A Global Analysis of the Fluctuation of Total Ozone

Abstract

The fluctuations of monthly mean total ozone from 1962 to 1976 are analyzed on a global basis, using the longitude-latitude grid point values obtained by the method described in part I (Hasebe, 1980), From these values, global mean, hemispheric mean, zonal mean, and meridional mean values for northern midlatitudes are calculated with the estimates of errors. With the application of numerical filters, non-stationary annual oscillation (NSA), quasi-biennial oscillation (QBO), and long-term variations (LTV) are examined. The results are summarized as follows: (i) NSA; The large amplitude of the oscillation in northern midlatitudes is situated near 40°E and 160°F where the time averaged distribution of total ozone shows large gradient; east of the maxima. In the northern hemisphere around 1970 to 1971, an apparent phase reversal is found, corresponding to the reduction of about 10% in the amplitude of the annual oscillation. (ii) QBO; Significant oscillation has been detected with larger amplitude in the northern hemisphere. The oscillation cores in northern midlatitudes are seen near 140°E and 20°W; on and to the west of the time averaged maxima of total ozone. The poleward propagation of the QBO phase is not always seen, because of the difference in the QBO period between low and high latitudes. When the QBO phase exhibits poleward propagation, total ozone maxima in midlatitudes are seen about π/2 later than the quasi-biennial west wind maxima at 50mb in the tropics. However, this relation does not exist when the ozone phase propagates equatorward. (iii) LTV; The existence of the four-year oscillation is found at high latitudes, particularly in the northern hemisphere. The positions of the oscillation core in northern midlatitudes resemble to those of the NSA, but enhanced near 40°E longitude. Maxima and minima of this oscillation are found in late winter or early spring of even years in both hemispheres, while the phase in the southern hemisphere is preceded by about 3π/4 to that in the northern hemisphere. The earlier investigations of long-term trends (e.g., Angell and Korshover, 1976) are qualitatively confirmed in this analysis. It remains still uncertain, however, whether such long-term trends are essentially explained by an autoregressive process because of the short period of coverage of the observational data.