Turbulent
eddy dissipation rate is estimated using an algorithm developed by Sand (Sand et al. 1976), based on earlier work
described in MacCready (1962). The
approach is based on the spectral properties of homogeneous turbulence in the
inertial subrange.
Basically a Fast-Fourier transform of the high-resolution true air speed
record is fit to the spectral form expected for homogeneous transport and the
result used to infer the eddy dissipation rate.
Figure
1: Flight 803, June 1, 2003.
Pilot-observed
short-term airspeed fluctuations also can be qualitatively correlated with turbulence
characteristics. Sand (1976) gives an empirical correlation between airspeed
fluctuations on few-seconds time scale and pilot-reported turbulence intensity
in aircraft of the weight and speed class of the T-28: Light 2.5 – 7.5 m s-1; Moderate 7.5
– 12.5 m s-1; and Severe > 12.5 m s-1.