A CIRCULAR MEDIAN FILTER APPROACH FOR RESOLVING DIRECTIONAL AMBIGUITIES IN WIND FIELDS RETRIEVED FROM SPACEBORNE SCATTEROMETER DATA

A common problem associated with spaceborne scatterometry, is that retrieval algorithms often compute multiple wind vectors per retrieval cell. Only one wind vector per retrieval cell corresponds to the true solution while the others are aliases that arise from symmetries in the response of small scale surface waves to wind forcing. Based on the mathematical properties of the likelihood assigment errors, an ambiguity removal algorithm is derived that utilizes a nonlinear circular median filter (CMF) to select the true solution in each retrieval cell. The CMF algorithm was tested by analyzing 12 simulated wind fields with an average likelihood assignment error rate of 389 per 1000 retrievals. After processing by the CMF algorithm, the error rate was significantly reduced to an average of only 36 per 1000. -from Author