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Report

Teaser, summary, work performed and final results

Periodic Reporting for period 1 - Blue-Action (Arctic Impact on Weather and Climate)

Teaser

Summary

Blue-Action provides fundamental and empirically-grounded, executable science that quantifies and explains the role of a changing Arctic in increasing predictive capability of weather and climate of the Northern Hemisphere. To achieve this, we take a transdisciplinary approach, bridging scientific understanding within Arctic climate, weather and risk management research, leading to the co-design of better services with key stakeholder. Blue-Action contributes to the improvement of climate models to represent Arctic warming realistically and address its impact on regional and global atmospheric and oceanic circulation. The improved robust and reliable forecasting helps meteorological and climate services to deliver better and tailored predictions and advice, including sub-seasonal to seasonal time scales, and takes Arctic climate prediction beyond seasons and to teleconnections over the Northern Hemisphere.

Work performed

Blue-Action has improved our ability to predict atmospheric variability over Europe on sub-seasonal to seasonal time scales, in particular the occurrence important winter cold air outbreaks. Using extreme value theory, we demonstrated increased predictive power using alternative indices relative to the classical NAO index also taking into account the role of the stratosphere. Results are being tested within both models and reanalysis, but form a starting point for a formally-founded analysis of extreme temperatures. We demonstrated that the representation of European cold spells is weaker in GCMs than in observations. This means that they cannot be directly forecasted by such models. Forecasting could go via forecasting the phase/strength of the NAO or alternative predictors, which we have found have links to the distribution of winter surface temperatures. Specific results address marine cold air outbreaks and show predictability of those several weeks ahead, in particular the associated surface temperatures. New datasets were developed in order to understand the seasonal to decadal scale drivers of arctic change, including optimized data series for warm inflow to the Arctic along the Greenland-Scotland Ridge, integrating satellite new earth observations with existing observations from moored ocean observatories. A new methodology for reconstructing the Atlantic Meridional Overturning Circulation by relaxing surface temperature and salinity in a model to observations has been pursued and aims at the availability of heat contained in the warm Atlantic water to melting of Arctic Sea Ice. New project results demonstrate that while leads in arctic sea-ice only make up a small fraction of the ice covered surface area, the very large temperature differences between the ocean and atmosphere lead to strong fluxes of heat and water-vapor from these leads. Accounting for these effects has been shown to lead to radically different surface energy budgets, as compared to simple flux-gradient approximations of the dynamics. Currently these effects are not included in most of CMIP5 models, even though the climatology of the boundary layer over ice has been shown to be one of the leading factors affecting simulated Arctic surface warming. The performance of state-of-art numerical prediction systems for a number of climate and ecosystem relevant quantities has been assessed, both in a multi-model framework and by using large decadal predictions ensemble. Results demonstrate significant decadal-scale predictability not only for surface temperature variations, but also for oceanic integrated quantities. Attribution studies demonstrated that the initialization of ocean circulation is central for achieving such an extended predictive capacity. Particular attention has also been given in quantifying our current capacity in predicting seasonal-to-decadal variations in the frequency of atmospheric winter blocking events in the North Atlantic that are associated with cold spells and precipitation extremes over western to central Europe. We have also shown skill in predicting the 2015 summer heat wave over Europe. Blue-Actionâ€™s Case Studies (CS) focus on the uptake of climate information and predictions. CS1 Weather and climate data for Northern Finnish winter tourism centers: The inclusion of the end-userâ€™s knowledge has been central in the co-design: Data on economic aspects related to customer behavior and the use of energy in artificial snowmaking as well as on observed weather conditions were obtained and integrated. We have established a basic connection between weather conditions and snowmaking costs. CS2 Temperature Related Mortality (TRM): Our network of contacts in the area of health/heat stress has been expanded by interacting with scientists in charge of similar initiatives and by interacting with decision-makers, stakeholders, and non-scientists. This helped us to understand the situation of operational heat early warning systems in E

Final results

-Improved capacity of climate models to represent Arctic warming and its impact on regional and global atmospheric and oceanic circulation and to predict the weather and climate of the Northern Hemisphere, and better forecast of extreme weather phenomena;
-Set up of a robust and reliable forecasting framework to 1) support meteorological and climate services to deliver better predictions and 2) improve stakeholdersâ€™ capacity to respond and adapt to the impact of climatic change on the environment and human activities; 3) better service business that rely on improved forecasting capacity and strengthening their competitiveness/growth.