Comparative analysis of optical turbulence measurements, processing methods and their effects on Cn2 estimations in the maritime environment of Den Helder (NL)

Reliable measurements of optical turbulence are crucial for the validation of propagation models relevant for Free Space Optical Communication (FSOC) efficiency studies. In a series of laser propagation trials, the so-called Marsdiep trials, turbulence measurements are made with sonic anemometers and scintillometers. Two sonic anemometers were located at a grass surface at the waterfront in Den Helder (The Netherlands). In this work, we compare the two most commonly used methods to estimate the strength of optical turbulence C2n from sonic anemometers: Structure Function and Power Spectra. The Structure Function method consistently yields the higher C2n values and appears more sensible to weather conditions. Point measurements of C2n derived with these two methods are compared to path-averaged direct measurements of C2n by a scintillometer, operating over a 3.6km path mostly over water. Surface heterogeneities translate into differences in surface fluxes that explain the overall lower values of C2n provided by the scintillometer.