Solar irradiance variability on hourly to decadal scale from SCIAMACHY and its impact on middle atmospheric ozone and ozone-climate interaction M. Weber, H. Bovensmann, J.P. Burrows, C. von Savigny, and J. Skupin Institute of Environmental Physics, University Bremen, Bremen Proposal submitted to DFG for funding within CAWSES (Climate and Waether of the Sun-Earth System) Schwerpunktsprogramm DFG CAWSES SPP Workshop, Bornheim, Jan 2005 SOLOZON

Overview climate change SCIAMACHY, GOME... solar irradiance solar proxies ozone and other trace gases chemistry & transport temperature & dynamics solar activity

New scientific questions  What can we learn about vis/nir spectral solar variability on short-term time scales from hours to solar rotation period?  What are suitable VIS/IR proxies for solar VIS/IR and TSI variability?  How do the solar proxies for UV and vis/NIR on hourly to monthly time scales correlate with corresponding changes in mesospheric and stratospheric ozone?  Can we detect a first sign of ozone recovery due to the turn around in the stratospheric halogen loading or is it related to changes in tropospheric forcings, dynamics, and solar forcing?

New scientific questions  What can we learn about vis/nir spectral solar variability on short-term time scales from hours to solar rotation period?  WP1: SCIAMACHY solar irradiance variability  What are suitable VIS/IR proxies for solar VIS/IR and TSI variability?  WP2: Solar activity proxy indicator from SCIAMACHY  How do the solar proxies for UV and vis/NIR on hourly to monthly time scales correlate with corresponding changes in mesospheric and stratospheric ozone?  WP3: Solar variability in ozone up to the mesopause  Can we detect a first sign of ozone recovery due to the turn around in the stratospheric halogen loading or is it related to changes in tropospheric forcings, dynamics, and solar forcing?  WP4: Ozone-climate-sun interaction

I SCIAMACHY solar irradiance variability  Sciamachy spectral range nm  About fifteen spectra per day (~1.5 hrs)  First routine space observation (along with SIM/SORCE) of VIS to NIR that contributes 70% to the total solar irradiance (TSI, „solar constant“) variability  Continuation of UV irradiance montoring (SBUV, SUSIM, GOME,SBUV2, SCIAMACHY,...)  Proposed work:  Investigate UV/vis/NIR irradiance variability from hourly to solar rotation period (27d)  Comparison with solar irradiance reconstruction models (SOLIVAR, PI Solanki) Skupin et al. 2004

II Solar activity proxy indicator from SCIAMACHY  Mg II index is an excellent solar activity proxy for UV irradiance variation down to 30 nm (Viereck et al. 2001)  longterm time series starting in 1979 (SBUV/ SUSIM/ GOME)  SCIAMACHY has high senstivity (order of ) for irradiance variation at visible wavelengths  Proposed work:  Search for suitable vis/NIR and TSI solar proxy  Extend and continue SCIAMACHY Mg II/Ca II index time series  Homogenisation of longterm composite Mg II index 500nm 280 nm Skupin et al % Update from Weber 1999

III Solar variability in ozone up to the mesopause SCIAMACHY data source  retrieval of upper atmospheric ozone (30-65 km) using Hartley band UV wavelengths (Rohen et al. 2004)  ozone information are derived for higher altitudes (50-90 km) using the O 2 ( 1  ) dayglow emission at 1.27µm (SICMA, PI Sinnhuber)  lower stratospheric ozone, NO2,… (v. Savigny et al. 2004) and total ozone (Weber et al., 2004)  Proposed work  Study short-term variability of upper stratospheric and mesospheric ozone linked to solar proxies (up to 27d periods) SCIAMACHY SCIAMACHY-MIPAS V4.6.1 comparison (434 profiles) Rohen et al. 2004

IV Ozone-climate-sun interaction  What are the causes of the rapid increase in NH ozone since mid nineties?  Are recent increase in eddy heat flux (HTF, tropospheric wave forcing) part of natural variability or related to climate change?  ozone recovery due to starting decline in effective stratospheric halogen loading still premature  Proposed Work:  Extend analysis to height-resolved ozone (SBUV/ SAGE/SCIAMACHY/GOME2)  Add more years (towards solar minimum) to better disentangle solar activity-dynamics-climate coupling in total ozone and ozonn profiles Dhomse et al. 2005

Outlook for future work Work in Phase 2 (Years 3 and 4):  Solar irradiance variability investigation and continuation of ozone trend evaluation during solar minimum condition  Solar variability in high altitude backscattered limb spectra using single scattering radiative transfer calculation for atmospheric corrections (very short time solar variability)  implementation of UV/vis irradiance variability in our 2D and 3D chemical transport models and scientific case studies  Combined interpretation of upper atmospheric temperatures and ozone variability to changes in the spectral solar irradiance.

Relation to themes in CAWSES  Characterisation of variable solar forcing thru electromagnetic radiation  Solar influence on atmospheric temperature, dynamics and chemical composition  Solar activity – climate interaction

Collaborations CAWSES Projects:  U. Langematz, Freie Universität Berlin, ProSECCO  J. Notholt, University of Bremen, SACOSAT  K. Pfeilsticker, University of Heidelberg, ABSOLAR  C. von Savigny, University of Bremen, SCIA-STOVE  S. Solanki, MPI für Sonnensystemforschung, SOLIVAR  M. Sinnhuber, University of Bremen, SICMA  Provision of updated solar proxies and írradiance variabilities  Mesospheric ozone from SCIAMACHY  Comparison to solar irradiance variability reconstruction  solar irradiance calibration External:  NRL (Floyd), NOAA (Viereck, Puga, Weatherhead), NASA (Hilsenrath, Janz), AWI Potsdam (Rex)

Requested resources  Personnel: Two scientists (2 X BATIIa)  solar variability (1 scientist, WPs 1 and 2)  ozone-sun-climate interaction (1 scientist, WPs 3 and 4)  Duration and start of project:  Start: July 2005  Phase 1: (2 years)  Phase 2: (2 years)