Sasaki’s Pathway to Deterministic Data Assimilation

  • John M. Lewis


Yoshikazu Sasaki developed the variational method of data assimilation, a cornerstone of modern-day analysis and prediction in meteorology. The generation of this idea is tracked by analyzing his education at the University of Tokyo in the immediate post-WWII period. Despite austere circumstances—including limited financial support for education, poor living conditions, and a lack of educational resources—Sasaki was highly motivated and overcame these obstacles on his path to developing this innovative method of weather map analysis. We follow the stages of his intellectual development where information comes from access to his early publications, oral histories, letters of reminiscence, and biographical data from the University of Tokyo and the University of Oklahoma. Based on this information, key steps in the development of his idea were: (1) a passion for science in his youth, (2) an intellectually stimulating undergraduate education in physics, mathematics, and geophysics, (3) a fascination with the theory of variational mechanics, and (4) a “bridge to America” and the exciting new developments in numerical weather prediction (NWP).

A comparison is made between Sasaki’s method and Optimal Interpolation (OI), a contemporary data assimilation strategy based on the work of Eliassen and Gandin. Finally, a biographical sketch of Sasaki including his scientific genealogy is found in the Appendix.


Data Assimilation Numerical Weather Prediction Optimal Interpolation Squall Line Track Forecast 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.


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© Springer-Verlag Berlin Heidelberg 2009

Authors and Affiliations

  • John M. Lewis
    • 1
  1. 1.National Severe Storms Laboratory and Desert Research Institute 2215 Raggio PrkyRenoUSA

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