Assuming nonlinear dynamics of baroclinic inertia-gravity ( BIG) waves to be dominated by resonant four-wave interactions, recent studies yielded simple analytical expressions for the energy spectra. The only parameter remaining unknown is a nondimensional constant of proportionality alpha, referred to as a "Kolmogorov constant'' in wave turbulence theory. The goals of the present study are 1) to validate the theoretical spectrum of the kinetic wave energy by comparing it with observed frequency spectra of horizontal velocities and 2) to obtain the first empirical estimate of alpha for this model.