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    <title>DRS Collection: Physical Sciences</title>
    <link>http://drs.nio.org/drs/handle/2264/10</link>
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      <title>The impact of global warming on the tropical Pacific ocean and El Nino</title>
      <link>http://drs.nio.org/drs/handle/2264/3647</link>
      <description>Title: The impact of global warming on the tropical Pacific ocean and El Nino
&lt;br/&gt;
&lt;br/&gt;Authors: Collins, M.; An, S.; Cai, W.; Ganachaud, A.; Guilyardi, E.; Jin, F.F.; Jochum, M.; Lengaigne, M.; Power, S.; Timmermann, A.; Vecchi, G.; Wittenberg, A.
&lt;br/&gt;
&lt;br/&gt;Abstract: The El Nino-Southern Oscillation (ENSO) is a naturally occurring fluctuation that originates in the tropical Pacific region and affects ecosystems, agriculture, freshwater supplies, hurricanes and other severe weather events worldwide. Under the influence of global warming, the mean climate of the Pacific region will probably undergo significant changes. The tropical easterly trade winds are expected to weaken; surface ocean temperatures are expected to warm fastest near the equator and more slowly farther away; the equatorial thermocline that marks the transition between the wind-mixed upper ocean and deeper layers is expected to shoal; and the temperature gradients across the thermocline are expected to become steeper. Year-to-year ENSO variability is controlled by a delicate balance of amplifying and damping feedbacks, and one or more of the physical processes that are responsible for determining the characteristics of ENSO will probably be modified by climate change. Therefore, despite considerable progress in our understanding of the impact of climate change on many of the processes that contribute to El Nino variability, it is not yet possible to say whether ENSO activity will be enhanced or damped, or if the frequency of events will change</description>
      <pubDate>Thu, 29 Oct 2009 22:58:59 GMT</pubDate>
    </item>
    <item>
      <title>November 2009 tropical cyclone Phyan in the eastern Arabian Sea: Oceanic response along west India coast and Kavaratti lagoon</title>
      <link>http://drs.nio.org/drs/handle/2264/3634</link>
      <description>Title: November 2009 tropical cyclone Phyan in the eastern Arabian Sea: Oceanic response along west India coast and Kavaratti lagoon
&lt;br/&gt;
&lt;br/&gt;Authors: Joseph, A.; Desai, R.G.P.; Mehra, P.; VijayKumar, K.; Agarwadekar, Y.; Ryan, L.; Rivankar, P.; Viegas, B.
&lt;br/&gt;
&lt;br/&gt;Abstract: Spatial and temporal response of the coastal waters of eastern Arabian Sea (AS) and Kavaratti lagoon to the tropical cyclonic storm 'Phyan', which developed in the southeastern AS and swept northward along the eastern AS during 9-12 November 2009 and finally made landfall at the northwest coast of India, is examined based on time-series measurements of seasurface wind (U sub(10)), gust, gust factor, barometric pressure, precipitation, atmospheric temperature, SST, and significant wave height from satellite-derived and in-situ measurements. The maximum wind-speed (U sub(10)) of approx. 16 m/s occurred at Kavaratti Island region followed by approx. 8 m/s at Dwarka in Gujarat, where the cyclone landfall occurred, and approx. 7 m/s at Diu located just south of Dwarka as well as two southwest Indian coastal locations at Mangalore and Malpe. All other west India coastal locations recorded maximum wind speed of approx. 5-6 m/s. Gust factor during peak storm event was highly variable with respect to topography, with steep hilly stations and proximate thick and tall vegetation exhibiting the largest value whereas coastal planes and Island stations exhibiting the least. Rainfall in association with Phyan was temporally scattered, with the highest 24-h accumulated precipitation (approx. 60 mm) at Karwar and approx. 45 mm at several other locations. Impact of Phyan on the west India coastal waters was manifested in terms of intensified significant wave height (approx. 3 m at Karwar, Panaji, and Ratnagiri), sea surface cooling (approx. 5 degrees C at Calicut), and surge flooding (approx. 80 cm at Verem). Several factors such as (1) water piling up at the coast supported by seaward flow of the excess water in the rivers due to heavy rains and westerly cross-shore wind, (2) water piling down at the coast supported by the northerly alongshore wind (by virtue of Coriolis effect) and upstream penetration of seawater into the rivers, and (3) possible interaction of upstream flow with river runoff, together resulted in the observed surge flooding at the west India coast. Despite the intense wind forcing, Kavaratti Island lagoon experienced insignificantly weak surge (approx. 7 cm) because of lack of river influx and absence of a sufficiently large land boundary required for the sustenance of wave/wind-driven water mass which tends to pile up at the land-sea interface</description>
      <pubDate>Thu, 29 Oct 2009 22:58:59 GMT</pubDate>
    </item>
    <item>
      <title>Impact of internal waves on sound propagation off Bhimilipatnam, east coast of India</title>
      <link>http://drs.nio.org/drs/handle/2264/3632</link>
      <description>Title: Impact of internal waves on sound propagation off Bhimilipatnam, east coast of India
&lt;br/&gt;
&lt;br/&gt;Authors: Sridevi, B.; Murty, T.V.R.; Sadhuram, Y.; Rao, M.M.M.; Maneesha, K.; SujithKumar, S.; Prasanna, P.L.
&lt;br/&gt;
&lt;br/&gt;Abstract: Internal waves (IW) are identified off Bhimilipatnam, east coast of India, from the time series CTD (hourly interval)and thermistor chain data (2 min interval) collected during 23-25 Feb 2007.The measurements were carried out at 94m water depth on the continental shelf edge. These datasets are used to describe the characteristics of IW and their impact on acoustic fields. Garrett and Munk (GM) model has been used to predict the characteristics of low frequency (LF) IW with space and time. Active IW are seen in the layers54m-94 m with a velocity of 0.548 km h sup(-1) and the wavelengths of the order of 0.03 km-21.8km. The model could capture the IW features in the thermocline region accurately than at the bottom.This could be due to the limitation of the model which considers linearity. High frequency IW observed at the bottom could be due to the advection of tidal currents over the shallow irregular bottom in the presence of stratification. The study emphasizes linear IW rather than transient non-linear waves induced by tidal interaction with topography. Acoustic simulation results for low frequency IW field reveal that the intensity loss anomaly of eigenrays was found to be 2.86 dB-15.59 dB in the water column and maximum(38.48dB) was observed at the bottom due to the bottom interaction. Our results are well compared with those reported earlier from simulation and acoustic field experiments in the Northern IndianOcean.</description>
      <pubDate>Thu, 29 Oct 2009 22:58:59 GMT</pubDate>
    </item>
    <item>
      <title>Observed intra-seasonal to interannual variability of the upper ocean thermal structure in the southeastern Arabian Sea during 2002-2008</title>
      <link>http://drs.nio.org/drs/handle/2264/3631</link>
      <description>Title: Observed intra-seasonal to interannual variability of the upper ocean thermal structure in the southeastern Arabian Sea during 2002-2008
&lt;br/&gt;
&lt;br/&gt;Authors: Gopalakrishna, V.V.; Durand, F.; Nisha, K.; Lengaigne, M.; Boyer, T.P.; Costa, J.; Rao, R.R.; Ravichandran, M.; Amrithash, S.; John, L.; Girish, K.; Ravichandran, C.; Suneel, V.
&lt;br/&gt;
&lt;br/&gt;Abstract: The southeastern Arabian Sea (SEAS), located in the Indian Ocean warmpool, is a key-region of the regional climate system. It is suspected to play an important role in the dynamics of the Asian summer monsoon system. The present study reports the salient features derived from a newly harvested observational dataset consisting of repeated fortnightly XBT transects in the SEAS over the period 2002-2008. The fortnightly resolution of such a multi-year record duration is unprecedented in this part of the world ocean and provides a unique opportunity to examine the observed variability of the near-surface thermal structure over a wide spectrum, from intra-seasonal to interannual timescales. It found that most of the variability is trapped in the thermocline, taking the form of upwelling and downwelling motions of the thermal stratification. The seasonal variations are consistent with past studies and confirm the role of the monsoonal wind forcing through linear baroclinic waves (coastally-trapped Kelvin and planetary Rossby waves). Sub-seasonal variability takes the form of anomalous events lasting a few weeks to a few months and occurs at two preferred timescales: in the 30-110 day band, within the frequency domain of the Madden-Julian oscillation and in the120-180 day band. While this sub-seasonal variability appears fairly barotropic in the offshore region, the sign of the anomaly in the upper thermocline is opposite to that in its lower part on many occasions along the coast. Our dataset also reveals relatively large interannual temperature variations of about 1 degrees C from 50 to 200 m depth that reflect a considerable year-to-year variability of the magnitude of both upwelling and downwelling events. This study clearly demonstrates the necessity for sustained long-term temperature measurements in the SEAS</description>
      <pubDate>Thu, 29 Oct 2009 22:58:59 GMT</pubDate>
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