Atmospheric turbulence as a function of height above various surface materials

The atmospheric refractive-index structure parameter C 2 sub n was determined at heights 0.5 to 5 meters above open-field grass, blacktop, concrete, and aluminized-Mylar sheets attached to plywood. Measurements were made of the temperature structure parameter with twin fast-response, temperature-sensing probes made of 2-micrometer diameter platinum wire which were separated 10 cm and optimally excited at 10 microwatts. The RMS value of the temperature difference between the probes was determined with R. W. Harris double-AC bridge/log-meter system. Probe height was changed approximately every 30 minutes. The differential temperature and the meteorological parameters comprising air temperature, dew point, wind speed and direction, solar insolation and barometric pressure were sampled at 1-second intervals. Results indicate a height dependence of the form C 2 sub n = KH to the minus M, where K is a function of the surface (0.84 < or = K/10 to the minus 13th power m to the minus 2/3 power < or = 1.8) and M = - 1.2 + or - 0.5, with the wide variation in M due to changing meteorological conditions, most importantly solar insolation and wind speed. In this experiment, no significant differences in average value of C 2 sub n could be determined for the four surfaces. Additionally, the anticipated reduction in turbulence over aluminized Mylar was not observed.