http://nopr.niscair.res.in/handle/123456789/1643 Search the Channel search http://nopr.niscair.res.in/simple-search http://nopr.niscair.res.in/handle/123456789/1655 Title: Trace gases over marine regions around India <br/> <br/>Authors: Naja, M; Chand, D; Sahu, L; Lal, S <br/> <br/>Abstract: Measurements of O3, CO, CH4, NO and SF6 were made during four ship cruises in January, February and March months of years 1996, 1997, 1998, and 1999 over the Arabian Sea and the Indian Ocean. Measurements were also made over the Bay of Bengal in February and March of the year 2001. All the measured trace gases show systematic gradient with decrease in their mixing ratios from the Coastal India to the South Indian Ocean. Transport of these gases also takes place from the surrounding countries over the marine regions. Ozone and CO show higher values over the Bay of Bengal than over the Arabian Sea, indicating stronger transport of polluted air-masses from northeast India and south Asia. Dramatic increase in ozone levels in the marine boundary layer (MBL) while showing no signature of in-situ photochemical production indicates the role of dynamical processes. The diurnal patterns in ozone are very different over the marine environments when compared with continental site, which is due to the nature and levels of pollutants transported from the continental regions and emissions of certain gases over the marine regions. Estimate shows that ozone production over India is less efficient, when compared to mid latitude. <br/> <br/>Page(s): 95-106 http://nopr.niscair.res.in/handle/123456789/1654 Title: Severe weather conditions in the Arabian Sea and their impact on atmospheric N₂O budget <br/> <br/>Authors: Patra, Prabir K; Maksyutov, Shamil; Nakazawa, Takakiyo <br/> <br/>Abstract: Influences of tropical cyclones and wide spread south-west monsoon on the ocean-atmosphere fluxes of nitrous oxide (N₂O) in the Arabian Sea are estimated. The NCEP/NCAR reanalysed wind speeds during a cyclone event are used to calculate N₂O fluxes from the Arabian Sea. It is found that net emission of N₂O from the Arabian Sea in a span of about 7 cyclonic days can contribute about 5.3% of its annual sources. This emission rate is about the same as that was observed (earlier estimates) during the south-west monsoon season in the Arabian Sea. The NIES/FRSGC global transport model is used to compute the tracer transport of monthly-mean high resolution fluxes to verify the significance of the Arabian Sea N₂O emission in comparison with 9 other source types of N₂O. The results show that the effect of N₂O flux from the Arabian Sea on its concentration at a coastal station is larger than some of the global scale anthropogenic sources. The transport model simulations suggest that some natural phenomena in the oceanic regions can even produce the fluctuations in the NvO time-series observed in the southern hemisphere. <br/> <br/>Page(s): 84-94 http://nopr.niscair.res.in/handle/123456789/1653 Title: Air-sea exchange of nitrous oxide and methane in the Arabian Sea: A simple model of the seasonal variability <br/> <br/>Authors: Bange, Hermann W. <br/> <br/>Abstract: With a simple box model the seasonal variability of N₂O and CH₄ were simulated in surface layers in the central and western Arabian Sea. The model was able to reproduce the N₂O measurements except for times when cold water filaments occur (i.e., during the SW monsoon). Based on the comparison of model results and measurements, it is concluded that the saturation of N₂O in the surface layer of the Arabian Sea is mainly controlled by (i) the wind-driven air-sea exchange during the SW monsoon, (ii) entrainment of N₂O from the subsurface layer, and (iii) sea surface temperature variability. However, the contribution of the factors listed above to the seasonality of the N₂O saturations is different in the selected areas. The overall good agreement of model results and the majority of N₂O measurements suggest that N₂O formation in the surface layer of the Arabian Sea is negligible. The comparison of model’s results and CH₄ measurements revealed a more complex situation, partly due to considerable inconsistencies in the available CH₄ data. Thus, the situation for CH₄ remains unresolved and inconclusive. <br/> <br/>Page(s): 77-83 http://nopr.niscair.res.in/handle/123456789/1652 Title: Atmospheric chemistry in the coastal ocean: A synopsis of processing, scavenging and inputs <br/> <br/>Authors: Church, T M; Jickells, T D <br/> <br/>Abstract: The coastal atmosphere provides a complicated chemical environment that can have global implications for climate. For example, the continents transport an array of gases and aerosols, both natural dusts and pollutant species, which can interact with sea-salt and affect coastal clouds and their processing for deposition. Once over the coastal ocean, different mixtures of acids, bases, minerals, sea-salt and water under different solar irradiation can induce a host of heterochemical chemical reactions. Deposition of the products of these reactions can make a significant contribution of nutrient inputs to coastal waters and impact coastal ecosystems. However, the steep gradients and complex physical and chemical processes occurring in this transitional area between terrestrial and marine atmospheric domains complicate the quantification of these inputs. This synopsis considers a group of key processes such as interaction of climatic aerosols that operate to regulate atmospheric scavenging and deposition to the coastal environment <br/> <br/>Page(s): 71-76