Articles | Volume 16, issue 13
Atmos. Chem. Phys., 16, 8423–8430, 2016
Atmos. Chem. Phys., 16, 8423–8430, 2016

Research article 12 Jul 2016

Research article | 12 Jul 2016

Investigation of aerosol indirect effects on monsoon clouds using ground-based measurements over a high-altitude site in Western Ghats

Vasudevan Anil Kumar, Govindan Pandithurai, Parakkatt Parambil Leena, Kundan K. Dani, Palani Murugavel, Sunil M. Sonbawne, Rohit D. Patil, and Rajamma Sukumaran Maheskumar Vasudevan Anil Kumar et al.
  • Indian Institute of Tropical Meteorology, Pune, 411008, India

Abstract. The effect of aerosols on cloud droplet number concentration and droplet effective radius is investigated from ground-based measurements over a high-altitude site where clouds pass over the surface. First aerosol indirect effect (AIE) estimates were made using (i) relative changes in cloud droplet number concentration (AIEn) and (ii) relative changes in droplet effective radius (AIEs) with relative changes in aerosol for different cloud liquid water contents (LWCs). AIE estimates from two different methods reveal that there is systematic overestimation in AIEn as compared to that of AIEs. Aerosol indirect effects (AIEn and AIEs) and dispersion effect (DE) at different LWC regimes ranging from 0.05 to 0.50 g m−3 were estimated. The analysis demonstrates that there is overestimation of AIEn as compared to AIEs, which is mainly due to DE. Aerosol effects on spectral dispersion in droplet size distribution play an important role in altering Twomey's cooling effect and thereby changes in climate. This study shows that the higher DE in the medium LWC regime offsets the AIE by 30 %.

Short summary
The effect of atmospheric aerosols on cloud properties is not very well understood in the Indian region, especially over Western Ghats, which is influenced by natural and anthropogenic aerosols. Collocated measurements of aerosol and cloud properties were used to estimate aerosol indirect effects using two methods: one with cloud drop number concentration and the other with cloud droplet size. Discrepancy between both methods is discussed, and the necessity of dispersion offset is emphasized.
Final-revised paper