Research Vessel Surface Meteorology Data Center


FSU/COAPS Objective Tropical Pacific Pseudostress Analyses
In-Situ :

A new objective technique has been created to produce monthly wind (pseudo-stress) products over the tropical Pacific Ocean. An overview of the new objective technique was presented at a recent AMS meeting. The fields are created through minimization of a cost function, which maximizes information from the observational data and minimizes smoothing. The objective technique treats various input data sources (volunteer observing ships and buoys) as independent. Weights related to each type of data and to penalty functions are objectively determined through cross validation. These weights are applied to constraints in the cost function. Three types of constraints are applied to each vector variable: misfits to each type of observation, a smoothing term, and a misfit of curl. The second and third terms are relative to a background field derived from the in situ data. The first two types of constraints are applied to scalar terms. The influence of the background field, relative to the observations, is controlled by the ratio of the weight for misfit to observations to the weights on the other constraints.

Fields of surface winds over the global oceans are necessary for a wide range of applications including ENSO forecasting and studies of ocean and atmospheric variability on a wide range of temporal and spatial scales. The objective method has significant advantages over the subjectively analyzed FSU winds for the Tropical Pacific Ocean. Comparisons plots between the new in-situ FSU winds and the old subjective FSU fields are available. In general, the new objective tropical Pacific fields have better defined convergence zones than the subjective product.

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