Photochemical and Dynamical Contributions to the Seasonal Variation of Total Ozone Amount over Japan

[摘要] The latitudinal and seasonal variations of ozone photochemical process are analyzed using the monthly means of ozone density observed by ozonesondes at Sapporo, Tateno and Kagoshima. The estimated photochemical change rate (creation minus destruction) and observed ozone density variation are used to evaluate the divergence of ozone.The seasonal variation of total ozone amount at Kagoshima is mainly due to the density variation in the quasi steady region, where the photochemical change rate of ozone density is effectively balanced with its divergence. On the other hand, the variation at Sapporo is dominated by the dynamical process in the non-steady region. In this case, the primary effect in the dynamical process is the seasonal variation of tropopause height and the secondary one is the accumulation in the lower stratosphere due to the meridional circulation in winter. The former tends to set the time of maximum of total ozone amount in mid-winter and the latter shifts it to early spring. Especially, the continuous increase in the total ozone amount during winter is an evidence that the distribution of ozone remains at a transient state for the winter circulation. Such a remarkable difference between the mechanisms of the seasonal variation of total ozone amount in the two stations is originated from the variation of tropopause structure. The major tropopause that effectively separates the stratospheric air mass from the tropospheric one is the tropical tropopause through all seasons over Kagoshima, but it is the tropical one in summer and the polar one in winter over Sapporo.Finally, from the view point of the longitudinal dependence, the ozone distribution over Japan is discussed.

[学科分类] 大气科学