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| q |
Bandwidth (Df)= width of the frequency band è resolution of spectrum
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Df = 1/N (cycle per unit time interval)
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For example, if a time series has 900 monthly-mean data:
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bandwidth = 1/900 (cycle
per month).
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Nyquist frequency = ½
(cycle per month)
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Total number of
frequency bands = (0-Nyquist frequency)/bandwidth
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=
(0.5)/(1/900) = 450 = N/2
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Each frequency band has
about 2 degree of freedom.
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If we average several bands together, we increase the
degrees of freedom
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but reduce the resolution (larger bandwidth).
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