PELTI: Measuring the Passing Efficiency of an Airborne Low Turbulence Aerosol Inlet

Abstract

In an effort to improve the accuracy of airborne aerosol studies, we compared a new porous-diffuser low-turbulence inlet (LTI) with three other inlets on the NSF/NCAR C-130, using both dust and sea salt as test aerosols. Analysis of bulk filters behind the LTI and an external reference total aerosol sampler (TAS) found no significant differences, while both the NASA shrouded solid diffuser inlet (SD) and NCAR community aerosol inlet (CAl) passed smaller amounts. However, scanning electron microscopic analyses of particles behind the LTI and TAS confirmed the model prediction that the LTI porous diffuser (PD) enhanced 7 J.Lm particle concentrations by about 60%. Aerodynamic particle size distributions behind the other inlets began to diverge from enhancement-corrected LTI values above 2 J.Lm, with mass concentrations of larger particles lower by as much as a factor of ten behind the CAl and a factor of 2 behind the SD. We conclude that the corrected LTI distributions were closer to ambient values than those from either the CAl or the SD. Since tubing losses contributed the most uncertainty when deducing ambient supermicron size distributions from LTI data, minimizing them should be a high priority for future experiments. Measured transfer tubing losses were larger than model estimates, in part because of some complex pieces for which no suitable model exists. The LTI represents a significant advance in our ability to It is always a pleasure to work with the staff of NCAR's RAF, who provided us with support well above and beyond the call of duty. Krista Laursen and Alan Schanot were instrumental in getting the equipment installed and the experiment into the field successfully. Darrel Baumgardner worked with the FSSPs and their data. We are particularly grateful to the National Science Foundation for a series of grants that made the LTI and PELTI a reality, including ATM-9813515 and ATM-0002698 to UH. This is SOEST contribution No. 6206.

Absorbing aerosol in the troposphere of the Western Arctic during the 2008 ARCTAS/ARCPAC airborne field campaigns

“…9 plots vertical profiles of NASA P-3B (red) and the NOAA WP3D (blue) supermicrometer volume (V coa ). Mean and median volume concentrations are likely higher aboard the NOAA WP-3D because of the use of an active low-turbulence inlet (Huebert et al, 2004b;Wilson et al, 2004) with a 50 % passing efficiency larger than the passive solid diffuser inlets used aboard the NASA DC-8 and P-3B . Intense plumes of coarse mode aerosol were rare during ARCTAS, however the WP-3D did encounter one such plume with 60-s average volume greater than 50 µm 3 m −3 .…”

“…The DC-8 solid diffuser inlet (UH-SDI) is that described in McNaughton et al (2007), whereas the P-3B employed a newly fabricated inlet with characteristics identical to those of the original UH-SDI. Aerosol size distributions between 0.004 and 7.0 µm were measured on board the NOAA WP-3D using a 5-channel condensation particle counter (CPC) (Brock et al, 2000) and optical particle counters operating behind a low-turbulence inlet (Huebert et al, 2004b;Wilson et al, 2004).…”

Arctic low-level boundary layer clouds: in situ measurements and simulations of mono- and bimodal supercooled droplet size distributions at the top layer of liquid phase clouds

“…However, due to the sampling inlet efficiency of the applied (solid diffuser) aerosol inlet (Huebert et al, 2004) for the POLAR 5, only aerosol particles of up to 1 µm in diameter are representatively sampled from the ambient air. Individual particles are detected by their light scattering signal within an angular range from 60 • to 120 • of a diode-laser with a wavelength of 655 nm.…”

Characterizations of Cloud Droplet Shatter Artifacts in Two Airborne Aerosol Inlets

“…• (Huebert et al 2004;McNaughton et al 2007). The sampling efficiency of this inlet has been characterized by Huebert et al (2004) and McNaughton et al (2007), and inlet cut size was determined to be ∼3-5 μm, aerodynamic diameter.…”

“…The sampling efficiency of this inlet has been characterized by Huebert et al (2004) and McNaughton et al (2007), and inlet cut size was determined to be ∼3-5 μm, aerodynamic diameter. During VOCALS, the SDI was mounted on the side of the aircraft, extending 30.5 cm from the surface of the aircraft skin.…”