WMOD00400

• Contract/Permit #: 14-06-D-6801
• Title: Structure and Seedability of San Juan Storms
• Date: 11/1/1976
• Weather Modification - Doc Type: Report

49

dissipation rates in the longitudinal (c 1/3).
x
1/3
(E ) components were calculated from the power spectrum of each flight
z

1/3
lateral (c ). and vertical
y

segment.

The largest value of the turbulent intensities was either p u'u' or

p v'v' depending whether the flight path was parallel or orthogonal to the

wind direction. The smallest turbulent intensity \vas 'always p u 'v ' .

The pmver spectra of U, V and W were calculated for each flight segment

(u. V and Ware the longitudinal, lateral and vertical winds with respect to

the aircraft). In that portion of the spectrum where the -5/3 power law

best fits the data a line was drawn. The -5/3 line corresponds to a par-

ticular value of

1/3
E. .
1

It was noted that E 1/3 < E 1/3 and E 1/3, for all
z x y

four flights and at every level. Other researchers have noted that the

vertical diffusion is less than or equal to the horizontal diffusion unless

convection is pronounced.

For each of the power spectra of W, a -2 po,ver law was fitted to that por-

tion of the spectra where it was appropriate. From Equations 3.6 and 3.8, the

values of TA, TE and TL were calculated for each -2 power spectra. In some

cases the -5/3 power law fits the spectra best while in other cases the -2

power law fits best. No general pattern was evident and in most cases either

power law fits the data equally well.

,2
Substituting the values of TL and w from each flight segment into

Equation 3.10, it was straightfonvard to calculate the standard deviation

in the vertical as a function of time [o3(t)]. The values of o3(t) vs. t

were calculated for each of the flight segments obtained upwind of the moun-

tain. The general functional relationship for each of tIle altitudes for the

10 March case are plotted in Fig. 3.7. The vertical diffusion was greatest

near the ground and decreased by 1/2 to 1/3 above Lt. 6 km (15 kft). From the

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