Models of Spectral Irradiance Variability
Origins in the solar atmosphere and impacts on Earth’s atmosphere
SORCE Science Meeting
Annapolis, Maryland * Sept. 18-19, 2012
Poster Session Abstracts
4:00-5:30 p.m., Tuesday, Sept. 18
Summary of Poster Presentations (in alphabetical order):
William Ball, Imperial College, London, UK
A New Spectral Solar Irradiance Dataset Using the SATIRE-S Model
Lauren Bearden, Colgate University, Hamilton, New York
Trends in the Short-Term SSI Variability during the Declining Phase of SC23: Spectral
decomposition of over 100 Carrington rotations from the UV through the near IR
Gary Chapman, San Fernando Observatory, California State University, Northridge
Comparison of Mg II Core-to-wing Ration with Ground-based Ca II K-line Photometric Sum
Angie Cookson, San Fernando Observatory, California State University, Northridge
Using SDO Images to Inform Ground-based Models to Better Understand Total and
Spectral Solar Irradiance Variability
Serena Criscuoli (presented by Han Uitenbroek), National Solar Observatory, Sunspot, NM
Effects of Unresolved Magnetic Field on Fe I 617.3 and 630.2 nm Line Shape
Sandip Dhomse (presented by Will Ball), University of Leeds, Leeds, UK
Is Solar Response on Stratospheric Ozone during Recent Solar Cycle Really Different?
Yanshi Huang (presented by Phil Chamberlin), Dept. of Physics, Univ. of Texas at Arlington
Wavelength Dependence of Solar Flare Irradiance Enhancement and its Influence
on the Thermosphere-Ionosphere System
King-Fai Li (presented by Shuhui Wang), California Institute of Technology, Pasadena, CA
Simulation of Solar Cycle Response in Tropical Total Column Ozone using SORCE Irradiance
Doug Lindholm, LASP, University of Colorado, Boulder
SORCE Solar Irradiance Data Products and the LASP Interactive Solar Irradiance
Data Center (LISIRD)
Erik Richard, LASP, University of Colorado, Boulder
Future of Solar Spectral Irradiance Measurements with TSIS (Total Solar Irradiance Sensor)
Marty Snow, LASP, University of Colorado, Boulder
Solar Outreach through Research and Continuing Education (SORCE)
Guoyong Wen, NASA GSFC, Greenbelt, MD and GESTART/Morgan State University
GCM Modeling Climate Response to Spectral Solar Forcing
1
A New Spectral Solar Irradiance Dataset Using the SATIRE-S Model
William T. Ball1 [william.ball08@imperial.ac.uk], Yvonne C. Unruh1, Natalie A. Krivova2,
Sami Solanki2, and Joanna D. Haigh1
1
Imperial College, London, UK
2
Max Planck Institute for Solar System Research, Germany
The variation in the spectral irradiance of the Sun influences the temperature and chemistry
within the Earth's atmosphere. The semi-empirical SATIRE-S model has demonstrated remarkable
agreement with observations of total solar irradiance. By design, the model computes spectral solar
irradiance (SSI) and here we present a new, consistent SSI dataset that spans 35 years from 1974 to
2009. We describe the construction of the dataset and show comparisons with the NRLSSI model
and observations from UARS and SORCE.
Trends in the Short-Term SSI Variability during the Declining Phase of SC23: Spectral
decomposition of over 100 Carrington rotations from the UV through the near IR
Lauren Bearden1, Odele Coddington2, Marty Snow2, and Erik Richard2
1
Colgate University, Hamilton, New York
2
Laboratory for Atmospheric and Space Physics, University of Colorado, Boulder
The Sun's energy output varies on timescales ranging from minutes to decades. This variability is
due to the turbulent convection-induced dynamical motions and magnetic phenomena within the
Sun. The UV chromospheric irradiance, at wavelengths shorter than 300 nm, is closely related to the
persistent chromospheric heating in plage and enhanced network lasting on rotational timescales
with little center-to-limb variation. In contrast, at wavelengths longer than 300 nm (in the visible and
near infrared) the irradiance variations are due to photospheric features related to sunspots and
faculae that evolve faster. While the integrated spectral variability (TSI) varies by small amounts
(typically <0.3% over days), the wavelength dependent spectral variability from the UV through the
infrared spans 5 orders. For modeling Earth atmospheric response, the temporal and spectral
irradiance variations across the full solar spectrum must be considered.
The Spectral Irradiance Monitor (SIM) instrument has been measuring solar spectral irradiance
from 200 to 2400 nm since 2003. In this work, we compute the spectral contrast, [(Imax – Imin )/
Imin]CR, in solar spectral irradiance over 109 Carrington rotations covering the declining phase of SC
23 through the last solar minimum. The periods of maximum and minimum solar activity are
determined using known indices that reflect changes in chromospheric activity: the Magnesium II
index (Mg II- near 280 nm) and Calcium II index (CaII- near 390 nm). We relate the rotational
variability to the Solar disk location of magnetic features on the surface of the Sun using Carrington
synoptic map images. In addition, we investigate case studies where the periods of maximum solar
activity as defined by the MgII and CaII indices were different.
Comparison of Mg II Core-to-Wing Ratio with Ground-based Ca II K-line Photometric Sum
Gary A. Chapman [gary.chapman@csun.edu], A. M. Cookson, and D. G. Preminger; San Fernando
Observatory, California State University, Northridge
Magnesium-II core-wing ratio data from three spacecraft composites have been compared with
ground-based K-line photometry for most of cycles 22 and 23. The ground-based data is the
photometric sum, Σ K, computed from the composite Ca II K-line obtained from the San Fernando
Observatory. The Mg II used were the SORCE c/w ratio, the Viereck composite and the SUSIM
composite. The linear regression coefficients, r2, with the Mg II versus ΣK are 0.92, 0.95 and 0.95,
respectively.
This work was partially supported by grants NNX11AK46G from NASA and ATM-0848518 from NSF.
2
Using SDO Images to Inform Ground-based Models to Better Understand Total and Spectral
Solar Irradiance Variability
Angela M. Cookson [angela.cookson@csun.edu], Gary A. Chapman, and Dora G. Preminger; San
Fernando Observatory, California State University, Northridge
Current models of Total Solar Irradiance (TSI), based on two-parameter fits of photometric data
(672.3nm red continuum and 393.4nm Ca II K-line) from the San Fernando Observatory (SFO), can
reconstruct up to 95% of the irradiance variations observed by SORCE/TIM. The Solar Dynamics
Observatory (SDO) images offer a unique opportunity to examine solar features without atmospheric
interference, applying our feature-analysis techniques to SDO images of the photosphere and the
chromosphere. We compare this with the same information extracted from SFO ground-based
images that probe similar depths in the solar atmosphere. We derive solar indices from SDO images,
model TSI with these indices, compare with SFO models, and investigate whether we can make
further advances in TSI models by including UV wavelengths that cannot be observed from the
ground. A small one-month study of sunspot deficit obtained from HMI intensitygrams demonstrates
the viability of our methods. In order to produce a parameter comparable to the SFO sunspot deficit
(-8.5%), we chose a contrast criterion, based on a cumulative histogram, that will select a similar set
of features on SDO/HMI contrast images (-15%). A graph of both SFO and HMI deficit over time
shows that they track each other closely but HMI images, as expected, produce much darker
sunspots since scattered light effects are negligible. Information gleaned from SDO images has the
potential to improve our existing ground-based models of solar irradiance and our understanding of
total and spectral irradiance variability.
Effects of Unresolved Magnetic Field on Fe I 617.3 and 630.2 nm Line Shape
Serena Criscuoli1 [mailto:scriscuo@nso.edu], I. Ermolli2, H. Uitenbroek1, and F. Giorgi2
(Presented by Han Uitenbroek)
1
National Solar Observatory, Sunspot, New Mexico
2
INAF-Osservatorio Astronomico di Roma, Italy
We studied the dependence on the magnetic flux of parameters describing the two Fe I lines at
630.2 and 617.3 nm. In particular, we analyze the line core intensity (IC), full width half maximum
(FWHM), and equivalent width (EQW) of Stokes I and circular polarized signals measured at the two
studied lines on NOAA 11169. This region was observed with IBIS at the Dunn Solar Telescope on
March 17th, 2011. Our study was aimed at obtaining a line diagnostic sensitive to effects of small
scale magnetic features unresolved on the observations. Our results show that IC is sensitive to both
temperature and magnetic flux variations, while FWHM is sensitive mostly to magnetic field
variations. On the other hand, EQW resulted almost insensitive to magnetic field variation and mostly
sensitive to temperature changes. Variations of few percents of the measured line parameters are
found on data spatially degraded to represent quiet Sun, disk-centre conditions on medium resolution
observations. Among the two investigated lines, the 617.3 nm proved to be sensitive to temperature
variations induced by unresolved magnetic fields, while the 630.2 nm turned out to be a good
diagnostic of magnetic flux. The amount of line parameters variations can be observed with
spectrographs and full-disk imagers as SOLIS/VSM and SDO/HMI; these can be therefore employed
to investigate physical properties of quiet Sun regions.
3
Is Solar Response on Stratospheric Ozone during Recent Solar Cycle Really Different?
Sandip Dhomse1 [S.S.Dhomse@leeds.ac.uk], M. P. Chipperfield1, W. Feng1, W. Ball2, Y. Unruh2,
J. D. Haigh2, N. Krivova3, and S. Solanki3 (Presented by William Ball)
1
2
3
University of Leeds, Leeds, UK
Imperial College, London, UK
Max Planck Institute, Katlenburg-Lindau, Germany
Some of the recent modeling studies have suggested that upper stratospheric ozone changes
during solar cycle 23 can be reproduced only if SORCE solar flux data are used. We have used a 3D
Chemical Transport Model (CTM), to simulate stratospheric ozone for using two different (NRLSSI
and SATIRE-S) solar flux data sets. The model is forced with recently available ECMWF ERAinterim re-analyses for 2001-2010. Simulated ozone changes are compared with Atmospheric
Chemistry Experiment (ACE), Microwave Limb Sounder (MLS) and Sounding of the Atmosphere
using Broadband Emission Radiometry (SABER) satellite instrument data sets. Modeled ozone
anomalies from the simulations with either sets of solar fluxes show excellent agreement with all
three satellite data sets. Here we argue that most of the ozone variability during solar cycle-23 can be
simulated with SATIRE and/or NRL solar fluxes and estimated differences are within the
uncertainties of the observation data sets. This study highlights the importance of realistic dynamics
to simulate solar response on the stratospheric ozone.
Wavelength Dependence of Solar Flare Irradiance Enhancement and its Influence on the
Thermosphere-Ionosphere System
Yanshi Huang [yanshi.huang@mavs.uta.edu] 1, Arthur D. Richmond2, Yue Deng1, Liying Qian2,
Stanley C. Solomon2, Phillip C. Chamberlin3 (Presented by Phil Chamberlin)
1
2
3
Department of Physics, University of Texas at Arlington
National Center for Atmospheric Research, Boulder, Colorado
NASA Goddard Space Flight Center, Greenbelt, Maryland
The wavelength dependence of irradiance enhancement during solar flare is one of the important
factors in determining how the Thermosphere-Ionosphere (T-I) system responds to flares. To
investigate the wavelength dependence of irradiance, the Flare Irradiance Spectral Model (FISM)
was run for 34 X-class flares. The results show that the percentage increases of solar irradiance at
flare peak have a clear wavelength dependence. In the wavelength range between 0 - 195 nm, it can
vary from 1% to 10000%. The solar irradiance enhancement is largest (~1000%) in the XUV range
(0 - 25 nm), and is about 100% in the EUV range (25 - 120 nm). The influence of different
wavebands on the T-I system during the October 28th, 2003 flare (X17.2-class) has also been
examined using the latest version of the National Center for Atmospheric Research (NCAR)
Thermosphere-Ionosphere-Electrodynamics General Circulation Model (TIE-GCM). While the
enhancement of the globally integrated solar energy deposition is largest in the 0 - 14 nm waveband,
the impact of solar irradiance enhancement on the thermosphere at 400km is largest for the 25 - 105
nm waveband. The effect of the enhancement of the 122 - 195 nm waveband is small in magnitude,
but it decays slowly.
4
Simulation of Solar Cycle Response in Tropical Total Column Ozone using SORCE Irradiance
King-Fai Li1 [kfl@gps.caltech.edu], Xun Jiang2, Mao-Chang Liang3, Yuk L. Yung1 (Presented
by Shuhui Wang)
1
2
3
California Institute of Technology, Pasadena, California
University of Houston, Texas
Academia Sinica, Taiwan
The solar-cycle signal of tropical column ozone (XO3) in the Whole Atmosphere Community
Climate Model (WACCM) model has been examined using solar spectral irradiance (SSI) estimated
from the Naval Research Laboratory (NRL) solar model and that from recent satellite measurements
observed by the Solar Radiation and Climate Experiment (SORCE). Four experiments have been
conducted with NRL/SORCE SSI and climatological/realistic sea surface temperatures and ice, and
all other variability is fixed to test the robustness of the simulated solar response in O3 against the
presence of El Niño/Southern oscillation (ENSO). We found that potential aliasing effects from
ENSO occurs below 20 km where tropical O3 concentration is low and has little impact (less than
~0.6 DU/100F10.7) on the regressed XO3 response. In the tropical region 24ºS–24ºN, using the
SORCE SSI as a model input leads to a solar-cycle response of ~5.4 DU/100F10.7, which agrees with
those obtained from the merged TOMS/SBUV satellite observations. The resultant vertical O3
response agrees with previous satellite measurements in the lower stratosphere but the negative
response in the upper stratosphere disagrees with the observed. In contrast, the XO3 responses is ~3
DU/100F10.7, which is ~half of that obtained using SORCE SSI but agrees better with the SAGE and
ground-based observations. The resultant vertical O3 response agrees with previous satellite
measurements in the upper stratosphere but the lower stratospheric response is much weaker than the
observed. This presents a dilemma to our current understanding of stratospheric O3 response to UV
perturbations.
SORCE Solar Irradiance Data Products and the LASP Interactive Solar Irradiance
Data Center (LISIRD)
Doug Lindholm [doug.lindholm@lasp.colorado.edu], Chris Pankratz, Stephane Beland, Barry
Knapp, Blake Vanier, Anne Wilson, Jerry Harder, Greg Kopp, Marty Snow, and Tom Woods;
Laboratory for Atmospheric and Space Physics, University of Colorado, Boulder
The Laboratory for Atmospheric and Space Physics (LASP) at the University of Colorado
manages the Solar Radiation and Climate Experiment (SORCE) Science Data System. This data
processing system routinely produces Total Solar Irradiance (TSI) and Spectral Solar Irradiance
(SSI) data products, which are formulated using measurements from the four primary instruments on
board the SORCE spacecraft along with calibration data and other ancillary information to correct
for all known instrumental and operational factors. The TIM instrument provides measurements of
the TSI, whereas the SIM, SOLSTICE, and XPS instruments collectively provide measurements of
the solar irradiance spectrum from 1 nm to 2400 nm (excluding 31-115 nm). "Level 3" data products
(time-averaged over daily and six-hourly periods and spectrally re-sampled onto uniform wavelength
scales) are routinely produced and delivered to the public via the SORCE web site
(http://lasp.colorado.edu/sorce/data/), and are archived at the Goddard Earth Sciences (GES) Data and
Information Services Center (DISC). The SORCE data are also available from the LASP Interactive
Solar Irradiance Data Center (LISIRD) web site (http://lasp.colorado.edu/lisird/) which provides
interactive access to over 25 years of LASP's solar irradiance measurements and is evolving to
become the ultimate source of solar irradiance data products. The data are also available to computer
programs via the LASP Time Series Server (LaTiS, which powers LISIRD). This poster provides an
overview of the SORCE solar irradiance data products and other related data that are now directly
available from LaTiS using a new IDL reader.
5
Future Measurements of Solar Spectral Irradiance by the TSIS Spectral Irradiance Monitor:
Improvements in Measurement Absolute Accuracy and Long-term Stability
Erik Richard1, Dave Harber1, Joel Rutkowski1, Kasandra O’Malia1, Matthew Triplett1, Ginger
Drake1, Jerald Harder1, Odele Coddington1, Tom Sparn1, Peter Pilewskie1, Steven Brown2, Allan
Smith2, and Keith Lykke2
1
2
Laboratory for Atmospheric and Space Physics, University of Colorado, Boulder
Optical Technology Division, National Institute of Standards and Technology (NIST),
Gaithersburg, Maryland
In order to advance understanding of how natural and anthropogenic processes affect climate it is
important to maintain accurate, long-term records of climate forcing. In particular, the continuation
of solar spectral irradiance (SSI) measurements is needed to characterize poorly understood
wavelength-dependent climate processes. Major measurement challenges in quantifying the
influence of SSI variability on climate are achieving sufficient radiometric absolute accuracy and
maintaining the long-term relative accuracy of the data record. The TSIS SIM is the next generation
space-borne SSI monitor that will fly as part of the joint agency (NASA/NOAA) JPSS program and
is scheduled for launch later this decade. It is designed to measure (twice daily) the SSI between 200
and 2400 nm and calibrated to achieve unprecedented levels of measurement accuracy (maintained
on-orbit) required to meet the needs of establishing a complete SSI climate data record. Significant
design improvements have been implemented over that of the first-generation (SORCE) SIM. Key
performance advances include improved radiometric detector design, reduced uncertainties in longterm stability, and significant improvement in pre-launch, SI-traceable calibration of absolute
accuracy. To quantify the absolute accuracy over the full spectral range, we have developed a
comprehensive spectral calibration facility utilizing the NIST Spectral Irradiance and Radiance
Responsivity Calibrations using Uniform Sources (SIRCUS) system. This LASP facility provides
continuously tuneable laser light sources from the ultraviolet to the near infrared that are matched in
radiant power to the solar spectrum and tied to a cryogenic radiometer traceable to the NIST Primary
Optical Watt Radiometer (POWR), the primary US standard for radiant power measurements. Based
on a measurement equation approach, directly measurable unit- and instrument-level quantities are
calibrated and then verified with an absolute end-to-end irradiance calibration.
Solar Outreach through Research and Continuing Education (SORCE)
Marty Snow [marty.snow@lasp.colorado.edu] and Erin Wood, Laboratory for Atmospheric and
Space Physics, University of Colorado, Boulder
The Education and Public Outreach program of the SORCE mission is primarily concerned with
educating the next generation of scientists. The two activities supported by SORCE are a workshop
for secondary teachers and participation in the Research Experience for Undergraduates (REU) site
at the University of Colorado. At the workshop, ten teachers from all over Colorado come to Boulder
for an intensive three-day weekend on the Sun, Sun-Earth connection, climate, and related Earth
science. Teachers hear lectures from scientists on current research topics, and conduct hands-on,
standards-based lab exercises. The SORCE REU students come to Boulder to conduct near-graduate
level research for eight weeks during the summer. After a first week of lectures and labs, the
students work closely with one or two scientist mentors for seven weeks. Their research is presented
orally and at a poster session at the REU student symposium in August. This poster will present the
synergies created with these two unique programs, while discussing the importance of authentic
research opportunities for undergraduates.
6
GCM Modeling Climate Response to Spectral Solar Forcing
Guoyong Wen 1, 2 [guoyong.wen-1@nasa.gov], Robert F. Cahalan1, David Rind3, Jeff Jonas3, Peter
Pilewskie4, and Jerald W. Harder4
1
2
3
4
NASA Goddard Space Flight Center (GSFC)
GESTART / Morgan State University
NASA Goddard Institute for Space Studies (GISS)
LASP, University of Colorado, Boulder
We perform a series of experiments to explore climate responses to two types of solar spectral
forcing on decadal and centennial time scales, one based on prior reconstructions and another
implied by recent observations from the SORCE (Solar Radiation and Climate Experiment) SIM
(Spectral Irradiance Monitor). We apply two types of solar forcing to the Goddard Institute for Space
Studies (GISS) Global/Middle Atmosphere Model (GCMAM) to examine the climate response. The
current version of GISS GCMAM couples atmosphere with ocean, and has a model top near the
mesopause, allowing us to examine the full response to the two solar forcing scenarios. We will
show different climate responses to the two solar forcing scenarios on decadal time scale (i.e., solar
minimum minus solar maximum) and long- term trends on centennial time scales. We will discuss
mechanisms for Sun Climate connection.
7