Comparison of Grid Averaged Altimeter and Buoy Significant Wave Heights in the Northern Indian Ocean

Abstract

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.

Keywords:

• Validation
• Northern Indian Ocean
• satellite altimeter
• significant wave height
• ocean buoys
• tropical cyclones

Acknowledgements

The authors thank the National Data Buoy Program of National Institute of Ocean Technology, the Chennai and Data Management Group of INCOIS for buoy data, and CNES for AVISO data. The authors gratefully acknowledge the financial support provided by the Earth System Science Organization, Ministry of Earth Sciences, Government of India to conduct this research. This is INCOIS contribution number 136.