AAAR 36th Annual Conference October 16 - October 20, 2017 Raleigh Convention Center Raleigh, North Carolina, USA
Abstract View
Evaluation of a Miniature, Low-Cost Black Carbon Sensor for Unmanned Platforms
GAVIN MCMEEKING, Julien Caubel, Troy Cados, Nicholas Good, Thomas W. Kirchstetter, Handix Scientific
Abstract Number: 689 Working Group: Instrumentation and Methods
Abstract Black carbon (BC) is an important light-absorbing aerosol component that affects radiative forcing, visibility and human health. Its spatial distribution in the atmosphere, particularly in the vertical, must be known in order to accurately represent its impacts on climate and health. To date most BC observations have been fixed to single points on the ground, such as monitoring stations, or performed for limited time periods during intensive field campaigns over a broader spatial extent. The increasing adoption of unmanned aerial platforms, including tethered and free balloons, allows for the bridging of these to measurement strategies, providing platforms for routine atmospheric soundings for various species of interest. Here we evaluate a low-cost, filter-based absorption sensor for measuring atmospheric BC developed by Lawrence Berkeley National Laboratory and UC Berkeley. We compare the BC sensor response with that of a photoacoustic-based absorption measurement for several mixtures of absorbing and non-absorbing aerosol produced in the laboratory, smoke from controlled biomass burning experiments, and ambient air. We controlled and varied relative humidity during a subset of experiments to examine the sensor response to conditions that would likely be encountered during vertical profiling in the atmosphere, and introduced a modified, heated cell to reduce the impact of varying RH. We also examined the response of the sensor for several different filter media. We find that the sensor response was consistent with measurement artifacts previously reported for other filter-based absorption measurement techniques. Sampling hygroscopic aerosol onto the measurement filter, coupled with variations in sample RH, lead to changes in apparent light absorption not captured by the clean reference filter. Consequently, the sharp RH changes that can be expected during vertical profiling may introduce apparent BC signals large in magnitude compared to the low BC concentrations aloft. Sample cell heating was shown to mitigate such artifacts that would affect its suitability for atmospheric vertical sampling.