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On the Contribution of Particulate Matter (PM2.5) to Direct Radiative Forcing over Two Urban Environments in India

Category: Optical/Radiative Properties and Remote Sensing

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DOI: 10.4209/aaqr.2018.04.0128
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Rama K. Krishna , Abhilash S. Panicker, Aslam M. Yusuf, Beig G. Ullah

  • Indian Institute of Tropical Meteorology, Pune 411008, India

Highlights

Measurements of Particulate matter (PM2.5) is carried out over two Indian regions.
Radiaitve forcing of PM2.5 is estimated over the regions.
Impact of albedo found to dominate the hygroscopic effect in forcing estimates.


Abstract

Radiative forcing of particulate matter (PM2.5) concentration has been estimated for a period of one year (January-December 2015) over Delhi and Pune (urban polluted metro cities in India). Insitu observations of PM2.5 and black carbon (BC) were obtained from system of air quality forecasting and research (SAFAR) ground-based network of stations over both the cities. Observations have shown that PM concentration over Pune had strong diurnal cycle as compared to Delhi in all the seasons. Also, comparisons of mode values and seasonal frequency distributions (FD) over Pune and Delhi showed that pollution levels over Delhi were consistently above National Ambient Air Quality Standards (NAAQS). The monthly mean PM2.5 values ranged from 61.5 to 162.9 over Delhi and from 17.4 to 74.05 over Pune. BC mass contribution to PM2.5 was found to be 10 to 25% over Pune. However, the contribution of BC to PM2.5 was up to 35% in Delhi. Radiative forcing due to PM2.5 (PRF) over both the sites was estimated using optical properties of aerosols and clouds (OPAC) model along with santa barbara discrete ordinate atmospheric radiative transfer (SBDART) model. The PRF in the atmosphere was between +7.73 Wm-2 to +14.51 Wm-2 over Delhi and varied from +3.12 Wm-2 to +12.15 Wm-2 over Pune. Sensitivity experiments showed that the impact of the increase in hygroscopicity of aerosols to PRF was overshadowed by the net changes in albedo.

Keywords

PM2.5 AOD Albedo Radiative forcing


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