A Two‐Dimensional Model Study of the QBO Signal in SAGE II NO₂ and O₃

Calculations of the QBO signal in SAGE II O 3 and NO 2 data between 1984 and 1991 are presented and have been investigated by using a two‐dimensional model. The isentropic 2D model is a fully interactive radiative‐dynamical‐chemical model in which the eddy fluxes of chemical species are calculated in a consistent manner. The QBO in the model has been forced by relaxing the equatorial zonal wind toward the observations at Singapore allowing the comparison of the model with observations from specific years. The model reproduces the observed vertical structure of the equatorial ozone anomaly with the well‐known transition from dynamical to photochemical control at around 28km. The model also reproduces the observed vertical structure of the SAGE II observed NO 2 anomaly. The model studies have shown that it is the QBO modulation of NO 2 which is the main cause of QBO signal in O 3 above 30km. The model also reproduces the observed latitudinal structure of the QBO signals in O 3 and NO 2 . Due to the differing horizontal distribution of O 3 and NO y the ozone signal shows a distinct phase change in the subtropics whereas the NO 2 anomaly gives a broader signal.