A Statistical Interpolation Code for Ocean Analysis and Forecasting

Ashwanth Srinivasan, T. M. Chin, E. P. Chassignet, M. Iskandarani, N. Groves

Research output: Contribution to journalArticlepeer-review


We present a data assimilation package for use with ocean circulation models in analysis, forecasting, and system evaluation applications. The basic functionality of the package is centered on a multivariate linear statistical estimation for a given predicted/background ocean state, observations, and error statistics. Novel features of the package include support for multiple covariance models, and the solution of the least squares normal equations either using the covariance matrix or its inverse_the information matrix. The main focus of this paper, however, is on the solution of the analysis equations using the information matrix, which offers several advantages for solving large problems efficiently. Details of the parameterization of the inverse covariance using Markov random fields are provided and its relationship to finite-difference discretizations of diffusion equations are pointed out. The package can assimilate a variety of observation types from both remote sensing and in situ platforms. The performance of the data assimilation methodology implemented in the package is demonstrated with a yearlong global ocean hindcast with a 1/4° ocean model. The code is implemented in modern Fortran, supports distributed memory, shared memory, multicore architectures, and uses climate and forecasts compliant Network Common Data Form for input/output. The package is freely available with an open source license from www.tendral.com/tsis/.

Original languageEnglish (US)
Pages (from-to)367-386
Number of pages20
JournalJournal of Atmospheric and Oceanic Technology
Issue number3
StatePublished - Mar 2022
Externally publishedYes


  • Data assimilation
  • Hindcasts
  • Numerical weather prediction/ forecasting
  • Ocean circulation
  • Operational forecasting

ASJC Scopus subject areas

  • Ocean Engineering
  • Atmospheric Science


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