Solar Spectral Irradiance Variability
Origins in the Solar Atmosphere and
Impacts on Earth’s Atmosphere
Meeting Summary
Tom Woods
LASP / University of Colorado
tom.woods@lasp.colorado.edu
Organizers
Bob Cahalan, Jerry Harder, Jae Lee,
Peter Pilewskie, Mark Rast, Gary Rottman,
Marty Snow, Tom Woods, Vanessa George
NASA SORCE Mission, GSFC-LASP Sun-Climate Research Center
2012 SORCE Meeting Summary – Tom Woods
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Key Questions for Meeting
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• How do three-dimensional models of the solar
atmosphere further our understanding of the radiative
properties of the solar atmosphere relative to static one
dimensional models?
• Do small scale processes on the Sun give a reasonable
explanation of solar spectral irradiance (SSI) variability?
• How does incorporating SSI data into GCM’s improve
the prediction skills of these models?
• Do different GCM models produce similar results with
the same solar input?
• How well do SSI model predictions agree with
observations over decadal time scales?
• How well do GCM model predictions agree with
observations over decadal time scales?
2012 SORCE Meeting Summary – Tom Woods
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Key Questions for Meeting - 1
• How do three-dimensional models of the solar atmosphere
further our understanding of the radiative properties of the
solar atmosphere relative to static one dimensional models?
– 1-D model radiance is expected to be lower than 3-D
model as result of averaging temperature (Uitenbroek)
– Flux tubes heat laterally and have brightness variations
with view angle (Uitenbroek, Trampedach)
– 3-D model significantly improved with updated opacities
(Trampedach)
– 3-D modeling is not yet practical for irradiance studies
– 1-D modeling is feasible and also necessary considering
that the physics of chromosphere and coronal heating is
not yet fully understood (Fontenla)
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Key Questions for Meeting - 2
• Do small scale processes on the Sun give a reasonable
explanation of solar spectral irradiance (SSI) variability?
– Simple answer could be Yes for both semi-empirical and
empirical models (Fontenla, Lean, Chamberlin, Shapiro)
• Semi-empirical: SRPM, COSI, & SATIRE has multiple features
• Empirical: NRLSSI & FISM has two component for daily variations
• Flare: FISM has two components now but needs more
– Solar rotation variations agree very well between
measurements and models (Lean, Shapiro)
– Agreement between measurements and models for solar
cycle variations is better for the shorter ultraviolet
wavelengths (< 250 nm)
– Wide range of possible secular variations presented for TSI
at MM, ranging from 0.5 W/m2 (Lean) to 2.7 W/m2 (Shapiro)
2012 SORCE Meeting Summary – Tom Woods
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Key Questions for Meeting - 3
• How does incorporating SSI (and solar particle) data into
GCM’s improve the prediction skills of these models?
– Modeling results indicate NAO response that has small
global temperature effect but possibly larger regional
effect in Europe (Ineson)
– Sensitivity studies with solar MUV bands is providing new
insights into predicting ozone changes (Swartz, Ball)
– This technique might even provide a check on solar MUV
variability that is needed to explain the ozone profile
(Ball). <accurate ozone data needed for this method>
– Solar energetic particles (SEP, SPE, EPP, EEP) have
large impact on polar NOy atmospheric chemistry that
can last for a few months (Jackman, Randall)
2012 SORCE Meeting Summary – Tom Woods
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Key Questions for Meeting - 4
• Do different GCM models produce similar results with the
same solar input?
– While not specific topic of any talk, there were
comparisons of 2-D and 3-D atmospheric models, and
there appears to some consistency of results between
different models.
– Several model comparisons done with solar variability
from NRLSSI model and SORCE SIM measurements
• Ineson, Swartz, Ball, Wang, Merkel, Wu
• These model comparisons indicate SIM variability should have
larger stratosphere-mesosphere change of O3 and OH than with
results using NRLSSI
• Different atmospheric measurements provide different, conflicting
conclusions on which solar MUV variability result might be more
accurate
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Key Questions for Meeting - 5
• How well do SSI model predictions agree with observations
over decadal time scales?
– Evidence for / against more UV variations during SORCE
• UARS SUSIM in 2003-2005 shows less UV (Floyd)
• Solar rotation in 2012 are similar to cycle variation (Snow)
• Analysis over SC minimum support more UV (Woods)
– Evidence for / against visible out-of-phase cycle variations:
• SOHO LASCO results suggest in-phase solar cycle variations near
500 nm (Howard)
– Mass outflow is important part of corona (Leamon, Howard)
• SFO solar images in blue, red, IR suggest out-of-phase solar cycle
variations of a small amount (Preminger)
• Sun-like stars give conflicting results (Rabin, Preminger)
– Small scale variations could affect SSI results (Rast)
– F10.7 and Sunspot record continues to diverge in interesting ways – SC24 may have had peak already (Tapping)
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2012 SORCE Meeting Summary – Tom Woods
Key Questions for Meeting - 6
• How well do GCM model predictions agree with observations
over decadal time scales?
– Several model comparisons done with solar variability from
NRLSSI model and SORCE SIM measurements and then
compared with O3, OH, & CO atmospheric observations
• Ineson, Swartz, Ball, Wang, Merkel, Wu
• These model comparisons indicate SIM variability
should have larger stratosphere-mesosphere change of
O3 and OH than with results using NRLSSI
• Different atmospheric measurements provide different,
conflicting conclusions on which solar MUV variability
result might be more accurate
– Do we understand the upper atmosphere photochemistry /
processes well enough for these comparisons? (Wang)
2012 SORCE Meeting Summary – Tom Woods
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Next SORCE Meeting
• Possible Topic:
• How Important is the Solar Forcing During Grand Minima?
– Reconstruction of TSI and SSI during Maunder Minimum
– Climate Change Model Results During Maunder Minimum
– Results for Other Grand Minima
– What do the Sun-like stars tell us?
• Other topic ideas ?
• Time Frame in 2013 ?
– January 25, 2013 is 10-year anniversary of SORCE launch
– Sept – Oct is usual time for SORCE meeting
• Location ?
2012 SORCE Meeting Summary – Tom Woods
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