CHAPEL HILL, NC, July 10, 2008 – Rainfall varies greatly across the mountains of North Carolina, falling as everything from light rain to torrents that cause landslides and widespread flooding. To learn more about the rainfall patterns in the mountains and how elevation effects rainfall amounts, RENCI has partnered with Duke University and the University of North Carolina at Asheville on a field research project funded by NASA.
Scientists from the three institutions will begin field operations on July 20 at Purchase Knob in the Great Smoky Mountains National Park in North Carolina. For 10 days, they will measure rainfall levels and how rainfall varies in size, velocity and intensity depending on elevation. The study, called the “NASA Precipitation Measurement Missions (PMM) Hydrometeorological Observations in the Southern Appalachians, NC,” should help researchers, government agencies, mountain communities and emergency workers understand how rainfall amounts—and water related problems such as floods—vary greatly due to the size, height and surface characteristics of the mountains.
“The highest rainfall accumulations in the eastern US after hurricane landfalls have been registered in the Appalachian Mountains in western North Carolina,” said Ana Barros, a professor in the civil and environmental engineering department at Duke University’s Pratt School of Engineering and lead researcher on the project. “How the terrain modifies the microphysical and dynamical processes that govern precipitation processes as tropical storms approach and pass over the mountains is not yet understood. This is also the case for convective storms generally, and it hampers our ability to forecast severe weather and anticipate and prepare for natural hazards.”
According to Barros, the field experiment in the Smokey Mountains is just one element of a comprehensive project that includes the development of high-resolution models for simulating summertime interaction between orography, or the average height of the land, and severe storms in western North Carolina.
“We plan to use the observations collected during the intense field observing period to evaluate the fidelity of existing models of mountain rain events and to test new ways to represent what happens with precipitation in the atmosphere and near the ground during major rainstorms in mountainous regions,” she said.
Central to the project will be RENCI’s Micro Rain Radar, a compact, vertically pointed radar that calculates and provides the rain rate, liquid water content, reflectivity and vertical fall velocity of precipitation in real time. The radar also predicts rain rates during severe storms. RENCI’s MRR, which has been used to determine at what level precipitation freezes during winter storms in order to help predict icing events, will be transported to the western mountains to measure how rain changes as it falls through the atmosphere. A high-speed camera will be attached to the MRR to provide visual observations of warm-weather precipitation.
The MRR system is particularly important to the experiment because it can provide detailed information on the size of raindrops at various heights above the ground surface, explained Barros. Other sensors, such as disdrometers and the high-speed camera can only provide observations at the point of measurement. The additional information from the MRR will be critical to understanding how rainfall changes from the point where it is produced in clouds to where it hits the land surface, she said.
To study atmospheric conditions, the field study will use a data collection system called a tethersonde system, consisting of meteorological sensor packages, which will be launched from the ground up to a maximum altitude of around 500 meters (1,640 feet). The system will record the vertical profile of air pressure, temperature, relative humidity, wind speed and wind direction. The launches will be scheduled hourly throughout the two weeks, except under rainy or high wind conditions. The researchers will also take 50 radiosonde soundings using a balloon-borne instrument platform with radio transmitting capabilities to obtain a profile of the atmospheric boundary layer. Microphysical investigation of warm season precipitation will rely on a high-speed camera capable of recording 1,000 frames per second.
“This project was underway between Duke and UNC Asheville and RENCI was able to join the collaboration and bring the added observing tool of the MRR,” said Ken Galluppi, head of disaster research projects at RENCI. “This is a perfect example of how RENCI likes to work—collaborate with research teams to add value to their work.”
RENCI…Catalyst for Innovation
The Renaissance Computing Institute brings together computer and discipline scientists, artists, humanists, industry leaders, entrepreneurs, state leaders and educators for collaborations designed to reshape science, the economy, the state of North Carolina and the world. RENCI leverages its expertise and resources in leading edge computing, networking and data technologies to ignite innovation and find solutions to previously intractable problems. Founded in 2004 as a major collaborative venture of Duke University, North Carolina State University, the University of North Carolina at Chapel Hill and the state of North Carolina, RENCI is a statewide virtual organization. For more, see www.renci.org.