APPEAR aims to bring together research exploiting perturbed parameter ensembles (PPEs) to understand and model the behaviour of the atmosphere and climate system. The atmospheric science community has made great progress using PPEs to interrogate climate model uncertainty in recent years. There are now a rapidly growing number of examples of PPEs being used to quantify uncertainty and to develop process-level understanding of the atmosphere across the full range of model systems (chemistry, aerosols, clouds, coupling) and scales from large eddy (LE) and single column (SC)  through to global climate (GC). Thus, there is a growing interest in creating and analysing various forms of atmospheric PPEs, as well as opportunities for joint initiatives. 

This community seminar series follows on from the APPEAR virtual workshop (October 2022) and shares the aims and values of that workshop. The seminar series is intended to support the growth of our community of researchers, reveal opportunities for further development and collaboration and highlight expertise on how the many challenges of PPE creation and analysis are being tackled. 

Strategic priorities from 2022 APPEAR workshop - using PPEs to : 

• • Identify structural errors (various types) 

  • Inform model development 

  • Design multi-model PPEs (opportunistic and parameter-equivalent) 

  • Tackle model equifinality 

  • Evaluate information across scales (LEMs and SCM PPEs to inform GCM PPEs) 

  • Link causes of uncertainty in atmosphere-only and coupled global simulations 

  • Strike a balance between increasing model fidelity and reliability 

  • Evaluate initial condition sensitivities and natural variability (LEM and SCM PPEs)

Toward fully addressing wider strategic priorities, the series also welcomes presentations and discussion on methods for generating and evaluating coupled PPEs whose components equilibrate on different timescales.