Articles | Volume 17, issue 11
Atmos. Chem. Phys., 17, 7229–7243, 2017
Atmos. Chem. Phys., 17, 7229–7243, 2017

Research article 16 Jun 2017

Research article | 16 Jun 2017

HSRL-2 aerosol optical measurements and microphysical retrievals vs. airborne in situ measurements during DISCOVER-AQ 2013: an intercomparison study

Patricia Sawamura1,2, Richard H. Moore1, Sharon P. Burton1, Eduard Chemyakin1,2, Detlef Müller3,2, Alexei Kolgotin4, Richard A. Ferrare1, Chris A. Hostetler1, Luke D. Ziemba1, Andreas J. Beyersdorf5, and Bruce E. Anderson1 Patricia Sawamura et al.
  • 1NASA Langley Research Center, Hampton, VA, USA
  • 2Science Systems and Applications, Inc., Hampton, VA, USA
  • 3University of Hertfordshire, Hatfield, Hertfordshire, UK
  • 4Physics Instrumentation Center, Troitsk, Russia
  • 5California State University, San Bernardino, CA, USA

Abstract. We present a detailed evaluation of remotely sensed aerosol microphysical properties obtained from an advanced, multi-wavelength high-spectral-resolution lidar (HSRL-2) during the 2013 NASA DISCOVER-AQ field campaign. Vertically resolved retrievals of fine-mode aerosol number, surface-area, and volume concentration as well as aerosol effective radius are compared to 108 collocated, airborne in situ measurement profiles in the wintertime San Joaquin Valley, California, and in summertime Houston, Texas. An algorithm for relating the dry in situ aerosol properties to those obtained by the HSRL at ambient relative humidity is discussed. We show that the HSRL-2 retrievals of ambient fine-mode aerosol surface-area and volume concentrations agree with the in situ measurements to within 25 and 10 %, respectively, once hygroscopic growth adjustments have been applied to the dry in situ data. Despite this excellent agreement for the microphysical properties, extinction and backscatter coefficients at ambient relative humidity derived from the in situ aerosol measurements using Mie theory are consistently smaller than those measured by the HSRL, with average differences of 31 ± 5 % and 53 ± 11 % for California and Texas, respectively. This low bias in the in situ estimates is attributed to the presence of coarse-mode aerosol that are detected by HSRL-2 but that are too large to be well sampled by the in situ instrumentation. Since the retrieval of aerosol volume is most relevant to current regulatory efforts targeting fine particle mass (PM2. 5), these findings highlight the advantages of an advanced 3β + 2α HSRL for constraining the vertical distribution of the aerosol volume or mass loading relevant for air quality.

Short summary
We present a detailed evaluation of physical properties of aerosols, like aerosol number concentration and aerosol size, obtained from an advanced, airborne, multi-wavelength high-spectral-resolution lidar (HSRL-2) system. These lidar-retrieved physical properties were compared to airborne in situ measurements. Our findings highlight the advantages of advanced HSRL measurements and retrievals to help constrain the vertical distribution of aerosol volume or mass loading relevant for air quality.
Final-revised paper