Predicting optical turbulence in the free atmosphere by means of a general circulation model

Turbulent fluctuations of the optical refractive index (“optical turbulence”) affect the propagation of light through the atmosphere and, therefore, the performance of a wide variety of ground-based, airborne, and space-based optical systems. The key characteristic of optical turbulence is the refractive-index structure parameter, C²_n, and reliable models of C²_n in the atmosphere are needed to reliably assess and predict the performance of those systems. Here we explore and discuss the usefulness of a general circulation model (GCM) for the prediction of C²_n in the free atmosphere. The GCM employs a T256 grid, such that the shortest resolved wavelength is 156km. The vertical grid spacing is about 500m. We present and discuss mean values and the large-scale variability of C²_n and other turbulence characteristics predicted with the GCM, and we compare the GCM-predicted vertical C²_n profiles with the empirical Hufnagel-Valley model.