Improvement of aerosol optical depth retrieval over Hong Kong from a geostationary meteorological satellite using critical reflectance with background optical depth correction

Mijin Kim, Jhoon Kim, Man Sing Wong, Jongmin Yoon, Jaehwa Lee, Dong Wu, P. W. Chan, Janet E. Nichol, Chu Yong Chung, Mi Lim Ou

Research output: Contribution to journalArticle

19 Citations (Scopus)

Abstract

Despite continuous efforts to retrieve aerosol optical depth (AOD) using a conventional 5-channel meteorological imager in geostationary orbit, the accuracy in urban areas has been poorer than other areas primarily due to complex urban surface properties and mixed aerosol types from different emission sources. The two largest error sources in aerosol retrieval have been aerosol type selection and surface reflectance. In selecting the aerosol type from a single visible channel, the season-dependent aerosol optical properties were adopted from long-term measurements of Aerosol Robotic Network (AERONET) sun-photometers. With the aerosol optical properties obtained from the AERONET inversion data, look-up tables were calculated by using a radiative transfer code: the Second Simulation of the Satellite Signal in the Solar Spectrum (6S). Surface reflectance was estimated using the clear sky composite method, a widely used technique for geostationary retrievals. Over East Asia, the AOD retrieved from the Meteorological Imager showed good agreement, although the values were affected by cloud contamination errors. However, the conventional retrieval of the AOD over Hong Kong was largely underestimated due to the lack of information on the aerosol type and surface properties. To detect spatial and temporal variation of aerosol type over the area, the critical reflectance method, a technique to retrieve single scattering albedo (SSA), was applied. Additionally, the background aerosol effect was corrected to improve the accuracy of the surface reflectance over Hong Kong. The AOD retrieved from a modified algorithm was compared to the collocated data measured by AERONET in Hong Kong. The comparison showed that the new aerosol type selection using the critical reflectance and the corrected surface reflectance significantly improved the accuracy of AODs in Hong Kong areas, with a correlation coefficient increase from 0.65 to 0.76 and a regression line change from τMI [basic algorithm]=0.41τAERONET+0.16 to τMI [new algorithm]=0.70τAERONET+0.01.

Original languageEnglish
Pages (from-to)176-187
Number of pages12
JournalRemote Sensing of Environment
Volume142
DOIs
Publication statusPublished - 2014 Feb 25

Fingerprint

Weather satellites
Geostationary satellites
aerosols
optical depth
reflectance
Aerosols
aerosol
China
surface reflectance
Robotics
optical property
optical properties
Image sensors
Surface properties
Optical properties
data inversion
albedo (reflectance)
photometers
photometer
Photometers

All Science Journal Classification (ASJC) codes

  • Soil Science
  • Geology
  • Computers in Earth Sciences

Cite this

Kim, Mijin ; Kim, Jhoon ; Wong, Man Sing ; Yoon, Jongmin ; Lee, Jaehwa ; Wu, Dong ; Chan, P. W. ; Nichol, Janet E. ; Chung, Chu Yong ; Ou, Mi Lim. / Improvement of aerosol optical depth retrieval over Hong Kong from a geostationary meteorological satellite using critical reflectance with background optical depth correction. In: Remote Sensing of Environment. 2014 ; Vol. 142. pp. 176-187.
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abstract = "Despite continuous efforts to retrieve aerosol optical depth (AOD) using a conventional 5-channel meteorological imager in geostationary orbit, the accuracy in urban areas has been poorer than other areas primarily due to complex urban surface properties and mixed aerosol types from different emission sources. The two largest error sources in aerosol retrieval have been aerosol type selection and surface reflectance. In selecting the aerosol type from a single visible channel, the season-dependent aerosol optical properties were adopted from long-term measurements of Aerosol Robotic Network (AERONET) sun-photometers. With the aerosol optical properties obtained from the AERONET inversion data, look-up tables were calculated by using a radiative transfer code: the Second Simulation of the Satellite Signal in the Solar Spectrum (6S). Surface reflectance was estimated using the clear sky composite method, a widely used technique for geostationary retrievals. Over East Asia, the AOD retrieved from the Meteorological Imager showed good agreement, although the values were affected by cloud contamination errors. However, the conventional retrieval of the AOD over Hong Kong was largely underestimated due to the lack of information on the aerosol type and surface properties. To detect spatial and temporal variation of aerosol type over the area, the critical reflectance method, a technique to retrieve single scattering albedo (SSA), was applied. Additionally, the background aerosol effect was corrected to improve the accuracy of the surface reflectance over Hong Kong. The AOD retrieved from a modified algorithm was compared to the collocated data measured by AERONET in Hong Kong. The comparison showed that the new aerosol type selection using the critical reflectance and the corrected surface reflectance significantly improved the accuracy of AODs in Hong Kong areas, with a correlation coefficient increase from 0.65 to 0.76 and a regression line change from τMI [basic algorithm]=0.41τAERONET+0.16 to τMI [new algorithm]=0.70τAERONET+0.01.",
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Improvement of aerosol optical depth retrieval over Hong Kong from a geostationary meteorological satellite using critical reflectance with background optical depth correction. / Kim, Mijin; Kim, Jhoon; Wong, Man Sing; Yoon, Jongmin; Lee, Jaehwa; Wu, Dong; Chan, P. W.; Nichol, Janet E.; Chung, Chu Yong; Ou, Mi Lim.

In: Remote Sensing of Environment, Vol. 142, 25.02.2014, p. 176-187.

Research output: Contribution to journalArticle

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AU - Kim, Mijin

AU - Kim, Jhoon

AU - Wong, Man Sing

AU - Yoon, Jongmin

AU - Lee, Jaehwa

AU - Wu, Dong

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AU - Nichol, Janet E.

AU - Chung, Chu Yong

AU - Ou, Mi Lim

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