Improved numerical weather forecasting and climate simulations

Project Description
Short Title: THORPEX-IPY
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The WMO/WWRP's THORPEX Global Research Programme involves nations from North America, Europe, Asia, Africa and the Southern Hemisphere. THORPEX intends to conduct research that will accelerate improvements in the prediction and understanding of high-impact weather on the 1 to 14-day time-scale for the benefit of society, the environment and the economy.

The aims of this cluster proposal are to improve numerical weather prediction model systems and climate models by utilizing remotely sensed and in situ observations taken during the IPY and to study and advance our knowledge of meteorological, surface and ocean phenomena typical for the region. The investigations will also improve our understanding and modelling of polar-global interactions. The scope ranges from high-resolution numerical weather prediction to climate and regional ocean modelling. The motivation comes from several applications: 1) Regional weather forecasting: In polar areas there are strong needs for accurate weather forecasts. Further model-based ocean, ice and wave forecasting need accurate forcing fields. 2) Medium range (global) weather forecasting: Improved model quality in polar areas influences forecasts at mid and high latitudes. 3) Climate studies.

The project has four objectives:

The first is on forecasting and to what degree an improved use of satellite data and an optimized observational network, including targeted observations, will improve forecasts of high impact weather events (IPY project numbers 294; 394; 638; 600; 798; 811; 113; 146; 206, 410, 92, 888, contribution related to meteorology). These studies will not be limited to forecasting conditions over the poles, but will also address polar-global interactions. These investigations will provide insight into the design of the global observing system and into the potential impact of any IPY legacy measurement sites. New satellite technologies will be used to develop products that can potentially improve weather forecasts.

The second objective is to better understand physical and dynamic processes in the polar regions, in general, with a specific emphasis on aerosols, the microphysical properties of clouds and the possibility of improving parameterisation schemes of clouds and radiation for use in numerical weather prediction and climate models (294; 638; 600; 798; 70; 116; 158; 206; 410; 113, 297). The spatial variations in surface characteristics, stable lapse rates and extreme seasonal variations in solar radiation make the polar environment unique and a challenge for parameterizations.

The third objective is a deeper understanding of the polar regions through a focus on small scale weather phenomena and the impacts of topography and surface variations (394; 638; 618; 811; 113; 134; 146; 167; 297; 888, contribution related to meteorology). Such research will also provide valuable insight on the limitations of coarse-grid models, since recent research has provided evidence for a wide variety of circulations (terrain-induced vortices, downslope winds, flow channelling, thermodynamic impacts of open water etc) that are often sub-grid-scale in climate and many forecast models. This work includes investigations of the flow distortion over Greenland and how it impacts the mesoscale thermohaline circulation. In some cases the higher resolution modelling capability will remain in place as a legacy of THORPEX-IPY activities.

Taken together the research results from first three objectives the potential to improve future predictions of the weather and climate over the polar regions. Improvement in the initial state means an improved time series of operational and research analyses for climate change research.

The final objective is to utilize improved forecast systems to benefit society, economy and environment. High-impact weather events in polar regions include spring thaws, sea ice movement, and severe winter cyclones resulting in strong winds, high seas, and heavy precipitation as defined by their impact on public safety, fisheries and fishery management, activities of the indigenous arctic populations, wildlife, energy production and transportation. These problems are not local to the poles as the intrusion of polar air masses into higher latitudes also has dramatic impacts and many of the polar events are linked to wave trains that are initiated at lower latitudes. During IPY, the major operational forecast centers of the world will co-operate to form a THORPEX Interactive Grand Global Ensemble (TIGGE) that will form the basis for research on ensemble prediction and on improving society's ability to utilize forecast information. TIGGE will also be made available for IPY field operations.