SOLAR IRRADIANCE VARIABILITY OF RELEVANCE FOR CLIMATE STUDIES N.A. Krivova.
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Transcript of SOLAR IRRADIANCE VARIABILITY OF RELEVANCE FOR CLIMATE STUDIES N.A. Krivova.
SOLAR IRRADIANCE VARIABILITY OF RELEVANCE
FOR CLIMATE STUDIES
N.A. Krivova
CGD, NCAR
SUN - CLIMATE
CGD, NCAR
SOLAR TOTAL IRRADIANCE:WHAT IS KNOWN?
PMOD TSI
0.1%
CGD, NCAR
BUT... (1)
CGD, NCAR
Long-term time series needed!!!
BUT... (1)
BUT... (2)
3 different composites!!!
CGD, NCAR
BUT... (3)Different trends in Mg II and TSI composites since 1999!!!
Froehlich, priv. comm.
SOLAR SPECTRAL IRRADIANCE:WHAT IS KNOWN?
SME (Solar Mesosphere Explorer): 1981-1989, 10-20% uncertainty in the UV
SOLSTICE & SUSIM on UARS: 1991-1.8.2005, daily, 120-400nm with ~1 nm resolution
BUT...
SME (Solar Mesosphere Explore)SME (Solar Mesosphere Explore):: 1981-1989, 10-20% uncertainty in the UV
SOLSTICE & SUSIM on UARSSOLSTICE & SUSIM on UARS:: 1991-1.8.2005, daily, 120-400nm with ~1 nm resolution
200-209 nm 270-274 nmSOLSTICE
SUSIM
difference
1=2-3%
SOLAR SPECTRAL IRRADIANCE:WHAT IS KNOWN?
SME (Solar Mesosphere Explorer): 1981-1989, 10-20% uncertainty in the UV
SOLSTICE & SUSIM on UARS: 1991-1.8.2005, daily, 120-400nm with ~1 nm resolution
SORCE andSCIAMACHY: since 2003, broadrange from UV to IR
SORCE: 310-1599 nm Dec 31, 2005
BUT... SCIAMACHY: March-May 2004
MODELS OF SOLAR IRRADIANCE
Changes in quiet photosphere:
r-mode oscillations, thermal shadowing, changes in the convection properties etc. (Wolff & Hickey 1987; Parker 1987, 1995; Kuhn et al. 1999)
Changes in surface structure:
darkening due to sunspots and brightening due to faculae and the network:
Stot(t)=Ss(t)+Sf(t)
MODELS OF SOLAR IRRADIANCE
Changes in surface structure:
darkening due to sunspots and brightening due to faculae and the network:
Stot(t)=Ss(t)+Sf(t)
1996 2000
FACULAE AGAINST SUNSPOTS
Data: MDI
1996 2000
FACULAE AGAINST SUNSPOTS
~-0.8Wm-2
1996 2000
FACULAE AGAINST SUNSPOTS
~-0.8Wm-2
~1.7Wm-2
Wenzler 2005
1996 2000
FACULAE AGAINST SUNSPOTS
~-0.8Wm-2
~1.7Wm-2
Wenzler 2005
0.1%
Fröhlich 2004
MODELS OF SOLAR IRRADIANCE
Changes in surface structure:
Regressions of sets of proxies:
Stot(t)=Sq+sSs(t)+fSf(t)
e.g., Foukal & Lean 1986, 1988; Chapman et al. 1994, 1996; Lean et al. 1998; Fligge et al. 1998; Preminger et al. 2002; Jain & Hasan 2004
Maps of a given proxy + semi-empirical model atmospheres:
Stot(t)=q(t)Sq+s(t)Ss+f(t)Sf
Fontenla et al. 1999, 2004; Unruh et al. 1999; Fligge et al. 2000; Krivova et al. 2003; Ermolli et al. 2003; Wenzler et al. 2004, 2005
quiet Sunsunspotsfaculae
MODELS OF SOLAR IRRADIANCE:
SATIRE (Spectral And Total Irradiance
REconstructions)Basic assumption: all solar irradiance changes on time scales longer than a day are due to solar surface magnetism
Input: magnetic field distribution (observations <e.g., MDI or KP> or model); spectra of photospheric components (model atmospheres)
Output: solar total and spectral irradiance vs. time
Free parameters: 1
Unruh et al. 1999; Fligge et al. 2000; Krivova et al. 2003;Wenzler et al. 2004, 2005
SATIRE: 4-component model
Iq() - quiet Sun intensity
T=5777K (Kurucz 1991)I
s() - sunspot int.; separate
umbra/penumbra (cool Kurucz models)
s( t ) - filling factor of
sunspots (MDI or KP continuum)I
f() - facular intensity
(modified P-model; Fontenla et al. 1993; Unruh et al. 1999)
f(t) - filling factor of
faculae (MDI or KP magnetograms)
SATIRE: cycle 23 (MDI-based)
Krivova et al. 2003
Data: VIRGO TSI
SATIRE:cycles 21-23 (KP-based)
Ground-based: variable seeing
2 different instruments: cross-calibration NASA/NSO 512-channel Diode Array Magnetograph (Feb. 1974 - Apr. 1992); NASA/NSO spectromagnetograph (Nov. 1992 - Sep. 2003)
Poorer quality of earlier data: identification of umbrae/ penumbrae
Wenzler et al. 2006
Data: PMOD TSI composite
SATIRE:cycles 21-23 (KP-based)
The dominant part of the solar irradiance variations are due to
the surface magnetic field
Rc=0.91
Reconstruction of TSI back to 1974
SATIRE:cycles 21-23 (KP-based)
Wenzler et al. 2006
Data: PMOD, ACRIM and IRMB TSI composites
Rc=0.84
Rc=0.91
Rc=0.87
PMOD
ACRIM
IRMB
SATIRE:cycles 21-23 (KP-based)
Wenzler et al. 2005
Data:Data: PMOD, ACRIM and PMOD, ACRIM and IRMB TSI compositesIRMB TSI composites
Rc=0.84
Rc=0.91
Rc=0.87
PMOD
ACRIM
IRMB
No minimum-to-minimum trend is seen (similarly to PMOD composite)
Krivova et al. 2003
MODELS OF SOLAR IRRADIANCE:
Spectral irradiance
Data: VIRGO channels (862, 500 & 402 nm)
Data: SUSIM
SATIRE
MODELS OF SOLAR IRRADIANCE:
Spectral irradiance
Krivova & Solanki 2004
SATIRESATIRE
SUSIM SUSIM
MODELS OF SOLAR IRRADIANCE:UV irradiance
Krivova et al. 2006
SATIRESUSIM
Regressions
F()/F(220 -240)
vs. F(220 -240)
for every
SUSIM: daily,1991- 2002 Rc=0.97
MODELS OF SOLAR IRRADIANCE:UV irradiance
Krivova et al. 2006
Krivova et al. 2006
All SATIRE reconstructions can be extended down to 115 nm
MODELS OF SOLAR IRRADIANCE:UV irradiance
Krivova et al. 2006
MODELS OF SOLAR IRRADIANCE:UV irradiance
MODELS OF SOLAR IRRADIANCE:
Krivova, Solanki & Floyd 2006
Solar cycle variation at 250-400 nm
MODELS OF SOLAR IRRADIANCE:
Spectral irradiance
Krivova et al. 2006
500 nm50 nm 100 nm
≈60%
≈8%
Krivova et al. 2006
500 nm50 nm 100 nm
≈60%
≈8%
More attention should be paid to the Sun's varying UV radiation
MODELS OF SOLAR IRRADIANCE:
Spectral irradiance
MODELS OF SOLAR IRRADIANCE:
Cyclic componentProxies: Zurich Sunspot Number, Rz
(1700 ff.)Group Sunspot Number, Rg
(1610 ff.)Sunspot areas, As (1874 ff.)Facular areas, Af (1874 ff.)Ca II plage areas, Ap
(1915 ff.)
Foukal & Lean 1990,Hoyt & Schatten 1993,Lean et al. 1995,Solanki & Fligge 1998, 1999,Lockwood & Stamper 1999,Fligge & Solanki 2000,Foster & Lockwood 2003
Solanki & Fligge 1999
SUN'S MAGNETIC FLUX:Secular change
Cyclic flux emergence in (large) active regions and (small) ephemeral regions
Take sunspot number (R) as a `proxy´
Extended cycle for ephemeral regions
ER start earlier
More extended, overlapping cycles
Open flux decays slowly
More extended cyclestime
active regionsephemeral regions
open flux
Solanki et al. 2002
MODEL OF THE SUN'S MAGNETIC FLUX:
Open flux
10Be Open solar flux
Interplanetary field
Solanki et al. 2000
Lockwood et al. 1999
Beer et al. 1990
MODEL OF THE SUN'S MAGNETIC FLUX:
Total flux
Balmaceda et al. 2006
take reconstructed magnetic fluxes: act(t),
eph(t), open (t)
use sunspot number Rz (or sunspot area) to separate sunspot and facular contributions to act
eph +open describes the evolution of the network
use the conversion scheme from the short-term rec. (Krivova et al. 2003) to convert magnetic flux into irradiance
MODELS OF SOLAR IRRADIANCE:
Long-term total flux
ephemeral regions active regions
open flux Solanki et al. 2002
MODEL OF SOLAR IRRADIANCE:Long-term
Balmaceda et al. 2006
MODEL OF SOLAR IRRADIANCE:Long-term
Balmaceda et al. 2006
~1W/m2
MODELS OF SOLAR IRRADIANCE:
SummaryContemporary models:
explain >≈90% of the observed TSI variations in cycles 23 and 22 and >≈80% of the observed variations in cycle 21;
show no bias between the 3 cycles;
do not show any significant minimum-to-minimum change;
reproduce measured variations of the solar spectral irradiance down to 115 nm;
emphasise the importance of the irradiance variations in the UV and stress the need for higher accuracy measurements between 300 and 400 nm;
point to a secular trend of about 1W/m2 (lower than previous estimates)
MODELS OF SOLAR IRRADIANCE:... and outlook
removal of the remaining free parameter;
tests for spectral irradiance using new data from SORCE
and SCIAMACHY and improvement of models on their
basis;
reconstruction of solar UV irradiance back to 1974 and
the end of the Maunder minimum;
reconstruction of solar irradiance on longer (millenia)
time scales
SATIRE:SATIRE:filling factorsfilling factors
Zakharov (priv. comm)
u= 0 or 1
p= 0 or 10≤f≤
1
q=1- u-p-
f
For each pixel:
I(t)=u(t)Iu()+p(t)Ip()+f(t)If()+q(t)Iq()
and sum up over all pixels