Abstract
Contrasting monsoons of 2008 and 2009 provided a test bed to enhance the understanding of the aerosol variability and aerosol-cloud interaction. Vertical aerosol profiles derived from the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) are used to delineate the aerosol properties during the two contrasting Indian summer monsoons. We observed a 30–40% increase in the aerosol occurrence frequency (AOF) in lower altitudes (below 6 km) in 2009 and a 5–8% enhancement in AOF at higher altitudes in 2008. The cloud occurrence frequency also showed more deep convective clouds in 2008 (13–15%) than in 2009. Cloud Fraction, Aerosol Optical Depth and TRMM precipitation data sets have been also used to investigate the aerosol-cloud interaction. We define the microphysical effect as the increase in cloud fraction with increase in aerosols (CCN) and the radiative effect as the decrease of cloud fraction with increase in aerosol loading. We observe a stronger microphysical effect than the radiative effect in 2008 as compared to 2009. In 2009, atmospheric brown clouds were observed from March to September, which slowed down the microphysical effect and enhanced the radiative effect. This resulted in a 30% reduction in the total cloud fraction that may have reduced precipitation, and invigorated the drought conditions during 2009.
Highlights
IntroductionPattern or cycle over the Indian region during monsoon season have a largescale impact on the life, agriculture or economy of India
Changes in precipitation intensity, pattern or cycle over the Indian region during monsoon season have a largescale impact on the life, agriculture or economy of India
In 2009, atmospheric brown clouds were observed from March to September, which slowed down the microphysical effect and enhanced the radiative effect
Summary
Pattern or cycle over the Indian region during monsoon season have a largescale impact on the life, agriculture or economy of India. A similar situation occurred during the summer monsoon (June–September) 2009, with a deficit in the allIndia rainfall of 54% of the long-term average for this period (Francis and Gadgil, 2009). Several satellite datasets have been used for studying aerosol-cloud interactions (Bréon et al, 2002) to observe the first indirect effect (Twomey, 1977), the second indirect effect (Albrecht, 1989), effect of biomass burning (Andreae et al, 2004), urban and industrial air pollution (Rosenfeld, 2000), and desert dust (Rosenfeld et al, 2001). Kim et al (2008) confirmed that the CALIPSO algorithms discriminate clouds and aerosols and detect the layer top and base altitudes reliably by comparing CALIOP and ground-based lidar data at a site far from the dust source, in Seoul, Korea Bhawar and Rahul, Aerosol and Air Quality Research, 13: 1384–1391, 2013 unique in its ability to measure high-resolution vertical profiles of both clouds and aerosols within the Earth’s atmosphere all over the world (Winker et al, 2003). Kim et al (2008) confirmed that the CALIPSO algorithms discriminate clouds and aerosols and detect the layer top and base altitudes reliably by comparing CALIOP and ground-based lidar data at a site far from the dust source, in Seoul, Korea
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