SCIAMACHY solar irradiances during solar cycle 23 and beyond

1. SCIAMACHY solar irradiances during solar cycle 23 and beyond Mark Weber, Joseph Pagaran, Stefan Noël, Klaus Bramstedt, and John P. Burrows weber@uni-bremen.de TOSCA Workshop, Berlin, 14-16 April 2012

2. Motivation • x • SCIAMACHY observes SSI in UV/vis/near-IR • solar irradiancechanges in theopticalrangeand (near) UV • relevant for TSI composition (near UV andvis) • atmosphericheatingrates (uv) • Challenges: • above 300 nm solar cyclevariabilityisbelow 1% • Optical degradationaffectslong-term stabilityof UV SSI • Atmosphericandclimateimpactrequiresknowlegeofspectral solar variability (particularly in theUV) Grey et al., 2010 continuous SCIA spectral range

3. Topics ENVISAT/SCIAMACHY mission Solar irradiance observations Comparisons with other SSI data SCIA proxy model Degradation correction

4. SCIAMACHY SCIAMACHY = SCanningImaging Absorption spectroMeter for Atmospheric CHartograpY • Features: • UV/Vis/NIR gratingspectrometers: • 220 - 2380 nm • Moderate spectralresolution: • 0.2 – 1.5 nm • Measurement Geometries: • Launch date: February 28, 2002 • Polar, sun-synchronous orbit • Descending node: 10:00 LST • Altitude: 800 (783) km

5. ENVISAT mission status TIRA radar image of ENVISAT (image courtesy Spiegel Online News, April 14, 2012) Photo from PLEIADES (April 15, 2012) • SCIAMACHY instrument: was healthy, no large data gaps (2002-2012) • lost complete communication with ENVISAT on Easter Sunday (April 8th) • ESA declared mission end (May 10th) • attempts to re-establish contact will continue until end of June /chances are slim • Causes of failure: • loss of the power regulator blocking irreversibly telemetry and telecommand • short circuit, triggering a 'safe mode' (kind of shutdown) with subsequent platform anomaly (orientation change)

6. SCIAMACHY data products • ozonechemistry (nadir/limb/occult) • NO2, O3, OClO, BrO, H2O, aerosol • greenhousegases (nadir) • CH4, CO, CO2 • airpollution/biogenic (nadir) • NO2, O3, BrO, IO, H2CO, glyoxal, SO2, H2O • Other: • Limb: PSC, NLC/PMC, OH* /mesopause T, mesosphericmetals • Nadir: pytoplanctons/oceancolour, clouds, surfacereflectance, mesosphericmetals, thermospheric NO • spectral solar irradiance (SSI)

7. Solar irradiance measurements by SCIAMACHY • Continuous coverage: 230-1700 nm • Spectral resolution: < 1.5 nm Spectrometer design: double monochromator (predisperser prism and gratings in each channel) Reticon linear diode array detector • Pagaran et al., 2011a

8. Solar irradiance measurements by SCIAMACHY • Daily full solar discmeasurementsusing diffuser • Radiometricallycalibratedbeforelaunch • Degradation correctionusingseveralopticalpaths (combinationofmirrorsand/or diffuser, lampsources) • So farassumesconstantirradiance • onlysuitableforatmosphericapplications • newdegradationcorrectionsare in preparation (seelater) • Challenges: instrumentand ENVISAT platformanomaliesmaintenances H2O • Pagaran et al., 2011a

9. SCIAMACHY irradiancecomparisons: VIS/NIR 0.2% March 2004 • Directcomparisonsto SOLSPEC/ATLAS3: • SCIA agreementtowithin 3% in thevisibleand 5% in near IR wrttootherdata • overseveral solar rotations • relative accuracy ~0.1%! • Pagaran et al., 2011a

10. SCIAMACHY SSI comparisons: UV w. WLS March 2004 w/o WLS Comparison of satellite data to Hall-Anderson spectra in the UV • SCIA data: • low SNR below 240 nm • optical degradation in the UV: ~-15% • Correction possible by using internal white lamp sources (WLS) • Agreement within 3% • However: data is over corrected since WLS also degrades with time

11. Solar proxiesfrom SCIAMACHY: Mg II index • Mg II core-to-wingrationear 280 nm • Correlateswellwith UV and EUV SSI changes (Deland andCebula 1993, Viereck et al., 2001) • insensitiveto instrumental degradation (tofirstorder) (Heath & Schlesinger 1986) • compositesavailablefrom multiple sensors • usedfor UV SSI reconstructionandcalibrationcorrections • Isthe solar cycle 24 minimum (~2009) lowerthanpriorminima? • thermosphericcontraction(unusuallylowneutral density) due tobelow normal solar activity? (Emmert et al. 2010, 2011, Solomon et al. 2011)

12. SCIAMACHY solar proxymodel SCIAMACHY proxy model • Parameterization of SCIAMACHY SSI changes in terms of scaled solar proxies, here Mg II index (faculae brightening) and photometric sunspot index PSI (sunspot darlening, Balmceda et al. 2009) • allows reconstruction of solar cycle change in SSI • assumes that magnetic surface activity are responsible for irradiance variations (Fligge et al., 2000) • assumes that solar rotation changes scale up to solar cycle like the proxies • similar approach: Lean et al., 1997, 2000 SCIAMACHY SSI at a referencedate Mg II index PSI index piecewisepolynomials (degradation, anomalycorrections) Scalingparametersderived fromseveral solar rotations Mg II index • Pagaran et al., 2009 PSI index

13. Halloween 2003 solar storm TSI ~ -0.4% • Pagaran et al., 2009 • Irradiancechangeduring Halloween 2003 solar storm • Lowest PSI valuesincethirtyyears • SCIA proxymodelseparates faculaeandsunspotcontributions • TSI reduction (-0.4%) aboutfour time highermagnitudethanchangeduring solar cycle (~0.1%) • darkfaculanear 1500 nmdetectedby SCIAMACHY, but isunderestimated(seealso Unruh et al. 2008)

14. SCIA proxy in solar cycle 23 • Pagaran et al., 2011b Irradiance change during solar cycle 23 (1996 to 2002) Below 400 nm faculae brightening dominating, with non-neglible contribution from sunspot blocking in the near UV (>300 nm) dark faculae near 1400-1600 nm

15. Error estimates for SCIA proxy • Pagaran et al., 2011b Error estimate from the proxy fit to observations Other systematic errors difficult to assess and are unknown Solar cycle changes in the visible/NIR are statistically insignificant except for 1400-1600 nm (dark faculae)

16. Comparisons over several solar cycles • Pagaran et al., 2011b Models • SATIRE SC variations are bit larger than NRLSSI & SCIA proxy • Lower variability in SIP/Solar2000 (Tobiska et al.) Observations: Some issues in the late 1980 with the de Land UV composite (related to N9/N11 SBUV2 data) in the late 1980s (see also Lockwood et al., 2011) Larger SIM trend in the UV in SC 23

17. Comparisons: SSI solar cyclechanges • Comparisonsof SSI changesduringpartofdescendingphasesof SC 21-23 • SCIA proxymodel (Pagaran et al., 2009, 2011b) • NRLSSI model (Lean 2000) • SATIRE model (Krivova et al. 2009) • Deland & Cebula(2008) UV composite • SIM/SORCE and SUSIM observations • SIM changesduring SC 23 fourtimes larger thanthemodelsanddoubledthechangesof SUSIM and UV compositeduring SC 22 • challengesthevalidityofmodelsassuming solar surfacemagneticactivityas a primarysourceof SSI changes • large impact on atmosphericheatingrates (Cahalan et al. 2010, Haigh et al. 2010, Oberländer et al., 2012) andmesosphericozone (Merkel et al., 2011) • Pagaran et al., 2011b

18. Summary & conclusions • Spectral solar irradiancefrom SCIAMACHY: • Daily irradianceand Mg II measurementssince2002-2012 • SCIA proxymodelforextrapolating SSI from solar rotationsto solar cycle (SC) • Not reproducingSC changesseenwith SIM • challengesthevalidityofproxybasedandempiricalmodelsassumingmagneticsurfaceactivityasprimarysourceof SSI variations • Clear needforcontinuedspectral solar measurements • Issues: long-term stability • SC changesabove 300 nmarewellbelow 1%! • Other solar related SCIA studies: • 27-day solar signature in stratosphericozone (Dikty et al., 2010) and polar mesosphericclouds/NLCs (Robert et al., 2009) • NH polar ozonelosses in connectionwith QBO and solar activity (Sonkaew et al., 2011) • Solar protonrelatedmesopshericozoneloss (Rohen et al., 2005)

19. Outlook 300-400 nm Goal: derivation of SC 23 (24) trends directly from SCIA SSI (w/o proxies) test if SSI UV changes scale from rotational to SC time scale in a different way than the Mg II index (and SCIA proxy) This requires the application of suitable degradation corrections to SCIA SSI: Exploit the different rate of optical degradation in the different optical paths Main cause of degradation: contaminants on mirror & diffuser surfaces (azimuth and elevation scanner)

20. Degradation correction: contamination model A opticaldegradationmodelhasbeendevelopedthatfitscontaminationthicknessesas a functionof time tothevariousopticalsurfaces • Promising results • But: thismodelassumesnonaturalvariabilityof SSI  Need toimprove upon separationof instrumental andnaturaleffects on SSI changes in thecontaminationmodel Detector heat up (ice removal on NIR detectors)

21. Further work • Improving optical degradation model for SCIAMACHY • derive SSI trends independent of proxies • Combine GOME1 (1995-2011) and GOME-2 (2007-present) SSI data to extend the SCIAMACHY SSI record • Channel 1-4 of the GOMEs (240-800 nm) similar to SCIAMACHY in terms of spectral resolution

22. Publications Oberländer, S., U. Langematz, K. Matthes, M. Kunze, A. Kubin, J. Harder, N. A. Krivova, S. K. Solanki, J. Pagaran, and M. Weber, The Influence of spectral solar irradiance data on stratospheric heating rates during the 11 year solar cycle, Geophys. Res. Lett., 39, L01801, doi:10.1029/2011GL049539, 2012. Pagaran, J., M. Weber, J. P. Burrows, Solar variability from 240 to 1750 nm in terms of faculae brightening and sunspot darkening from SCIAMACHY, Astrophys. J., 700, 1884-1895 , 2009. Pagaran, J., J. Harder, M. Weber, L. Floyd, and J. P. Burrows, Intercomparison of SCIAMACHY and SIM vis-IR irradiance over several solar rotational timescales, Astron. Astrophys., 528, A67, doi:10.1051/0004-6361/201015632, 2011. Pagaran, J., M. Weber, M. DeLand, L. Floyd, J. P. Burrows,Solar spectral irradiance variations in 240-1600 nm during the recent solar cycles 21-23, Sol. Phys., 272, 159-188, doi:10.1007/s11207-011-9808-4, 2011. Pagaran, J. A., Solar spectral irradiance variability from SCIAMACHY on daily to several decades timescales, Ph.D. thesis, University of Bremen, 2012. Weber, M., J. Pagaran, S. Dikty, C. von Savigny, J. P. Burrows, M. DeLand, L. E. Floyd, J. W. Harder, M. G. Mlynczak, H. Schmidt, Investigation of solar irradiance variations and their impact on middle atmospheric ozone, Chapter 3, in: Climate And Weather of the Sun-Earth System (CAWSES): Highlights from a priority program, ed. F.-J. Lübken, to be published by Springer, Dordrecht, The Netherlands, 2012.

23. additional slides

24. solar- earthatmospherecoupling solar irradiance chargedparticles (e,p) NH SH 49 km Rohen et al. 2005 courtesyLangematz • Solar influence on atmosphere via radiation & chargedparticles • Impacts chemistryanddynamics (transport/circulation)

25. Long-term trends in stratospheric O3 Adapted fromSteinbrecht et al., Ozone and temperature trends in the upper stratosphere at five stations of the Network for the Detection of Atmospheric Composition Change, Int. J. Rem. Sens. [2009] x

26. 27 daysignature in SCIAMACHY stratosphericozone blue: ozone black: Mg II index • Different frequencyanalysesofozone • CWT, FFT, cross-correlation • max. cross-correlationduring SC is 0.38, weakerthan in prior solar cycles (see also Fioletov, 2009) • 27d signalisvaryingandvanishesforselected 3-month periods(maxcorrelation r=0.7) • About a factor 2 smallerthanobserved in otherstudiesandearlier solar cycles (e.g. Gruzdev et al., 2009) Dikty et al. 2010b

27. NH polar chemicalozonelossand QBO Arcticozone hole 2010/11 W Sonkaew et al., 2011 • 10-50 hPa polar temperaturechange in Feb-Mar warm warm cold warm Camp & Tung, 2007 • SCIAMACHY observationduringdescendingphaseof SC23 (mostlycloseto solar min conditions) • Arctic winters with high PSC ratesand high ozonelossduring QBO west phase (in mostcases)