Journal article
Retrieval of aerosol microphysical properties from AERONET photopolarimetric measurements: 1. Information content analysis
Journal of geophysical research. Atmospheres, Vol.120(14), pp.7059-7078
07/27/2015
DOI: 10.1002/2015JD023108
Abstract
This paper is the first part of a two-part study that aims to retrieve aerosol particle size distribution (PSD) and refractive index from the multispectral and multiangular polarimetric measurements taken by the new-generation Sun photometer as part of the Aerosol Robotic Network (AERONET). It provides theoretical analysis and guidance to the companion study in which we have developed an inversion algorithm for retrieving 22 aerosol microphysical parameters associated with a bimodal PSD function from real AERONET measurements. Our theoretical analysis starts with generating the synthetic measurements at four spectral bands (440, 675, 870, and 1020 nm) with a Unified Linearized Vector Radiative Transfer Model for various types of spherical aerosol particles. Subsequently, the quantitative information content for retrieving aerosol parameters is investigated in four observation scenarios, i.e., I1, I2, P1, and P2. Measurements in the scenario (I1) comprise the solar direct radiances and almucantar radiances that are used in the current AERONET operational inversion algorithm. The other three scenarios include different additional measurements: (I2) the solar principal plane radiances, (P1) the solar principal plane radiances and polarization, and (P2) the solar almucantar polarization. Results indicate that adding polarization measurements can increase the degree of freedom for signal by 2–5 in the scenario P1, while not as much of an increase is found in the scenarios I2 and P2. Correspondingly, smallest retrieval errors are found in the scenario P1: 2.3% (2.9%) for the fine-mode (coarse-mode) aerosol volume concentration, 1.3% (3.5%) for the effective radius, 7.2% (12%) for the effective variance, 0.005 (0.035) for the real-part refractive index, and 0.019 (0.068) for the single-scattering albedo. These errors represent a reduction from their counterparts in scenario I1 of 79% (57%), 76% (49%), 69% (52%), 66% (46%), and 49% (20%), respectively. We further investigated those retrieval errors over a variety of aerosol loading and fine-/coarse-mode prevalence, which indicates that observations in scenario P1 can yield the retrieval of refractive index and single-scattering albedo for both fine and coarse aerosol modes, when aerosol optical depth at 440 nm is larger than 0.2 and 870/1020 nm Ångström exponent ranges between 0.7 and 1.6.
Details
- Title: Subtitle
- Retrieval of aerosol microphysical properties from AERONET photopolarimetric measurements: 1. Information content analysis
- Creators
- Xiaoguang Xu - Earth and Atmospheric Sciences, University of Nebraska-Lincoln, Nebraska, Lincoln, USAJun Wang - Earth and Atmospheric Sciences, University of Nebraska-Lincoln, Nebraska, Lincoln, USA
- Resource Type
- Journal article
- Publication Details
- Journal of geophysical research. Atmospheres, Vol.120(14), pp.7059-7078
- Publisher
- Blackwell Publishing Ltd
- DOI
- 10.1002/2015JD023108
- ISSN
- 2169-897X
- eISSN
- 2169-8996
- Number of pages
- 20
- Grant note
- name: NASA Earth and Space Science Fellowship; name: NASA Radiation Sciences Program; name: Glory Mission Program; name: Holland Computing Center at the University of Nebraska
- Language
- English
- Date published
- 07/27/2015
- Academic Unit
- Physics and Astronomy; Chemical and Biochemical Engineering; Iowa Technology Institute; Civil and Environmental Engineering; Electrical and Computer Engineering
- Record Identifier
- 9984104911302771
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