SMLT Ozone from SOFIE and Other Instruments – Validation and Seasonal Climatology

Ozone is an important trace gas in our atmosphere that plays key radiative roles in the stratosphere and the mesosphere. The highest ozone concentration in the atmosphere is in the low-mid stratospheric region. The maximum in ozone mixing ratio in the upper mesosphere and lower thermosphere (MLT) is the secondary ozone maximum and is typically located between ~ 85 km and 95 km. Altitude-resolved ozone profiles from satellite-borne instruments help understand the variation in ozone concentration through various altitudes, seasons, and seasonal anomalies (sudden stratospheric warmings in the polar winter). This research analyses ozone observations from the Solar Occultation for Ice Experiment (SOFIE) instruments onboard the Aeronomy of Ice in the Mesosphere (AIM) spacecraft. SOFIE makes sunrise and sunset measurements (relative to the spacecraft), most typically between 65o and 85o latitude in both hemispheres. We compare version 1.3 SOFIE ozone data to coincident profiles from the Atmospheric Chemistry Experiment (ACE) and the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) instruments in the SMLT (20 – 100 km). Comparison is made by season. SOFIE ozone measurements agree well with ACE and MIPAS but are consistently lower.
SOFIE measurements indicate that the seasonal ozone variation recorded in the low-mid stratosphere is consistent with theory. Large scale waves generated in the troposphere (due to flow over mountains and temperature contrasts of land-sea interfaces) propagate to the stratosphere during the winter, leading to a wintertime poleward/downward circulation. This circulation carries with it ozone produced at tropical photochemical source regions. This ozone-rich air moves to high latitudes where ozone is preserved in the wintertime due to effective shielding from UV radiation due to the low solar angle. Wintertime ozone accumulation leads to a springtime maximum. Large scale waves do not propagate into the summer easterlies, and the sun climbs higher, leading to effective photochemistry resulting in ozone destruction until a minimum is reached in late fall. In the MLT, anomalous winter dynamics due to sudden stratospheric warmings impact ozone concentration in the secondary maximum establishing a negative correlation between temperature and ozone. In summary, through this study, we demonstrate the robustness of SOFIE’s data quality and its ability to study the seasonal variation of ozone in the stratosphere-mesosphere- lower thermosphere (SMLT).