Characterization of Spectral Aerosol Optical Depth and transport over Bay of Bengal during Winter Monsoon
- Paper number
IAC-08.E2.1.8
- Author
Ms. NIVEDITA SANWLANI, Indian Space Research Organisation(ISRO), India
- Coauthor
Dr. Prakash Chauhan, Indian Space Research Organisation (ISRO), India
- Coauthor
Dr. Ranganath R. Navalgund, Space Applications Centre (ISRO), India
- Year
2008
- Abstract
Aerosols are crucial for understanding the complex changes in climatic patterns. Aerosols enter the atmosphere through natural processes e.g. dust storms, sea salt spray and anthropogenic activities such as burning of fossil fuels and biomass. The geographic distribution of aerosols, their particle size and concentration exerts notable climatic effects. Aerosol transport processes from continents to oceans are poorly understood due to lack of in-situ observations. In the present study we report results of spectral aerosol optical depth (AOD) measurements over the central Bay of Bengal during northeastern monsoon period. During this period the wind flows from northeast to southwest carrying anthropogenic aerosol generated over Indo-Gangetic plains towards the deeper parts of the Bay of Bengal. This season provides an ideal opportunity for studying the dispersal of continental aerosols with marine aerosols.
Spectral AOD measurements were carried out using five-channel (380, 440, 500, 675 and 870 nm) hand-held MICROTOPS Sunphotometer during November10 – December 13, 2007 onboard Oceanographic Research Vessel (ORV), Sagarkanya in the central Bay of Bengal. The daily mean AODs in the 500nm wavelength ranged between 0.16–1.0 with standard deviation 0.015 over open oceans which rose to 0.21 near the coastal regions. Higher AOD values ranging from 0.2 to 0.4 at 500nm were observed near Chennai coast. Relatively lower AOD values ranging between 0.15 - 0.30 were observed about 1100 km away from the coast. The daily mean AODs in 870 nm wavelength band ranged between 0.05–0.47 with low standard deviation 0.012 in open oceans which was 0.16 near coasts.
The mean of daily average of Angstrom exponent, α was found to be 1.23 and mean of daily average turbidity parameter, β was 0.183. Smaller Angstrom exponent (α) together with larger Angstrom turbidity coefficient (β) suggest an abundance of larger aerosol particles near the coast. Air mass back-trajectory analysis was also done to identify potential source regions of aerosols. Back-trajectory analysis shows that during the cruise period, the Bay of Bengal was mainly influenced by air masses from the central and east coast of India and also from winds coming towards Bangladesh.
- Abstract document
- Manuscript document
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