049.doc
Wind Speed and Significant Wave Height Distribution in the Western Indian
Ocean from Altimetry Data
Felix Jose*, Marine Sciences Division, Centre for Earth Science Studies,
Thiruvananthapuram –31, Kerala, India. email: felix-jose@lycos.com
Phone:+91-471-442451
Paul Samuel, Nansen Environmental and Remote Sensing Centre, Bergen-5059,
Norway. Phone : +47 55 29 72 88
Kurian N.P. Marine Sciences Division, Centre for Earth Science Studies,
Thiruvananthapuram –31, Kerala, India. email: npkurian@eth.net Phone:
+91-471-442451
Scanty availability of ocean wave data has been a severe limitation for coastal and
ocean engineering activities. Wave data collected over a long span of time will provide
a more reliable climatology for efficient off-shore operations, ship routing and design of
ships and marine structures with less uncertainties, normally associated with short term
observations. At present, for most of the practical applications, wave atlas compiled
from visual observations which has its own inherent limitations are being referred. The
collection of repetitive and high-density data by in situ measurements is not only a
difficult task, but extremely expensive also. Space-borne remote sensing techniques
have proven to be worthy partners of in situ collection methods. Since the wave
statistics derived from long-term data have more practical applications, in the present
study, altimeter data from ERS 2 and TOPEX/POSEIDON, for a period of 5 years, have
been used to generate monthly maps of average surface wind speed and significant
wave height (SWH) over the western Indian Ocean. While earlier researchers have used
a coarser grid of 2.5o lat/long, in the present work a finer grid of 1o is used. Validation
of the results with available measured data and ship observed data show good results.
The seasonal and spatial variability in the wind speed and SWH are also discussed in
the paper from the monthly distribution maps. The wind speeds are generally low
during the fair weather months of January, February and March. The average wind
speeds range up to 14.2 m/s during the peak south-west monsoon. The spatial and
temporal distribution of significant wave height (SWH) shows that the average values
range up to 3.9 m for the study area. The SWH is higher during the south-west monsoon
season. As in the case of wind speed distribution, the higher values are mainly confined
to the north-western region of the study area during the monsoon and south-western
region during the post-monsoon seasons. The satellite altimetry has proved to be a
viable and accurate alternative to the conventional oceanographic measurements.
Keywords: Significant wave height, Satellite Altimetry, monsoon,
Poster presentation in Oceanography
* Present Address: Dept. of Oceanography & Fisheries, University of Azores, PT-9901-862, Horta,
Azores, Portugal. Phone: +351 292 200400