Data Evaluation for a Newly Developed Slack-Line Mooring Buoy Deployed in the Eastern Indian Ocean

Abstract

For the purpose of climate research and forecasting the Research Moored Array for African?Asian?Australian Monsoon Analysis and Prediction (RAMA) in the Indian Ocean has been planned. Development of RAMA has been gradually accelerated in recent years as a multinational effort. To promote RAMA the authors have developed a small size buoy system, which uses the slack-line mooring method, intended for the easy handling of maintenance on a relatively small vessel. The authors have also conducted a field experiment of the simultaneous deployment of new slack-line mooring and conventional taut-line mooring in the eastern Indian Ocean. This paper describes the performance of the newly developed buoy system, especially the data consistency against the taut-line mooring system, which is usually used for a tropical moored buoy array. Although the slack-line mooring method has the advantage of downsizing the total mooring system, it also has the disadvantage of having relatively large vertical shifts of installed sensors produced by a large migration of the surface buoy. To offset this disadvantage to a certain extent, a data reconstruction method has been developed and evaluated. Through the data comparison between both mooring systems, it is confirmed that the reconstructed data of the newly developed buoy can basically capture the same features as that observed with a conventional taut-line mooring system. The maximum mean difference of ?0.16°C and the maximum root-mean-square (RMS) difference of 0.58°C for temperature appeared within the thermocline layer, whereas the maximum mean difference of 0.02 and the maximum RMS difference of 0.09 for salinity appeared within the mixed layer. Considering a distance of 8 n mi between the two moorings, these values are acceptable for regarding that the two moorings can observe same feature. Results of this study support the introduction of various types of mooring systems for a multinational approach of RAMA and contribute to the further progress of RAMA, climate research, and forecasting.