Atmospheric Dynamics and Predictability

New challenges face the climate science community, including the need to provide skilful and reliable regional climate predictions from months to decades ahead. On regional scales, unlike the global mean, it is the dynamics as much as the thermodynamics that determines climate. Regional variations in atmospheric circulation can greatly exacerbate or completely counter the thermodynamic component of climate change, especially for rainfall and circulation-related quantities such as storminess or atmospheric blocking. Because these quantities have crucial socio-economic impacts, they are foci of the WCRP Grand Challenges, and it is clear that atmospheric dynamics is a key focus area for future research in climate predictability. Similarly, there is a growing realisation that it is the shorter timescale, out to months or years ahead, where climate science can influence many government and business decisions. Given the dominance of climate variability on these timescales, a parallel focus on seasonal and decadal climate predictions, initialised with the current climate state, is also necessary. Although seasonal-to‐decadal prediction has been regarded as primarily a challenge of the coupled troposphere-ocean system, there is increasing evidence that for extra‐tropical regions stratosphere-troposphere coupling also plays an important role. This calls for involvement of new and existing APARC activities.

The APARC community includes leading atmospheric dynamicists who, as the focus on stratosphere-troposphere interaction has increased, have turned their attention more and more to surface and tropospheric climate in recent years. APARC scientists and others in the WCRP community have the atmospheric dynamics expertise to better understand tropospheric climate variability and near-term climate predictions. To help attain WCRP’s goals, and to aid development of a scientifically robust WMO Global Framework for Climate Services, this implementation plan steers the APARC community towards research activities focused on tropospheric variability and dynamics with an emphasis on near-term predictions.

Science questions:

Do models reproduce the pattern and strength of atmospheric teleconnections?
Are observed and modelled teleconnections robust given sampling and/or ensemble size limitations?
What are the mechanisms of stratosphere-troposphere coupling across time scales?
How do external forcings of both natural and anthropogenic origin affect regional climate, and how do the regional circulation changes influence processes on smaller scales?
How predictable is the atmosphere across time scales and regions?
What are the mechanisms underlying this predictability and what limits does unpredictable internal variability impose on regional climate predictions?
Are there emergent dynamical constraints that allow a reduction of uncertainty in future climate based on what we know about the recent past?
How representative is our relatively short sample of observed historical climate variability?
How is predictability affected by the atmosphere, ocean, sea-ice, and land surface conditions?
What patterns in atmospheric circulation will increase the risk of unprecedented and damaging climate extremes? Can these be predicted or at least understood so as to provide better warnings?
What dynamical circumstances are likely to lead to extreme regional events?

Related APARC activities:

Atmospheric Processes And their Role in Climate