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    • Keywords


      Atmospheric aerosols; aerosol optical depth; Angström parameters; ICARB; long-range transport; multiwavelength radiometer.

    • Abstract


      Spectral aerosol optical depth (AOD) measurements, carried out regularly from a network of observatories spread over the Indian mainland and adjoining islands in the Bay of Bengal and Arabian Sea, are used to examine the spatio-temporal and spectral variations during the period of ICARB (March to May 2006). The AODs and the derived ˚Angström parameters showed considerable variations across India during the above period. While at the southern peninsular stations the AODs decreased towards May after a peak in April, in the north Indian regions they increased continuously from March to May. The ˚Angström coefficients suggested enhanced coarse mode loading in the north Indian regions, compared to southern India. Nevertheless, as months progressed from March to May, the dominance of coarse mode aerosols increased in the columnar aerosol size spectrum over the entire Indian mainland, maintaining the regional distinctiveness. Compared to the above, the island stations showed considerably low AODs, so too the northeastern station Dibrugarh, indicating the prevalence of cleaner environment. Long-range transport of aerosols from the adjoining regions leads to remarkable changes in the magnitude of the AODs and their wavelength dependencies during March to May. HYSPLIT back-trajectory analysis shows that enhanced long-range transport of aerosols, particularly from the west Asia and northwest coastal India, contributed significantly to the enhancement of AOD and in the flattening of the spectra over entire regions; if it is the peninsular regions and the island Minicoy are more impacted in April, the north Indian regions including the Indo Gangetic Plain get affected the most during May, with the AODs soaring as high as 1.0 at 500 nm. Over the islands, the ˚Angström exponent (𝛼) remained significantly lower (∼1) over the Arabian Sea compared to Bay of Bengal (BoB) (∼1.4) as revealed by the data respectively from Minicoy and Port Blair. Occurrences of higher values of 𝛼, showing dominance of accumulation mode aerosols, over BoB are associated well with the advection, above the boundary layer, of fine particles from the east Asian region during March and April. The change in the airmass to marine in May results in a rapid decrease in 𝛼 over the BoB.

    • Author Affiliations


      S Naseema Beegum1 K Krishna Moorthy1 Vijayakumar S Nair1 S Suresh Babu1 S K Satheesh2 V Vinoj2 R Ramakrishna Reddy3 K Rama Gopal3 K V S Badarinath4 K Niranjan5 Santosh Kumar Pandey6 M Behera7 A Jeyaram7 P K Bhuyan8 M M Gogoi8 Sacchidanand Singh9 P Pant10 U C Dumka10 Yogesh Kant11 J C Kuniyal12 Darshan Singh13

      1. Space Physics Laboratory, Vikram Sarabhai Space Centre, Thiruvananthapuram 695 022, India.
      2. Centre of Atmospheric and Oceanic Sciences, Indian Institute of Science, Bangalore 560 012, India.
      3. Department of Physics, Sri Krishnadevaray University, Anantapur 515 003, India.
      4. National Remote Sensing Agency, Balanangar, Hyderabad 500 037, India.
      5. Department of Physics, Andhra University, Visakhapatnam 530 003, India.
      6. ISTRAC Ground Station, Dolly Gunj, Port Blair 744 101, India.
      7. Regional Remote Sensing Service Centre, Indian Institute of Technology Campus, Kharagpur 721 302, India.
      8. Department of Physics, Dibrugarh University, Dibrugarh 786 004, India.
      9. National Physical Laboratory, Dr. K S Krishnan Marg, New Delhi 110 012, India.
      10. Aryabhatta Research Institute of Observational Sciences, Nainital 263 129, India.
      11. Indian Institute of Remote Sensing, Dehra Dun 248 001, India.
      12. GB Pant Institute for Himalayan Environment and Development, Manali, Mohal-Kullu 175 126, India.
      13. Department of Physics, Punjabi University, Patiala 147 002, India.
    • Dates

  • Journal of Earth System Science | News

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