Progress towards a probabilistic Earth system model: examining the impact of stochasticity in the atmosphere and land component of EC-Earth v3.2

We introduce and study the impact of three stochastic schemes in the EC-Earth climate model: two atmospheric schemes and one stochastic land scheme. These form the basis for a probabilistic Earth system model in atmosphere-only mode. Stochastic parametrization have become standard in several operati...

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Bibliographic Details
Published in:Geoscientific Model Development 2019-07, Vol.12 (7), p.3099-3118
Main Authors: Strommen, Kristian, Christensen, Hannah M, MacLeod, Dave, Juricke, Stephan, Palmer, Tim N
Format: Article
Language:English
Subjects:
Analysis
Atmosphere
Atmospheric circulation
Atmospheric models
Budgets
Climate
Climate models
Earth
Earth atmosphere
El Nino
El Nino phenomena
El Nino-Southern Oscillation event
El Niño
Energy budget
Heat waves
Heatwaves
Monsoons
Parameterization
Physics
Probability theory
Retirement benefits
Soil
Soil improvement
Southern Oscillation
Stochasticity
Weather
Weather forecasting
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Summary:We introduce and study the impact of three stochastic schemes in the EC-Earth climate model: two atmospheric schemes and one stochastic land scheme. These form the basis for a probabilistic Earth system model in atmosphere-only mode. Stochastic parametrization have become standard in several operational weather-forecasting models, in particular due to their beneficial impact on model spread. In recent years, stochastic schemes in the atmospheric component of a model have been shown to improve aspects important for the models long-term climate, such as El Niño–Southern Oscillation (ENSO), North Atlantic weather regimes, and the Indian monsoon. Stochasticity in the land component has been shown to improve the variability of soil processes and improve the representation of heatwaves over Europe. However, the raw impact of such schemes on the model mean is less well studied. It is shown that the inclusion of all three schemes notably changes the model mean state. While many of the impacts are beneficial, some are too large in amplitude, leading to significant changes in the model's energy budget and atmospheric circulation. This implies that in order to maintain the benefits of stochastic physics without shifting the mean state too far from observations, a full re-tuning of the model will typically be required.
ISSN:1991-9603
1991-959X
1991-962X
1991-9603
1991-962X
DOI:10.5194/gmd-12-3099-2019