Characteristics Of The Near-ground Atmospheric Turbulence

From the astronomy site-testing point of view, this paper first explained in detail the origin of atmospheric turbulence and the optical propagation theory of in atmospheric turbulence. The descriptive parameter to the degradation of the astronomical image quality, seeing parameter, was discussed, as well as its survey techniques. It was then elaborated that the temperature difference between atmospheric and the ground medium was the main factor affecting the characteristic of the near-ground atmospheric turbulence.This paper stated the relationship between seeing parameter and exposure time in the image motion method measuring the seeing parameter, that is, the exposure time must be shorter than the atmospheric coherent time, otherwise the measured seeing parameter value would be artificially larger. An experimental method was designed to determine the exposure time of Video CCD, and it was demonstrated to be reliable.Experiments were conducted to investigate the influence of medium temperature difference to the near-ground atmospheric turbulence. As significant results, the relational curves were obtained to quantitatively provide the dependency of atmosphere water surfacetemperature difference at the Fuxian Lake site upon the near-ground horizontal seeing parameter and the near-ground refractive index structure parameter.