Improved electromagnetic bias theory

In this paper we describe modifications to a previous theory for the altimeter electromagnetic bias (EM bias) of Srokosz [1986]. A major correction introduces a scaling of Srokosz's model by nonnegligible dimensionless ratios that depend on the slope variance of both long and short waves. With these modifications the EM bias is no longer simply a function of the cross skewness between surface elevation and slope but now depends on the variance ratios that represent the modulation between short and long waves, Inclusion of these ratios can reduce previous EM bias estimates by as much as 50%. Different directions for the longwave and shortwave field are also accounted for in the two-dimensional development of our approach. A radar frequency dependence consistent with observation is also predicted by the new model. Derivation extending our development to the next higher order in wave statistics is also presented and discussed.