New Instrumentation for Rapid Aerosol Number Size Distribution Measurements from Unmanned Aerial Systems

Abstract:

Understanding the rapid reductions in polar ice amount requires improved model constraints on the atmospheric column radiative balance in polar regions. Vertical profiles of the aerosol number size distribution are a key model input to constrain column radiative closure calculations. Model simulations of cloud droplet spectra and subsequently precipitation require input of the aerosol number size distribution to initiate the droplet activation and growth process. New particle formation in the atmosphere appears to occur more frequently than previously believed. Fast time response aerosol number size distribution measurements in the sub-10nm range would help reveal the conditions under which new particle formation occurs. Underlying all of the measurement requirements mentioned above is the need to understand how the uptake of atmospheric water by particles alters their size and chemistry and therefore their “ambient” optical and cloud activation properties.

Scientists and engineers at Brechtel have been working on a suite of UAS-deployable aerosol instruments including a fast-response particle counter, an aerosol light absorption photometer, optical and electrical mobility size distribution measurement systems, and an 8-channel, remotely-controllable filter sampler. Typical dimensions of the various modules are between 5 and 15 cm with weights between 0.2 and 4 kg. In this work, we focus on the results of characterization tests of the optical and mobility size distribution instruments to evaluate time response, particle sizing and counting performance, and environmental chamber testing to assess the impacts of operating conditions on instrument performance.