Optical turbulence path integration: methodology

Abstract

Presently the propagation models used to assess ABL performance employ an onionskin atmosphere. Onionskin atmospheres ignore the profound horizontal intermittency in Cn2 found in experiment. The problems associated with modeling optical turbulence over shallow slant paths using balloon and aerothermal point measurements are presented. We describe a method developed by the authors, which integrates the horizontal intermittency evident in the aerothermal data with the balloon profiles. This methodology takes randomly drawn segments of the aerothermal data to provide the intermittency along a smoothed balloon profile. An Independent and Identically Distributed (IID) process describes this methodology. To date all methods known by the authors utilize an IID process to account for intermittency. However, IID processes fail to fully appreciate the information contained in a continuous stream of aerothermal data. We present a methodology that utilizes time series analysis of horizontal aerothermal segments. The result of the time-series methodology is that the distribution of expected integrated turbulence levels is broader than those calculated previously. This suggests that in reality there will be a greater probability that a beam will experience sustained periods of extreme turbulence along the path, strong or weak, than would be predicted using an IID model.