Overview and recent developments of aerosol hygroscopic growth, humidified light scattering, light absorption and UAV-deployable methods at Brechtel Mfg.

Description

More routine measurements of the aerosol direct and indirect effects on climate are required to reduce the uncertainties in model predictions of climate change, precipitation patterns, and weather. Scientists and engineers at Brechtel have been working on a variety of instruments to enable ARM AOS and other aerosol measurements. The Humidified Tandem Differential Mobility Analyser (Model 3100 HTDMA) allows particle size- and RH-dependent water uptake measurements to be performed quickly and over a broad RH and size range (up to 2 microns). Significant recent updates to the HTDMA will be presented. A redesigned version of the Humidigraph, a tool to measure the change in light scattering due to aerosol water uptake, has recently been delivered to DOE by Brechtel. Key features and improvements will be discussed. The Tri-color Absorption Photometer (TAP) measures light absorption at three wavelengths by measuring light attenuation through a filter on which particles are collected. Strengths and limitations of the TAP will be presented along with results from intercomparisons with other instruments. One possibility for providing measurements over broader spatial and temporal scales is to deploy miniaturized instruments on-board unmanned aerial vehicles (UAVs). Brechtel has developed a particle counter, absorption photometer, filter sampler and other modules small enough to be deployed on UAVs. The typical dimensions of the modules are between 5 and 15 cm with weights between 0.2 and 4 kg. Many of the aforementioned modules completed 80 flight hours successfully over the Arctic in 2011 and 2015 on-board a Manta UAV. The application of these devices on the DOE Tiger Shark for measurements over the Arctic will be discussed.