Raindrops to reveal clues about climate in complex terrain

Contact: Lynne Roeder, ARM Public Information Officer, 509.372.4331

Beginning today, the ARM Mobile Facility will collect data for 9 months in support of a long-term precipitation study in the Black Forest region of Germany. Requested by researchers at the University of Hohenheim, the facility is one of four heavily instrumented supersites established for the Convective and Orographically Induced Precipitation Study, or COPS. The ARM Mobile Facility will operate from its deployment site in the village of Baiersbronn-Heselbach in the Murg Valley.

For 9 months in 2007, the ARM Mobile Facility will collect data in support of a long-term precipitation study in the Black Forest region of Germany.  The facility is one of four heavily instrumented supersites established for the Convective and Orographically Induced Precipitation Study, or COPS.  By collecting measurements to document the 4-dimensional state of the atmosphere, data from the mobile facility will help scientists to better understand the role that complex terrain plays in cloud formation and precipitation.

During its deployment, the ARM Mobile Facility will collect measurements to document the 4-dimensional state of the atmosphere. These data will help scientists to better understand the role that complex terrain plays in cloud formation and precipitation, and improve the accuracy of these parameters in computer models that simulate weather and climate.

The yearlong study began in March 2007, with each supersite throughout the study area focused on collecting information about orographic rainfall. This particular type of heavy rainfall results from rapid atmospheric uplift—or convection—in mountainous terrain. The Black Forest area is known for significant amounts of orographic rain, particularly in the summertime.

"Typically, 'normal' rain forms when cold and warm weather fronts pass through an area. Orographic precipitation is a specific type of heavy rainfall that occurs in areas where mountains and complex terrain (called orographic terrain) force moist air to quickly rise, forming thick rain clouds," explained Mark Miller, lead scientist for the ARM Mobile Facility and part of the COPS science team. "Because convective processes in orographic terrain are not well understood, scientists have a difficult time representing them accurately in models that simulate these conditions."

This difficulty has prevented weather forecasters from predicting major rainfall events in the past, leading to catastrophic floods like the one that occurred in Saxonia (in eastern Germany) in 2002. Damage from the flood caused an economic loss estimated around $18.5 billion dollars.

Measurements obtained during the COPS field campaign will encompass the entire life cycle of precipitation—from pre-convective conditions to the development of clouds, followed by the onset, development, and organization of precipitation. These data will be combined with coincident radar, aircraft, and satellite data to improve how clouds and precipitation in low-mountain regions are represented in weather forecast and climate models. This will not only aid regional weather forecasts to help protect people and land, but will also help scientists determine how clouds affect the climate in complex terrain around the world.

The ARM Mobile Facility consists of a large collection of sophisticated instruments and radars to collect climate-related data from under-sampled climate regimes. Active remote sensors are used to characterize the location and evolution of clouds, aerosol, water vapor, and temperature profiles above the deployment location. Cloud radar is used to determine cloud location, reflectivity, particle vertical velocity, and velocity distribution above the facility.

Shipping containers that have been converted into portable laboratories house the computer systems connected to the ARM Mobile Facility instruments. The computers store the data continuously collected by the instruments, providing key data sets of atmospheric measurements for climate research.

While in Germany, trained local personnel will launch weather balloons four times each day, every day, around the clock. Atmospheric data collected as they ascend will be transmitted back to the ARM Mobile Facility laboratories.

Because of its relevance to society, COPS has been endorsed as a Research and Development Project by the World Weather Research Program. This program was established by the World Meteorological Organization to develop improved and cost-effective forecasting techniques, with an emphasis on high-impact weather. As one of their projects, COPS will be coordinated with additional program activities to result in one of the largest international weather research efforts performed to date in Europe.

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The ARM Climate Research Facility is national user facility funded by the U.S. Department of Energy's Office of Science. ARM operates permanent research sites at three locales worldwide, plus a mobile facility designed to explore under-sampled climate regimes for up to one year. Through its physical infrastructure and data systems, this unique asset provides scientists from across the globe the opportunity to conduct interdisciplinary research related to global change.