The seasonal cycle of the wintertime stratospheric ozone mixing ratio in northern hemispheric polar region and its relationship with stratospheric temperature variability

In this study, we study the seasonal cycle of the wintertime ozone mixing ratio in northern hemispheric polar region and investigate its relationship with stratospheric temperature variability. CSEOF analysis was employed to extract the seasonal cycle of mixing ratio for the 150 winter days (November 17-April 15) for the mid-to-lower stratosphere over the 30°-80°N zonal band based on the 20-year (1989-2009) ECMWF reanalysis product. The seasonal cycle of stratospheric ozone mixing ratio explains ~1/3 of the total variability and exhibits significant interannual variations with a recurrent period of ~4 years. Due to the significant interannual variation of the seasonal cycle, understanding the physical mechanism of the seasonal cycle of ozone mixing ratio is important also in association with the Brewer-Dobson circulation.

Maximum variability of ozone mixing ratio is found at ~10-20 hPa, which is converted into maximum variability of ozone concentration at ~20-30 hPa. The cooling of the stratosphere in early winter removes ozone molecules through the nucleation process resulting in a negative maximum ozone mixing ratio anomalies at ~10 hPa in late December. The ensuing warming slows the nucleation process resulting in a positive maximum ozone mixing ratio anomalies at ~7 hPa in late April. Correlation between the ozone mixing ratio anomalies and the stratospheric temperature anomalies in the 7-50 hPa layer is typically over 0.8 in the polar region to the north of ~60°N, well establishing the temperature-ozone relationship in the stratosphere of the northern hemispheric polar region. In the lower stratosphere below 100 hPa, however, potential vorticity appears to impact the ozone concentration significantly.