Cooperative Institute for Research in Environmental Sciences

Research Applications
Turbulence Statistical Variability

Long periods of stationary data can also be used to study the statistical variability of small-scale turbulence required to understand turbulence theory.

Computations of the probability density functions (PDFs) of C_T² and ε are made from 0.25 s estimates of C_T² and ε. The computed PDF of C_T² shown below, exhibits a lognormal distribution and agrees well with the predicted theoretical distribution based on the estimates of the mean and variance. The lognormal distributions of C_T² and ε (not shown) agree with previous surface layer measurements. These results are believed to be the first reported for the shear region of a nocturnal jet.

Click on image for larger version.

Click on image for larger version.

Note: The small amplitude altitude variations of the package have a negligible effect on the results as Taylor’s frozen hypothesis is valid for this 30 minutes-long time interval ( ). The estimation error for each measurement is less than 15% and the variability in ε and C_T² is from true atmospheric turbulence fluctuations.

For further details see the related publication:

2004 - Frehlich R, Meillier Y, Jensen ML, et al.: "A statistical description of small-scale turbulence in the low-level nocturnal jet". Journal of the Atmospheric Sciences 61 (9): 1079-1085 May 2004.