Dr. Baerbel Sinha
Associate Professor , Earth & Environmental Science

Research is pursued in four broad inter related areas of environmental science, namely

1. Investigating the mixing state and shape of atmospheric particles and understanding its impact on the radiative properties of aerosol particles by microscopic techniques
   
2. Understanding the effect of surface properties and the mixing state of atmospheric aerosol particles on rainfall formation and cloud lifetime through laboratory and field experiments
   
3. Source identification and apportionment of aerosol particles based on single particle studies
   
4. The effect of viable biological aerosol particles on air quality and health
   
   

The main analytical techniques used by the group are:

1. Single particle Electron Microscopy
   
2. Measurements of particle number density and size distributions
   
3. Collection and study of viable biological aerosol with an interdisciplinary approach

Research objective:
Aerosol particles in the atmosphere exert a strong influence on climate by interacting with sunlight. This interaction is responsible for the direct effect of aerosol particles on climate. Black carbon has a strong direct climate effect. Currently large uncertainties in the radiative forcing over India are caused by our poor understanding of the mixing state of black carbon, under ambient conditions. IISER Mohali will undertake fieldwork to close this gap in our current knowledge using electron microscopy based single particle techniques. The indirect climate impacts of aerosol particles are even more important in the Indian context for understanding the effects of aerosol on the hydrological cycle. This is because, for some given cloud water content, an increase in the number of particles which can act as seeds for cloud droplets (also called cloud condensation nuclei CCN) results in a proportional increase in droplet number at the cost of the droplet size, which decreases. Smaller droplets are less likely to precipitate and need to be transported to higher altitude, where freezing can occur. This leads to less frequent but more vigorous rainfall and hailstorms. We investigate the CCN properties of individual classes of particles both in the laboratory by studying ambient particles in an environmental scanning electron microscope and in the field by collecting particles inside clouds with a counter flow virtual impactor.

• Harris, E.*, Sinha, B.*, van Pinxteren, D., Tilgner, A., Fomba, K. W., Schneider, J., Roth, A., Gnauk, T., Fahlbusch, B., Mertes, S., Lee, T., Collett, J., Foley, S., Borrmann, S., Hoppe, P., and Herrmann, H., Enhanced Role of Transition Metal Ion Catalysis During In-Cloud Oxidation of SO2. Science 340, 727-730.
  
• Poschl, U.*, Martin, S. T., Sinha, B., Chen, Q., Gunthe, S. S., Huffman, J. A., Borrmann, S., Farmer, D. K., Garland, R. M., Helas, G., Jimenez, J. L., King, S. M., Manzi, A., Mikhailov, E., Pauliquevis, T., Petters, M. D., Prenni, A. J., Roldin, P., Rose, D., Schneider, J., Su, H., Zorn, S. R., Artaxo, P. and Andreae, M. O.: Rainforest aerosols as biogenic nuclei of clouds and precipitation. Science, 329, 1513-1516, 2010.
  
• Pohlker, C.*, Wiedemann, K., Sinha, B., Shiraiwa, M., Gunthe, S. S., Smith M., Hang, S., Artaxo, P., Chen, Q., Cheng, Y., Elbert, W., Gilles, M.K., Kilcoyne, A. L. D., Moffet, R., Weigand, M., Martin, S. T., C., Poschl, U.*, and Andreae, M. O.: Biogenic Potassium Salt Particles as Seeds for Secondary Organic Aerosol in the Amazon. Science 337, 1075-1078, 2012.
  
• Sinha, B. W.*, Hoppe, P., Huth, J., Foley, S. and Andreae, M. O.: Sulfur isotope analyses of individual aerosol particles in the urban aerosol at a Central European site (Mainz, Germany). Atmospheric Chemistry and Physics, 8, 7217-7238, 2008.
  
• Winterholler, B.*, Hoppe, P., Foley, S. and Andreae, M. O.: Sulfur isotope measurements of individual sulfate particles by NanoSIMS. International Journal of Mass Spectrometry, 272, 63-77, 2008. (Awarded Best Student Paper Prize 2008 by American Society for Mass Spectrometry)