Site selection for OWL using past, present, and future climate information

Selection of an ideal site for the new generation of Overwhelmingly Large (OWL) telescopes is dependent on many climatological and meteorological parameters. Among these are cloud cover, atmospheric humidity, aerosol content, air temperature, airflow direction, strength and turbulence. Even relatively minor changes in weather patterns can have a significant effect on seeing conditions. A composite climatological database has been designed and built for the site selection task at the Department of Geosciences, University of Fribourg, Switzerland. The database is mainly composed of ECMWF and NCEP-NCAR reanalysis data at a global resolution of between 1° and 2.5° latitude / longitude. Using a Java based interface, codenamed "FriOWL", and programmed in the style of a Geographical Information System, all of this relevant information can be interrogated in order to find the best possible sites for the new telescope. Perhaps the most important variable in site selection is the interaction between air-flow and topography, as atmospheric turbulence greatly affects the image quality produced by the telescope. Global climate is changing and it will continue to do throughout the 21st century. Therefore, it is important to ascertain the effect of global warming on potential sites. An ideal site in today’s climate may not prove ideal within 20 to 50 years. It is therefore planned to update the database with future climate data, using output from global climate models. High resolution modeling of the critical parameters at preferred sites under future climates is also planned.

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