WMOD00400

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

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The crux of the problem in applying Taylor's theory is, therefore, to

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determine the Lagrangian autocorrelation function. The Eulerian autocorrela-

tion function, R~, is rather more easily determined using instrumented towers
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and instrumented aircraft flying through "frozen turbulence fields".

Eulerian autocorrelation data have been shown to fit a decaying exponen-

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tial function both in the atmosphere and in wind tunnels (Comte-Bellot and

Corrisin, 1971). That is:

RE (T) ~ e-T/TE
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(3.4)

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where TE is the Eulerian characteristic time.

In the particular experiment, the characteristic time of the turbulence

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as observed by the NCAR aircraft (TA) was determined in a manner to be

described later. The relation between TE and TA is:

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GS
TE := TA lV'S

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(3.5)

where GS is ground speed of the aircraft and WS is the wind speed.

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By assuming similarity as suggested by Hay and pasquill (1959), we can

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write:

R~ (T)
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e-T/TL ~ e-T/STE ~ e-T WS/STA GS

(3.6)

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Fig. 3.6 is schematic of the three autocorrelation functions presented in

Equation 3.4, 3.5 and 3.6.

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