Preprints
https://doi.org/10.5194/amt-2021-251
https://doi.org/10.5194/amt-2021-251

  30 Aug 2021

30 Aug 2021

Review status: this preprint is currently under review for the journal AMT.

Laser Imaging Nephelometer for aircraft deployment

Adam T. Ahern1,2, Frank Erdesz1,2, Nicholas L. Wagner1,2,a, Charles A. Brock1, Ming Lyu3, Kyra Slovacek2,4, Richard H. Moore5, Elizabeth B. Wiggins5,6, and Daniel M. Murphy1 Adam T. Ahern et al.
  • 1NOAA Chemical Sciences Laboratory, Boulder, CO 80305, USA
  • 2Cooperative Institute for Research in Environmental Sciences, University of Colorado, Boulder, CO 80309, USA
  • 3Department of Chemistry, University of Alberta, Edmonton, AB T6G 2B4, Canada
  • 4Civil, Environmental, and Architectural Engineering, University of Colorado, Boulder, CO 80309, USA
  • 5NASA Langley Research Center, Hampton, VA 23666, USA
  • 6NASA Postdoctoral Program, Universities Space Research Association, Columbia, MD 21046, USA
  • anow at: Ball Aerospace, Westminster, CO 80021, USA

Abstract. Validation of remote sensing retrievals of aerosol microphysical and optical properties requires in situ measurements of the same properties. We present here an improved imaging nephelometer for measuring the directionality and polarization of light (i.e. polarimetry) scattered at two wavelengths (405 nm and 660 nm) with high temporal resolution. The instrument was designed for airborne deployment and is capable of ground-based measurements as well. The Laser Imaging Nephelometer (LiNeph) uses two orthogonal detectors with wide-angle lenses and linearly polarized light sources to measure both the phase function, P11(θ), and degree of linear polarization, -P12/P11(θ). In this work, we will describe the instrument function and calibration, as well as data acquisition and reduction. The instrument was first deployed aboard the NASA DC-8 during the 2019 FIREX-AQ campaign. Here, we present field measurements of smoke plumes that show that the LiNeph has sufficient resolution for 0.24 Hz polarimetric measurements at two wavelengths, 405 and 660 nm, at integrated scattering coefficients ranging from 50–80,000 Mm−1.

Adam T. Ahern et al.

Status: open (until 23 Oct 2021)

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Adam T. Ahern et al.

Adam T. Ahern et al.

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Short summary
Particles in the atmosphere play a significant role in climate change by scattering light back into space, reducing the amount of energy available to be absorbed by greenhouse gases. We built a new instrument to measure what direction light is scattered by particles, e.g. wildfire smoke. This is important because, depending on the angle of the sun, some particles scatter light into space (cooling the planet), but some light is also scattered towards the Earth (not cooling the planet.)