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 ? Should we expect any measurable climatic effect? How does the solar activity influence the Earth’s climate? Slide 2

Guises of the 11-yr solar cycle Geomagnetic flux Particle precipitation Galactic cosmic rays Total solar irradiance  1 W/m 2 or 0.1% Spectral solar irradiance  extreme UV: 100%  UV: 4-6% 100 % 10 % 1 % 0.1 % 0.01 % 100 nm 1 μm10 μm After Gray et al., 2010 Slide 3

Troposphere Stratosphere Ocean Suggested mechanisms Stratosphere VIS Adapted from Gray et al Total solar irradiance:  1 W/m 2 at the top of the atmosphere translates to 0.18 W/m 2 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 Slide 4 30 ° S30 ° N UV

1) How does the 11-yr solar cycle affect the tropical lower stratosphere? Secondary maximum: real or analysis artifact? Does ocean coupling matter? 2)How does the 11-yr solar cycle affect the tropical atmosphere-ocean system? El Nino- or La Nina-like? Research questions Slide 5

Outline 1)Introduction 2) Model description and analysis methodology 3)The response of the tropical lower stratosphere to the SC in ensemble simulations 4)The response of the tropical Pacific to the SC in ensemble simulations 5)Synthesis Slide 6

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 (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 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

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

Outline 1)Introduction 2) Model description and analysis methodology 3)The response of the tropical lower stratosphere (TLS) to the SC in ensemble simulations 4)The response of the tropical Pacific to the SC in ensemble simulations 5)Synthesis Slide 9

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

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

Temperature response ERA40 ( )MERRA ( ) 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 CENS-T63 ensemble ( ) Slide 11

Tropical (25S-25N) temperature profiles Temperature (K/100 sfu)  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 ( nm)  Trivial sensitivity to ocean coupling Slide 12

Intra-ensemble variability of the tropical temperature profiles Slide 13

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

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

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

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

Outline 1)Introduction 2) Model description and analysis methodology 3)The response of the tropical lower stratosphere (TLS) to the SC in ensemble simulations 4)The response of the tropical Pacific to the SC in ensemble simulations 5)Synthesis Slide 18

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 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. Slide 19 After Meehl et al., 2009

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

Regression of ensemble mean SST onto the F10.7 SC signature in CENS  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 (K/100 sfu) Slide 21 SC signature in MENS

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

Coupled vs Uncoupled: zonal winds AtlanticPacificIndian SC signature in CENS  Westerly anomalies independently of ocean coupling SC signature in AENS Slide 23 m/s/100 sfu K/100 sfu SC signature in MENS

ERA-40 reanalysis ( ) AtlanticPacificIndian Regression of equatorial zonal winds onto the F10.7 CENS ( ) 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? Slide 24

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

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

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

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

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

Outline 1)Introduction 2) Model description and analysis methodology 3)The response of the tropical lower stratosphere (TLS) to the SC in ensemble simulations 4)The response of the tropical Pacific to the SC in ensemble simulations 5)Synthesis Slide 30

Troposphere Stratosphere Ocean Stratosphere UV Synthesis 1)The tropical Pacific warms in solar maxima. 2)The surface response affects the troposphere but not the stratosphere. 3)Trivial changes in the tropical troposphere by solar signals in the stratosphere. 30 ° S30 ° N Ocean VIS Strong Weak Not tested Thank you Slide 31