Seasonal Changes in Atmospheric Optical Turbulence in a Near Maritime Environment Using Turbulence Flux Measurements

Abstract

Light propagation through the atmosphere is affected by fluctuations in the refractive index along the path of propagation, called optical turbulence. In the atmospheric surface layer, these fluctuations are due mostly to turbulent mixing of variations in temperature. To this end, a characterization of the atmospheric surface layer above the water in Maryland, USA, is presented. Meteorological data were collected from a sensor array comprising two sonic anemometers and an infrared gas analyzer (IRGASON) over the 12-month period from January to December, 2021. The instruments were positioned vertically at heights of approximately 4 m, 6 m, and 8 m above the water. The temperature structure parameter CT2 was calculated and scaled using Monin–Obukhov assumptions. We find that the distribution of atmospheric stability presents as an approximately normal distribution during the winter and early spring, but is skewed negatively during the summer and late fall. We hypothesize that this could be due to a more stable stratification of the underlying water during summer months. Under unstable (−z/L) conditions, turbulent quantities including the temperature structure parameter scale in a manner consistent with the literature, but with generally better agreement during the summer months. Additionally, the CT2 estimations appear more consistent during the summer months across all values of (z/L). Under stable (+z/L) conditions, there are wide variations in CT2, which is also consistent with the literature.