Retrieval of aerosol optical thickness using MODIS 500 × 500m 2, a study in Hong Kong and the Pearl River Delta region

Man Sing Wong, Kwon Ho Lee, Janet Elizabeth Nichol, Zhanqing Li

Research output: Journal article publicationJournal articleAcademic researchpeer-review

32 Citations (Scopus)


Aerosol detection and monitoring by satellite observations has been substantially developed over the past decades. While several state-of-the-art aerosol retrieval techniques provide aerosol properties at global scale, high spatial detail that is suitable for urbanized regions is unavailable because most of the satellite-based products are at coarse resolution. A refined aerosol retrieval algorithm using the MODerate Resolution Imaging Spectroradiometer (MODIS) to retrieve aerosol properties at 500-m resolution over land is described here. The rationale of our technique is to first estimate the aerosol reflectances by decomposing the top-of-atmosphere reflectance from surface reflectance and Rayleigh path reflectance. For the determination of surface reflectances, a modified minimum reflectance technique (MRT) is used, and MRT images are computed for different seasons. A good agreement is obtained between the surface reflectances of MRT images and MODIS land surface reflectance products (MOD09), with a correlation of 0.9. For conversion of aerosol reflectance to aerosol optical thickness (AOT), comprehensive lookup tables are constructed which consider aerosol properties and sun-viewing geometry in the radiative transfer calculations. The resulting 500-m AOT images are highly correlated (r = 0.937) with AErosol RObotic NETwork sunphotometer observations in Hong Kong for most of the year corresponding to the long dry season. This study demonstrates a method for aerosol retrieval at fine resolution over urbanized regions, which can assist the study of aerosol spatial distribution. In addition, the MODIS 500-m AOT images can also be used to pinpoint source areas of cross-boundary aerosols from the Pearl River Delta region.
Original languageEnglish
Article number5454279
Pages (from-to)3318-3327
Number of pages10
JournalIEEE Transactions on Geoscience and Remote Sensing
Issue number8
Publication statusPublished - 1 Aug 2010


  • Aerosols
  • air pollution
  • remote sensing

ASJC Scopus subject areas

  • Electrical and Electronic Engineering
  • Earth and Planetary Sciences(all)

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