Abstract

As part of the TRACE-P mission, ozonesondes were used to make ozone vertical profile measurements at nine locations in the North Pacific. At most of the sites there is a multi-year record of observations. From locations in the western Pacific (Hong Kong; Taipei; Jeju Island, Korea; and Naha, Kagoshima, Tsukuba, and Sapporo, Japan), a site in the central Pacific (Hilo, HI), and a site on the west coast of the U.S. (Trinidad, CA) both a seasonal and event specific picture of tropospheric ozone over the North Pacific emerges. At all of the sites there is a pronounced spring or summer maximum through much of the troposphere. There are, however, differences in the timing and strength of this feature at each site. Over Japan the northward movement of the jet during the spring and summer influences the timing of the seasonal maximum at the same time as the photochemical production of ozone also accelerates. During March and April at Hong Kong ozone is enhanced in the lower free troposphere and in the upper troposphere. Biomass burning in northern Southeast Asia (both the upper and lower layer) and possibly equatorial Africa (upper layer) is a likely contributor to the enhanced ozone seen at these sites during this time of year. During the winter in the upper troposphere the Pacific subtropical sites (latitude ~25N) are dominated by air with a lowlatitude source that gives low ozone amounts. In the summer in the boundary layer at all of the sites marine air dominates and ozone amounts are generally quite low (<25 ppb). The exception is near large population centers (Tokyo and Taipei but less so at Hong Kong) where pollution events can give amounts in excess of 80 ppb. During the TRACEP intensive campaign period (February-April 2001) tropospheric ozone amounts were rather typical of those seen in the long-term records of the stations with multi-year 2 soundings with the exception of the upper troposphere at Hong Kong and Taipei where ozone amounts were lower in 2001.