Influence of winds on temporally varying short and long period gravity waves in the near shore regions of the eastern Arabian Sea
J. Glejin1, V. Sanil Kumar1, T. M. Balakrishnan Nair2, and J. Singh1 J. Glejin et al. J. Glejin1, V. Sanil Kumar1, T. M. Balakrishnan Nair2, and J. Singh1
1Ocean Engineering, CSIR-National Institute of Oceanography (Council of Scientific & Industrial Research), Dona Paula, Goa 403 004 India
2Indian National Centre for Ocean Information System (Ministry of Earth Sciences), "Ocean Valley", Pragathi Nagar (BO), Nizampet (SO), Hyderabad 500 090 India
Received: 24 Jul 2012 – Discussion started: 25 Sep 2012 – Revised: 24 Feb 2013 – Accepted: 06 Mar 2013 – Published: 20 Mar 2013
Abstract. Wave data collected off Ratnagiri, west coast of India, during 1 May 2010 to 30 April 2012 are used in this study. Seasonal and annual variations in wave data controlled by the local wind system such as sea breeze and land breeze, and remote wind generated long period waves are also studied. The role of sea breeze on the sea state during pre- and postmonsoon seasons is studied and it is found that the maximum wave height is observed at 15:00 UTC during the premonsoon season, with an estimated difference in time lag of 1–2 h in maximum wave height between premonsoon and postmonsoon seasons. Observed waves are classified in to (i) short waves (Tp < 8 s), (ii) intermediate waves (8 < Tp < 13 s), and (iii) long waves (Tp> 13 s) based on peak period (Tp) and the percentages of occurrence of each category are estimated. Long period waves are observed mainly during the pre- and the postmonsoon seasons. During the southwest monsoon period, the waves with period > 13 s are a minimum. An event during 2011 is identified as swells propagated from the Southern Ocean with an estimated travelling time of 5–6 days. The swells reaching the Arabian Sea from the south Indian Ocean and Southern Ocean, due to storms during the pre- and postmonsoon periods, modify the near surface winds due to higher phase wave celerity than the wind speed. Estimation of inverse wave age using large-scale winds such as NCEP (National Centers for Environmental Prediction) reflects the presence of cyclonic activity during pre- and postmonsoon seasons but not the effect of the local sea breeze/land breeze wind system.
How to cite: Glejin, J., Sanil Kumar, V., Balakrishnan Nair, T. M., and Singh, J.: Influence of winds on temporally varying short and long period gravity waves in the near shore regions of the eastern Arabian Sea, Ocean Sci., 9, 343–353, https://doi.org/10.5194/os-9-343-2013, 2013.