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 turbulence \oJ3S termed homogeneous if the traces of u. appear
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reasonably similar along thE! flight path. It is preferable to fly

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either orthogonal or parallel.to the mean wind direction when possible.

2. Compute the covariance of u. ,2 and power spectrum distribution for
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each component of the winds, i.e., longitudinal, lateral and vertical.

3. Fit a -2 power law line to that segment of the power spectrum distri-

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but ion where appropriate so one can determine TL using Equation 3.4 and 3.8.

4. Compute the diffusion using Equation 3.10 and adjust for low values

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of t using Table 3.3 or Equation 3.9.

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2. Results of turbulent diffusion calculations

The NCAR Queen Air Has f1mvn over and up~.;rind of the San Juan Hountains

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to obtain transport and diffusion data on four days in Harch 1975. The dates

\o7ere rIarch 10, 14, 15 and 17. It ~'laS February 1975 when the air sensing

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("gust") probe ~vas first installl~d on the aircraft. The data for 10 and 14

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}Iarch Here taken in prestorm situations Hhi1e the data on 17 Harch were taken

during the dissipation stage of a storm. The data for 15 Harch were taken at

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the end of a storm ~oJith cold air advection, subsidence and nortll\oJest to

north ~vinds indicated at all levels. The results for 15 Harch will therefore

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not be presented. The data from 17 March were of some additional interest be-

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cause the Hyoming Queen Air was also flo~m over the San Juans on this day,

thus allm.;ring an opportunity to compare the results from the HRI Universal

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Turbulence Indicator Systeui on the Hyoming Queen Air with the NCAR system.

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The flight tracks \.;rere partitioned into several flight segments of < 15

minutes in length.

The covariance of the u.' perturbation quantities or
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turbulent intensities Cp u.u.) were calculated. TIle autocorrelation
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characteristic times of W for the aircraft (TA), Eulerian (TE) and Lagrangian

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(TL) coordinate systems Here ah;o calculated. The cube root of the eddy

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