Performance of the ocean state forecast system at Indian National Centre for Ocean Information Services

The reliability of the operational Ocean State Forecast system at the Indian National Centre for Ocean Information Services (INCOIS) during tropical cyclones that affect the coastline of India is described in this article. The performance of this system during cyclone Thane that severely affected the southeast coast of India during the last week of December 2011 is reported here. Spec-tral wave model is used for forecasting the wave fields generated by the tropical cyclone and vali-dation of the same is done using real-time automated observation systems. The validation results indicate that the forecasted wave parameters agree well with the measurements. The feedback from the user community indicates that the forecast was reliable and highly useful. Alerts based on this operational ocean state forecast system are thus useful for protecting the property and lives of the coastal communities along the coastline of India. INCOIS is extending this service for the benefit of the other countries along the Indian Ocean rim

Contribution of Southern Indian Ocean swells on the wave heights in the Northern Indian Ocean - A modeling study

Waves are important driving forces that have important ramifications for physics, chemistry and biology of the coastal and open ocean. An attempt is made to study the swell propagation from Southern Indian Ocean and to account for its contribution to the local wave climate in Northern Indian Ocean. The third generation ocean wave model, MIKE 21 SW is implemented and validated to simulate wave heights for the period starting from September 2008 to August 2009 for the Indian seas. Simulations were carried out by modifying the analyzed winds over the model domain (30°E120°E and 60°S30°N). It was found that Southern Indian Ocean swells play an important role in determining the Northern Indian Ocean wave climate. Under the influence of the southwest summer monsoon winds, the swell dominance on the local wave climate drops in the Bay of Bengal but not as much as in the Arabian Sea due to the strong and persistent southwest winds during the summer monsoon. During the rest of the year, the swell is a dominant factor in determining the wave climate of the Northern Indian Ocean

Comparison of grid averaged altimeter and buoy significant wave heights in the Northern Indian Ocean

A quantitative comparison of the collocated inter-annual significant wave height (SWH) data collected between 2006 and 2009 from buoys and altimeters at nine buoy locations (total n = 2241) in the Northern Indian Ocean is attempted for assessing the validity of daily averaged gridded altimeter significant wave height (ASWH) provided by AVISO for operational use. ASWH is underestimated by 0.20 m, the root-mean-square error (RMSE) is less than 0.30 m, the Scatter Index is less than 20%, and the correlation coefficient is greater than 0.90. Further, at three locations, the examination of the above statistics showed that the bias and RMSE is high during the southwest monsoon season compared with the Northeast monsoon. Scatter Index showed only slight variation (14–18%) for different ranges of SWH. The response of the daily average gridded ASWH data during extreme conditions (cyclones) in the vicinity of the buoy locations is poor at all compared buoy locations. The gridded ASWH from different satellite missions provided by AVISO can be used for basin scale validation experiments of the wave model and for climatological studies in the Indian Ocean, except during cyclone conditions

Wave forecasting system for operational use and its validation at coastal Puducherry, east coast of India

An incredible demand for coastal sea-state forecast in recent years has led to development and implementation of wave forecasting system in operational centers, having wide practical applications relevant to marine industry. The wave forecasting system takes advantage of parametric techniques, by nesting global ocean wave models to coastal and near-shore high-resolution wave models. The Indian National Centre for Ocean Information Services (INCOIS) at Hyderabad has a mandate for operational marine weather forecast services that envisages integration and coupling state-of-the-art weather models for operational oceanographic needs. In the present study, two state-of-art wave models viz; WAVEWATCH III (WW3) and Simulating WAves Nearshore (SWAN) are nested and forced with French Research Institute for Exploitation of the Sea/Laboratory of Oceanography From Space (IFREMER/CERSAT) blended surface winds. The objective is to investigate wave evolution at a coastal location off Puducherry in the east coast of India. To evaluate model performance, a detailed validation study is performed by comparing model-simulated wave parameters and wave spectra with corresponding in-situ wave rider buoy observations for four prominent seasons viz; northeast monsoon, southwest monsoon, pre- and post-monsoon. The study signifies applicability of nested wave model for operational use during normal weather condition at coastal Puducherry