What is atmospheric turbulence?

Atmospheric turbulence is described by the formula Cn2 The refractive index structure function, Cn2, is a parameter which describes the magnitude of the turbulence effects in the atmosphere for the optical range. Most studies refer to this as an effect of turbulent air motion and fluctuations where the source of energy for this motion are the gradients or changes in heating and cooling of the atmosphere and Earth surface caused mostly for sunlight and diurnal cycle. The physical meaning of the refractive index structure constant Cn2 is a measurement of the strength of the fluctuations in the refractive index in the atmosphere.

The effect of atmospheric turbulence over optical wave propagation has been an area of study over the past twenty years. Most of the effort in this area has been focused on a vertical propagation path system for astronomical imaging and observations. However, during the past few years, the study of horizontal laser beam propagation has increased due its applications on new laser communications technology and low altitude astronomical observations. Understanding and characterizing the effects of optical propagation through the atmosphere is a highly important step for the efficient implementation of free space laser communications. Our work has focused on the following topics:

  • Take measurements of the Cn2 in the weak turbulence sector.
  • Find a valid method to analyze possible contributions of local weather parameters to Cn2.
  • Identify and study the relationship between local climate and the refractive index structure constant, Cn2, and characterize the effects of atmospheric turbulence on optical beams propagating horizontally through the atmosphere. Data we collect includes:
    • Relative humidity
    • Temperature
    • Solar radiation
    • Wind speed and direction
    • Pressure