Ozone and temperature decadal responses to solar variability in the mesosphere and lower thermosphere, based on measurements from SABER on TIMED

Abstract

We have derived ozone and temperature responses to solar variability over a solar cycle, from June 2002 through June 2014, 50 to 100km, 48°S to 48°N, based on data from the Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) instrument on the Thermosphere-Ionosphere-Mesosphere-Energetics and Dynamics (TIMED) satellite. Results with this extent of coverage in the mesosphere and lower thermosphere have not been available previously. A multiple regression is applied to obtain responses as a function of the solar 10.7cm flux (solar flux units, sfu). Positive responses mean that they are larger at solar maximum than at solar minimum of the solar cycle. From ∼80 to 100km, both ozone and temperature responses are positive for all latitudes and are larger than those at lower altitudes. From ∼80 to 100km, ozone responses can exceed 10%(100sfu)-1, and temperature responses can approach 4°K. From 50 to ∼ 80km, the ozone responses at low latitudes ( ∼±35°) are mostly negative and can approach ∼negative 3%(100sfu)-1. However, they are mostly positive at midlatitudes in this region and can approach ∼2%(100sfu)-1. In contrast to ozone, from ∼50 to 80km, the temperature responses at low latitudes remain positive, with values up to ∼2.5K(100sfu)-1, but are weakly negative at midlatitudes. Consequently, there is a systematic and robust relation between the phases of the ozone and temperature responses. They are positively correlated (in phase) from ∼80 to 100km for all latitudes and negatively correlated (out of phase) from ∼50 to 80km, also for all latitudes. The negative correlation from 50 to 80km is maintained even though the ozone and temperature responses can change signs as a function of altitude and latitude, because the corresponding temperature responses change signs in step with ozone. This is consistent with the idea that dynamics have the larger influence between ∼ 80 and 100km, while photochemistry is more in control from ∼ 50 to 75km. The correlation coefficients between the solar 10.7cm flux and the ozone and temperature themselves from 2012 to 2014 are positive (negative) in regions where the responses are positive (negative). This supports our results since the correlations are independent of the multiple regression used to derive the responses. We also compare with previous results.