Analysis of temperature and velocity fluctuations in the atmospheric boundary layer

Abstract

Measurements of high frequency temperature and velocity fluctuations were made in the atmospheric boundary layer. These data were analyzed using analog correlating techniques to obtain the structure function rather than spectral methods to obtain the spectral densities. The autocorrelation function of temperature fluctuations at 4 meters and 2 meters was computed as was the autocorrelation function of downstream velocity fluctuations at 4 meters. The cross-correlation function of temperature and downstream velocity fluctuations at 4 meters was also examined. These results supported the Kolmogorov ideas at high wave numbers. There is apparently very little correlation between downstream velocity fluctuations and temperature fluctuations. This indicates the independence of the two sensing systems and that temperature fluctuations are related primarily to vertical air movement rather than random fluctuations in the horizontal air flow. This aspect is further clarified by examining the temperature fluctuation records at two heights.