Effects of Solar Irradiance Variability on Atmosphere

1. Poly Project: “Variability of the Sun and Global Climate” Sub-project: Effects of Solar irradiance variability on the atmosphere (steady-state sensitivity study) Progress report (final) IAC ETH, 26 October 2004

2. Goals of the sub-project: • development of the chemistry-climate model and its validation against available observations • study of global chemistry and climate response to solar irradiance variability

3. SOCOL : modeling tool to study SOlar-Climate-Ozone Links General Circulation component : MA-ECHAM4 (Manzini & McFarlane, 1998) Chemistry/transport component : MEZON(Rozanov et al., 1999, Egorova et al., 2003) • Winds and temperature • H2O (troposphere) GCM CTM • Ozone • H2O(stratosphere) Horizontal grid ~3.75ºx3.75º(T30); 39 levels in vertical; model top at ~80 km Ported on PC: 10 years of integration takes ~ 40 days of wall-clock time

4. Validation of SOCOL 40-year long control run for present day conditions: Monthly SST/SI prescribed from AMIPII (1979-1996) Lower boundary conditions for the source gases : 1995 CO2=356 ppm Initial distributions for meteorological quantities are from MA-ECHAM4 and gas mixing ratios from 8-year SCTM (Rozanov et al., 1999) Climatological data sets used for model validation. Data source Time period used Upper level UKMO 1992-1999 (8 years) 0.3hPa CPC 1979-1998 (20 years) 1 hPa NCEP 1979-1999 (21 years) 10hPa ERA-15 1979-1999 (15 years) 10hPa URAP 1992-1999 (8 years) 0.01hPa Discrepancies among data sets difficult to conclude about model performance One data set has been produced: 64 years, climatology of T and U and standart deviation: interannual variability and variability due to differences in the data sets.

5. Difference between simulated and observed climatology Temperature “hot” spots Latitude Latitude

6. Comparison of SOCOL total ozone with observations and other similar models OBSERVATIONS UMETRAC UIUC CCSR/NIES MAECHAM/CHEM ECHAM/CHEM/DLR October, Southern Hemispher ensemble mean (40-year long run) ULAQ CMAM SOCOL Austin et al.,2003

7. Conclusions • Overall performance of SOCOL is reasonable and many • futures of the atmosphere are simulated rather well. • SOCOL shows good wall-clock performance. • CCM SOCOL can be used for climate studies

8. Completed experiments of the sensitivity study Solar Max UV+VIS Solar rotation Solar Min Solar Max Only UV Solar Max Only VIS

9. Experimental design • Prescribed SST/SI, GHG, ODS (mid 90-ies), 20-year long runs • Two observed by SUSIM (UARS) solar spectral fluxes for maximum and minimum of the solar activity from 1992 to 1998 have been used for photolysis rates, radiation fluxes and heating rates calculations • Parameterization for the heating rate changes for the solar maximum case due to absorption in Ly-, Schumann-Runge bands, Herzberg continuum, Hartley band (based on Strobel formalism [1978] and detailed radiation code). Additional heating due to oxygen and ozone absorption has been calculated only for the Solar maximum case as: HRSMA = HRSMI + HR*SMA HR*SMAis the parameterized heating rate due to O2 and O3 absorption.

10. Tropical temperature response (23S-23N averaged) Black:ensemble averaged two 1-year long runs: Red :with UV absorption Blue :without UV absorption

11. Solar signal in ozone Red – observations Blue - simulated UV +Visible

12. Solar signal in ozone Visible only UV only

13. Solar signal in temperature SOCOL [Egorova et al, 2004] SSU/MSU [Hood and Soukharev, 2000] CPC [Hood, 2004] NCEP [Labitzke, 2002] MAECHAM/CHEM [Tourpali et al., 2003] UV +Visible

14. Solar signal in temperature Visible only UV only

15. Solar signal in zonal wind UV +Visible Visible only UV only

16. Solar signal in surface air temperature Visible only UV only UV +Visible Thomson & Wallace (GRL,1998)

17. Conclusions • Introducing of observed solar spectral flux variations into the model produced not only changes in the stratosphere but also changes in the troposphere and near the surface. • The obtained solar signal in surface air temperature resembles pattern of positive phase of AO. UV and VIS radiation both play a role in surface air temperature changes due to 11-year solar irradiance variability. • Simulated solar signal disagrees with the solar signal derived from satellite measurements. • The next step is to understand the mechanisms by which solar-induced circulation anomalies propagate poleward and downward to the troposphere. The crucial idea in current theory is that changes in thermal structure will change the wave-propagation properties in the lower stratosphere.

18. Solar flux variability during 27-daysolar rotation cycle and atmosphere Motivation: Why the steady-state run results are not in a reasonably good agreement with “observations”: - Forcing/response are not right (“bad” models)? - Experimental set-up is wrong (transient)? - Short time-series (“bad” observations)? • Do we have other possibilities to check? – Yes, 27-day cycle. Experimental set up: - Solar maximum for 1992, • nine 1-year long runs • with prescribed SST/SI, GHG,ODS • daily SUSIM spectral UV fluxes for 1992

19. Sensitivity of tropical ozone to UV changes Ensemble. mean SBUV MLS

20. Sensitivity of tropical T to UV changes SAMS MLS Ensemble mean

21. Conclusions • nine 1-year long runs with “SOCOL” have been completed • Ozone sensitivity is robust and in reasonable agreement with observations • Temperature sensitivity is not robust and deviates from the observations • We need more data and quantities to compare with observations (HALOE, ENVISAT?)

22. General conclusions • Goals of the sub-project are fulfilled: the model has been developed and experiments have been performed and analyzed. • UV does play a role in surface air temperature. • Analysis of the solar signal in several source gases, reservoirs and radicals (H2O, CH4, N2O, HCl, F12, HNO3, OH, HO2, ClO, NO2) has been performed and revealed agreement with theoretical expectations. Analysis of the solar signal for some species has no precedents. • The solar signal extracted from the transient runs might be different from the steady-state and closer to the observations. • Papers: - published in GRL: analysis of annual mean solar signal; - several papers in preparation (validation, chemical analysis, extended analysis of the steady-state runs and 27-day rotation cycle).

23. End of the presentation