Inversion residual. The multiplet of backscatter data is inverted to three parameters: wind speed, wind direction and MLE. Therefore, the MLE measures the difference of the measured backscatter multiplet and the multiplet given by the solution wind speed and direction in the given satellite geometry of the WVC, according to the GMF. Hence, the MLE is a measure of the inconsistency of the measured backscatter multiplet with the GMF.