We propose here a Norwegian 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), which is a part of the WMO World Weather Research Program (http://www.wmo.int/thorpex/). 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 environmen t'.
A lack of conventional observations is a major impediment for improving the forecasts of adverse Arctic weather such as Arctic fronts, polar lows and terrain-induced disturbances. This will by addressed in the project by developing methods for assimi lating new data from satellite and in-situ platforms into the numerical weather prediction models. An observational campaign is proposed, supported by modelling and data assimilation activities, and integrated with the international activity in THORPEX, a s well as the rest of IPY. Furthermore, we propose to study how climate change may impact on the frequency and character of adverse weather events. THORPEX-IPY-Norway will leave a legacy for the future in terms of an extended observational network in the Arctic, enhanced exploitation of data from polar orbiting satellites and improved numerical weather prediction models. The proposal includes the coordination of the international THORPEX-IPY-project.