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Doppler-velocity Spectra with Two Close Peaks

For the determination of regions in the F-layer where the double peaked Doppler velocity spectra occur, an automated selection process is used. The complete procedure can be outlined as follows.

These strict rules are applied to filter out noisy, marginal data as well as more complicated spectra. A comparison between these rules and a more relaxed set using a maximum peak separation of tex2html_wrap_inline5286 and a minimum velocity of only tex2html_wrap_inline5288 shows that they are sufficiently relaxed to identify double-peaked spectral regions, yet strict enough to avoid the misidentification of noisy ACFs. As mentioned before, the FFT-based methods are not used for regular analysis (exept for the comparisons) since they lack resolution and do not perform well on short data records. In the following figures (Figure 5.7 to Figure 5.15) both spectral estimation methods have been used on the same data in a search for double-peaked spectral features using the rules outlined above. One can see that the FFT-based methods produce many spurious finds, especially at the large ranges when backscatter intensities are low (16 Jan/95 and 26 Jan/95), or they do not find anything at all, due to the lack of resolution (18 Feb/95 and 25 Feb/95). There is good agreement between the methods when backscatter intensities and peak separations are high (6 Jan/95, 16 Jan/95 and 26 Jan/95).

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Figure 5.7: Comparison of maps of double-peak spectra derived from different methods: Jan 1/95

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Figure 5.8: Comparison of maps of double-peak spectra derived from different methods: Jan 6/95

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Figure 5.9: Comparison of maps of double-peak spectra derived from different methods: Jan 16/95

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Figure 5.10: Comparison of maps of double-peak spectra derived from different methods: 26 Jan/95

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Figure 5.11: Comparison of maps of double-peak spectra derived from different methods: 28 Jan/95

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Figure 5.12: Comparison of maps of double-peak spectra derived from different methods: 18 Feb/95

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Figure 5.13: Comparison of maps of double-peak spectra derived from different methods: 20 Feb/95

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Figure 5.14: Comparison of maps of double-peak spectra derived from different methods: 21 Feb/95

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Figure 5.15: Comparison of maps of double-peak spectra derived from different methods: 25 Feb/95


next up previous
Next: Morphology during a Complete Up: Experimental Results Previous: High-Resolution Autocorrelation Functions

Andreas Schiffler
Wed Oct 9 10:05:17 CST 1996