Statement of the Problem: The 2013 report from the International Panel on Climate Change states that the spatial extent of Arctic sea ice has decreased in every season, and in every successive decade since 1979. Arctic summer sea ice retreat is unprecedented (9.4 to 13.6% per decade). Numerical simulations predict a nearly ice-free summertime Arctic after the middle of the 21st century. It is now well established that clouds and aerosols have a major impact on warming in the Arctic and a concomitant reduction in sea ice. Mixed-phase clouds, which contain both supercooled water drops and ice, are prevalent and persistent in the Arctic. Yet, relatively few in situ cloud measurements exist in mixed-phase clouds. How the Problem is Addressed: To date, research aircraft have accounted for the modest dataset of in situ measurements in Arctic clouds, but research aircraft are expensive to operate in Polar Regions, have limited duration, and present safety concerns. In contrast, unmanned aerial systems (UAS), which include small unmanned aerial vehicles (UAVs) and tethered balloon systems, can operate for extended periods of time in the Arctic without risk to human life. Recent technological advances in small UAV have been impressive, including flights into hurricanes and across the Atlantic Ocean. Electrically-powered UAV are also making rapid gains in performance and duration due to improved composite designs and advances in battery technology. However, miniaturized sensors to measure cloud and aerosol properties lag behind the development of small UAV. This proposal is to develop a lightweight (5 kg) instrument package containing sensors to measure cloud microphysics, aerosols, position, three-dimensional winds, heading, aircraft pitch, roll, yaw, ambient temperature, humidity, airspeed and altitude. What will be Accomplished in Phase I and Phase II: Phase I research will provide solid-model designs, ray-tracing and laboratory tests of all components of the miniaturized instrument package. In Phase II, SPEC build and flight-test the instrument package on a small UAV provided by Vanilla Aircraft LLC, a leader in the design and fabrication of small unmanned aerial vehicles, or a Scaneagle provided by the DOE. Flight tests will be conducted in clear air within the Ft. Pickett restricted airspace, and in mixed-phase clouds at Ft. Pickett and/or the DOE facility at Oliktok Point, Alaska. The miniaturized instrument package will take advantage of SPECs previous experience developing microphysics probes for research aircraft, and advances in electronics that facilitate miniaturization of computers and signal conditioning. SPEC developed the cloud particle imager (CPI) in 1997 and its 2D-S (stereo) optical array probe in 2004. Both of these instruments have been installed on over twenty research aircraft. Highly-miniaturized versions of these instruments will be incorporated into the instrument package. Borrowing from it previous experience, SPEC will design and fabricate a combination particle probe that incorporates 1) a forward scattering probe that measures the size of particles from 1 to 50 microns, 2) a CPI that has a digital camera with 256 gray levels and at least 3-micron pixel resolution in the sample volume, and 3) a precipitation imager with 25 micron pixel resolution that fully images rain and ice particles out to 3.2 mm, and sizes all particles out to 1 cm. An off-the-shelf optical aerosol particle sizer that measures from 0.2 to 10 microns, a cloud condensation counter (CCN) developed at Scripps Institute and an ice nuclei filter system will be included, along with sensors for position, winds and state parameters. The instrument package is anticipated to weigh less than 5 kg and consume less than 50 W. A CPI with the highest possible (submicron) pixel resolution for imaging very small ice and large aerosols will also be developed and tested. Commercial and Other
Benefits: Improvements to climate prediction models require better measurements of the properties of Arctic clouds and aerosols. A highly-miniaturized instrument package will be designed, built and installed on a small unmanned aerial vehicle (UAV), and deployed at Oliktok Point on the North Slope of Alaska, or other Polar location (e.g., Svalbard). A successful demonstration project in Arctic clouds will establish the viability of small, electrically-powered UAV to make long-term in situ measurements of the properties of aerosols and Arctic mixed-phase clouds, which predominate in the Arctic. The miniaturized instrument package developed in Phase II and installed on a small electrically-powered UAV will find application in other areas, including measurements of the near-field properties of volcanic ash and measurements of aerosols on battlefields and in urban areas. Key Words: unmanned aerial systems, climate change, Arctic clouds, cloud microphysics, aerosols. Summary for Congress: The Arctic, a region that is warming at twice the rate of the global average, is considered a harbinger of global warming. Long-term measurements in Arctic stratus clouds are needed to improve climate prediction models. A highly-miniaturized instrument package that measures cloud and aerosol properties will be built, installed on a small, electrically-powered unmanned aerial system (UAV), and deployed in Arctic clouds and aerosols. A demonstration field project will show proof-of-concept for collecting long-term data in Arctic stratus clouds.
