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Influences of the 11-year solar cycle on the tropical atmosphere and oceans

Influences of the 11-year solar cycle on the tropical atmosphere and oceans. Stergios Misios and Hauke Schmidt Max Planck Institute for Meteorology TOSCA workshop , 2012. Heading to a solar maximum in 2013. 2013 ?. 2008. Should we expect any measurable climatic effect?

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Influences of the 11-year solar cycle on the tropical atmosphere and oceans

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  1. Influences of the 11-year solar cycle on the tropical atmosphere and oceans Stergios Misiosand Hauke Schmidt Max Planck Institute forMeteorology TOSCA workshop, 2012

  2. Heading to a solar maximum in 2013 2013 ? 2008 Should we expect any measurable climatic effect? How does the solar activity influence the Earth’s climate? Slide 2

  3. Guises of the 11-yr solar cycle Geomagnetic flux Particle precipitation Galactic cosmic rays Total solar irradiance • 1 W/m2 or 0.1% Spectral solar irradiance • extreme UV: 100% • UV: 4-6% 100 % 10 % 1 % 0.1 % 0.01 % 100 nm 1 μm 10 μm After Gray et al., 2010 Slide 3

  4. Suggested mechanisms Total solar irradiance: • 1 W/m2 at the top of the atmosphere translates to 0.18 W/m2 at the surface • Energy balance models predict ~0.1 K global-mean warming ! Spectral solar irradiance: • Affects ozone • Stratospheric warming of about 1 K Two main mechanisms: • Top-down • Bottom-up UV VIS Stratosphere Stratosphere ? ? Troposphere ? Ocean 30°S 30°N Adapted from Gray et al. 2010 Slide 4

  5. Research questions 1) How does the 11-yr solar cycle affect the tropical lower stratosphere? Secondary maximum: real or analysis artifact? • Does ocean coupling matter? • How does the 11-yr solar cycle affect the tropical atmosphere-ocean system? • El Nino- or La Nina-like? Slide 5

  6. Outline Introduction Model description and analysis methodology The response of the tropical lower stratosphere to the SC in ensemble simulations The response of the tropical Pacific to the SC in ensemble simulations Synthesis Slide 6

  7. Model description and analysis methodology Middle Atmosphere version of ECHAM5/MPIOM • Detailed stratospheric dynamics: internal QBO • Present-day greenhouse gas concentrations Modifications to simulate a realistic solar cycle forcing • Solar spectral irradiances from 1955-2006 (Lean et al., 2000) • Solar-induced ozone anomalies from HAMMONIA (Schmidt et al., 2010) Experiments • CENS: coupled ensemble (11 members, T31L90/GR30L40 ) • AENS: uncoupled ensemble ( 9 members, T31L90 ) • MENS: mixed layer ocean ensemble (11 members, T31L90 ) • CENS-ST: twin to CENS but with stronger forcing in the 185-250 nm band ssssssssssssssssssssssssssssssssssssssssssssssss ( 9 members, T31L90/GR30L40) • CENS-T63: twin to CENS-ST but in a finer horizontal resolution ssssssssssssssssssssssssssssssssssssssssssssssss (15 members, T63L95/GR15L40) Slide 7

  8. Model description and analysis methodology • Observations • MERRA reanalysis (1979-2008) • ERA-40 reanalysis (1979-2001) • Solar signals are extracted with: • MRA model with AR1 (Frame and Gray, 2010): • Multi-channel Singular Spectrum Analysis (MSSA, Ghil et al. 2002) Slide 8

  9. Outline Introduction Model description and analysis methodology The response of the tropical lower stratosphere (TLS) to the SC in ensemble simulations The response of the tropical Pacific to the SC in ensemble simulations Synthesis Slide 9

  10. How does the 11-yr solar cycle affect the tropical lower stratosphere? • Secondary maximum: real or analysis artifact? • Does ocean coupling matter? Data: • MERRA and ERA-40 • Coupled and uncoupled ensembles • Ensemble-mean temperature anomalies • Ensemble-mean zonal wind anomalies • Methods: • AR1 multiple linear regression analysis • Regression coefficients are scaled per 100 sfu • See Schmidt et al., 2012, Springer Slide 10

  11. Discontinuities in MERRA(Modern Era Retrospective-analysis for Research and Applications) ~50 Km ~35 Km Solar signal of 1K?

  12. Temperature response CENS-T63 ensemble (1955-2006) ERA40 (1979-2001) MERRA (1979-2008) K/100 sfu MERRA: weaker warming in the lower tropical stratosphere compared to ERA-40 Our simulations: lacking of any strong secondary warming in ensemble averages Slide 11

  13. Tropical (25S-25N) temperature profiles • Lacking of any strong secondary warming in the TLS in all model configurations • Stronger warming throughout the stratosphere in the simulations with amplified UV forcing (185-250 nm) • Trivial sensitivity to ocean coupling Temperature (K/100 sfu) Slide 12

  14. Intra-ensemble variability of the tropical temperature profiles Slide 13

  15. Effects of collinearity Solar regression coefficients @ 70 hPa Correlation between F10.7 and Nino-3.4 • Positive correlations result in weaker regression coefficients • -0.06 K/100 sfu per 0.1 increment • Observed correlation (1979-2003): -0.15 Slide 14

  16. Zonal wind anomalies • Stronger solar heating improves the time evolution • Increased horizontal resolution gives more realistic evolution Slide 15

  17. Inter-ensemble variability in February (CENS-ST) Positive and negative anomalies up to 7 m/s Slide 16

  18. Summary 1 • How does the 11-yr solar cycle affect the tropical lower stratosphere (TLS)? • Secondary maximum: real or analysis artifact? • None of the experiments shows a temperature response maximum in the TLS in ensemble averages. • Many individual ensemble members do show well-formed annual temperature maxima in the TLS. • CENS-T63 shows closer agreement with observations but the intra-ensemble variability is very high • Collinearity between the ENSO and solar cycle term in the multiple linear regression model biases the estimates • Does ocean coupling matter? • The ensemble mean stratospheric solar do not critically depend on the ocean coupling Slide 17

  19. Outline Introduction Model description and analysis methodology The response of the tropical lower stratosphere (TLS) to the SC in ensemble simulations The response of the tropical Pacific to the SC in ensemble simulations Synthesis Slide 18

  20. How does the 11-yr solar cycle affect the tropical oceans? El Nino- or La Nina-like response ? Data: • Coupled and uncoupled ensembles • Simulations of Bal et al. 2011 with EGMAM • Ensemble-mean SST and zonal wind anomalies • Low-order ENSO model • Methods: • Regression analysis • MSSA • More details in Misios and Schmidt, 2012, J.Clim. After Meehl et al., 2009 Slide 19

  21. Reexamination: Observed solar cycle signals ? Misios and Schmidt, in prep. Slide 20

  22. Regression of ensemble mean SST onto the F10.7 SC signature in MENS SC signature in CENS (K/100 sfu) • Warming up to 0.12 K/100 sfu in CENS • Warmer tropical Pacific in MENS • Radiative balance calculations do not explain the simulated warming in CENS Slide 21

  23. Comparison of simulations with and without ocean coupling Dynamic Ocean (CENS) Mixed layer (MENS) • Excess precipitation in the western Pacific • Implies eastward displacement of the deep convection Slide 22

  24. Coupled vs Uncoupled: zonal winds SC signature in CENS SC signature in AENS m/s/100 sfu K/100 sfu SC signature in MENS Indian Pacific Atlantic • Westerly anomalies independently of ocean coupling Slide 23

  25. Regression of equatorial zonal winds onto the F10.7 Simulations: westerly anomalies independent of ocean coupling. Observations? Westerly anomalies are detected in ERA-40 with an AR1-MRA model. Do westerly anomalies explain the surface warming? CENS (1955-2006) ERA-40 reanalysis (1958-2001) Indian Pacific Atlantic Slide 24

  26. Low order ENSO model heat fluxes heat fluxes wind stress zonal advection eastern Pacific vertical advection western Pacific Subsurface After Jin 1997 with parameters of Timmerman and Jin 2002 temperature in the eastern Pacific Slide 25

  27. Solar forcing of LO-ENSO temperature in the eastern Pacific Months • A decadal warming is simulated when LO-ENSO is forced with westerly anomalies Slide 26

  28. Simulated Pacific warming in solar maxima • Idealized simulations • Model setup as CENS • 3x sinusoidal solar cycle • 11 solar cycles, 9 ensembles Bal et al., 2011 simulations • EGMAM • 2.5x sinusoidal solar cycle • 3 ensembles, 10 solar cycles Idealized solar forcing Slide 27

  29. Top-Down or Bottom-Up? Lagged regression coefficients (25S-25N) (K/100 sfu) Tropospheric response lags the stratospheric response by 1-2 years Slide 28

  30. Summary 2 • How does the 11-yr solar cycle affect the tropical oceans? • The coupled ensemble shows a basin-wide warming with increased solar cycle forcing. • Tempo is given by the westerly anomalies over the tropical Pacific. • Both the surface and the tropospheric temperature response lags the solar forcing by ~1-2 years Slide 29

  31. Outline Introduction Model description and analysis methodology The response of the tropical lower stratosphere (TLS) to the SC in ensemble simulations The response of the tropical Pacific to the SC in ensemble simulations Synthesis Slide 30

  32. Synthesis UV VIS The tropical Pacific warms in solar maxima. The surface response affects the troposphere but not the stratosphere. Trivial changes in the tropical troposphere by solar signals in the stratosphere. Stratosphere Stratosphere Weak Weak ? ? Troposphere Strong Not tested ? Ocean Ocean Thank you Thank you 30°S 30°N Slide 31

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