Balchand, A N; Jossia, Joseph K; Hareeshkumar, P V; Rajesh,G(Current Science, March , 2007)
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Abstract:
Time-series measurements from a moored data buoy
located in the Bay of Bengal captured signals of inertial
oscillation forced by the September 1997 cyclone. The
progressive vector diagram showed mean northeastward
current with well-defined clockwise circulation.
Spectral analysis exhibited inertial peak at 0.67 cpd
with blue shift and high rotary coefficient of –0.99, which
signifies strong circular inertial oscillation. The wind
and SST also exhibited spectral peak at inertial band
(0.69 cpd) with higher blue shift. The inertial amplitude
of 148.8 cm/s corresponding to a wind stress of 0.99 N/m2
and spectral peak near the local inertial frequency
(0.653 cpd) indicate that the transfer of momentum
was high.
Balchand, A N; Chiranjivi Jayaram; Chacko, Neethu; Ajith,Joseph K(Ocean Science Journal, March 23, 2010)
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Abstract:
Increase in sea surface temperature with global
warming has an impact on coastal upwelling. Past two decades
(1988 to 2007) of satellite observed sea surface temperatures
and space borne scatterometer measured winds have provided
an insight into the dynamics of coastal upwelling in the
southeastern Arabian Sea, in the global warming scenario.
These high resolution data products have shown inconsistent
variability with a rapid rise in sea surface temperature between
1992 and 1998 and again from 2004 to 2007. The upwelling
indices derived from both sea surface temperature and wind have
shown that there is an increase in the intensity of upwelling
during the period 1998 to 2004 than the previous decade. These
indices have been modulated by the extreme climatic events
like El–Nino and Indian Ocean Dipole that happened during
1991–92 and 1997–98. A considerable drop in the intensity of
upwelling was observed concurrent with these events. Apart
from the impact of global warming on the upwelling, the
present study also provides an insight into spatial variability of
upwelling along the coast. Noticeable fact is that the intensity of
offshore Ekman transport off 8oN during the winter monsoon is
as high as that during the usual upwelling season in summer
monsoon. A drop in the meridional wind speed during the years
2005, 2006 and 2007 has resulted in extreme decrease in
upwelling though the zonal wind and the total wind magnitude
are a notch higher than the previous years. This decrease in
upwelling strength has resulted in reduced productivity too.
