Abstract
Determining an oceanographic parameter on regular grid positions, using a set of data at random locations both in space and time, is the most sought after typical problem since long in the field of oceanography. This is usually called the gridding problem, and the outcome is useful for many applications such as data analysis, graphical display, forcing or initialization of models, etc. In the present study temperature and salinity profiles data obtained from Argo profiling floats were used, and data on regular grids were generated. Data-interpolating variational analysis (DIVA) method was chosen for generating the gridded product. Extensive analysis was done to obtain correct choices of correlation length (L) and signal-to-noise ratio (λ), which results in an optimal gridded product. The gridded data obtained for different choices of L and λ were later validated with datasets deliberately set aside before performing the analyses. For each combination of L and λ, the resultant gridded data was also validated with subsurface data from OMNI buoys. Based on the statistics of comparison with OMNI, the best-fit choice for L and λ was concluded. Later, a comparative analysis was performed with the obtained gridded products from DIVA against the gridded product obtained from objective analysis (OA) to demonstrate the method's reliability. The resultant optimal combination of L and λ will be used for generating Argo gridded data, which will be subsequently used for generating value-added products like mixed layer depth, ocean heat content, D20, etc., and will be made available on INCOIS Live Access Server.
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Acknowledgements
The authors are grateful to the Director, Indian National Centre for Ocean Information Services (INCOIS), Hyderabad for his constant encouragement and providing the facilities to carry out the work. We also encourage the efforts of the scientific team of Argo data collection and distribution. The authors express gratitude for the DIVA software developer at GHER, ULiège, Belgium (modb.oce.ulg.ac.be/mediawiki/index.php/DIVA). We wish to acknowledge the use of the Ferret program, a product of NOAA’s Pacific Marine Environmental Laboratory, for analysis and graphics in this paper. We thank the anonymous reviewers for their constructive remarks in improving the manuscript. This is INCOIS contribution number 424.
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Ravi Kumar Jha has performed all the analysis, picture generations, and prepared the original manuscript. T V S Udaya Bhaskar established the methods configuration, reviewed and edited the original manuscript.
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Communicated by C Gnanaseelan
Supplementary material pertaining to this article is available on the Journal of Earth System Science website (http://www.ias.ac.in/Journals/Journal_of_Earth_System_Science).
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Jha, R.K., Udaya Bhaskar, T.V.S. Optimal parameters for generation of gridded product of Argo temperature and salinity using DIVA. J Earth Syst Sci 130, 170 (2021). https://doi.org/10.1007/s12040-021-01675-2
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DOI: https://doi.org/10.1007/s12040-021-01675-2