Multi-Model Comparisons of the Sensitivity of the Atmospheric Response to the SORCE Solar Irradiance Data Set within the SPARC-SOLARIS Activity K. Matthes (1,2), J.D. Haigh (3), F. Hansen (1,2), J.W. Harder (4), S. Ineson (5), K. Kodera (6,7), U. Langematz (2), D.R. Marsh (8), A.W. Merkel (4), P.A. Newman (9), S. Oberländer (2), A.A. Scaife (5), R.S. Stolarski (9,10), W.H. Swartz (11) (1) Helmholtz-Zentrum Potsdam Deutsches GeoForschungsZentrum (GFZ), Potsdam, Germany; (2) Freie Universität Berlin, Institute für Meteorologie, Berlin, Germany; (3) Imperial College, London, UK; (4) LASP, CU, Boulder, USA; (5) Met Office Hadley Centre, Exeter, UK; (6) Meteorological Research Institute, Tsukuba, Japan; (7) STEL University of Nagoya, Nagoya, Japan; (8) NCAR, Boulder USA; (9) NASA GSFC, Greenbelt, USA; (10) John Hopkins University, Baltimore, USA; (11) JHU Applied Physics Laboratory, Laurel, USA LASP seminar, 18 October 2011, Boulder

Outline Introduction/Motivation: Solar influences on climate SOLARIS project and objectives Uncertainty in solar irradiance data Preliminary results from the multi-model comparison Summary Outlook 2

IPCC (2007) Introduction/Motivation: natural vs. anthropogenic climate factors

Solar Influences on Climate Reviews in Geophysics 2010 (open access sponsored by SCOSTEP) 1.Introduction 2. Solar Variability Causes of TSI variability Decadal-scale solar variability Century-scale variability TSI and Galactic cosmic rays 3. Climate Observations Decadal variations in the stratosphere Decadal variations in the troposphere Decadal variations at the Earth’s surface Century-scale variations 4. Mechanisms TSI UV Centennial-scale irradiance variations Charged particle effects 5. Solar Variability and Global Climate Change 6. Summary / Future Directions

Sunspot number F10.7 cm flux Magnesium ii Open solar flux Galactic cosmic ray counts Total solar irradiance Geomagnetic Ap index Solar Variability ( ) Gray et al. (2010)

Labitzke, Labitzke and van Loon hPa Heights North Pole vs. F10.7 cm flux - February Climate Observations Correlations F10.7cm flux vs. 30hPa temperatures in July....beginning with the pioneering work of Karin Labitzke and Harry van Loon

Tropospheric winds Haigh, Blackburn, Simpson Schematic of Jetstream NCEP Zonal Mean Wind (m/s) ( ) 11-year Solar Signal (Max-Min) blocking events => cold winds from the east over Europe blocking events longer lived for solar minima (Barriepedro et al., 2008)

Observed Annual Mean Solar Signal in Ozone (%/100 f10.7) and Temperature (K/100 f10.7) Randel and Wu (2007) +2% 95% significant SAGE I/II Data ( ) SSU/MSU4 ( ) Randel et al. (2009) +1K Solar Maximum: More UV radiation => higher temperatures More ozone => higher temperatures

11-year Solar Signal (Max-Min) Composites Dec/Jan/Feb Climate Observations Sea surface temperature: 11 Max peak years Precipitation: 3 Max peak years van Loon, Meehl, White

anthropogenic + natural forcings natural forcings only Surface Temperatures: IPCC Solar variations cannot explain observed 20 th century global temperature changes long-term trend in solar activity appears to be decreasing, as we come out of the current ‘Grand Maximum’

Climate Observations: Summary Lots of examples of 11-yr solar influence in the stratosphere, troposphere and at the surface (e.g., temperatures (LvL), SSTs, mean sea level pressure, zonal and vertical winds, tropical circulations: Hadley, Walker, annular modes, clouds, precipitation), but predominantly regional response and sporadic in time. No evidence that solar variations are a major factor in driving recent climate change; if anything, radiative forcing looks as though it is reducing as we possibly come out of the current grand maximum. BUT, as we start to predict climate on a regional basis, it will be important to include solar variations in our models.

Climate Models: Majority of coupled ocean-atmosphere climate models include only total solar irradiance (TSI) variations, i.e. the so- called ‘bottom-up’ mechanism. More recent climate models now include the ‘top-down’ mechanism via the stratosphere. Some specialist models also now include charged particle effects, e.g. energetic particle fluxes, solar proton events etc.

Mechanisms: Sun - Climate Gray et al. (2010)

based on Kodera and Kuroda (2002) “Top-down mechanism”

u Stratospheric waves (direct solar effect) Tropospheric waves (response to stratospheric changes) Matthes et al. (2006) „Top-down“: Dynamical Interactions and Transfer to the Troposphere 10-day mean wave-mean flow interactions (Max-Min) EPF

Modeled Signal near Earth Surface Monthly mean Differences geop. Height (Max-Min) – 1000hPa Significant tropospheric effects (AO-like pattern) result from changes in wave forcing in the stratosphere and troposphere which changes the meridional circulation and surface pressure Matthes et al. (2006) +2K ΔT

SPARC-SOLARIS SOLARIS Goal: investigate solar influence on climate with special focus on the importance of middle atmosphere chemical and dynamical processes and their coupling to the Earth‘s surface with CCMs, mechanistic models and observations Activities: detailed coordinated studies on „top- down“ solar UV and „bottom-up“ TSI mechanisms as well as impact of high energy particles solar irradiance data recommendations (CCMVal, CMIP5)

SOLARIS Activities regular workshops: 2006 (Boulder, CO/USA), 2010 (Potsdam, Germany), 8-12 Oct 2012 (Boulder, CO/USA) side meetings: 2005 (IAGA conference, Toulouse, France), 2008 (SPARC, Bologna, Italy), 2010 (SCOSTEP, Berlin, Germany), 2011 (IUGG, Melbourne, Australia) new website:

SOLARIS Objectives What is the characteristic of the observed solar climate signal? What is the mechanism for solar influence on climate? (dynamical and chemical response in the middle atmosphere and its transfer down to the Earth’s surface) How do the different natural and anthropogenic forcings interact? (solar, ENSO, QBO, volcanoes, CO 2 ) 19

SOLARIS Experiments and Analyses Coordinated model runs to investigate aliasing of different factors in the tropical lower stratosphere Coordinated model runs to study the uncertainty in solar forcing Analysis of CMIP5 simulations 20

Uncertainty in Solar Irradiance Data 21 Lean et al. (2005)Krivova et al. (2006) Solar Max-Min Lean vs. Krivova Haigh et al., Nature (2010) Lean vs. SIM/SORCE larger variation in Krivova data in and nm range SORCE measurements from 2004 through 2007 show very different spectral distribution (in-phase with solar cycle in UV, out-of-phase in VIS and NIR) => Implications for solar heating and ozone chemistry

1. Compare Existing Model Runs Participating Models 22 Caveat: all the models used a slightly different experimental setup, so it won’t be possible to do an exact comparison

Differences in Experimental Setup 23 NRL SSISORCE (SOLSTICE&SIM) ozone EMAC-FUB2004 & 2007 No GEOS-5 CCM2004 & 2007 Yes HadGEM-Scaled up to Max & Min only UV ( nm) No IC2D2004 & 2007 Yes WACCM2004 & Yes

Experimental Design 24 Time series of F10.7cm solar flux „solar max“ 2004 „solar min“ : “solar max” (declining phase of SC23) 2007: “solar min” (close to minimum of SC23)

January Mean Differences (25N-25S) 25 Shortwave Heating Rate (K/d)Temperature (K) Pressure (hPa) Height (km) Pressure (hPa) NRL SSI SORCE larger shortwave heating rate and temperature differences for SORCE than NRL SSI data FUB-EMAC and HadGEM only include radiation, not ozone effects

January Mean Differences (25N-25S) 26 Ozone (%)Temperature (K) Pressure (hPa) Height (km) Pressure (hPa) larger ozone variations below 10hPa and smaller variations above for SORCE than NRL SSI data height for negative ozone signal in upper strat. differs between models NRL SSI SORCE

Shortwave Heating Rate Differences January (K/d) EMAC-FUBGEOS IC2DHadGEMWACCM NRL SSI SORCE NRL SSI shortwave heating rates: 0.2 to 0.3 K/d SORCE shortwave heating rates: 0.7 to >1.0 K/d (3x NRL SSI response)

28 Temperature Differences January (K) EMAC-FUBGEOS IC2DHadGEMWACCM NRL SSI SORCE NRL SSI temperatures: 0.5 to 1.0 K (stratopause) SORCE temperatures: 2.5 to 4.0 K (4-5x NRL SSI response) colder polar stratosphere

Ozone Differences January (%) EMAC-FUBGEOS IC2DHadGEMWACCM NRL SSI SORCE larger ozone variations below 10hPa and smaller variations above for SORCE than NRL SSI data height for negative ozone signal in upper strat. differs between models

Zonal Wind Differences January (m/s) EMAC-FUBGEOS IC2DHadGEMWACCM NRL SSI SORCE consistently stronger zonal wind signals for SORCE than NRL SSI data wind signal in SORCE data characterized by strong westerly winds at polar latitudes, and significant and similar signals in NH troposphere

SORCE Wind Differences NH Winter 31 EMAC-FUBGEOS IC2DHadGEMWACCM Dec Jan Feb

SORCE Geopot. Height Differences January (gpdm) EMAC-FUBGEOS HadGEMWACCM 500 hPa 100 hPa 10 hPa NAO/AO positive signal during solar max strongest for HadGEM and WACCM

Solar Cycle and the NAO 33 Solar Max: NAO positive (high index) Colder stratosphere => stronger NAO, i.e. stronger Iceland low, higher pressure over Azores  amplified storm track  mild conditions over northern Europe and eastern US => dry conditions in the mediterranean

Solar Min Surface Pressure Signal 34 Ineson et al. (2011) Model (HadGEM) Observations (Reanalyses) 90 (95%) significances 25 (50%) of interannual standard deviation

Solar Cycle and the NAO 35 Solar Max: NAO positive (high index) Solar Min: NAO negative (low index) Matthes (2011)

Summary  Consistently larger amplitudes in 2004 to 2007 in solar signals for SORCE than for NRL SSI data in temperature, ozone, shortwave heating rates, zonal winds and geopotential heights  Larger ozone variations below 10hPa and smaller variations above for SORCE than NRL SSI data; height for negative ozone signal in upper stratosphere differs between models  Solar cycle effect on AO/NAO contributes to substantial fraction of typical year-to-year variations and therefore is a potentially useful source of improved decadal climate predictability (Ineson et al. (2011))  Results for the SORCE spectral irradiance data are provisional because of the need for continued degradation correction validation and because of the short length of the SORCE time series which does not cover a full solar cycle 36

Outlook Next step: coordinated sensitivity experiments for a typical solar max (2002) and solar min (2008) spectrum from the NRL SSI and the SORCE data to investigate the atmospheric and surface climate response between the models in a more consistent way => White paper until early December, experiments to be started early 2012 in order to be ready for the SOLARIS/HEPPA workshop 8-12 October 2012 here in Boulder! 37

Thank you very much! Estes Park/RMNP,