Solar Spectral Irradiance (SSI) changes, atmospheric effects?. J. Fontenla NorthWest Research Associates and LASP-University of Colorado. The topic: SSI changes, and does it matter?. Solar Physics issues: Solar atmosphere structure and SSI Non-LTE radiative transfer
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NorthWest Research Associates
LASP-University of Colorado
Fontenla, Avrett, & Loeser 1991, FAL 2, The Astrophysical Journal, 377:712-725
Transition region: EUV/FUV emission lines
Upper chromosphere: deep absorption line cores and UV emission lines
Lower chromosphere: NUV, visible, IR absorption lines
Photosphere: visible,IR continuum and weak absorption lines
A-weak internetwork (new)
B-internetwork (changed C)
E-active network (changed F)
H-normal plage (new)
P-bright plage (changed P)
Q-very hot plage (new)
S-sunspot umbra (temp)
R-sunspot penumbra (new/temp)
Fontenla et al. 2006,The Astrophysical Journal, 639:441–458,
Models cross at ~6500 K, in NLTE.
Fontenla et al. 2011, JGR, 116, full NLTE, Tmin very different
Solanki & Unruh 1998, Astron. Astrophys. 329, 747-753, LTE.
No crossing in these models, SSI computed in LTE from FAL P with modifications.
Photospheric and chromospheric layers
Transition-region and Coronal layers
Features continuum contrast varies with wavelength and heliocentric angle, corresponds to the slope of T vs p, SRPM model set used detailed radiance observations
Sanchez Cuberes et al. 2002, The Astrophysical Journal, 570:886–899
Topka et al. 1997, The Astrophysical Journal, 484:479-486
San Fernando Observatory modelsGround-based radiance observations confirm that ARs are dim in the visible, over the solar cycle plage near the limb do not increase the visible SSI.Preminger et al. 2011, ApJ
Ca II K
Solanki & Unruh 1998,
Astron. Astrophys. 329, 747-753
According to this paper: «The dotted curve shows the observed relative irradiance variation for λ < 400 nm between solar activity minimum and maximum vs. wavelength, compiled by Lean et al. (1997) and extrapolated to longer wavelengths by Lean (1991). »
Relative changes between Solar Cycle 23 peak/min that I am using for WACCM4 simulation runs.
Nocorr – Fontenla et al 2011, SRPM + PSPT images
Corr - same as above with a correction to match TSI
NRLSSI – WACCM4 default.
Extension of the granulation structure. Some localized energy dissipation in the walls of downdrafts.
Loops and mechanical dissipation
C I 5381 models
Mg I 4572
Pressure (dyne cm^-2)3D Radiation Transport & NLTE
Computed for photospheric convection simulation snapshot
with data from Stein & Nordlund 2005
lowNetwork and its change over the cycle, what is “quiet-Sun”?
In the so-called “quiet-Sun”, i.e. locations where no obvious AR are present, the intensity distribution of the network is observed to change with the solar cycle (maybe not strictly in phase with the sunspot index).
This has implications for SSI and for TSI.
But available images lack reliable absolute calibration. Day to day matching was done with the median.
Feature, model, TSI
Intensity distribution at the disk center
Various instruments claiming reliable calibration for long term
Most instruments show variation of about ~50/1000~5% except for SUSIM.
Only SUSIM measured one peak, since UARS/SOLSTICE hardware failed in 2000
Both SORCE instruments show ~6% variations; their decreasing SSI turned around to increasing as SC 24 started in ~2010, but later data is not shown here.
Calculations were carried out by Merkel et al (see GRL38, L13802 2011), using SORCE data extrapolated in time. These are done with WACCM3 in static SSI runs.
Other authors also made simplified calculations showing important differences.
I am carrying out transient WACCM4 (NCAR Community Earth System Model 1.0.3 ) runs with coupled atmosphere, ocean, land, and ice. O3 is included but so are many other processes.
YearSSI “nocorr” model of SC23, vs NRLSSI
mW m-2 nm-1
delta.CLOUDT const models
delta.PS nrlssiPreliminary WACCM surface results
Does the SSI choice affect these?
More “realizations” are needed
How to cancel volcanic effects?
Volcanic eruptions are a big issue:
Mt. St. Helens 1980
El Chichon 1982
(relat)Zonal mean T and H2O changes
“const” displays changes that are not due to the SSI choice, difference of difference can eliminate some but is affected by the “noise” in both “nocorr” and const”
Issues analyzing simulation results to separate SSI effects from other effectstropical (±25 deg) annual differences between peak and min years
Other WACCM Simulation Interesting Results from other effects
Shows the downwelling solar shortwave flux at the surface increases of ~30 W m-2 at the Pacific Ocean Warm Pool region at solar max times. But was shown before that the surface temperature does not increase much there. Ocean effects, Kuroshio stream, moderate T?
The NRLSSI dif. of dif. have also some of this behavior on the Pacific Ocean Warm Pool but the details are quite different. Also, NRLSSI results show several differences in other regions, e.g. the patterns in Mexico Pacific area, Brasil Atlantic, and Madagascar Indian Ocean which are not shown by “nocorr” results
Ocean currents couple to atmospheric winds and tropospheric energy transport. This is represented in CESM1.0.3/WACCM4 by the integration of the atmospheric model (CAM2) with the deep ocean model (POP).
The tropospheric and ocean phenomena are very tangled!
Analysis is very complex but these simulations contain a wealth of data which could nail down the physical processes induced by SSI changes.
That is, if one could also figure out other forcing and variability.
A nice example on 2/3/2007 shows two large magnetic active regions sunspots side-by-side and one is associated with a lot of chromospheric and coronal heating but the other is not showing much heating.
The magnetic flux of the sunspots is not too different but the bright region is bipolar and more complex.