Abstract: The complexity of aerosol and cloud models makes it very challenging to understand system behaviour and to reduce the persistent large uncertainty in the outputs. For example, in terms of system behaviour, cloud behaviour depends on numerous covarying environmental factors whose effects can be difficult to disentangle. In terms of uncertainty, the magnitude of aerosol-cloud interaction (ACI) radiative forcing has remained stubbornly uncertain in models despite many advances in model realism. In this presentation I will show several examples of how perturbed parameter ensembles (PPEs) have helped us to make progress with these related problems. I will show how PPEs of a large eddy simulator can be used to visualise how the transition from stratocumulus to cumulus clouds depends on aerosol in combination with five environmental conditions. The results highlight the limitations of trying to understand this system using smalls sets of simulations. For the model uncertainty question, I will show a PPE of 37 uncertain parameters in a global climate model. I will show that is possible to calibrate the model parameters to obtain good model-observation agreement and thereby robustly reduce uncertainty in ACI forcing. I will also show preliminary work using the PPE in combination with multiple observations to expose the model’s structural deficiencies, which could provide a new way to prioritize model developments.
What is the Joint Oslo Seminar (JOS):
- Atmospheric and climate sciences have a stronghold in Oslo among the four institutions University of Oslo, the Meteorological Institute, CICERO and NILU.
- This joint seminar invites renowned international experts to contribute to an informal series of lectures, meant to create interaction with the Oslo atmospheric and climate science community on recent highlights and analysis in the field.
- Normally seminars will be held on Thursdays (12:15 pm -1pm).