High-Resolution Cloud Probe for the ArcticShark UAV and Tethered Balloon Systems

The Arctic is warming at a rate that is nearly twice the global average. Low, shallow, stratus clouds are persistent from spring through early winter in the Arctic and are strong contributors to warming and ice melt in the Arctic. These clouds allow visible sunlight to penetrate to the surface, but trap long- wave radiation emanating upwards from the surface. The result is a cloud blanket that warms the Arctic and promotes melting. The melting creates more open water, which is a better absorber of sunlight than ice, thereby facilitating a positive feedback that increasingly warms the Arctic. The Arctic stratus clouds are called mixed-phase clouds because they generally contain both supercooled water drops and ice crystals. Precise measurements of the size distributions of water drops and ice particle in mixed-phase clouds can only be accomplished by in situ instrumentation. Manned research aircraft used to make in situ measurements are expensive, have relatively short duration and pose safety risks for the crew. Safer, more efficient in situ measurements are needed. Addressing the Problem: Unmanned aerial vehicles (UAVs) and tethered balloon systems (collectively UAS) offer significant advantages over manned research aircraft. They are capable of long-duration measurements of cloud properties in regions where piloted aircraft are unsafe, e.g., at very low altitudes over remote regions, such as tundra and open ocean. UAS are now widely recognized as a technology that can provide unprecedented insights into cloud and radiation processes, but development of miniature sensors capable of providing sophisticated measurements of cloud, aerosol and radiative properties lag behind. The DOE recently purchased a midsize UAV, called an ArcticShark, which will be used to collect data in Arctic mixed-phase clouds. The proposed research is to develop a combination optical particle probe that will be installed on the ArcticShark and make measurements of water and ice particles in Arctic mixed-phase clouds. Phase I: The company designed and performed feasibility laboratory tests on a state-of-the-art instrument, called a SharkEye, which combines three optical cloud particle probes in a small, lightweight (4 kg) instrument that can be installed on the DOE ArcticShark and tethered balloons. The SharkEye combines a scattering probe that measures the sizes of cloud particles from 2 to 50 microns, an optical array imaging probe with 5-micron pixel resolution and four gray levels, and a cloud particle imager that records high-definition images with 1-micron pixel resolution. The size resolutions of the optical array imaging probe and cloud particle imager are superior to all existing instruments and are unique to the field of in situ optical cloud particle probes. The SharkEye will collect unprecedented data in mixed-phase clouds, enabling it to precisely measure the water and ice size distributions. Laboratory tests in Phase I demonstrated the feasibility of fabricating a SharkEye capable of installation and successful operation on the ArcticShark in Phase II. Phase II: We propose to install the SharkEye on the DOE ArcticShark and conduct a pilot field project at the DOE’s research site at Oliktok Point, Alaska. Collected data will be placed in the DOE archives and analyzed by company scientists. Anticipated results include improved radiative transfer retrievals and climate models. Anticipated Benefits and Commercial Applications: Long-term in situ measurements of the effects that clouds and aerosols have on climate in Polar Regions will improve the parameterizations of climate prediction models, giving scientists and politicians a better awareness of how to prepare for ice melt, habitat change, sea-level rise and the impact on coastal populations. UAV’s are an emerging market that will eventually routinely monitor gases and aerosols in urban environments, thereby aiding in identifying statutory violators; aerosols and clouds that are generated from forest fires, and ash from volcanic eruptions that have a strong impact on aviation safety.