Development of calibration instrument for precise stratospheric and tropospheric ozone measurement

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To investigate the ozone decrease in the lower stratosphere and ozone increase in the upper troposphere, the precision of the measurement should be improved significantly. It is crucial to calibrate instruments for ozone measurement under the low-pressure condition similar to the upper troposphere/lower stratosphere. For this purpose, we have developed an instrument for calibration of ozone monitor under low-pressure condition. At first, we used a commercial standard ozone generator as the ozone source and made a Teflon chamber with backward pressure controller to reduce the pressure of ozone from the ozone generator. However, the adjustment of the pressure of the chamber was difficult and critical although the pressure reduction was successful. Thus we have improved this system : 1) pressure-stabilize the inlet and exhaust ports of the ozone generator, 2) flow monitor from ozone generator, 3) some capillaries (instead of needle valve) are used to make pressure drop between ozone generator and the Teflon chamber, and so on. After these improvements, the developed calibration system worked stably. By comparing a precise ozone monitor, this ozone calibration system can calibrate a ozone measurement instrument with an accuracy of 3%. However, for using this system easily in the observation field, the operation should be automated.