Themes

The Polar Climate Predictability Initiative is divided into 6 areas to help efficiently manage the project.  More information on each theme is below.

1: Improve knowledge and understanding of past polar climate variations (100+ years)

Co-leads: Sarah Gille (Scripps Institution of Oceanography, USA) and Julie Jones (University of Sheffield, UK)

The goal of theme 1 is to understand changes in the polar regions that are occurring and the processes behind them by considering a variety of resources that are available from the last century and longer in a unified, multi-disciplinary way. Theme participants will bring together estimates of past behavior in the polar regions, such as instrumental and proxy data records, modeling, and reanalyses techniques, in an optimal manner, to obtain estimates of past variability and change. These efforts can also help in the design of optimized observing systems for detecting and attributing changes, and quantifying the impact of maintaining or obtaining certain observations. We intend to identify new data records of the 20th century that have recently become available, which are especially important in the presatellite era. Models can potentially be used to enhance state reconstructions through forward data simulations.

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2: Assess reanalyses in polar regions

Co-leads: Dave Bromwich (Ohio State University, USA) and Jim Renwick (Victoria University, New Zealand)

The goal of theme 2 is to assess the reliability and self-consistency of atmospheric and oceanic reanalyses in the polar regions in light of the comparatively limited observational at the poles. Metrics should be developed that reflect the coupling processes between the different components of the climate system, which can then inform the development of coupled reanalyses. Uncertainties in reanalyses should be investigated (e.g. by looking at increments) to determine whether they reflect biases in modelled processes.

This text was adapted from the PCPI proposal. We are waiting for input about next steps from the co-leads on this theme.

3: Improve understanding of polar predictability on seasonal to decadal timescales

Co-Leads: Ed Hawkins (University of Reading, UK) and John Fyfe (CCCma, Canada)

The goal of theme 3 is to coordinate research that investigates the physical mechanisms that give rise to polar climate predictability on seasonal to multi-decadal timescales. The intent is to ascertain the potential for improving the actual skill of operational climate predictions for polar regions. The participants of this group will coordinate and collaborate with operational forecasters wherever possible. An important focus would be the impacts of polar variability on lower latitudes, for which there is growing evidence. This theme aims to apply understanding of the system gained through investigating seasonal to decadal prediction to guide observational network design and deepen our understanding of longer timescales and validate and/or improve models for all timescales.

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4: Assessing model performance in the polar regions

Co-leads: Hugues Goosse (Université catholique de Louvain, Belgium) and Jennifer Kay (National Center for Atmospheric Research, USA)

The goal of theme 4 is to perform comprehensive evaluation coupled models in the polar regions. This assessment of model performance must go beyond identifying model biases against trusted observational benchmarks and quantifying inter-model spread. The activities within this theme must ask "Why" questions to assess model performance.  Why do models behave in a different ways? Why do they or don't they match observations?  Answering "why" questions requires understanding important climate forcings and feedbacks and their process representation in models.  This theme seeks to mitigate problems that arise from the frequent disconnect between model development and model evaluation timescales and barriers from limited personnel.  As a result, a process-level link between model evaluation and improvement is a backbone of this initiative.  Model evaluation and improvement should address the mean climate state but also changes in response to internal variability and external forcing.

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5: Model error

Co-leads: Gunilla Svensson (Stockholm University, Sweden) and Markus Jochum (University of Copenhagen, Denmark).

This theme, focusing on model error, will initially concentrate on two goals: (a) to determine what processes in GCMs contribute most to error growth on hourly to seasonal time scales and seasonal to interannual time scales in the polar regions, and (b) to develop observational and modelling strategies to improve these processes. The current understanding is that the processes contributing to model error are the same over all these timescales when focusing on the atmosphere, ocean and sea-ice physics.

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6: Improve understanding of how jets and non-zonal circulation couple to the rest of the system in the Southern Hemisphere

Co-leads: Marilyn Raphael (UCLA, USA) and Gareth Marshall (British Antarctic Survey, UK)

The goal of this theme is to improve understanding of atmospheric circulation and its role on climate variability and climate change in the Southern Hemisphere. Many of the current pressing scientific questions involve the response of the atmospheric circulation to ozone depletion/recovery and greenhouse-gas increases, and how this impacts surface climate, ocean circulation, sea ice, and ice shelves. These interactions have implications for carbon and heat uptake and the stability of ice sheets. We need to understand the observed relationships and how they are represented in models, in order to improve decadal prediction and longer term projections of Antarctic climate. Recent studies suggest that the zonal and non-zonal circulation influence the climate system of the high latitude Southern Hemisphere. This influence may be reflected in the variability in Antarctic sea ice extent as well as the climate over the Antarctic continent. Activities associated with this theme could examine the coupling between the larger scale atmospheric circulation and the climate system of the Southern Hemisphere, especially with regard to how the southern jets and the non-zonal circulation couple to the rest of the system (ocean, sea ice and land ice). These activities may include but are not limited to, theoretical, observational and modeling studies on the vertically coupled processes.

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