A Versatile Droplet Sizing Spectrometer for Aerosol Hygroscopic Growth Measurements from Research Aircraft

The change in size of ambient particles with relative humidity impacts the global atmospheric radiation budget, regional visibility, and the ability to remotely sense plumes from naval and other vessels. There are currently no viable techniques to perform airborne observations of the size-resolved hygroscopic properties of ambient aerosols. This work focuses on the development of a new measurement technology, the Differential Aerosol Size and Hygroscopicity Spectrometer Probe (DASH-SP), that employs differential mobility analysis in-concert with multiple humidification and optical sizing steps to observe the size-resolved water uptake by aerosols. During the Phase I effort, the technical feasibility of the proposed technique was demonstrated through a variety of modeling studies of the optical particle counter (OPC) response leading to the construction of a bench top prototype OPC. Objectives of the Phase II include construction, testing and calibration studies of the prototype airborne DASH-SP. The DASH-SP will be delivered to CIRPAS and designed for field deployment on the Twin Otter research aircraft in a fully automated fashion. The DASH-SP should be capable of observing hygroscopic growth factors at multiple sizes and RHs with a time resolution two orders of magnitude better than existing techniques, making it appropriate for aircraft operations.