Optimal Estimation Retrieval of Aerosol Fine-Mode Fraction from Ground-Based Sky Light Measurements

Abstract

In this paper, the feasibility of retrieving the aerosol fine-mode fraction (FMF) from ground-based sky light measurements is investigated. An inversion algorithm, based on the optimal estimation (OE) theory, is presented to retrieve FMF from single-viewing multi-spectral radiance measurements and to evaluate the impact of utilization of near-infrared (NIR) measurements at a wavelength of 1610 nm in aerosol remote sensing. Self-consistency tests based on synthetic data produced a mean relative retrieval error of 4.5%, which represented the good performance of the OE inversion algorithm. The proposed algorithm was also performed on real data taken from field experiments in Beijing during a haze pollution event. The correlation coefficients (R) for the retrieved aerosol volume fine-mode fraction (FMFv) and optical fine-mode fraction (FMFo) against AErosol RObotic NETwork (AERONET) products were 0.94 and 0.95 respectively, and the mean residual error was 4.95%. Consequently, the inversion of FMFv and FMFo could be well constrained by single-viewing multi-spectral radiance measurement. In addition, by introducing measurements of 1610 nm wavelength into the retrieval, the validation results showed a significant improvement in the R value for FMFo (from 0.89–0.94). These results confirm the high value of NIR measurements for the retrieval of coarse mode aerosols.

Direct Retrieval of NO 2 Vertical Columns from UV-Vis (390-495 nm) Spectral Radiances Using a Neural Network

“…UNL-VRTM facilitates a userfriendly interface for modifying surface and atmospheric optical parameters, which were fed to the Vector Linearized Discrete Ordinate Radiative Transfer (VLIDORT) [67] RT code to calculate the top of atmosphere (TOA) radiances. UNL-VRTM has been widely used for aerosol retrieval and relevant sensitivity studies based on both band-averaged and hyperspectral radiances [68][69][70][71]. To exploit the full information possible for NO 2 retrieval in the UV-Vis measurements, we simulated radiances between 320 and 500 nm, with an interval of 0.01 nm.…”

Preliminary Sensitivity Study of Aerosol Layer Height From Synthetic Multiangle Polarimetric Remote Sensing Measurements

“…UNL-VRTM integrates the VLIDORT code (Spurr et al, 2006), a linearized Mie code, a linearized T-Matrix code, a Rayleigh scattering module, line-by-line gas absorption calculation with HITRAN database, and some easy-used surface modules including the bidirectional reflectance distribution function (BRDF) and bidirectional polarized reflectance distribution function (BPDF). Based on UNL-VRTM, many studies have been carried to analyse the information content and develop the inversion algorithm for retrievals from the various measurements (Chen et al, 2017;Ding et al, 2016;Hou et al, 2016Hou et al, , 2017Hou et al, , 2018aXu et al, , 2017aXu et al, , b, 2018Xu et al, , 2019Li et al, 2018;Zheng et al, 2019aZheng et al, , 2019b).…”

Industrial Plume Properties Retrieved by Optimal Estimation Using Combined Hyperspectral and Sentinel-2 Data

“…Inverse model analysis applied to aerosol satellite remote sensing is an ill-posed problem, for which statistical frameworks, such as optimal inversion [19][20][21][22][23], have been proposed. Thompson et al [24,25] and Hou et al [26,27] have presented a method based on the formalism of Rodgers [28], in order to simultaneously retrieve the atmospheric properties and the surface reflectance from VIS-SWIR images.…”