The refractive index structure parameter, C2n, for a year over the frozen Beaufort Sea


  • Edgar L. Andreas


The Arctic Ice Dynamics Joint Experiment (AIDJEX) produced a year of continuous, 6-hourly observations of the surface fluxes of momentum and sensible and latent heat over the drifting ice of the Beaufort Sea. From this data set I compute the refractive index structure parameter C2n at four electromagnetic wavelengths—one each in the visible (0.55 μm), the mid-infrared (10.6 μm), the near-millimeter (0.337 mm or 890 GHz), and the radio regions. I present the resulting C2n values as histograms sorted according to the four seasons, spring, summer, autumn, and winter. Because each histogram derives from at least 300 C2n values, this is one of the largest studies of C2n climatology ever reported. For all four wavelengths the winter C2n histograms are the narrowest and have the highest peaks; the summer histograms are the broadest and most uniform. For the shorter wavelengths (0.55 and 10.6 μ) the mode value of C2n shows a seasonal progression; the maximum is in winter, the minimum in summer. The longer wavelengths (0.337 mm and radio) do not show a clear seasonal trend in the mode C2n value; although the C2n distributions change shape with season, the mode value is fairly constant. The beta distribution is a useful probabilistic model for the C2n histograms.