IMPALA: Improving Model Processes for African cLimAte

Lead Research Organisation: Met Office
Department Name: Government Business

Abstract

IMPALA will deliver a step change in global model climate prediction for Africa on the 5-40 year timescale by delivering reductions in model systematic errors, resulting in reduced uncertainty in predictions of African climate and enabling improved assessment of the robustness of multi-model projections for the continent. IMPALA will include key foci on continental convection and land-atmosphere coupling as fundamental drivers of local rainfall, and oceanic convection and aerosols as influencing global modes of variability and the teleconnection pathways by which they drive rainfall over various parts of the continent. Convection, land-atmosphere coupling and aerosols have been identified in the DFID/Met Office Climate Science Research Partnership (CSRP) as first order drivers of African rainfall and processes where contemporary models show significant uncertainties and biases.

IMPALA will use a single multi-temporal, multi-spatial resolution model, the Met Office Unified Model (MetUM), to allow rapid pull through of improvements made in the project into improved African climate modelling capability although the methodology and understanding will be widely applicable across all contemporary models. We will work through a pan-Africa lens to develop a benchmark suite of metrics targeted on key processes and user-relevant variables and will use the most relevant observations from past and future campaigns and latest remote sensing data. Strong links to partners and Regional Consortia (RC) will facilitate two-way evaluation and feedback, ensuring local understanding of relevant climate processes and required climate information in the regions. Evaluation of the impacts of the global model improvements, developed both within the project and through gearing from the ongoing model development process at the Met Office will be tested in idealised-scenarios of climate change.

The unique capability of the MetUM to run across a broad range of spatial and temporal scales will be central to the project. Running the MetUM as a cloud-resolving weather model, through to a multi-decadal climate model, will allow evaluation of physical processes controlling the uncertainty in key metrics of pan-African climate variability and climate change on the 5-40 year time scale. The latest global coupled models available at the Met Office will be harnessed to drive a higher resolution (4km) convection-permitting regional model, for the first time across the entire African continent, under both current and idealised future climates. This will deliver understanding of the roles played by improved local representation of convective processes and high impact weather on the climate variability and change over the continent and be used to improve convective, land-atmosphere coupling and aerosol parametrizations in the coarser-scale models. The results will also provide an important new resource for RC and other African-focused climate research, enabling better-informed evaluation of the robustness of multi-model projections. This, in turn, can be utilised by decision makers to improve risk management for health, agriculture and water resources and help protect the livelihoods of the most vulnerable, safeguarding societal development already achieved.

Key model results, metrics and observations will be made available to the FCFA RC and local partners through an interactive webpage. The consortium will also work closely with the FCFA Coordination, Capacity Development and Knowledge Exchange (CCKE) Unit in their pan-African cross-programme research activities.

Planned Impact

IMPALA research will have significant impact locally, nationally and regionally in Africa as well as globally via the following beneficiaries and pathways.
FCFA Regional Consortia adaptation and impacts researchers and regional climate information providers will have direct access to new scientific understanding on, and improved simulations of, African climate variability and change via inclusion in the established Africa-focused process evaluation group (PEG). CP4-Africa climate change simulations will be disseminated through the NERC JASMIN data cluster for regional consortia to test multi-model projection robustness in key stakeholder-relevant local processes and extremes often poorly represented in coarser resolution models.
Model development Scientists in Africa: The 5 African model evaluation and development scientists in IMPALA will make extended visits to the Met Office focused on MetUM evaluation, development and training. They and their institutes will be offered the opportunity to install MetUM technical infrastructure and support for its configuration and application, developing local and regional expertise which is currently in very limited supply.
Policymakers: Policy briefings on improved reliability of model predictions relevant to climate resilience and adaptation planning across Africa will be delivered to UK Government through DFID and, via the Met Office Hadley Centre Knowledge Integration team, DECC. Internationally they will be communicated to the Conferences of the Parties and the Nairobi Work Programme of the UNFCCC and IPCC through active engagement in its scientific assessments and special reports. Close contact will be maintained with the African Climate Policy Centre and the African Development Bank.
People and communities in Africa and beyond: The ultimate beneficiaries of the research will be people of sub-Saharan Africa and IMPALA scientists will work with the CCKE Unit to assist in generating cross-programme outputs, e.g. material demonstrating improved capability to assess risks of key agriculture-relevant rainfall events, for their user training workshops and interactions with other DFID programmes and broader capacity development and adaptation activities.
Operational weather, seasonal forecasting and climate service capability in Africa: IMPALA model developments will imply improved representation of processes important for short-range to seasonal forecasting. With the MetUM being used across all timescales these developments will rapidly deliver improved weather and seasonal forecasts relevant to existing severe weather to seasonal forecasting activities the Met Office is already feeding directly into as well as to future programmes such as SHEAR funded by DFID.
Scientific community, CMIP6 and other modelling centres: To broaden the Africa-lens approach to the international stage IMPALA's methodology for model diagnosis, understanding and improvement will be disseminated through papers, at international science meetings and included in the planned CMIP6 benchmarking and evaluation software tools (overseen by the WCRP Working Group for Coupled Models co-chaired by the PI).
Cross programme Activities: IMPALA scientists will work with the CCKE Unit to ensure full engagement in cross-programme activities and knowledge transfer through relevant networks. Scientists from regional consortia will be included in the Africa PEG to enable a rapid exchange of model developments, datasets and understanding and ideas on relevant metrics of model performance.
Wider FCFA programme activities through the Programme Executive Committee (PEC): The PI will work with the Programme Management Unit and PEC to increase IMPALA impact and reach beyond FCFA. The PI and CO-Is have broad experience in communicating work on African science to inter-disciplinary scientists and policy makers through their engagement in previous DFID or NERC projects and are already active in many outreach events in Africa.

Publications

10 25 50
 
Description Findings are numbered and paired for cross-reference with entries on potential use in the following section.
1) The importance of convection-permitting high-resolution climate modelling: The present-day and idealised future CP4-Africa simulations have been made available to all FCFA RC researchers. Important findings are emerging that: a) identify how these new simulations improve representation of present-day African climate, and b) enhance our understanding of how the improved modelling of the weather scale in CP4-Africa (e.g. convective storms) can impact on projections of future climate. Example impacts include: future increases in extreme 3-hourly precipitation are greater in CP4-Africa than in traditional modelling. At the same time, we see a greater tendency for a lengthening of dry spells during the wet season in CP4-Africa.
2) IMPALA research has advanced understanding of how model biases influence large-scale drivers and teleconnections to African rainfall - notably on the East African Long- and Short-Rains seasons and the West African monsoon.
3) Techniques and diagnostic tools to test causes and locations of model biases have been developed and applied. These include simulation "nudging", PV tracers, comparison of short-range prediction and climate simulation biases). Findings include new discoveries on the specific source of errors over Africa (e.g. transmission/growth of errors associated with the Asian monsoon) as well as understanding of the strengths and limitations of the each method.
4) Model developments that improve the physical basis of the MetUM have been pioneered and refined through IMPALA research and implemented in new versions of the MetUM.
Exploitation Route 1) Improved climate modelling will lead to improved resilience to climate variability and change. Benefits to society and economy can include improved food security, health and resilience of built infrastructure (e.g. roads, dams, urban environment). The CP4-Africa simulations (with e.g. the greater increases in extreme rainfall frequency and longer dry spells) can add very significant value to the FCFA regional case studies with stakeholders - leading to better planning and adaptation.
2) Improved understanding of the mechanisms of model biases is informing model development. For example, the importance of the common low-level easterly flow bias in the Indian Ocean - and feedbacks on SST - to model errors in the East Africa Short Rains points to the need to accelerate the improvement of modelling of the Indian Ocean regional ocean/land/atmosphere system.
3) Publications on diagnostics and model evaluation will contribute to improving the physical basis of the next generation of international models used in IPCC climate change assessments. To facilitate this, new diagnostics and metrics of model performance are being identified for use by the wider modelling community (this activity is supported and promoted by the BAMS paper "Evaluating Climate Models with an African Lens" (James et al. 2017)). In the long-term, improved climate modelling will lead to improved resilience to climate variability and change -through more informed planning, decison-making and adaptation. Benefits to society and economy can include improved food security, health and resilience of built infrastructure (e.g. roads, dams, urban environment).
4) Improvements to the MetUM will have an impact not only on the quality of its climate scenarios but also, because of the unified timescale configuration of the MetUM, on short, seasonal and decadal range predictions. Such improvements can be used to improve early warning systems of weather and climate hazards across all timescales.
Sectors Agriculture, Food and Drink,Communities and Social Services/Policy,Construction,Creative Economy,Education,Energy,Environment,Financial Services, and Management Consultancy,Healthcare,Leisure Activities, including Sports, Recreation and Tourism,Government, Democracy and Justice,Security and Diplomacy,Transport

 
Title CP4-Africa 
Description The convection permitting pan-Africa simulation, CP4-Africa, uses a ~4.5km horizontal grid length and has been configured to use the latest model physics and revised Africa soil properties. The domain covers the entire African continent and boundary region to allow representation of impinging systems such as tropical temperate troughs. Simulation of the planned 10 years of present-day climate (1997-2006) has now been completed. The model specification and initial analysis of results is now published in Stratton et al, 2018. Five years of idealised simulations of future climate (representative of 2100) have been completed and will be extended to 10 years. For both present day and future simulations a control non-convection permitting regional simulation at 25km resolution (nCP25-Africa) is being run to measure the CP4-Africa benefits. Analysis of the present day simulations shows marked benefits in CP4-Africa's simulation of African climate relative to the control. The CP4-Africa and nCP25-Africa simulations have been made widely available to the FCFA Regional Consortia (RCs) via the JASMIN facility. Analysis and comparison of both present-day and future idealised simulations and with the controls is underway within IMPALA and the RCs and excellent science is now pulling through with several papers close to publication. 
Type Of Material Improvements to research infrastructure 
Year Produced 2017 
Provided To Others? Yes  
Impact Impacts on model performance include that the variability and spatio-temporal characteristics of the rainfall all appear to be better represented in the CP4-Africa model. There is evidence of better capture of westward propagating convective systems and a better intensity/frequency distribution of 3-hourly precipitation events compared with observations. The diurnal cycle of convective precipitation over land is better handled in CP4-Africa and the most extreme intense but short-lived rainfall events are also better captured. Additionally a pan-African study of heatwaves has found that CP4-Africa has more heatwaves than nCP25-Africa and the mean magnitude of heatwaves is higher, particularly over the Congo basin. Analysis of future idealised simulations: the CP4-AfricA future simulation has completed 5 years to date. Analysis of these runs, is providing a first insight into how the improved representation of convection in CP4-Africa impacts on projections of future climate change across Africa. Example impacts include: future increases in extreme 3-hourly (and to a lesser extent daily) precipitation are greater in CP4-Africa compared to the nCP25-Africa regional model. Also at the same time, we see a greater tendency for a lengthening of dry spells during the wet season in CP4-Africa. Other impacts from Regional Consortia studies include: AMMA2050: reduction in the Sahel dry bias and bias in rainday frequency (much fewer rain days in CP4-Africa - though higher annual totals). Reduced (improved) canopy interception of rainfall due to heavier rain episodes with increased (sub-surface) run off. HyCRISTAL: CP4-Africa shows improved propagation of storm cells in the Lake Victoria region of East Africa; improved timing of the EASR season through changed moisture budget; plausible representations of mesoscale land/mountain/lake breezes and convergence over Lake Victoria with more lake convergence overnight and in the early morning - with potential to study the impact of climate change on these features using the future idealised simulations. UMFULA: CP4-Africa has a much-improved simulation of the seasonal cycle of Tropical Temperate Cloud Bands - a major rain bringing system to southern Africa (the nCP25-Africa and global models have too many TTCBs in southern winter). 
 
Description FCFA regional consortia: UMFULA, FRACTAL, AMMA-2050, HyCRISTAL 
Organisation London School of Economics and Political Science (University of London)
Department Grantham Research Institute on Climate Change and the Environment
Country United Kingdom 
Sector Academic/University 
PI Contribution The collaborators listed are the lead institutions for the 4 FCFA regional consortia: UMFULA, FRACTAL, AMMA-2050, HyCRISTAL IMPALA contribution is sharing of plans for model improvement and idealised climate scenarios with the CP4-Africa model (a pan-Africa high resolution, convection permitting regional model)
Collaborator Contribution The collaborators will use IMPALA outputs, notably the CP4-Africa simulations, their input has been to provide feedback on the design of the CP4-Africa simulations and to climate model evaluation metrics
Impact Working document on recommended metrics for model evaluation
Start Year 2015
 
Description FCFA regional consortia: UMFULA, FRACTAL, AMMA-2050, HyCRISTAL 
Organisation Natural Environment Research Council
Department Centre for Ecology & Hydrology (CEH)
Country United Kingdom 
Sector Academic/University 
PI Contribution The collaborators listed are the lead institutions for the 4 FCFA regional consortia: UMFULA, FRACTAL, AMMA-2050, HyCRISTAL IMPALA contribution is sharing of plans for model improvement and idealised climate scenarios with the CP4-Africa model (a pan-Africa high resolution, convection permitting regional model)
Collaborator Contribution The collaborators will use IMPALA outputs, notably the CP4-Africa simulations, their input has been to provide feedback on the design of the CP4-Africa simulations and to climate model evaluation metrics
Impact Working document on recommended metrics for model evaluation
Start Year 2015
 
Description FCFA regional consortia: UMFULA, FRACTAL, AMMA-2050, HyCRISTAL 
Organisation University of Cape Town
Country South Africa 
Sector Academic/University 
PI Contribution The collaborators listed are the lead institutions for the 4 FCFA regional consortia: UMFULA, FRACTAL, AMMA-2050, HyCRISTAL IMPALA contribution is sharing of plans for model improvement and idealised climate scenarios with the CP4-Africa model (a pan-Africa high resolution, convection permitting regional model)
Collaborator Contribution The collaborators will use IMPALA outputs, notably the CP4-Africa simulations, their input has been to provide feedback on the design of the CP4-Africa simulations and to climate model evaluation metrics
Impact Working document on recommended metrics for model evaluation
Start Year 2015
 
Description FCFA regional consortia: UMFULA, FRACTAL, AMMA-2050, HyCRISTAL 
Organisation University of Leeds
Country United Kingdom 
Sector Academic/University 
PI Contribution The collaborators listed are the lead institutions for the 4 FCFA regional consortia: UMFULA, FRACTAL, AMMA-2050, HyCRISTAL IMPALA contribution is sharing of plans for model improvement and idealised climate scenarios with the CP4-Africa model (a pan-Africa high resolution, convection permitting regional model)
Collaborator Contribution The collaborators will use IMPALA outputs, notably the CP4-Africa simulations, their input has been to provide feedback on the design of the CP4-Africa simulations and to climate model evaluation metrics
Impact Working document on recommended metrics for model evaluation
Start Year 2015
 
Description Contribution to online article in CarbonBrief: Q&A: How do climate models work 
Form Of Engagement Activity Engagement focused website, blog or social media channel
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Public/other audiences
Results and Impact The article is an educational piece explaining the benefits of high resolution convection-permitting modelling and referencing the CP4-Africa model in use in IMPALA and FCFA Regional Consortia. The relevant text is copied below.

Convectional rainfall can occur on short timescales and in very specific areas. Global climate models, therefore, have a resolution that is too coarse to capture these rainfall events. Instead, scientists use "parameterisations" (see above) that represent the average effects of convection over an individual grid cell. This means GCMs do not simulate individual storms and local high rainfall events, explains Dr Lizzie Kendon, senior climate extremes scientist at the Met Office Hadley Centre, to Carbon Brief: "As a consequence, GCMs are unable to capture precipitation intensities on sub-daily timescales and summertime precipitation extremes. Thus, we would have low confidence in future projections of hourly rainfall or convective extremes from GCMs or coarse resolution RCMs."

(Carbon Brief will be publishing an article later this week exploring climate model projections of precipitation.)

To help overcome this issue, scientists have been developing very high resolution climate models. These have grid cells that are a few kilometres wide, rather than tens of kilometres. These "convective-permitting" models can simulate larger convective storms without the need of parameterisation. However, the tradeoff of having greater detail is that the models cannot yet cover the whole globe. Despite the smaller area - and using supercomputers - these models still take a very long time to run, particularly if scientists want to run lots of variations of the model, known as an "ensemble".

For example, simulations that are part of the Future Climate For Africa IMPALA project ("Improving Model Processes for African Climate") use convection-permitting models covering all of Africa, but only for one ensemble member, says Kendon. Similarly, the next set of UK Climate Projections, due next year ("UKCP18"), will be run for 10 ensemble members, but for just the UK. But expanding these convection-permitting models to the global scale is still some way away, notes Kendon:

"It is likely to be many years before we can afford [the computing power for] convection-permitting global climate simulations, especially for multiple ensemble members."
Year(s) Of Engagement Activity 2018
URL https://www.carbonbrief.org/qa-how-do-climate-models-work
 
Description Fifth conference on Climate Change and Development for Africa (CCDA-5), October 2015, Victorial Falls, Zimbabwe 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact The Climate Change and Development in Africa (CCDA) conference series was conceived as an annual forum to enable linkages between climate science and development policy by promoting transparent discussions between key stakeholders in the climate and development community. It coordinated by the African Climate Policy Centre (ACPC). A primary objective is to prepare Africa for the UNFCCC COP negotiations in the following December.

A presentation on IMPALA and FCFA was made in the Climate Science session of the conference and the FCFA programme was launched. There was lively discussion including follow of potential links with the World Bank's 'Enhancing the Climate Resilience of Africa's Infrastructure' programme
Year(s) Of Engagement Activity 2015
URL http://www.climdev-africa.org/ccda5
 
Description Met Office and SouthSouthNorth Side Event at COP22: From science to services: Improving climate resilience in Africa 
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 The event shared learning from FCFA and other international research and Climate Information Service (CIS) programmes that are making fundamental advances in African climate science and its application. It also looked at the application of climate information to inform specific adaptation and development decisions in diverse African contexts. The discussion focused on key questions, including:
• What are the "burning questions" that are shaping frontier climate research and CIS for Africa?
• How can research agendas be aligned to support implementation of the Paris Agreement (notably Article 7)?
• How are scientific advances being translated into improved CIS to support development objectives?
• What are the key challenges to progressing this work?
• What are the key opportunities for partnerships and learning?
Year(s) Of Engagement Activity 2016
URL http://www.futureclimateafrica.org/news/cop22-delegates-hear-how-african-climate-information-is-gett...