1. Modeling of the 11-year Solar Cycle Response in Upper Atmospheric Hydroxyl Radicals Yuk Yung 3-1-2012 ESE

4.  The solar-cycle modulation recently reported by Shuhui Wang et al. (2011) OH column shows 10±3 %  Modeled OH column response using previous solar model predicts 3.7 % only  Recent satellite UV measurements show unexpectedly large 11-year solar-cycle variability Motivation NRL FluxSORCE Flux

5. An “Error Estimation” (Conservative) 5% SOLSTICE 2% SIM  Error estimates are as important as the measured means  Spectral uncertainty should also propagate in the models  Very very conservative uncertainty limits will be tested

6. Backward Extrapolation  Extrapolate to the solar max in Jan 2002 using Mg-II index  Uncertainty = regression error + instrument uncertainty

7. OH Photochemistry A A BB C C D A: H 2 O photolysis B: OH + O( 3 P) → H + O 2 O( 3 P) comes from photolysis of O 2 and O 3. C. H 2 O + O( 1 D) → OH + O 2 O( 1 D) comes from the photolysis of O 3 + h → O 2 + O( 1 D). D. Shielding effect due to the increased overhead O 3 opacity

8. Modeled Response (1D) (Blue) Solar-cycle modulation using the extrapolated UV changes (Shade) Uncertainty related to extrapolation (Black) Simulation using Lean’s spectrum (Orange) Canty and Minschwaner (2007).  OH column = 6.4 ± 2.5 % versus obs 10 ± 3%

9. Modeled Response (3D)

10.  Simulated solar response of the mid-latitude OH column abundance is much closer to observations when the latest satellite solar UV measurements are used.  Nevertheless, the observed solar response is still slightly greater than the simulated value.  Future OH measurements through the next solar maximum (expected in 2013) will be extremely valuable for investigating these differences further. Summary

11. Daytime Merkel et al. (2011) How about O 3 ?  Merkel et al. examined the effect in the lower mesosphere  Stratosphere ???  Continuous satellite measurements too short

12. Ground-based measurements  LIDAR O 3 measurement over Mauna Loa, Hawaii (MLO) MLO agrees with 1D/2D photochemical models  Max level of WACCM is wrong  WACCM zero level too low

13. O 3 chemistry is much simpler

14. Acknowledgements NASA and ESA Yung’s Group at Caltech Fai Li, Stan Sander, Shuhui Wang Yung and DeMore (1999) Book