Science Update: The stratospheric ozone diurnal cycle: global, regional, and seasonal variability simulated by WACCM

In a new ACPD paper, A. Schanz and co-authors use the WACCM model to study the diurnal ozone cycle in the stratosphere, exploring its underlying photochemical and dynamical processes. The analysis is focused on the middle stratosphere at 5hPa where the simulated ozone diurnal cycle shows a minimum after sunrise and maximum in the late afternoon. They find that this diurnal cycle varies seasonally and spatially, with a maximum amplitude of 15% (0.8ppmv) occurring at the polar circle in summer. They show that the global pattern of the diurnal ozone cycle is governed by the solar zenith angle and sunshine duration. They also find that the synoptic scale variability of the diurnal ozone cycle is often anti-correlated with regional temperature anomalies due to the temperature dependence of the Chapman cycle reactions. Furthermore, at high latitudes increased westerly (easterly) winds cause a decrease (increase) in the sunshine duration of an air parcel leading to a weaker (stronger) diurnal ozone cycle. The full abstract can be found here.