Abstract
Abstract. The 11-yr solar cycle in solar spectral irradiance (SSI) inferred from measurements by the SOlar Radiation & Climate Experiment (SORCE) suggests a much larger variation in the ultraviolet than previously accepted. We present middle atmosphere ozone and temperature responses to the solar cycles in SORCE SSI and the ubiquitous Naval Research Laboratory (NRL) SSI reconstruction using the Goddard Earth Observing System chemistry-climate model (GEOSCCM). The results are largely consistent with other recent modeling studies. The modeled ozone response is positive throughout the stratosphere and lower mesosphere using the NRL SSI, while the SORCE SSI produces a response that is larger in the lower stratosphere but out of phase with respect to total solar irradiance above 45 km. The modeled responses in total ozone are similar to those derived from satellite and ground-based measurements, 3–6 Dobson Units per 100 units of 10.7-cm radio flux (F10.7) in the tropics. The peak zonal mean tropical temperature response using the SORCE SSI is nearly 2 K per 100 units F10.7 – 3 times larger than the simulation using the NRL SSI. The GEOSCCM and the Goddard Space Flight Center (GSFC) 2-D coupled model are used to examine how the SSI solar cycle affects the atmosphere through direct solar heating and photolysis processes individually. Middle atmosphere ozone is affected almost entirely through photolysis, whereas the solar cycle in temperature is caused both through direct heating and photolysis feedbacks, processes that are mostly linearly separable. This is important in that it means that chemistry-transport models should simulate the solar cycle in ozone well, while general circulation models without coupled chemistry will underestimate the temperature response to the solar cycle significantly in the middle atmosphere. Further, the net ozone response results from the balance of ozone production at wavelengths less than 242 nm and destruction at longer wavelengths, coincidentally corresponding to the wavelength regimes of the SOLar STellar Irradiance Comparison Experiment (SOLSTICE) and Spectral Irradiance Monitor (SIM) on SORCE, respectively. A higher wavelength-resolution analysis of the spectral response could allow for a better prediction of the atmospheric response to arbitrary SSI variations.
Highlights
Recent measurements of the solar spectral irradiance (SSI) made by the the SOlar Radiation & Climate Experiment (SORCE) mission (Rottman, 2005) have brought into question long-held views of how the SSI varies as a function of the 11-yr solar cycle
Several studies (Cahalan et al, 2010; Haigh et al, 2010; Merkel et al, 2011; Ineson et al, 2011) suggest that atmospheric models forced with the SORCE SSI lead to better agreement with the solar cycle response inferred from observations than simulations based on the widely accepted Naval Research Laboratory (NRL) SSI reconstruction derived from long-term solar observations (Lean, 2000), implying that the solar cycle in SSI derived from SORCE data is more consistent with observations
Using the Goddard Earth Observing System chemistry-climate model (GEOSCCM) to explore the effects of SSI variations on direct atmospheric heating and photolysis both separately and when combined, we have quantified their relative contributions in relaying solar cycle variations to stratospheric ozone and temperature
Summary
Recent measurements of the solar spectral irradiance (SSI) made by the the SOlar Radiation & Climate Experiment (SORCE) mission (Rottman, 2005) have brought into question long-held views of how the SSI varies as a function of the 11-yr solar cycle. Based on SORCE observations during the latter part of the declining phase of solar cycle 23 (2004– 2007), Harder et al (2009) suggested that the magnitude of the solar cycle variation in the ultraviolet (UV), from 200 to 400 nm, is several times larger than previously thought. Several studies (Cahalan et al, 2010; Haigh et al, 2010; Merkel et al, 2011; Ineson et al, 2011) suggest that atmospheric models forced with the SORCE SSI lead to better agreement with the solar cycle response inferred from observations than simulations based on the widely accepted Naval Research Laboratory (NRL) SSI reconstruction derived from long-term solar observations (Lean, 2000), implying that the solar cycle in SSI derived from SORCE data is more consistent with observations.
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
