October 18 (15:00-19:00 UTC) and October 19 (08:00-11:00 UTC)

Organising Committee: Ken Carslaw, Ben Booth, Yun Qian and Leighton Regayre

APPEAR aims to bring together research exploiting perturbed parameter ensembles (PPEs) to understand and predict 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, climate) and scales (from large eddy through to global GCMs). Thus, there is a growing interest in creating and analysing various forms of atmospheric PPE, as well as opportunities for joint initiatives.

The APPEAR virtual workshop, organised under the new WCRP Earth System Modelling and Observations (ESMO) Core Project, will showcase the wide range of PPE-related research across atmospheric science. The overall aims are to define the range of approaches and applications, to share expertise on how the many challenges of PPE creation and analysis are being tackled, to build a community of researchers, and to scope out the opportunities for further development and collaboration.

The workshop will be organised around short invited presentations and there will be opportunity for contributions from participants during facilitated discussion sessions.

Workshop themes will include:

• Model responses and sensitivities

• Development of process-level understanding

• Quantifying and constraining model uncertainty against observations

• Learning about structural deficiencies in models

• Contrasting with related techniques for exploring complex model behaviour and uncertainty

• Opportunities for collaboration and links to other activities

• Expanding this field of research, including opportunities for more advanced approaches that take advantage of increased (exascale) computing power.

Analysis of PPEs in Atmospheric Research (APPEAR) WCRP workshop