Langematz, Oberländer, Kunze Ulrike Langematz, Sophie Oberländer and Markus Kunze Institut für Meteorologie, Freie Universität Berlin, Germany The effects of different solar irradiance datasets on stratospheric heating rates and temperatures Workshop on "Recent variability of the solar spectral irradiance and its impact on climate modelling”, Berlin,

Langematz, Oberländer, Kunze 2  Largest solar cycle variations in short wavelengths – up to several tens of percent in the ultraviolet (UV) spectral range Lean et al., 1997 >50% in 121,6 nm (Lyman-α) 5-12% in nm 3-5% in nm 0.1 % change in TSI 11-year solar max minus min

Langematz, Oberländer, Kunze 3 SPARC (Stratospheric Processes and their Role in Climate) CCMVal (Chemistry-Climate Model Validation Activity), Chapter 3 (Radiation) (Figure 17, from Forster et al., 2011)  Simulation of the stratospheric solar signal requires … Solar only O 3 only Solar + O 3 spectrally resolved short-wave radiation scheme Heating rate differences solar max-min

Langematz, Oberländer, Kunze  Simulation of the stratospheric solar signal requires … spectrally resolved solar fluxes at TOA Spectral solar fluxes need to be prescribed at top of a GCM or CCM Standard data set: NRLSSI (Lean, 2000; Lean et al., 2005) Several new spectral solar irradiance data sets from different measurement platforms exist. To which extent is the simulated solar signal affected by the prescribed solar fluxes at the top of the atmosphere?

Langematz, Oberländer, Kunze 5  NRLSSI: Standard spectral irradiance data set  Alternative irradiance data sets  Effects of irradiance data sets on shortwave heating and temperature  Solar signal from SIM data set  Uncertainty factors Outline

Langematz, Oberländer, Kunze 6 NRLSSI: Standard spectral irradiance data set First daily spectral solar flux data set from Naval Research Laboratory, Washington D.C. Based on empirical model adjusted to measurements from  TIMED/SEE (Thermosphere Ionosphere Mesosphere Energetics and Dynamics - Solar EUV Experiment),  SOLSTICE (Solar Stellar Irradiance Comparison Experiment) on board UARS (Upper Atmosphere Research Satellite),  completed with SOLSPEC (Solar Spectral Irradiance Measurements) on ISS Most widely used dataset Input for SPARC CCMVal climate scenario simulations Maximum heating (~14 K/day) at summer stratopause (~1 hPa) Shortwave Heating Rates in K/day from FUBRad* scheme with NRLSSI data (Lean, 2000; Lean et al., 2005) 15 Jan * Nissen et al., 2007

Langematz, Oberländer, Kunze 7 Alternative Irradiance Data Sets I NRLSSI Lean, 2000; Lean et al., 2005 Naval Research Laboratory, Washington D.C. TIMED/SEE (Thermosphere Ionosphere Mesosphere Energetics and Dynamics - Solar EUV Experiment), SOLSTICE (Solar Stellar Irradiance Comparison Experiment) on board UARS, completed with SOLSPEC (Solar Spectral Irradiance Measurements) Empirical model Spectral range: nm Sampling: 1-5 nm MPS Krivova et al., 2009, 2011 MPl für Sonnensystem- forschung, Katlenburg-L. KPNSO (Kitt Peak National Solar Observatory) magnetograms and SOHO (Solar and Heliospheric Observatory) MDI (Michelson Doppler Imager) images SATIRE model Spectral range: nm Sampling: 1 nm IUP Pagaran et al., 2009 Institut für Umweltphysik, Universität Bremen SCIAMACHY (Scanning Imaging Absorption Spectrometer for Atmospheric Chartography) on ENVISAT (Environmental Satellite) Empirical SCIA proxy model Wavelength range: 230 – 1750 nm Sampling: 1 nm

Langematz, Oberländer, Kunze 10 – 20% differences between data sets in multi-annual mean ( ) in ultraviolet (UV), less than 5% in visible (VIS) and infrared (IR) Differences in incoming spectral solar flux (Fig. 16 and 17 from Pagaran et al., 2011) Pagaran et al., 2011

Langematz, Oberländer, Kunze 9 Slightly higher incoming fluxes in the Hartley bands for the IUP data set Largest incoming fluxes for the MPS data set in main parts of the Huggins bands, relevant for ozone absorption TOA solar flux in the Hartley and Huggins bands from IUP, NRLSSI and MPS data at solar minimum, September Differences in incoming spectral solar flux Central wavelengths of FUBRad spectral intervals [nm] integrated to 49 spectral intervals of FUBRad SW CCM radiation scheme

Langematz, Oberländer, Kunze 10 Effects of different spectral input data on radiative heating I Zhong et al., 2008: Two different solar irradiance spectra in line-by-line radiative transfer code 1.Spectral data from a theoretical spectral line model (Kurucz spectrum) 2.NRLSSI data Significant differences of up to 1.1 K/day in shortwave (SW) heating rates between spectra Heating rates in nm region (ozone Hartley band) for mid-latitude summer atmosphere Thick: line-by-line model Thin: broad-band model (Figure 2 from Zhong et al., 2008)

Langematz, Oberländer, Kunze 11 Changes in SW heating rates offline calculations with FUBRad shortwave radiation parameterisation (Nissen et al., 2007) ‏  high resolution CCM SW radiation scheme  49 spectral intervals: nm 15 th January conditions for solar zenith angle and orbital parameters mean O 3 -climatology (for January) ‏ Changes in temperatures and circulation GCM-type experiments with the Chemistry-Climate Model EMAC (ECHAM/MESSy Atmospheric Chemistry) (Jöckel et al., 2006) ‏ in EMAC-FUB configuration  FUBRad included  horizontal resolution: T42  39 levels (up to 0.01hPa) ‏ January conditions for zenith angle and orbital parameters mean O 3 -climatology (for January) 11-Year Solar Cycle number 22: Solar minimum: September 1986 Solar maximum: November 1989 Effects of irradiance data sets on shortwave heating and temperature II

Langematz, Oberländer, Kunze 12 Largest heating rates for MPS data set around 1 – 10 hPa (Huggins bands) Slightly higher values for IUP data set around 0.1 – 1 hPa (Hartley bands) ‏ MPS data set produces up to 5% higher SW heating rates than NRLSSI in global mean SW heating rate differences for solar minimum [K/day] Global mean (Oberländer et al., 2012, GRL)

Langematz, Oberländer, Kunze 13 Temperature signal – MPS minus NRLSSI Solar Minimum11-Year Solar Cycle Differences No significant effect on solar temperature signal Large dynamical variability in winter hemisphere Significantly warmer stratosphere for MPS data Impact of enhanced solar fluxes in MPS data directly reflected in temperature changes (Oberländer et al., 2012, GRL)

Langematz, Oberländer, Kunze Year solar cycle signal SW heating rate differences [K/day], (Cycle 22: Max: Nov 1989; Min: Sep 1986) NRLSSI ‚reference‘ data set 15 th January conditions (Oberländer et al., 2012, GRL) Stratospheric solar signal up to 0.2K/day at the summer stratopause (~50km) ↔ Hartley/Huggins bands (O3) Strong increase in heating rates in upper mesosphere ↔ Lyman-α-line (O2)

Langematz, Oberländer, Kunze 15 MPS Strongest solar signal (max to min) 0.03 K/day higher than NRLSSI in global mean; up to 0.05 K/day at summer stratopause IUP(/MPS) 20-40% higher global mean solar heating signal in lower and middle stratosphere 10-20% higher for upper strato- sphere and mesosphere Global mean (Oberländer et al., 2012, GRL) 11-Year solar cycle signal: Differences between data sets

Langematz, Oberländer, Kunze 16 Temperature signal – MPS minus NRLSSI Solar Minimum11-Year Solar Cycle Differences No significant effect on solar temperature signal Large dynamical variability in winter hemisphere Significantly warmer stratosphere for MPS data Impact of enhanced solar fluxes in MPS data directly reflected in temperature changes (Oberländer et al., 2012, GRL)

Langematz, Oberländer, Kunze 17 Solar signal from SIM data set SIM data Harder et al., 2009 SIM (Spectral Irradiance Monitor) on board SORCE (Solar Radiation and Climate Experiment) Available wavelength range: nm Sampling: 1-34 nm Available since April 2004 Up to six times larger changes in UV than NRLSSI from 2004 to 2007 Variations in the visible (VIS) and near- infrared (NIR) out of phase to changes in TSI and UV with increasing irradiance towards the minimum of solar cycle 23 (Figure 1 from Haigh et al., 2010) Differences in spectral irradiance: April 2004 minus November 2007

Langematz, Oberländer, Kunze SIM data show larger SSI changes SIM data changes out-of-phase in VIS compared to SCIA, SATIRE and NRLSSI SIM and SCIA proxy changes out-of-phase in NIR for decending solar cycle 23 in contrast to NRLSSI and SATIRE Differences in incoming spectral solar flux (Figure 18 from Pagaran et al., 2011) (Pagaran et al., 2011)

Langematz, Oberländer, Kunze 19 Prescribed solar flux: mean (May 2004) to minimum phase (Nov 2007) of SC 23 Modelling setup as before for NRLSSI, IUP, MPS (January conditions, O 3 fixed) Wavelengths < 200nm from SOLSTICE Solar Signal from SIM-data – modelling studies at FUB SW heating rate differences [K/day] at solar minimum SIM: lower absolute irradiance → weaker heating in UV bands (up to 0.5 K/day at summer polar stratopause, 0.3 K/day in global mean) SIM: slightly higher VIS heating at solar min (Oberländer et al., 2012, GRL) SIM-NRLSSI

Langematz, Oberländer, Kunze 20 Temperature signal – SIM minus NRLSSI Solar Minimum 2007 Significantly cooler stratosphere and mesosphere in summer for SIM data due to weaker UV- heating Significantly warmer summer upper stratosphere in 2004 compared to 2007 for SIM than for NRLSSI data Negative contribution from VIS flux more than compensated May 2004 minus November 2007

Langematz, Oberländer, Kunze 21 Solar cycle signal difference SIM  NRLSSI SW heating rates [K/day], May 2004 minus November 2007 SIM solar signal exceeds NRLSSI by 0.28 K/day at summer stratopause (0.18 K/day in global mean) SIM produces lower VIS heating for 2004 (solar mean) compared to 2007 (solar minimum), opposite to NRLSSI data (Oberländer et al., 2012, GRL)

Langematz, Oberländer, Kunze 22 Temperature signal – SIM minus NRLSSI Solar Minimum 2007 Significantly cooler stratosphere and mesosphere in summer for SIM data due to weaker UV- heating Significantly stronger warming in summer upper stratosphere in 2004 compared to 2007 for SIM than for NRLSSI data Negative contribution from VIS flux more than compensated May 2004 minus November 2007

Langematz, Oberländer, Kunze 23 Haigh et al., 2010: 2D CTM SIM data produces lower O3 above 45 km in 2004 Very different temperature structure compared to NRLSSI Solar Signal from SIM Data Set – Haigh et al., 2010 (Fig. 2 (left) and Supp. Fig. 1 (right), from Haigh et al., 2010) December 2004 minus 2007 NRLSSI SIM ΔO 3 ΔT 0.3 K 1.6 K

Langematz, Oberländer, Kunze Integrating spectral flux data sets into spectral radiation codes Spectral flux data sets have individual spectral resolution. SW radiation parameterization have individual spectral resolution. Spectral flux data need to be integrated to spectral intervals of SW radiation codes. 2 examples:

Langematz, Oberländer, Kunze 1. Effect of increased spectral resolution in SW radiation code FUBRad: Increase of spectral resolution in Chappuis band from 1 to 57 bands 49 FUBRad bands 106 FUBRad bands VIS: SIM > NRLSSI VIS: NRLSSI > SIM Global mean SW heating rate differences, Nov NRLSSI  SIM

Langematz, Oberländer, Kunze 2. Effect of integration method Comparison of two integration procedures to calculate spectrally integrated solar fluxes for SW radiation code form solar flux input data: int_tabulated (idl) bin_trapez SIM data

Langematz, Oberländer, Kunze SW heating rates for different integration methods Chappuis bandsUV + Chappuis bands Int_tab (idl) produces wrong integrated fluxes for input data sets with insufficient spectral resolution

Langematz, Oberländer, Kunze 11-year solar signal [K/day] for different integration methods and spectral resolutions Solar signal is not strongly affected due to the dominance of the UV. Work in progress

Langematz, Oberländer, Kunze