Om IPY-Thorpex

Overall objective: To improve the accuracy of high-impact weather forecasts in the Arctic region for the benefit of society, the economy and the environment.

Project Leader: Jón Egill Kristjánsson (UiO)

Principal Investigators: Øystein Hov (met.no), Idar Barstad (UiB), Anne Sandvik
(UiB), Jakob J. Stamnes (UiB), Erik Kolstad (UiB), Øyvind Sætra (met.no), Asgeir
Sorteberg (BCCR), Lars-Anders Breivik (met.no), Trond Iversen (met.no), Thor Erik
Nordeng (met.no)

Introduction
In the Arctic region of the North Atlantic, an array of adverse weather phenomena takes place exposing the expanding human activities - such as oil and gas exploration and marine transport - and the region’s vulnerable environment to high risks. There is a need for improving the understanding and forecasting of adverse weather in the region. During winter, advection of extremely cold and stable air from the seaice/ land over the open ocean can lead to intense weather features such as Arctic fronts, polar lows and terrain-induced disturbances. A major impediment for forecasting these features is the sparse network of conventional observations. Polar orbiting satellites cover high latitudes well, and new instrumentation on meteorological satellites provides new and promising sources of information for the Arctic atmosphere. However, satellite observations need to be co-located with other independent observations.

The extensive international observational activity planned during IPY offers an unequalled opportunity to address this problem and to conduct intensive research for enhanced understanding and forecasting of Arctic weather extremes. We propose a Norwegian co-ordination of and contribution to the International Polar Year (IPY) project THORPEX-IPY. THORPEX-IPY is the Arctic component of the international program THORPEX (The Observing System Research and Predictability Program) under the WMO World Weather Research Program.

The main objective of THORPEX is to “Accelerate improvements in the accuracy of one-day to two-week high impact weather forecasts for the benefit of society, the economy and the environment” (http://www.wmo.int/thorpex/). This is also one of the nine societal themes in Global Earth Observation System of Systems (GEOSS). In the Norwegian THORPEX-IPY proposal we aim to significantly improve forecasts of high-impact weather events in the Arctic. This will be done by designated observations including campaigns integrated with the IPY international logistics, exploitation of data and efforts by international collaborators, and by modelling and data assimilation activities, integrated with the international activity in THORPEX and the rest of IPY. Furthermore, we propose to study how climate change may influence the frequency and character of adverse weather events. The Norwegian THORPEX-IPY will leave a legacy in terms of an improved and extended observational network in the Arctic, enhanced exploitation of data from polar orbiting satellites, and improved numerical weather prediction.

To achieve the overall project goal the observational programme is designed to drive the theoretical work addressing the following objectives:

• To realistically model the latent heat cycle, from evaporation at the surface, through moist convection and latent heat release, to precipitation processes.
• To improve the treatment of cloud-radiation-sea-ice interactions in numerical model simulations for the Arctic.
• To investigate relations between synoptic and climatic conditions and the onset, evolution, and frequency of small-scale extreme weather events.
• To significantly improve the characterization of initial conditions for Arctic weather forecasts by assimilation of new satellite and radar data.
• To introduce probabilistic forecasts of Arctic weather extremes by implementing a high-resolution limited area ensemble prediction system.