Analysis of Aerosol Optical Depth from Sun Photometer at Shouxian, China

Abstract

We use two cloud screening methods—the clustering method and the multiplet method—to process the measurements of a sun photometer from March 2020 to April 2021 in Shouxian. The aerosol optical depth (AOD) and Angström parameters α and β are retrieved; variation characteristics and single scattering albedo are studied. The results show that: (1) The fitting coefficient of AOD retrieved by the two methods is 0.921, and the changing trend is consistent. The clustering method has fewer effective data points and days, reducing the overall average of AOD by 0.0542 (500 nm). (2) Diurnal variation of AOD can be divided into flat type, convex type, and concave type. Concave type and convex type occurred the most frequently, whereas flat type the least. (3) During observation, the overall average of AOD is 0.48, which is relatively high. Among them, AOD had a winter maximum (0.70), autumn and spring next (0.54 and 0.40), and a summer minimum (0.26). The variation trend of AOD and β is highly consistent, and the monthly mean of α is between 0.69 and 1.61, concerning mainly continental and urban aerosols. (4) Compared with others, the single scattering albedo in Shouxian is higher, reflecting strong scattering and weak aerosol absorption.

Development and Testing a Method for Retrieving Atmospheric Aerosol Optical Thickness based on the Solar Intensity from the Sun-photometer Data

“…The parameters utilized in this estimation are derived from applying several corrections. Comparing the method in processing the sun-photometer data (Xun et al, 2021;Bărbulescu, 2022), the Langley plot and Lambert-Beer Law are useful to support several methods in retrieving the solar intensity from the extraterrestrial atmosphere. In several atmospheric corrections of optical remote sensing using satellite sensors, the AOT's values play an essential role in arranging a Look Up Table (LUT) for scattering parameters (Aminuddin et al, 2018a;Jin et al, 2021;Kuze, 2012b).…”

Improved Imaging Model in the Presence of Multiplicative Spatially Extended Cloaking Interference

“…where I 0 is the radiation intensity at the initial point (on the Earth's surface); I 1 is the radiation intensity at the final point (on the satellite orbit); τ is a optical thickness (the natural logarithm of the ratio of incident to transmitted radiant power through a material [8][9]).…”

“…Laven Ph. [9] notes that the scattering of light by gas molecules, water droplets, dust grains obeys certain laws. The intensity of molecular scattering for light with a wavelength λ is proportional to λ -4 , the effect is most noticeable in the short-wavelength part of the spectrum, it is responsible for the blue color of the sky.…”

“…It is assumed that the estimate of the parameter α is its value α' at which the variance D of the image fragment reconstructed according to formula (9) in the window, r w =r w (α) takes the maximum value ( 11 . (11) In (11) the variance D is considered as a function D(r w (α)) of the argument α.…”

Validating Aerosol Optical Depth Estimation Methods Using the National Institute of Environmental Research Operational Numerical Forecast Model

“…Atmospheric aerosols influence the Earth's radiation balance by absorbing or scattering radiation and induce climate change [1]. As a representing parameter of atmospheric aerosol, aerosol optical depth (AOD), defined as the extinction of solar radiation caused by aerosol and integrated into the whole atmospheric column, is a fundamental optical property parameter and is widely used [2] in the scientific community. Generally, AOD is measured by satellite and ground-based remote sensing.…”