The interaction between stratospheric sudden warmings and ozone

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Wednesday, 7 January 2015
Steven C. Hardiman, Met Office, Exeter, Devon, United Kingdom; and N. Butchart and F. M. O'Connor

Handout (1.1 MB)

Mid-winter stratospheric sudden warmings of the northern hemisphere polar vortex and the associated enhanced meridional circulation in the extratropics are known to influence ozone concentrations in the northern high latitudes. This phenomenon has been poorly studied over the past decade but has recently seen a renewed interest. The ERA-Interim reanalysis data suggests that ozone concentrations in the high latitude mid-to-lower stratosphere are increased by as much as 20% following a sudden warming. Furthermore, these ozone concentration anomalies outlast the corresponding temperature anomalies that follow a sudden warming, remaining significant for up to a week longer. This signal is found to be accurately simulated in the current generation Met Office Earth System model.

A series of ensemble integrations are performed to study the inverse question of whether ozone feedbacks can significantly alter a simulated sudden warming. The effect of radiatively coupled ozone on the strength, duration, and predictability of the simulated sudden warmings is investigated, along with the associated changes in surface climate. The potential benefits of including radiatively coupled ozone in seasonal forecast models is discussed.