IMPALA: Improving Model Processes for African cLimAte

Lead Research Organisation: University of Exeter
Department Name: Engineering Computer Science and Maths


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Planned Impact

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.
Description We have found that the performance of the HadGEM2-ES coupled climate model is considerably enhanced if we can achieve the cross equatorial transport of heat in the ocean and the atmosphere that is evident in observations (publication, GRL).

We have also found that when the latitudinal distribution of the TOA imbalance is corrected, there is not necessarily an improvement in the African (and global) monsoon (publication, Climate Dynamics).

We have investigated and improved the simulation of biomass burning aerosols within the HadGEM model. The improved size distribution will mean that the indirect effects are better represented than in earlier versions of the model (publication ACP).
Exploitation Route The findings, particularly of the enhanced performance on the model precipitation under the equilibrated hemispheric albedos is of considerable interest to GCM modellers - i.e. those pursuing climate modelling.
Sectors Agriculture, Food and Drink,Environment