Research News
1. Source attributed premature mortality from ambient PM2.5 exposureLelieveld, J., J. S. Evans, M. Fnais, D. Glannadaki and A. Pozzer (2015): The contribution of outdoor air pollution sources to premature mortality on a global scale,Nature, 525: 367-371.
Estimate of premature mortality burden due to ambient air pollution continues to be a hot topic among researchers across the world. Such estimates have large uncertainty because of the lack of adequate in-situ measurements of PM2.5 and region-specific concentration risk function across large range of ambient air pollution exposure. More importantly, lack information about source-attributed exposure hinders in formulating appropriate policy to curb pollution. Using a global chemistry model, the authors concluded that emissions from household energy use for cooking and heating, primarily in China and India, have the largest contribution to global premature mortality. In large part of USA, traffic and power generations are dominant contributors, while agricultural emissions are largest contributor in eastern USA, Europe, Russia and East Asia.
2. Aerosol acidity remains high despite declining sulfate concentrationWeber, R. J., H. Guo, A. G. Russell and A. Nenes (2016):High aerosol acidity despite declining atmospheric sulfate concentrations over the past 15 years, Nature Geoscience, doi:10.1038/ngeo2665.
Atmospheric sulfate aerosol concentration has decreased over the last 15 years, while ammonium nitrate concentration remains almost constant. pH buffering by partitioning of NH3 between particle and gaseous phases led to a relatively constant particle pH of 0-2. Particle acidity is important to understand the health impacts of aerosols, especially for fine particulate matter (PM2.5). Until atmospheric sulfate concentration reduces to near pre-industrial level, aerosol acidity is unlikely to reduce.
3. Aerosol burden expected to increase in a warmer world
Allen, R. J., W. Landuyt and S. T. Rumbold (2016): An increase in aerosol burden and radiative effects in a warmer world, Nature Climate Change, 6: 269-274.
Analysis of state-of-the-art climate models revealed that climate change is associated with a negative aerosol-climate feedback of -0.02 to -0.09 W m-2 K-1 for direct effect with indirect effect to be likely larger. This is due to an increase in aerosol burden in tropics and northern hemispheric midlatitudes, because of a decrease in wet deposition due to less large scale precipitation over land.
4. Challenges in quantifying aerosol-induced changes in cloud properties
Ghan, S., M. Wang, S. Zhang, S. Ferrachat, A. Gettelman, J. Griesfeller, Z. Kipling, U. Lohmann, H. Morrison, D. Neubauer, D. G. Patridge, P. Stier, T. Takemura, H. Wang and K. Zhang (2016): Challenges in constraining anthropogenic aerosol effects on cloud radiative forcing using present-day spatiotemporal variability, Proceedings of the National Academy of Sciences of the United States of America, doi:10.1073/pnas.1514036113.
Aerosol-cloud interaction depends on numerous confounding factors, many of which are difficult to measure or model. Uncertainty at every step, starting from emission inventory to relationships between aerosol and cloud parameters, and cloud parameters and precipitation, results in a large uncertainty to isolate aerosol impact on cloud and precipitation.
5. Recent Indo-Pacific SST trends suppress rainfall in mid-latitude East Asia
Ueda, H., Y. Kamae, M. Hayasaki, A. Kitoh, S. Watanabe, Y. Miki and A. Kumai (2015): Combined effects of recent Pacific cooling and Indian Ocean warming on Asian monsoon, Nature Communications, 6, doi:10.1038/ncomms9854.
While SST shows a cooling trend in the tropical Pacific Ocean in the last 15 years, it continues to increase in the Indian Ocean. Indo-Pacific SST anomalies cause intensification of convection over the tropical western Pacific basin, resulting in suppression of rainfall in East Asia through tele-connection. Though the Indian Ocean SST effect opposes the tropical Pacific SST effect, it is not strong enough to compensate it completely.
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Dr Sagnik Dey
Asst Professor
CAS, IIT Delhi
sagnik@cas.iitd.ac.in
Dr P. C. S. Devara
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devara@tropmet.res.in
Dr A Jayaraman
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Dr B. K. Sapra
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BARC
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