Surface ozone observation

7.2.6 Surface ozone observation


   Surface ozone is observed using a UV light absorption ozone monitor, utilizing the characteristics of UV radiation to be absorbed by ozone. The system models used at the observation stations are listed in Tables 7.1.1.2, 7.1.1.3, and 7.1.1.4, with the appearance of the system shown in Figure 7.2.6.1.

   Air samples are introduced to the observation system from a dedicated observatory rooftop intake (ground heights: 8 m at Ryori, and 10 m at Minamitorishima and Yonagunijima) at a rate of 10 L per minute, and is diverted to the ozone monitor at 1.5 L per minute. All the piping systems use Teflon, by which ozone is not readily destroyed upon contact. In Syowa Station in Antarctica, air samples are directly introduced to the ozone monitor at a height of about 5 m from the ground via Teflon tubes at a rate of 1.5 L per minute. Ozone monitors are calibrated using an ozone generator at the JMA headquarters as described in Section 7.3.5.

   The air samples are observed by first introducing them into the observation system, which has a calibrated ozone monitor installed, and analyzing the ozone concentration of the air once every 15 seconds. The observations at 15-second interval are subjected to quality control by JMA before they are statistically processed. Hourly mean values are calculated from all the observations excluding those during inspections or malfuction of the system and other such situations. At Syowa Station, measurements are taken every 12 seconds.

   Observations for surface ozone may contain local variations within the surface boundary layer. However, as concentrations of ozone in the atmosphere naturally vary from moment to moment as a result of photochemical formation and destruction, or destruction upon contact with ground surface, BG data based on standard deviation or differences before and after the measurement is not selected when calculating daily and monthly mean values. The daily and monthly mean values are calculated based on the hourly mean values, that are calculated from more than half the observations every 15 seconds (12 seconds), meaning at least 120 (150) observations per hour.


Surface O3 observation system at Yonagunijima.

Fig. 7.2.6.1 Surface O3 observation system at Yonagunijima.

Time series of hourly mean surface O3 concentrations at Ryori in 2008

Fig. 7.2.6.2 Time series of hourly mean surface O3 concentrations at Ryori in 2008.

Time series of hourly mean surface O3 concentrations at Minamitorishima in 2008

Fig. 7.2.6.3 Time series of hourly mean surface O3 concentrations at Minamitorishima in 2008.

Time series of hourly mean surface O3 concentrations at Yonagunijima in 2008

Fig. 7.2.6.4 Time series of hourly mean surface O3 concentrations at Yonagunijima in 2008.

Time series of hourly mean surface O3 concentrations at Syowa in 2008

Fig. 7.2.6.5 Time series of hourly mean surface O3 concentrations at Syowa in 2008.



Contents

GAW Stations for greenhouse and reactive gas observation | Surface ozone observation | Calibration for surface ozone observation

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