Z-LESS STRATIFICATION UNDER STABLE CONDITIONS

Turbulent fluctuations were measured at a height of 2.5 m in stable co nditions over grass to investigate the variability of the second- and third-order moments involving temperature, humidity and vertical wind velocity. With the exception of the normalized second moment of temper ature, very little variation of the normalized moments was found with changes in the dimensionless stability parameter zeta = z/L, where L i s the Obukhov stability length. Such limited variation is expected for stable conditions, and the normalized second moment of temperature mi ght have been affected by nonstationary conditions. In addition, the v ariability of the normalized moments was lessened by computing the tur bulence statistics over 56 min, instead of 26 min. Values of third-ord er moments involving the vertical velocity were all dose to zero.