Representation of the ozone quasi-biennial oscillation in JRA-3Q

This study evaluates how the ozone quasi-biennial oscillation (ozone QBO) is represented in the Japanese Reanalysis of Three Quarters of a Century (JRA-3Q) by comparison with satellite observations and three major reanalyses: the Japanese 55-year Reanalysis (JRA-55), the fifth-generation European Centre for Medium-Range Weather Forecasts reanalysis (ERA5), and the Modern-Era Retrospective Analysis for Research and Applications, version 2 (MERRA-2). Satellite observations show that the ozone QBO exhibits a two-component vertical structure, with a transition near 15 hPa separating an upper chemistry-driven regime from a lower dynamics-driven regime with opposite phases. JRA-3Q ozone reproduces this vertical structure and its phase reversal relatively well, including during the pre-satellite era from the 1960s onward, owing to its realistic zonal-wind QBO inherited from JRA-55 wind and the incorporation of a three-dimensional full-chemistry ozone model, albeit in an off-line configuration. However, for 1958–1978, the quadrature component of the cross-wavelet spectrum between zonal wind and ozone QBOs is substantially weakened, consistent with a degraded zonal wind QBO in JRA-3Q. JRA-55 captures the main vertical features during the satellite era but exhibits limited inter-cycle ozone variability. ERA5 and MERRA-2 show good agreement with satellite observations during the recent period (2004 onward), although their representation of the vertical phase reversal becomes less distinct in earlier decades. This study provides a useful benchmark for evaluating the representation of the ozone QBO in reanalyses, based on its two-component vertical structure and the transition layer near 15 hPa, and offers guidance for improving the representation of stratospheric processes in future reanalyses.