Tropospheric ozone studies in Japan

Abstract

Routine ozone measurement have been undertaken continuously by the Japan Meteorological Agency, for about 30 years at five meteorological stations: Sapporo, Tateno, Kagoshima, Naha and Antarctic Syowa Station. Dobson spectrometers and ozone sondes are used for measuring total column ozone and height distribution of ozone concentration. At the Meteorological Research Institute, we have made studies of the behaviour of tropospheric ozone and other relevant species. Here, we make a brief presentation of three aspects of our studies i.e., measurements of surface ozone, methane and aircraft observations of the tropospheric ozone over the western part of the Pacific Ocean.

We have measured surface ozone concentration at Tsukuba continually since May 1988, using a UV absorption ozone meter. The ozone data are collected every minute and averaged every 10 minutes. This gives us an hourly mean, daily mean, daily maximum and daily minimum etc. The Surface Ozone Concentration in the Spring Figure 1 shows monthly means of surface level ozone. It is found that ozone concentration is high in the spring, especially in April, May and June. From this, it is concluded that ozone transportation from the upper troposphere to the surface is most active in the spring season over northern mid-latitude. In general, both ozone production and photodissociation are dominant in the tropical stratosphere and this ozone may be transported northward and slightly downward by the global circulation and planetary scale wave activities (Figure 2; Kida, 1983). Therefore, high latitude stratosphere usually has high ozone concentration. The ozone-rich air is thought to be transported from stratosphere into the upper trospophere following the vital spring activity of low pressure. The stratospheric air which contains higher concentration of ozone intrudes into the troposphere at the back of the low.