Decadal Cycles in the Sun, Sun-like Stars, and Earth’s Climate System
SORCE Science Meeting
Sedona, Arizona * Sept. 13-16, 2011
Session 1 Abstracts –Solar Irradiance Cycles
(Sept. 13, Tuesday a.m. and p.m.)
Modelling Spectral Solar Irradiance
Yvonne Unruh [y.unruh@imperial.ac.uk] and William Ball, Blackett Laboratory, Imperial College,
London, UK; and Natasha Krivova, Sami Solanki, and Thomas Wenzler, Max Planck Institute for Solar
System Research, Germany
Changes in the total solar irradiance on time scales of days up to the solar cycle can be
modelled well by considering the evolution of the solar surface magnetic field. The ability of
such models to reproduce long-term spectral irradiance changes has been explored to a lesser
extent. We here plan to present spectral irradiance reconstructions obtained with the SATIRE
model. These are based on MDI and KPNO magnetograms and continuum images and now
cover the best part of 3 solar cycles. We compare these reconstructions with some of the
available spectral irradiance measurements during the last two solar cycles.
Solar Cycle UV Irradiance Variability
Matthew DeLand [matthew_deland@ssaihq.com], Science Systems and Applications, Inc. (SSAI),
Lanham, Maryland
Satellite measurements of solar UV variability have been made by at least eight different
instruments since 1978. Although it is difficult to keep a single instrument operating throughout
a complete solar cycle, many of these instruments (Nimbus-7 SBUV, SME, NOAA-9 SBUV/2,
NOAA-11 SBUV/2, UARS SUSIM, UARS SOLSTICE) were able to observe both maximum
and minimum irradiance levels during either rising or declining phases of solar activity.
Comparisons of these published results for solar cycles 21, 22, and 23 show consistent solar
cycle irradiance changes at key wavelengths (e.g. 205 nm, 240 nm) within instrumental
uncertainties. All historical data sets also show the same relative spectral dependence for both
short-term (rotational) and long-term (solar cycle) variations. Empirical solar irradiance models
that employ multiple proxy data sets produce long-term solar UV variations that are in good
agreement with merged observational data through 2005. Recent UV irradiance data from the
SORCE SIM and SORCE SOLSTICE instruments covering the declining phase of Cycle 23
present a different picture of long-term solar variations, with significantly larger temporal
changes and different spectral dependence. We will present comparisons of the SORCE data
with previous observations and current model predictions. Short-term variability in SIM and
SOLSTICE data is consistent with concurrent NOAA-17 SBUV/2 data and previous results. The
SORCE long-term solar UV irradiance results can be explained by undercorrection of instrument
response changes during the first few years of measurements.
1
The Impact of Solar Spectral Irradiance Variability on Middle Atmospheric Ozone
Jerald Harder1 [Jerry.Harder@lasp.colorado.edu], Aimee Merkel1, Dan Marsh2, Anne Smith2, Juan
Fontenla1, and Tom Woods1
1
Laboratory for Atmospheric and Space Physics, University of Colorado-Boulder
2
Atmospheric Chemistry Division, National Center for Atmospheric Research, Boulder, Colorado
We present a study of the impact of solar spectral irradiance (SSI) variability on middle atmospheric
ozone over the declining phase of solar cycle 23. Two different types of spectral forcing are applied to
the Whole Atmosphere Community Climate Model (WACCM) to simulate the ozone response between
periods of quiet and high solar activity. One scenario uses the solar proxy reconstructions model from
the Naval Research Laboratory (NRLSSI), and the other is based on SSI observations from the Solar
Radiation and Climate Experiment (SORCE). The SORCE observations show 3–to-5 times more
variability in ultraviolet (UV) radiation than predicted by the proxy model. The NRLSSI forcing had
minimal impact on ozone, however, the higher UV variability from SORCE induced a 4% reduction in
ozone concentration above 40 km at solar active conditions. The model result is supported by 8 years
(2002–2010) of ozone observations from the Sounding of the Atmosphere using Broadband Emission
Radiometry (SABER) instrument. The SABER ozone variations have greater similarity with the
SORCE SSI model simulations. The model and satellite data suggests that the ozone response is due to
enhanced photochemical activity associated with larger UV variability.
LASP/TRF Diagnostic Test Results for the ACRIM3 Experiment and Their Implications for
the Multi-Decadal TSI Database
Richard C. Willson [acrim@acrim.com], NASA Jet Propulsion Laboratory, Pasadena, California
The scale difference between the ACRIMSAT/ACRIM3 and SORCE/TIM TSI results has been
investigated through diagnostic testing of ACRIM3 flight backup instrumentation in the Laboratory
for Atmospheric and Space Physics Total Solar Irradiance Radiometer Facility (LASP/TRF).
Preliminary results indicate a correction factor for ACRIM3 results of 5000 ppm is required to account
for scattering (~3500 ppm), diffraction (~1000 ppm) and basic radiation scale traceability to NIST
(~500 ppm). Additional testing and analysis is required to reduce the uncertainties of these results,
particularly for the scattering component which may be overestimated. The net effect of the TRF
correction is to reduce the scale for ACRIM3 results to about 0.04 % below the SORCE/TIM results.
The scale correction does not alter the trending between solar activity minima found in the ACRIM
Composite TSI database.
Status of the Total Solar Irradiance Climate Data Record
Greg Kopp [Greg.Kopp@lasp.colorado.edu], Laboratory for Atmospheric and Space Physics (LASP),
University of Colorado, Boulder
Recent efforts by the international total solar irradiance (TSI) instrumentation community have led
to enhanced understandings of instrument sensitivities and the causes of measurement offsets,
resulting in improved accuracy of the TSI data record needed for discerning solar influences in climate
studies. Experiments on the TSI Radiometer Facility (TRF), the world’s only facility capable of
directly comparing a TSI instrument to a NIST-calibrated cryogenic radiometer measuring irradiances
at solar power levels in vacuum, permit not only optical power and irradiance measurement
validations, but also diagnostics of instrument artifacts such as scatter that can lead to erroneously high
measurements. Understanding these instrument artifacts allows for retroactive corrections to flight
data and better estimates of measurement uncertainties. Instrument validations on the TRF have been
performed by ground-based or flight versions of the SORCE/TIM, Glory/TIM, PICARD/PREMOS,
SoHO/VIRGO, and ACRIMSat/ACRIM3. I summarize what these improved understandings indicate
for the 33-year long TSI climate data record and discuss the future of this critical, uninterrupted record
given the recent launch failure of the Glory spacecraft.
2
Future SSI Record for JPSS TSIS
Erik Richard [erik.richard@lasp.colorado.edu], D. Harber, J. Harder, and P. Pilewskie, Laboratory
for Atmospheric and Space Physics (LASP), University of Colorado, Boulder; S. Brown, A. Smith, and
K. Lykke, NIST, Gaithersburg, Maryland
To advance scientific understanding of how solar variability affects climate processes it is
important to maintain accurate, long-term records of solar irradiance. Continuation of solar
spectral irradiance (SSI) measurements is needed to characterize poorly understood
wavelength-dependent climate processes. Measurement challenges in quantifying the influence
of SSI variability on climate are achieving sufficient radiometric absolute accuracy and
maintaining the long-term relative accuracy. The Total and Spectral Solar Irradiance Sensor
(TSIS) is a dual-instrument package that will acquire solar irradiance as part of the Joint Polar
Satellite System (JPSS). The TSIS SIM instrument will continue the SSI measurements that
began with the SORCE SIM.
The TSIS SIM incorporates design and calibration improvements to better quantify longterm SSI variability. Specific improvements include the pre-launch SI-traceable calibration, the
measurement precision, and the long-term relative stability needed to meet the requirements for
establishing a climate record of SSI into the future. To quantify the absolute accuracy over the
full spectral range, we have developed a SIM Radiometer Facility (SIMRF) utilizing the NIST
Spectral Irradiance and Radiance Responsivity Calibrations using Uniform Sources
(SIRCUS). This comprehensive facility includes tuneable laser light sources from the
ultraviolet to the near infrared matched in radiant power to the solar spectrum and tied to a
cryogenic radiometer traceable to the NIST Primary Optical Watt Radiometer (POWR). The
full characterization and calibration follows a measurement equation approach at the unit-level
for full validation of the end-to-end performance at the instrument-level to achieve a combined
standard uncertainty (uc) of 0.25%.
PREMOS TSI Results
Werner Schmutz [werner.schmutz@pmodwrc.ch], Physikalisch-Meteorologisches Observatorium
Davos and World Radiation Center, Davos, Switzerland
PREMOS is an experiment on the French satellite PICARD consisting of absolute
radiometers and filter radiometers, which were, build by PMOD/WRC (Thuillier G., Dewitte
S., Schmutz W., 2006, Adv. Space Res. 38, 1792-1806). PREMOS measures Total Solar
Irradiance and spectral solar irradiance in selected wavelength bands. PICARD was launched
on June 15, and first light of PREMOS was on July 27, 2010. PREMOS is operational since
September 6, 2010. The PMO6-A instrument of PREMOS is the first radiometer in space,
which has a SI-traceable irradiance calibration in vacuum. The calibration has an uncertainty
that is smaller than the difference between the discrepant absolute TSI values from
VIRGO/SOHO and TIM/SORCE. Thus, the PREMOS measurements decide the question
which of the two is more correct. The result is that the Total Solar Irradiance value of PMO6A agrees with TIM/SORCE within its uncertainty and disagrees by more than five sigma from
VIRGO/SOHO. The initial sensitivity changes of the PREMOS radiometers are studied using
internal assessment and by relative comparison to other operational TSI measurements. The
deduced sensitivity changes for PMO6-type instruments in space leads to a re-investigation of
the early VIRGO/SOHO measurements. This re-analysis questions the published trend of the
VIRGO TSI values for 1996 and 1997. A new estimate for between the solar minimum in
1996 and the recent minimum in 2008 is derived.
3
First Results of the Sova-Picard TSI Instrument
Steven Dewitte [steven.dewitte@meteo.be], Andre Chevalier, Christian Conscience, and Sami Bali, Royal
Meteorological Institute of Belgium, Brussels; and Sabri Mekaoui, Joint Research Center, Ispra, Italy
The Picard satellite was successfully launched in a 6-18 orbit on 15 June 2010. Our Sovap
TSI instrument started its measurements on 21 July 2010. From July to October 2010 Sovap
made low exposure measurements in its nominal operation mode, roughly once per month. On
18 October the operation mode was changed. The right channel has been opened permanently.
For ageing verification additional left channel measurements are made monthly.
For the first period of nominal operation we present the relative TSI variation and its
comparison with Diarad/Virgo. For the new mode of operation we demonstrate the ability to
measure p mode TSI variations without aliasing.
Reconstruction of TSI and Ly- Back to 1913
Claus Fröhlich [cfrohlich@pmodwrc.ch], Physikalisch Meteorologisches Observatorium Davos
(PMOD), World Radiation Center (WRC), Davos, Switzerland
The PMOD composite has been updated with a new version of VIRGO TSI which improves
the internal consistency. With this composite a 4-component proxy model is calibrated over the
full range of the last three solar cycles and explains more than 85 % of the variance. The model
is based on a new version of the photometric sunspot index (PSI) using SOON data since 1976,
on a composite MgII index from space observations, separated into long- and short-term
components and a trend deduced from the open magnetic flux from the Sun at activity minima.
This model can be expanded with PSI from Royal Greenwich Observatory sunspot data back to
1876, with CaII K observations from Mt. Wilson since 1913 and with the open field from e.g. the
aa index back to late 19th century. The daily CaII K observations are transformed into a MgII
proxy which then can be separated into long- and short-term components and thus the proxy
model can be expanded back to 1913. With these data and the calibration during the last 3 cycles
TSI is reconstructed. Moreover, as the model explains also the Ly- record, a correspondingly
reliable reconstruction back to 1913 is presented.
Solar Irradiance Decadal Trends: Real Variability or Instrument Instability?
Judith L. Lean [jlean@ssd5.nrl.navy.mil], Naval Research Laboratory, Washington DC
Observations of total solar irradiance exist now for three 11-year solar activity cycles.
Evident throughout the 33-year database are significant deviations among individual
measurements that signify the presence of instrument instabilities. These instabilities contribute
uncertainty to knowledge of solar irradiance variability during the solar cycle and on longer time
scales. Three different composite records of total solar irradiance constructed from the extant
database are analyzed to quantify uncertainties, with the result that irradiance levels during the
2008 extended solar minimum cannot be claimed to differ from levels during prior minima.
Separating real solar variability and instrumental instabilities in measurements of the solar
spectral irradiance that composes the total is even more challenging because the database is very
short, lacks independent validation, and has uncertainties that are difficult to establish.
Understanding and quantifying the contributions of dark sunspots and bright faculae to solar total
and spectral irradiance variability using empirical models can help identify unequivocal solar
variability in the measurements. Differences between the observed and modeled solar irradiance
are then analyzed for insight as to their origin, whether instrumental instability or real variability
missing in the model. This approach is applied to the total solar irradiance composite records
and to the SORCE/SIM spectral irradiance measurements.
4
A Blind Source Separation Approach to the Solar Spectral Irradiance: What does the
coherence of its variability tell us?
Thierry Dudok de Wit [ddwit@cnrs-orleans.fr]1, Sean Bruinsma2, Gael Cessateur1,3, Matthieu
Kretzschmar2, Jean Lilensten3, and Luis Vieira1
1
University of Orléans, France; 2 Centre national d'études spatiales (CNES), Toulouse, France; and 3
Institute of Planetology and Astrophysics of Grenoble (IPAG), France
One of the striking properties of the solar spectral irradiance is the remarkable coherence of its
variability, from the EUV up to the visible range. Indeed, most of the variability is captured by a few
common contributions only. Various statistical techniques allow us to extract these contributions,
each having different assumptions. This decomposition is directly connected to the problem of blind
source separation, which has become a very fertile domain of research in acoustics and in astronomy.
In the first part, we shall show how spectral irradiance observations from TIMED and SORCE can
be decomposed into different contributions and what this tells us about the underlying physical
processes… and also on the not-so-wanted instrumental artifacts. In the second part, we shall
concentrate on the dynamical response of the solar spectral variability to the onset of active regions.
The Effects of Active Regions on Solar Spectral Variability: Implications for the Sun’s
influence on climate
Dora Preminger [dora.preminger@csun.edu], Gary Chapman, and Angela Cookson, San Fernando
Observatory, California State University, Northridge
We use photometric parameters from the San Fernando Observatory’s solar data archive to
model the Total Solar Irradiance (TSI) for two full solar cycles. Our results have implications for
the ways in which the Sun might affect Earth’s climate. The TSI, incident at the top of the Earth’s
atmosphere, is about 1365 Wm-2 and varies from solar minimum to solar maximum by an amount
ΔTSI of order 1 Wm-2. Our TSI model, which successfully reconstructs observed TSI values,
implies that, to a first approximation, ΔTSI is caused by solar active regions and can be attributed to
two components: the change in the visible continuum radiation from the photosphere and the change
in the spectral line blanketing from the chromosphere. The visible continuum component of TSI,
which can pass through the Earth’s atmosphere and warm the ground and oceans directly, changes
by a small fraction, of order 0.01%, from solar minimum to solar maximum, and its variability is
anti-correlated with the solar cycle. If high solar activity is associated with high global
temperatures, then this component cannot be the cause. The energy in chromospheric spectral lines,
which are mostly concentrated at ultraviolet wavelengths, changes by an amount of order +ΔTSI
from solar minimum to solar maximum. Ultraviolet radiation is absorbed in the Earth’s atmosphere
and could constitute a different mechanism for driving climate change that would be positively
correlated with solar activity.
Status and Last Results from the PROBA2/LYRA Solar Radiometer
Matthieu Kretzschmar1,2 [matthieu.kretzschmar@cnrs-orleans.fr], I. E. Dammasch1, M. Dominique1, W.
Schmutz3, and A. I Shapiro3
1
Royal Observatory of Belgium / SIDC, Brussels, Belgium
LPC2E, UMR6115 CNRS /University of Orléans, France
3
PMOD, Davos, Switzerland
2
Since early 2010, LYRA has been monitoring the solar flux in four passbands. Originally
designed as a technological demonstration, the LYRA observations are well suited to study the solar
variability over a large spectral range. We will first present an up-to-date view on LYRA
performances, including calibration, degradation, data products, and observation strategy. We will
next present some results obtained with LYRA data and ongoing efforts to understand striking
LYRA observations.
5
Solar UV Spectral Irradiance Measured by SUSIM During Solar Cycle 22 and 23
Jeff Morrill [Jeff.Morrill@nrl.navy.mil], Naval Research Laboratory, Washington DC; Linton Floyd,
Interferometrics, Virginia; and Donald McMullin, Space Systems Research Corp., Virginia
Understanding the impact of solar variability on terrestrial climate requires detailed
knowledge of both solar spectral irradiance (SSI) and total solar irradiance (TSI). Observations
of SSI in the ultraviolet (UV) have been made by various space-based missions since 1978. Of
these missions, the Upper Atmosphere Research Satellite (UARS) included the Solar Ultraviolet
Spectral Irradiance Monitor (SUSIM) experiment which measured the UV SSI from 1991 into
2005. In this talk, we present the UV spectral irradiance observations from SUSIM on UARS
during solar cycles 22 and 23 along with results of a recent review of the calibration, stability,
and in-flight performance. Another more recent mission is the Solar Radiation and Climate
Experiment (SORCE) satellite which carries the Solar-Stellar Irradiance Comparison Experiment
(SOLSTICE) and Solar Irradiance Monitor (SIM). Together, the SORCE instruments have
measured the UV, Visible, and IR SSI over the period of 2003 to the present. This talk will
include a comparison between SUSIM and SORCE during the period of overlapping
observations as well as comparisons of UV spectra observed at various times, particularly during
the last two solar minima. These comparisons show that the UV observations by SORCE are
inconsistent with those measured by SUSIM.
Solar Variability 1981 to 1989 as Measured by the Solar Mesosphere Explorer
Gary Rottman [Gary.Rottman@lasp.colorado.edu], Laboratory for Atmospheric and Space Physics
(LASP), University of Colorado, Boulder
The Solar Mesosphere Explorer was launched October 6, 1981 and data reception ended
April 4, 1989. The solar instrument on the spacecraft made daily irradiance measurements
between 115 to 305 nm with a spectral resolution of 0.75nm. We have now reexamined and
improved the solar data and present new time series. The SME irradiance data set begins just
after the peak of solar cycle 21, extends through solar minimum in 1986 and back to the peak of
cycle 22. During this time period of about three quarters of a solar cycle SME recorded more
than 100 individual solar rotation periods. We are now preparing for the 30th anniversary of
SME and will hold a special symposium October 6-7 in Boulder, Colorado.
Session 2 Abstracts – Climate System Decadal Variability
(Sept. 14, Wednesday a.m.)
A Multi-Century History of Solar and Climate Variabilities at Decadal Timescales
Vikram M. Mehta [vikram@crces.org], The Center for Research on the Changing Earth System,
Clarksville, Maryland
Legend has it that an Athenian irrigation engineer in 400 B.C. was perhaps the first human
being to speculate that varying dark spots on the Sun were perhaps associated with varying
rainfall around Athens. In the last 300 years or so, this speculation has become one of the major
but as-yet-unproven hypotheses of terrestrial climate variability. In the last 20-30 years, sunspot
numbers have been replaced with estimated solar irradiance, solar and cosmic ray particle fluxes,
electromagnetic radiation fluxes at various wavelengths, and magnetic fields to explain and
predict climate variability. Of the variety of timescales of climate variability presumed to be
affected by variability of solar emissions, this talk will focus on the decadal timescales (8-25
years) and review the research history to date.
6
Decadal Variability of Tropical Pacific Temperature in Relation to Solar Cycles
Alexander Ruzmaikin [alexander.ruzmaikin@jpl.nasa.gov], Jet Propulsion Laboratory, California
Institute of Technology, Pasadena, California
Global response of the Earth's climate system to solar variability appears to be weak and
more strong responses are expected from the Earth climate patterns. These large-scale spatial
patterns are associated with the Earth's atmospheric and ocean dynamics. Examples of the
patterns are the Northern and Southern Annular Oscillations and tropical El Niño. I will discuss
how solar variability influences the tropical climate pattern on decadal time scale.
The 8-year long satellite temperature and water vapor data (2002-2010) from Atmospheric
InfraRed Sounder (AIRS) and Atmospheric Microwave Sounding Unit (AMSU) on the Aqua
satellite show temperature and water vapor trends in the troposphere and low stratosphere over
the Niño 3.4 region of the Tropical Ocean in the most recent 11-year solar cycle. Linear
discriminant analysis of more extended sea surface temperature (SST) data for five solar cycles
(1950-2009) in this region demonstrates that the satellite trends reflect a typical decrease of the
SST in the Niño 3.4 region in the declining phase of the solar cycle. The magnitude of the SST
decrease depends on the solar cycle and ranges between 0.5K and 1.9K for the last five solar
cycles. The mechanisms of solar forcing that might lead to the trends are discussed.
Characterizing the Global Impacts of Solar Variability from the Ground to the Thermosphere
Using Data Assimilation
John McCormack [John.McCormack@nrl.navy.mil] and Fabrizio Sassi, Space Science Division, Naval
Research Laboratory, Washington DC
Understanding the atmospheric response to decadal changes in solar irradiance is crucial for
accurate projections of future climate scenarios. To date, our understanding of the atmospheric
response to solar variability is based on: (1) A large body of disparate observations from satellite
and ground-based measurements whose spatial and temporal coverage vary widely; and (2)
Theoretical studies based on atmospheric models of widely varying complexity and spatial
scales. To improve the observational characterization of the atmospheric response to solar
variations, a high-altitude atmospheric data assimilation system (DAS) capable of generating
global synoptic meteorological analyses every 6 hours from the ground to the lower
thermosphere (~90 km altitude) has recently been developed. This DAS is based on the existing
high-altitude version of the Navy Operational Global Atmospheric Prediction System
(NOGAPS), known as NOGAPS-ALPHA (Advanced Level Physics-High Altitude). In addition
to operational meteorological observations in the 0-50 km altitude range, the NOGAPS-ALPHA
DAS currently assimilates temperature and constituent measurements from instruments on
NASA research satellites such as Aura MLS and TIMED SABER. We present NOGAPSALPHA wind, temperature, and constituent fields for the recent record solar minimum period
(2005-2010), and validate these results with available independent measurements. We also
demonstrate how the DAS output can be used to specify lower atmospheric dynamical variability
in the Whole Atmospheric Community Climate Model (WACCM), thereby extending
simulations of the atmospheric response to solar variability up to 150 km. The extension of the
analysis in time through solar cycle 24 and beyond will also be discussed.
7
External Forcing, Internal Climate Variability and the Arctic’s Rapidly Shrinking Sea Ice Cover
Mark C. Serreze [Serreze@nsidc.org] and Julienne Stroeve, National Snow and Ice Data Center /
Cooperative Institute for Research in Environmental Sciences (NSIDC/CIRES), University of ColoradoBoulder
As assessed over the available satellite record, 1979-present, Arctic sea ice extent in
September is shrinking at a rate of approximately 12% per decade. The observed trend is larger
than depicted in hindcasts from most global climate models using observed climate forcings and
furthermore appears to have steepened over the past decade, hastening the transition towards a
seasonally open Arctic Ocean. This apparent strong sensitivity of the sea ice cover to external
forcing appears to reflect several mutually supporting processes. Because of the extensive open
water in recent Septembers, ice cover in the following spring is increasingly dominated by thin,
first-year ice (ice formed during the previous autumn and winter) that is vulnerable to melting
out in summer. Thinner ice in spring in turn fosters a stronger summer ice-albedo feedback
through earlier formation of open water areas. A thin ice cover is also more vulnerable to strong
summer retreat under anomalous atmospheric forcing on seasonal to decadal timescales scales.
Finally, general warming of the Arctic in all seasons has reduced the likelihood of cold years that
could bring about temporary recovery of the ice cover. Events leading to the September ice
extent minima of recent years exemplify these processes.
Mechanisms Involved in the Amplification of the Solar Cycle Signal in the Tropical
Pacific Ocean
Stergios Misios [stergios.misios@zmaw.de] and Hauke Schmidt, Max Planck Institute for Meteorology,
Hamburg, Germany
It is debated whether the response of the tropical Pacific Ocean to 11-year solar cycle forcing
resembles a La Niña- or El Niño-like signal. To address this issue, we conduct ensemble simulations
employing an atmospheric general circulation model with and without ocean coupling. In our
coupled simulations the tropically averaged sea surface temperature rises almost in phase with the
11-year solar cycle. In the Pacific, a basin-wide warming of approximately 0.1 K is simulated
whereas the warming in the Indian and Atlantic oceans is weaker. Outside the Pacific the surface
warming is mainly caused by a water-vapor feedback. In the western Pacific, the region of deep
convection shifts to the east thus reducing the surface easterlies. This shift is independent of the
ocean coupling; the deep convection moves to the east in the uncoupled simulations, too. The
reduced surface easterlies cool the subsurface western Pacific but warm the surface. The surface
warming is attributed to the reduction of the heat transport divergence which operates together with
the water-vapor feedback. These results suggest that, firstly, the surface heating in the Pacific Ocean
should be ascribed to a synergetic effect of climate feedbacks and secondly, the atmospheric
response to the 11-year solar cycle drives the ocean. The latter implies that the Pacific response to
the 11-year solar cycle does not result from atmosphere-ocean feedbacks and thus the solar surface
signature should stand out neither as El Niño-like nor as La Niña-like.
On the QBO-Solar Relationship throughout the Year
Karin Labitzke [karin.labitzke@met.fu-berlin.de], Meteorologisches Institut der Freien Universitaet
Berlin, Germany
Large effects of solar variability related to the 11-year sunspot cycle (SSC) are seen in the
stratosphere throughout the year, but only if the data are grouped according to the phase of the
QBO (Quasi-Biennial Oscillation). New results based on an extended, 70- year long data set,
fully confirm earlier findings.
8
Non-linear and Non-stationary Influences of Geomagnetic Activity on the Winter North
Atlantic Oscillation
Yun Li, CSIRO Mathematics, Informatics and Statistics, Wembley, Australia; Hua Lu [hlu@bas.ac.uk],
Martin J. Jarvis, and Mark A. Clilverd, British Antarctic Survey, High Cross, Madingley Road,
Cambridge, England, U.K.; and Bryson Bates, CSIRO Marine & Atmospheric Research, Wembley,
Australia
The relationship between the geomagnetic aa index and the winter North Atlantic
Oscillation (NAO) has previously been found to be non-stationary, being weakly negative
during the early 20th century and significantly positive since the1970s. The study reported here
applies a statistical method called the Generalised Additive Modelling (GAM) to elucidate the
underlying physical reasons.
We find that the relationship between aa index and the NAO during the Northern
Hemispheric winter is generally non-linear and can be described by a concave shape with a
negative relation for small to medium aa and a positive relation for medium to large aa. The
non-stationary character of the aa-NAO relationship may be ascribed to two factors. Firstly, it
is modulated by the multi-decadal variation of solar activity. This solar modulation is indicated
by significant change points of the trends of solar indices around the beginning of solar cycle
14, 20 and 22 (i.e. ~1902/1903, ~1962/1963, and ~1995/1996). Coherent changes of the trend
in the winter time NAO followed the solar trend changes a few years later. Secondly, the aaNAO relationship is dominated by the aa data from the declining phase of even-numbered
solar cycles, implying that the 27-day recurrent solar wind streams may be responsible for the
observed aa-NAO relationship. It is possible that an increase of long-duration recurrent solar
wind streams from high latitude coronal holes during solar cycles 20 and 22 may partially
account for the significant positive aa-NAO relationship during the last 30 years of the 20th
century.
Physical and Optical Properties of the Stratospheric Aerosol Layer
Patrick Hamill [Patrick.Hamill@sjsu.edu], Dept. of Physics and Astronomy, San Jose State University,
California
The stratospheric aerosol layer consists of a fine mist of sulfuric acid particles residing in the
lower stratosphere. Under normal conditions this layer is of minimal climatic importance, but
when it is perturbed by violent volcanic eruptions, it has an immediate, direct and measurable
effect on the temperature of Earth. The Mt. Pinatubo eruption resulted in a 0.3 degree cooling of
the average surface temperature of Earth. This effect was short-lived because the aerosol was
removed from the atmosphere within a few years. Time series plots of the properties of the layer
show sudden increases following the eruptions of El Chichon and Mt. Pinatubo followed by a
gradual return to background values.
We describe the physical and optical properties of the stratospheric aerosol particles, show
historical trends in the aerosol, and discuss how these are related to global temperature. The
microphysical processes that are responsible for the formation of the layer will be considered
briefly and recent climatologies of the layer will be discussed. The results presented are
primarily those obtained with the SAGE II satellite system, but we shall also describe other
observations of the layer, including measurements by space-borne lidars and balloon-borne
instruments. Finally, we mention geo-engineering schemes for modifying the layer.
9
The Tropical Lower Stratospheric Response to 11-Year Solar Forcing: Dynamical Feedbacks
from the Troposphere-Ocean Response
Lon L. Hood [lon@lpl.arizona.edu] and Boris E. Soukharev, Lunar and Planetary Laboratory,
University of Arizona, Tucson, Arizona
We investigate whether dynamical feedbacks from the 11-year troposphere-ocean response
(specifically the Pacific climate system response) contribute significantly to driving the
observed lower stratospheric response, including the solar cycle variation of total ozone. To
characterize the troposphere-ocean response, multiple linear regression (MLR) analyses of
Hadley Centre SST and SLP data are performed as a function of phase lag relative to the solar
cycle. Aliasing by strong ENSO events is minimized by carrying out MLR analyses for two
separate, relatively long, time periods: 1880-1945 and 1946-2009. In agreement with previous
analysts, the most persistent response to 11-year solar forcing is found for SLP in the North
Pacific during NH winter, consisting of a weakening and westward shift of the Aleutian low
near and approaching solar maxima. An associated SST response is also present but is less
reproducible for separate time periods. The derived solar cycle SLP response is similar to that
which occurs during La Niña events and is consistent with a “La Niña-like” Pacific climate
response near and approaching solar maxima. The weakened Aleutian low reduces the
amplitude of planetary wave forcing of the Brewer-Dobson circulation (BDC), as verified by
regressing North Pacific SLP against zonal mean v'T' in the extratropical lower stratosphere.
Some evidence for the expected decadal v'T' variation is obtained using NCEP/NCAR
reanalysis data in the Northern Hemisphere. A simplified analytic model suggests that this
decadal variation of wave forcing contributes substantially to the observed 11-year tropical
lower stratospheric ozone response through a modulation of the BDC.
Aura Microwave Limb Sounder Observations of the Polar Middle Atmosphere: Dynamics and
Transport of CO and H2O
Jae N. Lee [Jae.N.Lee@jpl.nasa.gov] and Dong L. Wu, Jet Propulsion Laboratory, California Institute of
Technology, Pasadena, California
Internal variability in the middle atmosphere needs be fully understood in order to address
Sun-Climate interaction problems. To improve our understanding of middle atmospheric
dynamics and transport, the vertical structure of the polar atmosphere is studied in terms of
wintertime annular modes using six years of geopotential height (GPH), carbon monoxide
(CO) and water vapor (H2O) data from Aura Microwave Limb Sounder (MLS). The Northern
Hemisphere annular mode (NAM) and the Southern Hemisphere annular mode (SAM) reveal a
strong coupling of the dynamics in the stratosphere and mesosphere. The maximum of the CO
NAM and SAM (CNAM and CSAM) indices is used to monitor and characterize the evolution
of wintertime polar dynamics as a function of time and height. The CNAM analysis reveals
reformation of a stronger mesospheric polar vortex after significant stratospheric sudden
warmings (SSWs) in 2006, 2009, and 2010. There is a significant anti-correlation between the
mesospheric and stratospheric CNAM indices during 2005-2010 winters, supporting the
hypothesis of mesosphere-stratosphere coupling through planetary-gravity wave interactions.
Although the six years of data do not cover one 11 year solar cycle, a near term trend on the
top of the interannual variability of upper atmosphere temperature and tracers is likely
contributed by the solar variation.
10
Decadal Variations of Solar Magnetic Field, Heliosphere and the Cosmic Rays, and their
Impact on Climate Change
Hiroko Miyahara1[hmiya@icrr.u-tokyo.ac.jp], Yusuke Yokoyama1, Yasuhiko T. Yamaguchi1, Wataru
Sakashita1, Peng K. Hong1, Kazuoki Munakata2, Yukihiro Takahashi3, Mitsuteru Sato3, Yosuke
Yamashiki4, Shuhei Masuda5, Takeshi Nakatsuka3
1
University of Tokyo, Kashiwa City, Chiba, Japan; 2 Shinshu University, Nagano
Japan; 3 Hokkaido University, Japan; 4 Kyoto University, Japan; 5 Japan Agency for Marine-Earth
Science and Technology (JAMSTEC), Japan; and 6 Nagoya University, Japan
Based on records of cosmogenic nuclides, we discuss the long-term variability of solar
decadal cycle, the structure of heliospheric magnetic field, and the subsequent variations of
galactic cosmic rays. We suggest that peculiar variation of solar magnetic field and the incident
cosmic rays had played some role in determining the pattern of climate variations during the
Little Ice Age. Records of beryllium-10 content from ice cores have suggested that the Hale
cycle of cosmic rays had been amplified at the Maunder Minimum, and that there had been
several annual-scale anomalous increases in cosmic rays around every other solar cycle minima.
Climate anomalies synchronized to those cosmic ray increases have been also observed in proxy
records. The amplification of the Hale cycle in cosmic rays may be due to the extreme flattening
of heliospheric current sheet and its impact on the drift effect of cosmic rays in the heliosphere.
We also discuss the possible pathway of cosmic ray influence on regional and global climate.
Atmospheric OH Response to the 11-Year Solar Cycle ― Could the gap between model and
observations be filled by SORCE data?
Shuhui Wang[Shuhui.Wang@jpl.nasa.gov], Thomas J. Pongetti, and Stanley P. Sander, Jet Propulsion
Laboratory, California Institute of Technology, Pasadena, California; King-Fai Li and Yuk L. Yung,
Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, California;
and Mao-Chang Liang, Research Center for Environmental Changes, Academia Sinica, TaiPei, Taiwan
Middle atmospheric OH is a key species in the ozone-destroying HOx reaction cycle
(involving OH, HO2, and H). It is mainly produced through photolysis of ozone and water
vapor in UV. The solar UV variation during the 11-year solar cycle is thus expected to affect
the natural variability in OH and related ozone chemistry. However, such studies had been
limited in the past due to the lack of long-term systematic observations. Here we present the
first effort to investigate such variability using long-term observations from space
(AURA/MLS) and the surface (FTUVS).
Both ground-based OH column record and MLS data suggest a ~10% decrease from solar
maximum to solar minimum. The observed OH variability is highly correlated with changes in
the total solar irradiance (TSI), the solar Mg II index, and Lyman-α during solar cycle 23.
However, chemical transport model simulations using a commonly accepted solar UV
variability parameterization give much smaller OH column variability (~3%). This
discrepancy implies either much-larger-than-expected solar UV variability or a mystery in
middle atmospheric hydrogen chemistry. The recent solar spectral irradiance (SSI)
measurements from SORCE show significantly larger solar UV variability than previously
believed. Model simulations using these new SSI data as solar forcing produce OH variability
that is much closer to observations (~7%). Such OH variability needs to be further understood
in order to accurately assess related impacts on ozone chemistry and better identify ozone layer
changes due to anthropogenic activities.
11
Session 3 Abstracts – Comparative Sun-Star Cycles
(Sept. 14, Wednesday p.m.)
Cyclic Variations of Sun-like Stars
Richard R. Radick [Richard.Radick@hanscom.af.mil], Air Force Research Laboratory, National Solar
Observatory, Sunspot, New Mexico
In 1968, Mount Wilson Observatory astronomer Olin Wilson wrote “…it is quite reasonable
to suppose that suitable measures of the strengths of these [Ca II H&K] chromospheric emissions
in stars should provide information on the stellar analogues of the solar cycle.” He offered the
prospect of discovering stellar activity cycles analogous to the 11-year sunspot cycle, using the
new coudé photoelectric spectrum scanner at the 100-inch telescope. At the same time, he made
the prescient prediction that luminosity variations of the Sun and Sun-like stars would not exceed
roughly 0.001 mag (0.1%), thus making their detection impracticable. In the classic paper that
appeared a decade later, he exhibited a variety of chromospheric activity patterns including, for a
number of stars, unmistakable cyclic variations. After Wilson’s retirement, the Mount Wilson
“HK program” continued until 2000, overlapping with Lowell Observatory’s Solar-Stellar
Spectroscopy (“SSS”) project that began routine operation in 1994. The SSS project measures
the Sun on a 3x/week cadence and monitors ~100 Sun-like stars with the same fiber-fed
instrument. The project continues to observe some of Wilson’s stars, thereby providing more
than 40 years of continuing coverage. More recently, it has focused more on a handful of stars
whose physical characteristics (and generally low levels of photometric and Ca II activity) mark
them as close solar analogues. A recent updated analysis of the best candidate solar twin, the 5th
magnitude star 18 Sco, now shows 0.1% photometric variation in phase with Ca II emission,
reinforcing our previously published results.
Solar Variability after Dark: Photometric Evidence from Stars and Planets
Wes Lockwood [gwl@lowell.edu], Lowell Observatory, Flagstaff, Arizona
Two long photometric projects seeking evidence of solar variability in the light reflected
from planets ended in frustration as one target after another proved intrinsically unstable. U. S.
Weather Bureau Chief of Scientific Services Harry Wexler sponsored the first effort at Lowell
Observatory from 1950 to 1966. Delays in proposed solar irradiance measurements from Earth
orbit prompted NOAA climatologist J. Murray Mitchell, Jr. to urge resumption of planetary
measurements in 1971. Ambiguous results from Uranus, Neptune, and Titan kept luring us into
proposing various solar related hypotheses, but we ultimately came to realize that outer solar
system planetary atmospheres exhibit mainly seasonal variations.
All was not in vain, however, as the planetary measurements spawned long-term studies of
Sun-like stars, historically thought to be paragons of stability. Observations of sixteen stars from
1953 to 1966 yielded upper limits of variability below 1% and the important conclusion that
“…if the Sun acts in similar fashion, its variability over a 15-year period probably does not
exceed one half of one percent.” New measurements beginning in 1984 at Lowell and
continuing at Fairborn Observatory after 2000 pushed the detection threshold down to the 0.1%
level and solidified the demographics of variability among Sun-like stars including several “solar
twins.” Parallel Ca II observations from Lowell’s Solar Stellar Spectrograph add to an
increasingly comprehensive assessment of the patterns of chromospheric and photometric
variation of the stars most like the Sun.
12
Modeling Sun-like Stars
Benjamin P. Brown [bpbrown@astro.wisc.edu], Dept. of Astronomy and Center for Magnetic SelfOrganization in Laboratory and Astrophysical Plasmas (CMSO), University of Wisconsin, Madison
Magnetism is a ubiquitous feature of solar-type stars. The magnetic fields observed at the
stellar photospheres arise from dynamo action in the convective envelopes, where plasma
motions couple with rotation to build global-scale magnetic fields. Here we discuss recent
global-scale, 3-D MHD simulations of convection and dynamo action in stellar interiors with the
anelastic spherical harmonic (ASH) code. For the first time, a variety of global-scale simulations
are building global magnetic fields without relying on stable tachoclines of shear for storage or
large-scale organization. Instead, these global-scale magnetic fields are built in the bulk of the
convection zone, forming large wreath-like structures that coexist with the turbulent convection.
These dynamos can undergo regular and cyclic reversals of magnetic polarity and some are now
even building magnetic structures that become buoyantly unstable and rise toward the stellar
photospheres. We’ll explore these cyclic wreath-building dynamos in G- and K-type stars
rotating at the solar rate and faster, as the Sun did when younger.
The HAO-NOAO-SMARTS Southern HK Project
Travis Metcalfe [travis@ucar.edu], High Altitude Observatory, National Center for Atmospheric
Research, Boulder, Colorado
The Mount Wilson Ca HK survey revealed magnetic activity variations in a large sample of
solar-type stars with timescales ranging from 2.5 to 25 years. This broad range of cycle periods
is thought to reflect differences in the rotational properties and the depths of the surface
convection zones for stars with various masses and ages. In 2007 we initiated a long-term
monitoring campaign of Ca II H and K emission for a sample of 57 southern solar-type stars to
measure their magnetic activity cycles and their rotational properties when possible. I will
provide an overview of the program, including an update on our discovery of the shortest activity
cycle ever measured for a solar-type star (1.6 years in the exoplanet host star iota Horologii), and
I will preview the short-term variations that we have identified in several other targets.
What about the other Suns?
Thomas R. Ayres [Thomas.Ayres@colorado.edu], University of Colorado, Center for Astrophysics and
Space Astronomy (CASA), Boulder, Colorado
This is a progress report concerning high-energy observations of nearby solar-twins, young
and old. One topic is the venerable Alpha Centauri system, and the intricate coronal cycle dance
that the G dwarf and its K-type companion have been performing over the past decade, as
documented by Chandra X-ray Observatory. The solar-twin appears stuck in a long-term
minimum, much as our own Sun was at the end of its past Cycle 23; while the cooler companion
has displayed a very regular 8-year X-ray cycle. A second topic is the young (50 Myr) solar
analog EK Draconis, observed last year by HST with its new COS spectrograph. The mere 20minute "SNAPshot" FUV exposure of EK Dra revealed very broad chromospheric and transition
zone lines; erratic variability of Si IV, but not C II or coronal Fe XXI; and strong redshifts of the
Si IV lines (but again not C II or Fe XXI). In fact, it appears that the Si IV-bearing gas mainly is
flowing down onto the lower atmosphere, something like an actively accreting T-Tauri star; but
EK Dra is far beyond that evolutionary stage. Instead, what we likely are witnessing is a supersized version of solar "coronal rain;" emphasizing that the coronal heating and cooling is a highly
dynamic process in these super-active objects; but at the same time the underlying mechanisms
might not be so different from the Sun, at least if recent heretical ideas concerning the role of
"Type II" spicules are correct.
13
Session 4 Abstracts – Climate Sensitivity and Global Energy Imbalance
(Sept. 15, Thursday a.m.)
Climate Sensitivity
Jerry North [g-north@geos.tamu.edu], Texas A & M University, College Station, Texas
The notion of climate sensitivity has been around for half a century. Budyko was the first
that I heard discuss it. He raised the solar constant by 1% and looked at the global average
response in his model. He became interested in the greenhouse effect and started to ask about
doubling CO2 instead. In the energy balance climate models he and William Sellers made
popular the response (equilibrium to equilibrium) to doubling carbon dioxide (now referred to as
the equilibrium sensitivity) is in the neighborhood of 2.0 K. These models in their empirical
parameterization of outgoing radiation include water vapor and lapse rate feedback, but probably
do not include cloud feedback. In the early days they included ice-albedo feedback but probably
overestimated it. Very comprehensive radiative transfer models suggest that without any of the
conventional feedbacks the sensitivity is about 1.0 K. The feedbacks may double or triple this
value. Another sensitivity of interest is transient sensitivity: the response to increasing carbon
dioxide at a fixed percentage per year (usually 1%/ year) until it doubles (seventy years).
Because of lags in the system transient sensitivity is less than equilibrium sensitivity. Estimating
both kinds of sensitivity requires the use of coupled ocean/atmosphere general circulation
models, but there remains considerable spread among the IPCC AR4 models. Dessler and Soden
will delve deeper into the feedbacks.
Understanding Climate Feedbacks Using Radiative Kernels
Brian Soden [bsoden@rsmas.miami.edu], Rosenstiel School for Marine and Atmospheric Science,
University of Miami, Florida
There are a variety of issues that complicate the analysis of radiative feedbacks in global
climate models. These complications often create misconceptions regarding their strengths and
distributions. In this talk, I will present a method for quantifying climate feedbacks based on
“radiative kernels”. This method provides insight into the physics which underlie the feedbacks,
and offers a simple way to intercompare climate feedbacks in both models and observations.
Observational Constraints on the Water Vapor and Cloud Feedbacks
Andrew E. Dessler [adessler@tamu.edu], Dept. of Atmospheric Sciences, Texas A&M University,
College Station, Texas
Most of the warming expected over the next century comes from feedbacks rather than direct
warming from greenhouse gases. In this talk, I will describe the observational evidence
supporting the existence of a strongly amplifying water vapor + lapse rate feedback and a more
uncertain, but likely amplifying, cloud feedback.
14
Tracking Earth’s Energy: From El Niño to global warming
Kevin E. Trenberth [trenbert@ucar.edu] and John T. Fasullo, National Center for Atmospheric
Research, Climate Analysis Section, Boulder, Colorado
The state of knowledge and outstanding issues with respect to the global mean energy budget of
planet Earth will be described, along with the ability to track changes over time. Best estimates of the
main energy components involved in radiative transfer and energy flows through the climate system do
not satisfy physical constraints for conservation of energy without adjustments. The main issues relate
to the downwelling longwave radiation and the hydrological cycle, and thus the surface evaporative
cooling. It is argued that the discrepancy is 18% of the surface latent energy flux, but only 4% of the
downwelling LW flux, and most likely that the latter is seriously astray in some calculations, including
many models. Good knowledge of the total solar irradiance and its changes over time are vital.
Beginning in 2000, the top-of-atmosphere radiation measurements provide stable estimates of the net
global radiative imbalance changes over a decade, but after 2004 there is “missing energy” as the
observing system of the changes in ocean heat content, melting of land ice, and so on, is unable to
account for where it has gone. Based upon a number of climate model experiments for the 21st century
where there is a stasis in global surface temperature and upper ocean heat content in spite of decade long
periods with a known net energy input into the climate system, we infer that the main sink of the missing
energy is likely the deep ocean below 275 m depth.
Recent Energy Balance of Earth – Update
David Douglass[douglass@pas.rochester.edu], University of Rochester, New York
A recently published estimate of Earth’s global warming trend is 0.63 ± 0.28 W/m2, as calculated
from ocean heat content anomaly data spanning 1993-2008. This value is not representative of the
recent (2003-2008) warming/cooling rate because of a “flattening” that occurred around 2001-2002.
Using only 2003-2008 data from Argo floats, we find by four different algorithms that the recent
trend ranges from –0.010 to –0.161 W/m2 with a typical error bar of ±0.2 W/m2. These results fail to
support the existence of a frequently-cited large positive computed radiative imbalance.
Interannual Variability of Top-of-Atmosphere Albedo Observed by CERES Instruments
Seiji Kato [seiji.kato@nasa.gov], NASA Langley Research Center, Hampton, Virginia
Interannual variability of global radiation budget, regions where contribute to the variability,
and what limits albedo variability are investigated using Clouds and the Earth's Radiant Energy
System (CERES) data taken from March 2000 through February 2004. Area weighted mean topof-atmosphere (TOA) reflected shortwave, longwave, and net irradiance standard deviations
computed from monthly anomalies over a 1 degree by 1 degree region are 9.6, 7.6, and 7.6 W/m2
, respectively. When standard deviations are computed from global monthly anomalies, they
drop to 0.5, 0.4, and 0.4 W/m-2, respectively. Regions with a large standard deviation of TOA
reflected shortwave and longwave are tropical western and central pacific, which is caused by
shifting from La Niña to El Niño during this period. However, a larger standard deviation of 300
- 1000 hPa thickness anomalies occur in polar region instead of tropics. The correlation
coefficient between atmospheric net irradiance anomalies and 300 - 1000 hPa thickness
anomalies is negative. These indicate that temperature anomalies in the atmosphere are mostly a
result of anomalies in longwave and dynamical processes that transport energy poleward, instead
of albedo anomalies by clouds directly affecting temperature anomalies in the atmosphere. It is
demonstrated using a simple zonal mean thermodynamic energy equation that temperature
anomalies decay exponentially with time by longwave emission and by dynamical processes. As
a result, the mean meridional temperature gradient is maintained, mean meridional circulations
are not greatly altered by albedo anomalies on an annual time scale. These provide small
interannual variability of the global mean albedo.
15
The Spectral Radiative Effects of Inhomogeneous Clouds and Aerosols
Sebastian Schmidt [Sebastian.Schmidt@lasp.colorado.edu] and Peter Pilewskie, Laboratory for
Atmospheric and Space Physics (LASP), University of Colorado, Boulder
Recent experiments and model calculations have shown that cloud-aerosol shortwave
radiative effects have unique spectral features in presence of cloud inhomogeneities.
Neglecting them can lead to biases in estimates of cloud-aerosol absorption and radiative
forcing. We will show examples and discuss how much detail needs to be known about
spatial structure to determine the spectral and broadband properties of cloud-aerosol fields.
Session 5 Abstracts – Solar Rotational Variability
(Sept. 15, Thursday p.m.)
Rotational Variability in the Ultraviolet Solar Spectral Irradiance
Marty Snow [Marty.Snow@lasp.colorado.edu], Laboratory for Atmospheric and Space Physics (LASP),
University of Colorado, Boulder
As active regions rotate in and out of view on the Sun, the irradiance varies on a 27-day
timescale. The magnitude of this rotation depends on the strength of the active regions, but
also on the center-to-limb variance as a function of wavelengths. Early in the solar cycle,
active regions are typically formed at higher latitudes than later in the solar cycle. All of
these factors lead to a different character of the rotational variability seen in the solar spectral
irradiance record. We will compare the rotational variability observed by the SORCE
ultraviolet instruments (SIM and SOLSTICE) to other observations (SOLSPEC, SOL-ACES,
etc.) as well as to results from irradiance proxy models such as NRLSSI.
Do We Understand Solar Irradiance Variations During Solar Rotations? A multi instrument
study
Matthieu Kretzschmar1,2 [matthieu.kretzschmar@cnrs-orleans.fr], T. Dudok de Wit2, and C. Froment2
1
2
Royal Observatory of Belgium / SIDC, Brussels, Belgium
LPC2E, UMR6115 CNRS /University of Orléans, France
Solar irradiance modeling, as well as inter-calibration of existing datasets (e.g. for the
TSI or in the UV), often rely on linear relations between the observed solar flux and proxies,
and on the appearance and evolution of dark (sunspot) and bright (faculae) features on the
solar disk. Improving these reconstructions necessitates a deep understanding of how the
passage of solar features affects the spectral solar flux, depending on their strength, size, and
position.
Here we will focus on a few solar rotations displaying clear 27-days period, and analyze
in details the available observations, solar images and solar flux. We investigate how well
the irradiance variations observed at various wavelengths by various experiments (from
SDO, PROBA2, TIMED, SOHO) can be understood and reproduced from proxies that are
currently used in solar irradiance models.
16
Photoelectrons as a Tool to Evaluate Solar EUV and XUV Model Irradiance Spectra
William K. Peterson [Bill.Peterson@lasp.colorado.edu], T. N. Woods, and J. M. Fontenla, LASP,
University of Colorado-Boulder; P. G. Richards, George Mason University; W. K. Tobiska, Utah State
University; S. C. Solomon, NCAR, High Altitude Observatory, Boulder, Colorado; and H. P. Warren,
Naval Research Laboratory, Washington, DC
Solar radiation below 50 nm produces a substantial portion of the F region ionization and
most of the E region ionization that drives chemical reactions in the thermosphere. At times
before the launch of the SDO spacecraft there is a lack of high temporal and spectral resolution
Solar EUV and XUV observations, particularly below 27 nm. To fill these temporal and
spectral data gaps various solar irradiance models have been developed. We have developed a
technique to use observations of escaping photoelectron fluxes from the FAST satellite and two
different photoelectron production codes driven by model solar irradiance values to
systematically examine differences between observed and calculated escaping photoelectron
fluxes.
We have compared modeled and observed photoelectron fluxes for the interval from
September 14, 2006 to January 1, 2007. This is an interval included ~ 4 solar rotations and is
characterized by modest solar and geomagnetic activity. Solar irradiance models included
TIMED/SEE data, which is derived from a model below 27 nm, and the FISM Version 1, the
SRPM predictive model based on solar observations, HEUVAC, S2000, and NRL, solar
irradiance models. We used the GLOW and FLIP photoelectron production codes.
Here we focus on the differences between solar irradiance models and small differences
between photoelectron production code outputs using the same solar irradiance spectra over
this time period.
Rotational Modulation on Total Solar Irradiance
Hari Om Vats [vats@prl.res.in], Astronomy Astrophysics Division, Physical Research Laboratory,
Ahmedabad, India
The Sun –weather relationship is becoming increasingly important. It is true that our
understanding of the Sun and solar processes has increased dramatically during recent years,
however, it is realized that the Sun affects the Earth’s environment in a much more
complicated manner than we have imagined. It is impossible to describe the effects of the Sun
on Earth by just a few parameters. The most important solar parameter is the total power as
irradiance received from the Sun at Earth. The solar angular rotation velocity is a function of
latitude, time and height above or depth below the solar photosphere. This phenomenon is
known as the solar differential rotation. Earlier we had used VIRGO experiment on board
ESA/NASA collaborative SOHO mission measures the total solar irradiance (TSI) with two
absolute radiometers (DIARAD and PMO6) for the period 1996- 2001. The modulation of this
TSI by solar rotation was investigated. The solar irradiance is essentially the contribution from
the small scale solar surface structures integrated over the solar disk. The modulation will
represent rotation period. Recent data of SORCE is used for the period 2003-2011 to look for
the rotational modulation on TSI. It is found that the rotational modulation varies from 9 – 42
% and it apparently varies in opposition of sunspot numbers. The derived sidereal rotation
period varies from 22.5 to 30.5 days. These results are compared with other investigation e.g.
(1) disk integrated radio emission (2) IMF and (3) solar radio and X-ray images.
17
Session 6 Abstracts – Modeling and Forecasting Solar Cycles and Climate Impacts
(Sept. 16, Friday a.m.)
Tropical Internal Variability and its Reflection on the Global Climate System
Kyle Swanson [kswanson@uwm.edu], Atmospheric Sciences Program, University of Wisconsin-Milwaukee
Variability internal to the climate system presents a significant challenge to the detailed
attribution of climate change, as well as to usefulness of cyclic variability, most notably the solar
cycle, as a means to study the climate response. Here, we will focus on how variability in the
tropical climate system, primarily due to changes in the character of the El Niño/Southern
Oscillation, impacts the global climate system. Emphasis will be on: (i) bounding the magnitude
of internal variability and its reflection in radiative/precipitation subsystems, using both satellite
and surface observations; (ii) extending those results to the climate shift of the 1970’s, as well as
more recent climate shifts; and (iii) the character of apparent recent wild variability in the
tropical hydrologic cycle and its ramifications for near-term global climate variability.
Modeling Climate Responses to Variations in Spectral Solar Irradiance
Robert Cahalan [Robert.F.Cahalan@nasa.gov], NASA-Goddard Climate and Radiation Laboratory,
Greenbelt, Maryland
Observations show Earth's surface to be warming in recent decades, while the stratosphere has
been cooling, particularly the upper stratosphere. This is usually taken as evidence that the forcing is
primarily due to the greenhouse effect, and not the Sun. However, evaluating the Sun's impact on
climate requires knowledge of variations not only in Total Solar Irradiance (TSI, formerly "solar
constant") but also variations in the Spectral Solar Irradiance (SSI). Initial findings from SIM indicate
that multiyear changes in visible and near-infrared parts of the spectrum may be out of phase with
those of TSI, while near ultraviolet changes are in phase, but larger than expected. To consider the
climate impact of such changes, we compute climate responses to two classes of SSI variations, both
having the same variations in TSI. We find that out-of-phase forcing leads to much larger temperature
variations in the upper stratosphere, but smaller variations in the troposphere and upper ocean. These
differences underscore the importance of the calibration effort for SSI that has been initiated at LASP
with the assistance of NIST. With SORCE follow-on missions such as the Total and Spectral Solar
Irradiance Sensor (TSIS), we anticipate narrowing uncertainties in SSI variability that will be
important to improving our understanding of the climate responses to solar forcing.
Middle Atmosphere Sensitivity to SSI Solar Cycle Variations
William H. Swartz1 [Bill.Swartz@jhuapl.edu], R. S. Stolarski2,3, L. D. Oman3, E. L. Fleming3, and C. H. Jackman3
1
Johns Hopkins University, Applied Physics Laboratory, Laurel, Maryland
Johns Hopkins University, Laurel, Maryland
3
NASA Goddard Space Flight Center, Greenbelt, Maryland
2
Variation of the solar spectral irradiance (SSI) with solar cycle impacts the composition and
temperature of the atmosphere. Stratosphere ozone and temperature, for example, respond through
both direct solar heating and photolysis. We have implemented an 11-year solar cycle in the Goddard
Earth Observing System Chemistry–Climate Model (GEOS CCM). Simulations based on a multidecadal historical reconstruction derived from contemporary observations of solar irradiance and
historical proxies for solar activity (Lean SSI) and a reconstruction from the SORCE dataset are
compared and contrasted. We find that the magnitude and morphology of the atmospheric response is
highly dependent on the spectral characteristics of the SSI dataset used, and we examine the sensitivity
of the atmospheric response to both the relative and absolute variations of the solar spectrum
represented by the two datasets. The model output is also compared with observations in order to test
the validity of the results.
18
Modeling of the 11-year Solar Cycle Response in Upper Atmospheric Hydroxyl Radicals
King-Fai Li1,2[kfl@gps.caltech.edu], Shuhui Wang3, Thomas J Pongetti3, Stanley P. Sander3, Yuk L.
Yung1, Jerald W. Harder4, Marty Snow4, and Franklin P. Mills2,5
1
2
3
4
5
Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena,
California
Atomic and Molecular Physics Laboratories, Research School of Physics and Engineering, Australian
National University, Canberra, ACT, Australia
Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California
Laboratory for Atmospheric and Space Physics, University of Colorado, Boulder, Colorado
The Fenner School of Environment and Society, Australian National University, Canberra, ACT,
Australia
The solar-cycle modulation recently reported [Wang et al., 2011] in the hydroxyl radical
(OH) column during Solar Cycle 23 over the Table Mountain Facility, California, has
important implications for the catalytic destruction of odd oxygen [atomic oxygen (O) and
ozone (O3)]. Here the solar response of OH is simulated using a one-dimensional
photochemical model with the latest solar ultraviolet (UV) measurements from SORCE since
2004. By extrapolating the UV measurements back to the year of solar maximum in 2002
using the Magnesium-II core-to-wing ratio (Mg-II c/w) index, the model solar response of the
mid-latitude OH column abundance is 6.4 ± 2.5 %, which is lower than the observed value,
~10 ± 3 %, but within the mutual uncertainty limits. The vertical response shows a doublepeak structure with largest amplitudes in the mesosphere due to water vapor (H2O) photolysis
at the hydrogen Lyman-α wavelength and in the stratopause region due to O3 photolysis in the
Hartley band. The shielding effect from enhancement of O3 above 45 km reduces OH in the
middle stratosphere at solar maximum. The predicted response for the OH column abundance
in this model is about two times greater than that using a commonly accepted model for solar
spectral variability which was based on the observed solar variability during 1992 – 2001 and
the peak response in the stratopause region is about three times greater. The predicted vertical
response may be verified by altitude-resolved observations during the next solar maximum.
These changes in OH will affect upper stratospheric ozone and hence stratospheric
temperatures and circulation patterns. Therefore, they must be considered in future climate
simulations.
Modeling TSI Variations from SORCE/TIM
Gary A. Chapman [gary.chapman@csun.edu], A. M. Cookson, and D. G. Preminger, San
Fernando Observatory, California State University, Northridge
Total Solar Irradiance (TSI) measurements have been available from the TIM instrument
on the SORCE spacecraft since 2003. We compare TSI data with photometric indices from red
and K-line images obtained on a daily basis at the San Fernando Observatory (SFO). For 1375
days of data from 2003 March 02 to 2010 May 05 we compare the data in linear multiple
regression analyses. The best results come from using only two photometric indices, the red
and K-line photometric sums, and SORCE TSI 6-hour averages interpolated to the SFO time of
observation. For this case, we obtain a coefficient of multiple correlation, R2, of 0.94798 and a
quiet-Sun irradiance, S_o = 1360.778 +/- 0.004 W/m2. These results provide further evidence
against hypotheses that link TSI variations to assumed changes in the quiet Sun.
19
Heliospheric Oscillations and their Implication for Climate Oscillations and Climate Forecast
Nicola Scafetta [nicola.scafetta@gmail.com], ACRIM, Duke University, Durham, North Carolina
We investigate whether or not the decadal and multi-decadal climate oscillations have an
astronomical origin. Several global surface temperature records since 1850 and heliospheric
oscillations deduced from the orbits of the planets present very similar power spectra. Eleven
frequencies with period between 5 and 100 years closely correspond in the two records.
Among them, large climate oscillations with peak-to-trough amplitude of about 0.1 oC and
0.25 oC, and periods of about 20 and 60 years, respectively, are synchronized to the orbital
periods of Jupiter and Saturn. Schwabe and Hale solar cycles are also visible in the
temperature records. A 9.1-year cycle is synchronized to the Moon's orbital cycles. A
phenomenological model based on these astronomical cycles can be used to well reconstruct
the temperature oscillations since 1850 and to make partial forecasts for the 21st century. It is
found that at least 60% of the global warming observed since 1970 has been induced by the
combined effect of the above natural climate oscillations. Additional discussions about a
quasi-millennial cycle are added to the discussion. The partial forecast indicates that climate
may stabilize or cool until 2030-2040. Possible physical mechanisms are qualitatively
discussed with an emphasis on the phenomenon of collective synchronization of coupled
oscillators.
N. Scafetta, “Empirical evidence for a celestial origin of the climate oscillations and its implications”. J. of
Atmospheric and Solar-Terrestrial Physics 72, 951–970 (2010), doi:10.1016/j.jastp.2010.04.015
Forecasting Climate and Ozone Changes on Multi Decadal Time Scales
Judith L. Lean [jlean@ssd5.nrl.navy.mil], Naval Research Laboratory, Washington DC
Growing empirical evidence attests to the Sun’s role in altering the Earth’s climate and
atmosphere, including the ozone layer, in ways that can mitigate or exacerbate anthropogenic
effects on time scales of decades. Furthermore, solar and anthropogenic influences occur
simultaneously with natural variability driven by dynamical motions within the global system.
A multiple regression analysis is used to identify and characterize the specific mix of natural
and anthropogenic components that influences the Earth’s surface temperature and ozone layer,
respectively. Changes in surface temperature and ozone are forecast during future decades
using scenarios for upcoming 11-year cycles in total and UV irradiance, projections of
greenhouse gases including chloroflurocarbons, and propagation of internal variability cycles.
The forecasts suggest that during the next three to four years, global surface temperature will
increase at a faster rate than is attributable to greenhouse gases alone, as a result of increasing
solar irradiance during the ascending phase of solar cycle 24. The occurrence of a significant
El Niño or volcanic event notably impacts the scenarios for decadal climate change in the near
future. Forecasts of future ozone levels suggest that total global ozone has already reached its
minimum level and may recover to 1980 levels as soon as 2025. This recovery precedes the
return of CFCs to 1980 levels, after which total ozone will continue to increase due to
greenhouse gas cooling. By 2050 total ozone levels may exceed those of the past century.
20
Solar Irradiance Variations During Solar Cycle 24
Tom Woods [Tom.Woods@lasp.colorado.edu], Laboratory for Atmospheric and Space Physics (LASP),
University of Colorado, Boulder
The solar cycle 23/24 minimum in 2008-2009 is deeper and broader than recent cycle
minima and appears to be similar to the low minima in the early 1900s. This minimum offers a
unique opportunity to advance our understanding of secular (long-term) changes in the solar
irradiance and its influence on Earth’s climate and atmosphere. The Total Solar Irradiance
(TSI) appears to have lower irradiance in 2008 than in 1996 by about 200 ppm according to
some of the TSI observations and also for some of the TSI models. The solar extreme
ultraviolet irradiance appears to be even lower at about 10% less in 2008 than in 1996. The
rise of solar activity during the current cycle 24 has been slow, more than a factor of two
slower than recent solar cycles but slightly faster than the low Dalton Minimum cycles in the
early 1800s. This slow rise, as well as many other predictions for this cycle, suggests that a
low solar cycle maximum is expected for solar cycle 24.
The Next Generation in Solar Radio Monitoring
Ken Tapping [Ken.Tapping@nrc-cnrc.gc.ca], National Research Council of Canada, Herzberg Institute
of Astrophysics, Penticton, BC, Canada
Even though spaceborne instrumentation is currently the main source of solar variability
measurements, for decades to come they will have the problem of inadequate record lengths,
breaks in the time-series and discontinuities in calibration. These problems underline a
continuing need for ground-based solar monitoring and proxies.
The 10.7cm solar radio flux index has been measured for more than 60 years. A possible
problem with it is that it is a composite of at least two different emission mechanisms: thermal
free-free emission and thermal gyroresonance. There is also the possibility of contributions
from non-thermal processes on occasion. Indices that are at least more assignable to individual
emission mechanisms will provide more focused indicators of particular aspects of solar
activity and may provide better proxies.
We are in the process of building a “Next Generation Solar Flux Monitor”, which will
measure the absolute solar radio flux at six different wavelengths simultaneously using a
common antenna and feed. In order to better record bursts and other transient events, and for
interference mitigation, the receiver outputs will be logged simultaneously at a rate of 1000
samples a second. In addition, a spectrometer will be recording the whole bandwidth of the
instrument with millisecond time resolution. Using the spectrometer in parallel with the
discrete wavelength flux measurements, the whole flux spectrum should be available between
21 and 2.8 cm wavelengths.
21
Solar Spectral Irradiance and Climate
Peter Pilewskie [Peter.Pilewskie@lasp.colorado.edu], Laboratory for Atmospheric and Space Physics
(LASP), University of Colorado, Boulder
Spectrally resolved solar irradiance is recognized as being increasingly important to
improving our understanding of the manner in which the Sun influences climate. There is
strong empirical evidence linking total solar irradiance to surface temperature trends - even
though the Sun has likely made only a small contribution to the last half-century's global
temperature anomaly - but the amplitudes cannot be explained by direct solar heating alone.
The wavelength and height dependence of solar radiation deposition, for example, ozone
absorption in the stratosphere, absorption in the ocean mixed layer, and water vapor absorption
in the lower troposphere, contribute to the "top-down" and "bottom-up" mechanisms that have
been proposed as possible amplifiers of the solar signal. New observations and models of solar
spectral irradiance are needed to study these processes and to quantify their impacts on climate.
Some of the most recent observations of solar spectral variability from the mid-ultraviolet
to the near-infrared have revealed some unexpected behavior that was not anticipated prior to
their measurement, based on an understanding from model reconstructions. The atmospheric
response to the observed spectral variability, as quantified in climate model simulations, have
revealed similarly surprising and in some cases, conflicting results. This paper will provide an
overview on the state of our understanding of the spectrally resolved solar irradiance, its
variability over several time scales, potential climate impacts, and finally, a discussion on what
is required for improving our understanding of Sun-climate connections, including a look
forward to the Total and Spectral Solar Irradiance Sensor mission.
NASA’s Living With a Star Program
Madhulika (Lika) Guhathakurta [Madhulika.Guhathakurta@nasa.gov], NASA Headquarters,
Washington, DC
22