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A prototype strong-constraint incremental four-dimensional variational (4DVAR) assimilation system is now available from the NASA/Global Modeling and Assimilation Office. Preliminary work is experimenting with both a 6- and a 12-hour assimilation time window configuration. Already, results show the benefit of using the larger 12-hour window over the 6-hour window, since the former embraces more observations than the latter. Extending the time window beyond 12 hours will require a weak-constrain formulation of 4DVAR. The challenge that researchers face in weak-constraint 4DVAR is to know how much to trust the forecast model. In mathematical terms, the problem is one of specifying the model error statistics related to our confidence in the model. This proposal is dedicated to exploring methodologies to estimate and parameterize the statistics of model uncertainties. The main goal of this proposal is to allow enlargment of the assimilation time window used in 4DVAR by provinding it with the necessary model error statistics. This will maximize the utility of observations in data assimilation. Ultimately, enlarging the assimilation time window is expected to bring improvements to weather and climate predictions, one of the main NASA goals. An additional contribution this proposal hopes to make to the overall interests of the organization is to foster improvements in the atmospheric forecasting model through the weak-constraint 4DVAR capability to estimate model errors. This can help modelers determine and improve upon deficiencies in the predictive model.

Project PI: Ricardo Todling/NASA Goddard Space Flight Center

NASA/GSFC, Code 910.3, Greenbelt, MD 20771



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Started: Aug 10, 2010

Last Activity: Mar 17, 2011


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