An empirical relationship between PM2.5 and aerosol optical depth in Delhi Metropolitan

Naresh Kumar, Allen Chu, Andrew Foster

Research output: Contribution to journalArticlepeer-review

178 Scopus citations


Atmospheric remote sensing offers a unique opportunity to compute indirect estimates of air quality, which are critically important for the management and surveillance of air quality in megacities of developing countries, particularly in India and China, which have experienced elevated concentration of air pollution but lack adequate spatial-temporal coverage of air pollution monitoring. This article examines the relationship between aerosol optical depth (AOD) estimated from satellite data at 5 km spatial resolution and the mass of fine particles ≤2.5 μm in aerodynamic diameter (PM2.5) monitored on the ground in Delhi Metropolitan where a series of environmental laws have been instituted in recent years. PM2.5 monitored at 113 sites were collocated by time and space with the AOD computed using the data from Moderate Resolution Imaging Spectroradiometer (MODIS onboard the Terra satellite). MODIS data were acquired from NASA's Goddard Space Flight Center Earth Sciences Distributed Active Archive Center (DAAC). Our analysis shows a significant positive association between AOD and PM2.5. After controlling for weather conditions, a 1% change in AOD explains 0.52±0.202% and 0.39±0.15% change in PM2.5 monitored within ±45 and 150 min intervals of AOD data. This relationship will be used to estimate air quality surface for previous years, which will allow us to examine the time-space dynamics of air pollution in Delhi following recent air quality regulations, and to assess exposure to air pollution before and after the regulations and its impact on health.

Original languageEnglish (US)
Pages (from-to)4492-4503
Number of pages12
JournalAtmospheric Environment
Issue number21
StatePublished - Jul 2007
Externally publishedYes


  • Aerosol optical depth (AOD)
  • Air pollution
  • PM
  • Remote sensing

ASJC Scopus subject areas

  • Atmospheric Science
  • Environmental Science(all)
  • Pollution


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