Abstract
The fine-mode fraction (FMF) of aerosol optical depth (AOD) is a key optical parameter that represents the proportion of fine particles relative to total aerosols in the atmosphere. However, in comparison to ground-based measurements, the FMF is still difficult to retrieve from satellite observations, as attempted by a Moderate-resolution Imaging Spectroradiometer (MODIS) algorithm. In this paper, we introduce the retrieval of FMF based on Polarization and Anisotropy of Reflectances for Atmospheric Science coupled with Observations from a Lidar (PARASOL) data. This method takes advantage of the coincident multi-angle intensity and polarization measurements from a single satellite platform. In our method, we use intensity measurements to retrieve the total AOD and polarization measurements to retrieve the fine-mode AOD. The FMF is then calculated as the ratio of the retrieved fine-mode AOD to the total AOD. The important processes in our method include the estimation of the surface intensity and polarized reflectance by using two semi-empirical models, and the building of two sets of aerosol retrieval lookup tables for the intensity and polarized measurements via the 6SV radiative transfer code. We apply this method to East Asia, and comparisons of the retrieved FMFs for the Beijing, Xianghe and Seoul_SNU sites with those of the Aerosol Robotic Network (AERONET) ground-based observations produce correlation coefficients (R2) of 0.838, 0.818, and 0.877, respectively. However, the comparison results are relatively poor (R2 = 0.537) in low-AOD areas, such as the Osaka site, due to the low signal-to-noise ratio of the satellite observations.
Highlights
Atmospheric aerosols play an important role in the global climate and environmental changes.They alter the radiation balance of the atmosphere, resulting in circulatory changes [1,2], and cause atmospheric pollution, which has an important influence on the biosphere
The key function of our method is the retrieval of the total aerosol optical depth (AOD) and fine-mode AOD based on intensity and polarization measurements, respectively, in order to calculate the fine-mode fraction (FMF)
Assume that the top of atmosphere (TOA) reflectance is composed of the contributions of the atmosphere and surface radiation and that the atmosphere reflectance is the weighted average of a pure fine- and coarse-mode with the same optical depth, such that the FMF can be determined by the minimum residual error between the calculated and the observed TOA reflectance
Summary
Atmospheric aerosols play an important role in the global climate and environmental changes. They alter the radiation balance of the atmosphere, resulting in circulatory changes [1,2], and cause atmospheric pollution, which has an important influence on the biosphere. With the development of satellite-based remote sensing technologies, the method of retrieving the first parameter to reflect the optical properties of aerosols—aerosol optical depth. (AOD)—has become more and more mature, and the retrieval algorithms of AOD have been developed based on many satellite platforms. The use of this single parameter is insufficient to estimate the anthropogenic aerosol content and to understand the influence of human effects on climate change and air pollution
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
