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Abstract
The Zenith Sky Cloud Detector (ZSCD) was developed to detect clouds present in the zenith sky. The Japan Meteorological Agency (JMA) incorporated the ZSCD into the ozone observation network to achieve real-time quality control of Umkehr observation in 2007. A Dobson spectrophotometer is used as one of the instruments for accurately monitoring the ozone layer, and JMA is performing regular observations at Sapporo, Tsukuba, Naha, and Syowa in the Antarctic. The Dobson spectrophotometer monitors the ozone layers of the Earth's atmosphere. However, the accuracy of Dobson measurements depends on the presence of clouds in the Zenith Sky. ZSCDs for detecting clouds were first developed by the National Oceanic and Atmospheric Administration (NOAA) in the 1980s. ZSCDs use an 862nm (center wavelength) interference filter for the near-infrared region and can detect light scattered by the main clouds at Zenith. This optical device is composed of an interference filter, a lens, its aperture, and a high-sensitivity, near-infrared photodiode. The amplified output is input through the A/D interface of the Dobson automated system. The Umkehr observation using ZSCD modifies the influence of clouds and can help achieve a good ozone profile. JMA developed this unit based on the ZSCD used for the Global Atmosphere Watch (GAW) ozone observation network in NOAA. The effect of the clouds of measurement N-value can evaluate the clouds using the standard deviation from time series of ZSCD output.
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