Ozone Trend over Taiwan from TOMS Data

Abstract

Ozone column data obtained from Nimbus 7 satellite instrument, TOMS, were analyzed. Total ozone data over Taiwan starts November 1978 till May 1993. Daily observations were changed into monthly data for trend analysis. First, spectral analyses were performed to find possible atmospheric movements. Significant peaks were found at periods of 6, 12, 19, and 29 months. The first two are due to seasonal variations. The last one corresponds to the quasi-biennial oscillation (QBO) in stratosphere. It is suggested that the 19-months period is the difference of the annual and the equatorial QBD frequencies. A linear regression model (LRM) described by Yang and Tung (J. of Geophysical Res. 100, 9091, 1995) were adapted to the deseasoned ozone data. Besides the QBD, the solar flux and ENSO are known to affect the amount of ozone in the Earth atmosphere. The 30-mbar Singapore wind and F10.7-cm solar flux were chosen to represent variations of QBD and solar flux, respectively. The estimated total ozone decreasing trends due to anthropogenic activities are 0.92 + - 0.46% and 1.77 + - 0.52% per decade over Taipei and Cheng-Kung, respectively. Increase in tropospheric production of ozone in Taipei may explain the lower trend in Taipei than that in Cheng-Kung. Estimated contributions from natural variables to the total ozone variations are: 3.2% and 2.8% form QBD maximum to minimum; 2.0% and 2.3% per 100 solar units for Taipei and Cheng-Kung, respectively. Influence from ENSO seems to be insignificant. Comparison with ground total ozone stations will be discussed.