Climatology of aerosol component concentrations derived from multi-angular polarimetric POLDER-3 observations using GRASP algorithm
Authors: Li Lei , Derimian Yevgeny , Chen Cheng , Zhang Xindan , Che Huizheng , Schuster Gregory L. , Fuertes David , Litvinov Pavel , Lapyonok Tatyana , Lopatin Anton , Matar Christian , Ducos Fabrice , Karol Yana , Torres Benjamin , Gui Ke , Zheng Yu , Liang Yuanxin , Lei Yadong , Zhu Jibiao , Zhang Lei , Zhong Junting , Zhang Xiaoye , Dubovik Oleg 
Published: July 2022

Abstract. The study presents a climatology of aerosol composition
concentrations obtained by a recently developed algorithm approach, namely the Generalized Retrieval of Atmosphere and Surface Properties (GRASP)/Component. It is applied to the whole archive of observations from the POLarization
and Directionality of the Earth's Reflectances (POLDER-3). The conceptual
specifics of the GRASP/Component approach is in the direct retrieval of aerosol
speciation (component fraction) without intermediate retrievals of aerosol
optical characteristics. Although a global validation of the derived aerosol
component product is challenging, the results obtained are in line with
general knowledge about aerosol types in different regions. In addition, we
compare the GRASP-derived black carbon (BC) and dust components with those of the Modern-Era Retrospective Analysis for Research and Applications,
version 2 (MERRA-2) product. Quite a reasonable general agreement was found between the spatial and
temporal distribution of the species provided by GRASP and MERRA-2. The differences, however, appeared in regions known for strong biomass
burning and dust emissions; the reasons for the discrepancies are discussed.
The other derived components, such as concentrations of absorbing (BC, brown carbon (BrC), iron-oxide content in mineral dust) and scattering
(ammonium sulfate and nitrate, organic carbon, non-absorbing dust)
aerosols, represent scarce but imperative information for validation and
potential adjustment of chemical transport models. The aerosol optical
properties (e.g., aerosol optical depth (AOD), Ångström exponent (AE),
single-scattering albedo (SSA), fine- and coarse-mode aerosol optical depth (AODF AND AODC))
derived from GRASP/Component were found to agree well with the Aerosol Robotic Network (AERONET) ground reference data, and were fully consistent with
the previous GRASP Optimized, High Precision (HP) and Models retrieval versions
applied to POLDER-3 data. Thus, the presented extensive climatology product
provides an opportunity for understanding variabilities and trends in global
and regional distributions of aerosol species. The climatology of the
aerosol components obtained in addition to the aerosol optical properties
provides additional valuable, qualitatively new insight about aerosol
distributions and, therefore, demonstrates advantages of multi-angular
polarimetric (MAP) satellite observations as the next frontier for aerosol
inversion from advanced satellite observations. The extensive
satellite-based aerosol component dataset is expected to be useful for
improving global aerosol emissions and component-resolved radiative forcing
estimations. The GRASP/Component products are publicly available (https://www.grasp-open.com/products/, last access: 15 March 2022) and the
dataset used in the current study is registered under https://doi.org/10.5281/zenodo.6395384 (Li et al., 2022b).