. Collected reprints / Atlantic Oceanographic and Meteorological Laboratories [and] Pacific Oceanographic Laboratories. Oceanography cr < CD cc < o â 100 o UJ cc or UJ i- 020 u. 90| 30 20 1513|ll| 9 8 7 6 5 4°°° 45 12 10 SAMPLE INTERVAL Figure Tower spectrum of upwelling spectral irradiance shown in Figure The narrow line is the high frequency motion caused by surface waves reflecting specularly; the heavy line is the response of the Fourier filter to low-pass the data. The response of the filter chosen to remove these high frequency signals is show
. Collected reprints / Atlantic Oceanographic and Meteorological Laboratories [and] Pacific Oceanographic Laboratories. Oceanography cr < CD cc < o â 100 o UJ cc or UJ i- 020 u. 90| 30 20 1513|ll| 9 8 7 6 5 4°°° 45 12 10 SAMPLE INTERVAL Figure Tower spectrum of upwelling spectral irradiance shown in Figure The narrow line is the high frequency motion caused by surface waves reflecting specularly; the heavy line is the response of the Fourier filter to low-pass the data. The response of the filter chosen to remove these high frequency signals is shown by the heavy, solid curve in Fig. This response is in terms of a ratio of the contribution various frequencies make to the form of the original trace, to the con- tribution the same frequencies are allowed to make to the form of the filtered result. Thus in the example chosen, no contri- bution is allowed for periods smaller than about 9 data points per cycle (10 nm); full contribution is allowed for periods greater than about 9 0 points per cycle (10 0 nm), and half contributions are allowed at about 25 points per cycle (30 nm), which was the longest period of the major peak in Fig. In general, all filters were chosen to remove the short period (high frequency) signals in the same way. Power spectra of different spectrometry scans did not always closely resemble each other however, and each filter had to be chosen on the basis of an individual inspection of each scan. c) Wavelength Calibration Irradiance and wavelength are indicated by separate voltage outputs. The wavelength voltage is produced by a potentiometer directly connected to the diffraction grating, voltage varying with angle. In addition, an inscribed wavelength scale is connected directly to the potentiometer. Thus it is possible to compare the voltage of the wavelength output as recorded by whatever strip chart recorder is used with the wavelength indicated by the scale. Such a comparison was p
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