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Calculating Time-Averaged Wind Profiles

The most effective way to calculate time-averaged wind estimates is to average the cross correlation functions over a time period. This provides a less noisy correlation function to the wind calculation, since random correlations vanish in the averaging process. Even a weak aerosol correlation peak dominates the cross correlation function after an appropriate averaging time. Figure 27 compares the results of two averaging methods. The first method averages subsequent correlation functions to produce a consistent wind profile. The second method averages the wind estimates calculated from shorter time-average cross correlation functions. Some estimates from the second method have large fluctuations between adjacent points due to spurious results which were averaged with more accurate results. All results presented in this study are generated by averaging correlation functions.

Figure 27: Wind profiles after different averaging methods on August 9, 1989, from 10:30 to 10:45 CDT. The solid line with solid circles is a wind profile calculated from the average of five subsequent cross correlation functions. The dashed line with open circles is a wind profile calculated by averaging five wind profiles estimated from individual subsequent cross correlation functions. The vertical dashed line at 500 m marks the convective boundary layer mean depth.

Antti Piironen
Tue Mar 26 20:53:05 CST 1996