Effect of finite sampling on atmospheric spectra |
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| Authors: | J C Kaimal S F Clifford R J Lataitis |
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| Institution: | (1) Wave Propagation Laboratory/NOAA/ERL, 325 Broadway, 80303 Boulder, Colorado, USA |
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| Abstract: | The effect of a finite averaging time on variances is well known, but its effect on power spectra is less clearly understood. We present numerical solutions for the spectral distortion arising from sampling over a finite time interval T and show that the commonly used filter function (1 – sinc2 f
T), valid for variances, is a reasonable approximation for power spectra only when T  10
m
, where f is the cyclic frequency, and
m
is the dominant time scale of the process. Our results exhibit an increasingly steeper low-frequency roll-off as T decreases relative to
m
, indicating that the measured spectrum is subject to a greater suppression of the lower frequencies (f > 1/T) than predicted by (1 – sinc2f
T). This suppression is, in a sense, compensated by an overestimation of spectral estimates in the frequency range f 1/T. |
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| Keywords: | |
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