Seasonal Behaviour of Mesoscale Eddy Trajectories in the North Indian Ocean Based on Satellite Altimetry ()
ABSTRACT
In the north Indian Ocean (NIO), maps of sea level anomaly from satellite
altimetry were analysed from January-1995 to December-2000. The study attempted
to trace the trajectories of the individual mesoscale anomalies manually and to
understand seasonal changes in terms of phase speed. Mesoscale anomalies are
detected as concentric circular shapes and diameters of ~90 km to 600 km and
the minimum 30 days life cycle. Relatively higher eddy kinetic energy was
noticed in the northwestern region of the NIO. Individual mesoscale anomalies,
namely positive (warm, anticyclonic eddies) and negative (cold, cyclonic
eddies) showing travelling direction westward in the NIO basins. In autumn, the
number of negative anomalies detected is more than positive anomalies and vice
versa during summer. The westward propagating positive (negative) anomalies in
the Arabian Sea start appearing in winter (spring) along (away from) the west
coast of India and west of 65°E; individual anomalies move to the west in
spring/summer/autumn and collide along Somalia’s & Arabian coast. A group
of positive (negative) anomalies trajectories appears as a tail at the southern
tip of India are located west of the Laccadive ridge in winter (summer to
autumn) associated with LH (LL). The Bay of Bengal (BB) trajectories show
southwestward in northern BB, westward in central BB and northwestward in
southern BB; individual anomalies are appearing along the west coast of Andaman
& Nicobar ridge. The zonal phase speed decreases away from the equator, and
the magnitude varies longitudinally in each season in the form of a wave-like
pattern propagating westward from autumn to summer; the life cycle of the wave
is almost 365 days (a year). The theoretical phase speed of the first mode of
the baroclinic Rossby waves is quite similar to that of averaged zonal speed.
Therefore mesoscale anomalies (eddies) are embedded into the large waves like
phenomenon (Rossby waves), responsible for creating high variability and EKE in
the region of NIO along the western boundaries.
Share and Cite:
Pednekar, S. (2022) Seasonal Behaviour of Mesoscale Eddy Trajectories in the North Indian Ocean Based on Satellite Altimetry.
International Journal of Geosciences,
13, 93-114. doi:
10.4236/ijg.2022.132006.