity A formal working group, expert panel or dialogue
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact Presentation on ACCACIA science to SSG and NMEFC audience
Year(s) Of Engagement Activity 2016
Description UEA Christmas Lectures for Children 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach Regional
Primary Audience Schools
Results and Impact I delivered one of UEA's Christmas Lectures. These are a local and regional institution, with a sell out audience of 500, and repeated earlier in the week to an audience of local primary schools. Total audience ~800. My talk was entitled 'Journey to a Frozen Land'. The main purpose was inspiration of the next generation.
Year(s) Of Engagement Activity 2015
Description Year of Polar Prediction - Town Hall Meeting 
Form Of Engagement Activity A formal working group, expert panel or dialogue
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact Year of Polar Prediction Town Hall meeting, in FMI, Helsinki, Finland. An evening event that was part of the Arctic Science Week. April 2014
Year(s) Of Engagement Activity 2014