Observational study of the quasi‐biennial oscillation in ozone

Abstract

The structures of the quasi‐biennial oscillations (QBOs) in zonal wind, temperature, and layer ozone amounts are investigated using 11.5 years (January 1979 to June 1990) of National Meteorological Center (NMC) global geopotential height data and global ozone data from the solar backscatter ultraviolet spectrometer (SBUV) on Nimbus 7. The QBO signals are isolated by computing lagged correlations between the deseasonalized, detrended variable fields and a reference signal representative of the equatorial QBO. Lagged correlations are calculated for the full time series and for each season separately to determine seasonal effects. The results depict an equatorial zonal wind QBO in good agreement with the observed QBO in ground‐based equatorial zonal wind measurements, although the amplitude of the derived QBO in the NMC data is ∼30% too weak. The vertical extent of the oscillation is significantly higher (2 mbar) than that previously reported. The temperature QBO is consistent with ground‐based observations in the lower stratosphere but weakens with height above ∼50 mbar. The ozone QBO is strong at all levels from 5 mbar into the lower stratosphere. Though the annual average total ozone QBO is quite symmetric about the equator, the oscillation is highly variable from layer to layer. The phase of the ozone QBO near the equator is consistent with that of the zonal wind and temperature in the middle and upper stratosphere, but the vertical resolution of the SBUV data in the lower stratosphere is too low to accurately represent the vertical phase of the ozone QBO in this region. Subtropical temperature and total ozone anomalies are found to be dependent on season.