Tethered Balloon Systems for Arctic Measurements in the Near-Surface Atmosphere

The Arctic as a region of particular sensitivity to climate change. In the past few decades, the annual average temperature over the Northern high latitude land surface has risen at almost twice the rate of the global average, disrupting the region and its people. Clouds are the primary factors that influence radioactive fluxes in the Arctic, and thus the rate of warming and ice melt. Long-term in situ measurements of Arctic cloud properties are needed to improve climate prediction models. Tethered balloon systems with sensors to measure cloud properties have recently been flown in Arctic and Antarctic. However, the technology is still in its infancy and new and innovative approaches are needed to reliably deploy more sophisticated instrument packages. Second-generation tethered balloon systems are being designed to be more robust and the instruments are being made smaller, lighter and capable of collecting even more sophisticated measurements. In Phase I the winch and tether systems that were previously used to deploy balloons with instrument packages underwent extensive engineering and laboratory tests, resulting in a design of a far more robust deployment system. The instrument package was evaluated and new miniature instruments were designed in-house or subcontracts were arranged for them to be built in Phase II. Proof-of-concept laboratory tests were performed and a top- down design of a new tethered balloon deployment and measurement package was designed. The focus of the second-generation tethered balloon system is to improve our understanding of the properties of Arctic clouds and thereby reduce the uncertainties in climate prediction models. The results from laboratory tests and engineering designs generated in Phase I will be used to build and field-test a second-generation tethered balloon system in Phase II. A redesigned, more robust winch and tether system will loft a balloon to 2 km within a restricted area near the companys home office. An automatic balloon deflation and tracking system will be tested with a dummy instrument package. A new composite optical probe that records high-resolution digital images and size distributions of cloud particles from 1 micron to 6.4 mm will be fabricated and calibrated in the laboratory. Other new instruments that will be integrated and tested are a near infrared radiometer, filter systems to collect and analyze aerosols and ice nuclei, an optical cloud condensation nucleus counter and a lidar that makes volumetric measurements of cloud drop size and water content. The second-generation tethered balloon system will then be deployed to a DOE site at Oliktok Point on the North Slope of Alaska to conduct a demonstration project to collect data in Arctic mixed-phase clouds. Commercial Applications and Other Benefits: If global warming continues at its present rate in the Arctic, the effects on the region and its people will be devastating. In addition, if warming continues and melts the Greenland icecap, the effect on coastal areas will be disastrous. To prepare for and possibly mitigate these potential effects, improved climate prediction models are needed, which requires a better understanding of the properties of Arctic clouds. The demonstration project planned in Phase II at the DOE site, Oliktok Point on the North Slope of Alaska, will establish the viability of tethered balloon systems to make long- term in situ measurements of the properties of Arctic mixed-phase clouds, which predominate in the Arctic. Once the viability and value of the tethered balloon system is established, other sites in the Arctic are likely to be established, providing commercial opportunities and a better global representation of the effects of Arctic clouds in climate prediction models.