Intercomparison of airborne and surface-based measurements during the CLARIFY, ORACLES and LASIC field experiments
Authors: Barrett Paul A. , Abel Steven J. , Coe Hugh , Crawford Ian , Dobracki Amie , Haywood James , Howell Steve , Jones Anthony , Langridge Justin , McFarquhar Greg M. , Nott Graeme J. , Price Hannah , Redemann Jens , Shinozuka Yohei , Szpek Kate , Taylor Jonathan W. , Wood Robert , Wu Huihui , Zuidema Paquita , Bauguitte Stéphane , Bennett Ryan , Bower Keith , Chen Hong , Cochrane Sabrina , Cotterell Michael , Davies Nicholas , Delene David , Flynn Connor , Freedman Andrew , Freitag Steffen , Gupta Siddhant , Noone David , Onasch Timothy B. , Podolske James , Poellot Michael R. , Schmidt Sebastian , Springston Stephen , Sedlacek III Arthur J. , Trembath Jamie , Vance Alan , Zawadowicz Maria A. , Zhang Jianhao 
Published: November 2022

Abstract. Data are presented from intercomparisons between two
research aircraft, the FAAM BAe-146 and the NASA Lockheed P3, and between
the BAe-146 and the surface-based DOE (Department of Energy) ARM
(Atmospheric Radiation Measurement) Mobile Facility at Ascension Island
(8∘ S, 14.5∘ W; a remote island in the mid-Atlantic).
These took place from 17 August to 5 September 2017, during the African
biomass burning (BB) season. The primary motivation was to give confidence in the
use of data from multiple platforms with which to evaluate numerical climate
models. The three platforms were involved in the CLouds–Aerosol–Radiation
Interaction and Forcing for Year 2017 (CLARIFY-2017), ObseRvations of
Aerosols above CLouds and their intEractionS (ORACLES), and Layered Atlantic
Smoke and Interactions with Clouds (LASIC) field experiments. Comparisons
from flight segments on 6 d where the BAe-146 flew alongside the ARM
facility on Ascension Island are presented, along with comparisons from the
wing-tip-to-wing-tip flight of the P3 and BAe-146 on 18 August 2017.
The intercomparison flight sampled a relatively clean atmosphere overlying a
moderately polluted boundary layer, while the six fly-bys of the ARM site
sampled both clean and polluted conditions 2–4 km upwind. We compare and
validate characterisations of aerosol physical, chemical and optical
properties as well as atmospheric radiation and cloud microphysics between platforms.
We assess the performance of measurement instrumentation in the field, under
conditions where sampling conditions are not as tightly controlled as in
laboratory measurements where calibrations are performed. Solar radiation
measurements compared well enough to permit radiative closure studies.
Optical absorption coefficient measurements from all three platforms were
within uncertainty limits, although absolute magnitudes were too low
(<10 Mm−1) to fully support a comparison of the absorption
Ångström exponents. Aerosol optical absorption measurements from
airborne platforms were more comparable than aircraft-to-ground
observations. Scattering coefficient observations compared adequately
between airborne platforms, but agreement with ground-based measurements was
worse, potentially caused by small differences in sampling conditions or
actual aerosol population differences over land. Chemical composition
measurements followed a similar pattern, with better comparisons between the
airborne platforms. Thermodynamics, aerosol and cloud microphysical
properties generally agreed given uncertainties.