Features of ozone quasi-biennial oscillation in the vertical structure of tropics and subtropics

Latitude-altitude structure of ozone QBO over the tropical-subtropical stratosphere (40 degrees S-40 degrees N) has been explored by analyzing Microwave Limb Sounder (MLS) aboard Upper Atmospheric Research Satellite (UARS) data for the period 1992-1999 using the multifunctional regression model. The inferred ozone QBO shows two maxima located at 22 hPa and 10 hPa with coefficient of 2-3% per 10 m/s centered at the equator. The equatorial maxima are out of phase with each other. Subtropics exhibit two peak structure near 14 hPa but of opposite sign to that of equatorial maximum near 10 hPa. Over the equatorial region, positive (zonal winds westerly) coefficients overlay negative (zonal winds easterlies) coefficients which descend with time. A pattern of equatorial maximum and two subtropical minima appears in the months December to February near 10 hpa and it propagates upward with progression of seasons. Equatorial QBO is seasonally asynchronous while subtropical QBO is seasonally synchronous.