Field Notes: The Polar Field Services Newsletter

Scientist’s Head in the Clouds

Scientists Von Walden (University of Idaho, Moscow), Matthew Shupe (University of Colorado, Boulder), and David Turner (University of Oklahoma) officially have their heads in the clouds. The team, which includes researchers from UI, CU, UO, and the University of Wisconsin-Madison, spent time at Greenland’s Summit Station last summer installing and calibrating instruments for a multi-year, NSF-funded study of arctic cloud properties. Dubbed ICECAPS (Integrated Characterization of Energy, Clouds, Atmospheric state, and Precipitation at Summit), the research team wishes to explore the energy balance of the Arctic and better understand how the arctic climate interacts with the global climate system.

“To properly model the past, present, and future changes of the Greenland Ice Sheet, the various components of the polar climate system must be understood,” Walden said recently. “The atmosphere is a very important component and its effects on the climatic conditions of the Greenland Ice Sheet have not been studied extensively. In particular, there is very little known about the properties of tropospheric clouds over Greenland.”

Before embarking on fieldwork, Walden and his colleagues worked closely with CH2M HILL Polar Services staff to establish what was needed to set up the many ICECAPS instruments in Summit’s Mobile Science Facility (MFS), a building that can be towed on skis to fit the needs of the project(s) occupying the structure.

Auroras over MSF

Auroras over MSF October 6, 2010. Photo: Ed Stockard

The building’s mobility enables the researchers to collect samples upwind of the station (and therefore clear of Summit influence). Inside, the ventilation system will help keep temperatures stable, which is critical for the sensitive instruments and computers collecting data.

The ICECAPS instrument suite includes a cloud radar (monitors cloud structure), two microwave radiometers (measure precipitable water vapor), an Atmospheric Emitted Radiance Interferometer (measures infrared radiation), a precipitation sensor, a ceilometer (determines the height of the cloud base), two LiDAR instruments (measure cloud height and thickness), and radiosondes.

Although much of the equipment is automated, humans are needed to launch the radiosondes, helium-filled weather balloons, twice daily. Humidity and temperature sensors on the radiosondes relay data to the ground station during a ninety-minute flight in which the balloon ascends to about 25-27 kilometers above sea level. The physical properties of clouds and precipitation in the troposphere and stratosphere are profiled using the radiosonde data and the other ICECAPS measurements.

University of Idaho researcher Brad Halter remained at Summit until August to train station techs to run the instruments, interpret raw data for quality control, and trouble shoot any obstacles that may have arisen. A full-time ICECAPS tech is now overseeing data collection and launching balloons during the winter. Personnel will swap out every three months for the project’s duration. Lance Roth assumed the duties last week of the Summit phase II winter ICECAPS tech.

Uncertainty in the properties of polar clouds remains problematic in creating climate models of the Greenland Ice Sheet and the Arctic. The ICECAPS team expects the data collected through this research will provide a better understanding of Greenland’s atmosphere including the factors contributing to cloud development, precipitation, and how clouds, the ice sheet surface, and the atmosphere interact.

“It is essential to document how cloud properties vary throughout the year, both in terms of macrophysical (cloud height, fractional cloud cover) and microphysical (cloud particle phase (water, ice, or mixed), effective particle radius, optical depth) properties,” Walden explains. “Since we are also characterizing the state of the atmosphere using weather balloons and other instruments, we hope to deduce the conditions under which particular types of clouds form. This is quite important since the Intergovernmental Panel on Climate Change (IPCC) has identified “clouds” as being one of the largest uncertainties in global climate models.”

These data—the first of their kind on the Greenland Ice Sheet—will be merged with similar data sets from around the Arctic as part of the Arctic Observing Network, an NSF Initiative to establish long-term measurement stations for understanding Arctic change. Walden says the ICECAPS data sets will be useful to many other scientists across a wide range of disciplines including, but not limited to, climate modeling, remote sensing, atmospheric sciences, and glaciology. Conversely, their team will integrate other types of data sets and compare their results with field stations from around the Arctic where similar measurements are being made.

“The Greenland Ice Sheet is such a unique place, so we’re very excited to see how the properties of the atmosphere and clouds over Greenland compare with other locations in the Arctic,” Walden says. “The measurements made by the ICECAPS team at Summit will ultimately help to improve how clouds are represented in weather and climate models.”—Marcy Davis

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