Weather watching for science

Research in focus November 2012

Are we talking about variable cloud cover or persistent rain after all? Is our climate slowly warming up or is it in fact simply a case of weather cycles that recur repeatedly over several decades? Very few topics engage us as much as the weather, and in so many different ways, whether as a routine topic of small talk, in the planning of outdoor activities or indeed as a sound point of departure from which to discuss the climate change we see today. Researchers at the Fraunhofer Institute for Building Physics IBP already have 60 years of relevant experience in dealing with the topic of weather and tracking its development. If at the outset this once involved obtaining climate data through local measurements in the field, high-tech measuring equipment and data collected by computers today combine to yield detailed records of weather conditions. Weather forecasts are based on these records, of course, but they also serve as the basis of many research projects at Fraunhofer IBP’s Holzkirchen site.

Searching for a site to take weather readings in the course of the 1950s, there was good reason to settle on Holzkirchen in Oberbayern. Close to the Alps, the rural area lies south of Munich at 700 m above sea level. “There are clearly defined criteria for collecting climate data. For instance, there must not be any tall buildings around the measurement station and the measurement tower must stand 10m above ground level”, advises Johann Gottschling, technician at Fraunhofer IBP and the person responsible for collecting climate data. What began as an interim solution has developed over the years into a permanent institution. In addition, a separate measurement station for swiss-based weather service Meteomedia has been housed on the site since 1999.

Fraunhofer IBP employees began keeping manual records at the weather tower, as it is called, from the beginning of the 1970s, and this lasted until 1984. Since 1985, climate data has been collected electronically using a variety of data logging equipment. Since January 1, 1987, records have been saved onto the IMEDAS database and are made available online. In October 2010 a new weather station was set up at Fraunhofer IBP, which came into service in February 2011.

What, where and how are things measured?

Weather is not just about temperature and precipitation. A whole array of different measurements are taken at the Fraunhofer weather station. The most important measurements relate to exterior air temperature and humidity, levels of global, Western and diffuse radiation, normal and driving rain, wind velocity and direction, barometric pressure, soil temperature at various depths as well as the surface temperature of light and dark-colored surfaces. Data collected is transmitted to a computer via a cable, fed into the IMEDAS database and is then made available online and in real time to anyone visiting the site. In contrast to the updates recorded every20 seconds in the past, the new weather station since entering service provides updates every second. “Particularly when measuring wind speeds, a rapid and precise record is extremely important”, says Gottschling. 

Why do we take measurements?

Alongside the weather station, Fraunhofer IBP’s site at Holzkirchen also possesses the largest area in the world for testing building structures, components and materials, as well as equipment and components for heating, air-conditioning and energy systems, all on a 1:1 scale under real conditions of use and climate. For those involved in applied research into building components and building materials for outside use, weather conditions play a decisive role. Compared to the German average, weather conditions in Holzkirchen are unusually extreme – an advantage where research is concerned. They allow roofs and walls or painted façades to be tested and analyzed in close conjunction with levels of wind, rain and radiation as well as any winter freeze-thaw cycles. An exact record of the weather is indispensable to this type of research. In addition, the climate data collected at the Holzkirchen site serves as the basis for Fraunhofer IBP’s WUFI software, developed at the Institute and used successfully around the world. This PC-based software program calculates coupled heat and moisture transfer in building components. For this purpose, WUFI makes use of the measured outdoor climate conditions, including driving rain and solar radiation, which allow researchers to predict how a building component will behave when exposed to weathering.



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