Nighttime Mesospheric/Lower Thermospheric Tropical Ozone Response to the 27‐Day Solar Rotational Cycle: ENVISAT‐GOMOS Satellite Observations Versus HAMMONIA Idealized Chemistry‐Climate Model Simulations

• Published in: Journal of geophysical research. Atmospheres 2018-08, Vol.123 (16), p.8883-8896
• Main Authors: Thiéblemont, R., Bekki, S., Marchand, M., Bossay, S., Schmidt, H., Meftah, M., Hauchecorne, A.
• Format: Article
• Language: English
• Subjects: Altitude; Atmospheric chemistry; Climate; Climate models; Computer simulation; Correlation; Data processing; Envisat satellite; Geophysics; Global ozone; GOMOS‐ENVISAT; Irradiance; Lower thermosphere; Mesosphere; middle atmosphere; Night; Night-time; Nighttime; Organic chemistry; Ozone; Ozone monitoring; Ozone variations; Regression analysis; Satellite data; Satellite observation; Satellites; Sensitivity; Solar cycle; solar forcing; Solar spectral irradiance; Thermosphere; Tropical climate; Vertical profiles
• ISSN: 2169-897X; 2169-8996
• DOI: 10.1029/2017JD027789

Global Ozone Monitoring by Occultation of Stars (GOMOS) satellite data are analyzed to estimate the first observation‐based nighttime (22:00 median local time) ozone response to the 27‐day solar rotational cycle in the tropical mesosphere/lower thermosphere (50–110 km altitude). The ozone response to solar rotational variability is derived from linear correlation and regressions using Lyman‐α line (121.6 nm) as solar index that varies by about 10–15% over solar rotational cycles. In the lower mesosphere (50–70 km), the GOMOS ozone is found to be correlated with the solar fluctuations and exhibits a sensitivity of ~0.1 (expressed in percent change of ozone for 1% change in Lyman‐α). In the upper mesosphere/lower thermosphere (above 80 km), ozone variations become anticorrelated with solar rotational variations. In this region, the vertical profile of ozone sensitivity to the 27‐day solar cycle exhibits a maximum of 1.8 at 81 km, a minimum of 0.3 at 100 km, and a sharp increase above. Such high ozone sensitivities are observed for the first time. The observed ozone response is compared with chemistry‐climate simulations from the Hamburg model of the neutral and ionized atmosphere (HAMMONIA) that is forced with an idealized 27‐day solar spectral irradiance time series. Although observational and model results share some common features, substantial discrepancies are found. Namely, the altitude of transition from positive to negative solar ozone correlation signal in the model simulation is found about 10 km below the altitude of the observations and the amplitude of the ozone sensitivity is generally vastly underestimated by the model. Key Points First observational estimate of the nighttime tropical O3 response to the 27‐day solar cycle in the mesosphere/lower thermosphere GOMOS observes a maximum absolute sensitivity of 1.8% change of ozone for 1% change in Lyman‐α at 81 km HAMMONIA reproduces most of the features in the observed O3 response to the 27‐day solar cycle but underestimates its magnitude