Retrievals of aerosol single scattering albedo by multiwavelength lidar measurements: evaluations with nasa langley hsrl-2 during discover-aq field campaigns
Identificadores
URI: https://hdl.handle.net/10481/85745Metadata
Show full item recordEditorial
Elsevier
Date
2019Referencia bibliográfica
Published version: Remote Sensing of Environment 222 (2019) 144–164
Sponsorship
Marie Skłodowska-Curie Research Innovation and Staff Exchange (RISE) GRASP-ACE (grant agreement no 778349)Abstract
This work focuses on the study and evaluation of the retrievals of aerosol complex refractive index
(m = m r + im i ) and single scattering albedo (SSA) from the inversion of multi-wavelength lidar measurements,
particularly of three backscattering coefficients (β) at 355, 532 and 1064 nm and two extinction coefficients (α)
at 355 and 532 nm, typically known as the stand-alone 3β + 2α lidar inversion. The focus is on the well-known
regularization technique for spherical particles. It is well known that constraints in the range of refractive indices
allowed in the inversion are essential, both for the real (m r ) and imaginary (m i ) parts, due to the under-de-
termined nature of the problem. Usually these constraints are fixed for a given set of inversions. Using a large
database of AERONET retrievals, correlations between retrieved m r and mi are observed and those correlations
together with results from the GOCART model are used to define optimized, case-dependent, constraints in the
stand-alone 3β + 2α lidar inversion. For each inversion performed, the optimized constraints are computed from
the 3β + 2α data using a-priori information of extinction-to-backscattered ratio (LR) and the Angstrom exponent
computed with α at 355 and 532 nm. The stand-alone 3β + 2α lidar inversion with optimized, case-dependent,
constraints is applied to airborne NASA LaRC HSRL-2 experimental measurements during DISCOVER-AQ. The
optimized constraints selected from the measured 3β + 2α are compared with the typing classification based on
additional multiwavelength depolarization measurements, showing consistency between aerosol size and ab-
sorption range and aerosol typing. Evaluations of the SSA retrieved by the stand-alone 3β + 2α lidar inversion
with optimized constraints are done by comparisons with correlative airborne in-situ measured SSA. The
agreement between both methodologies is satisfactory for most aerosol types as differences are within the uncertainties of each methodology.