The Impact of Solar Spectral
Irradiance Variability on Middle
Atmospheric Ozone
Jerald Harder1, Aimee Merkel1, Dan Marsh2,
Anne Smith2, Juan Fontenla1, and Tom Woods1
Laboratory for Atmospheric and Space Physics (LASP),
University of Colorado
Special thanks to:
Mark Rast & Martin Snow, LASP
SORCE Meeting, Sedona Arizona
The Impact of Solar Spectral Irradiance Variability on Middle Atmospheric Ozone
September 12, 2011
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Overview
• Observations of SSI with SIM
– Status of SIM observations
– Degradation corrections
– Irradiance trends
• Solar variability as seen in Precision Solar Photometric Telescope (PSPT)
the Solar Radiation Physical Model (SRPM)
• Modeling study using NCAR’s WACCM (Whole Atmosphere Community
Climate Model).
– Response of middle atmospheric ozone when forced by solar spectral
irradiance (SSI).
– Compare and contrast to model results when forced with solar proxy Naval
Research Laboratory SSI model (NRLSSI = Lean (2000) model) SORCE (Solar
Radiation and Climate Experiment) SSI observations from SIM and SOLSTICE.
• Is the predicted ozone signal from the WACCM simulations present in
observations? Are they consistent with the findings from the UARS era?
SORCE Meeting, Sedona Arizona
The Impact of Solar Spectral Irradiance Variability on Middle Atmospheric Ozone
September 12, 2011
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Status of SIM after October 2010
•
4 different safe-hold events since September 26, 2010 caused observatory temperatures to
drop below -15oC producing small be noticeable changes in the responsivity of SIM.
– Detection of these On-board Computer (OBC) anomalies has been corrected in flight software
•
Because of decreased battery capacity, power cycling on every orbit started on 2011/05/04
– Power cycling has no instrument safety issues
– Detectors have 3-5 degree temperature swings
• Effects detector radiant sensitivity especially in the 900-1000 nm region
• There are temperature drifts longer that a single orbit
– ESR requires ~30 minutes to achieve full control on each orbit
– Prism temperature drifts continuously (~1.5°C)
• Drift may not affect data processing, i.e. may not need an explicit wavelength shifting algorithm
• ~1 year of data may be needed to detect second order effects
• These events have disrupted cadence of SIM A SIM B comparisons
SORCE Meeting, Sedona Arizona
The Impact of Solar Spectral Irradiance Variability on Middle Atmospheric Ozone
September 12, 2011
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SIM degradation correction and long-term uncertainty
• Degradation Corrections:
– Exposure related (prism transmission)
• Correct by comparing two spectrometers at
different exposure rates
– Non-exposure related (photodiode
degradation)
• Correct by comparing ESR’s and photodiode
detectors
• Physically based correction:
– No assumptions are made about magnitude,
slope, or time dependent behavior of SSI
– Prism degradation obeys Lambert’s Law
• See Auxiliary material to Harder et al., GRL,
(2009) for details
SORCE Meeting, Sedona Arizona
The Impact of Solar Spectral Irradiance Variability on Middle Atmospheric Ozone
September 12, 2011
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SIM degradation correction and long-term uncertainty
SORCE Meeting, Sedona Arizona
The Impact of Solar Spectral Irradiance Variability on Middle Atmospheric Ozone
September 12, 2011
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Time series of solar spectral variability from SORCE
SORCE Meeting, Sedona Arizona
The Impact of Solar Spectral Irradiance Variability on Middle Atmospheric Ozone
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Mauna Loa PSPT
•
•
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Clear indication of the rise of
SC24 both in sunspot area and
bright active regions
– Disk fractions for active
regions and network are
approaching 2004-2005
values
~160 days separate the
minimum in the longitudinal
B-field from the minimum
active region area in PSPT
The Impact of Solar Spectral Irradiance Variability on Middle Atmospheric Ozone
September 12, 2011
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PSPT observations of faculae
•Some faculae and plage have negative contrast at red
continuum wavelengths
• The fraction of dark faculae decreases into SC23
minimum and increases into rising phase of SC24
SORCE Meeting, Sedona Arizona
The Impact of Solar Spectral Irradiance Variability on Middle Atmospheric Ozone
September 12, 2011
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Solar spectral irradiance variability in SRPM
Fontenla, J. M. M., et al. (2011), High-resolution solar spectral irradiance from extreme ultraviolet
to far infrared,J. Geophys. Res., doi:10.1029/2011JD016032, in press.
SORCE Meeting, Sedona Arizona
The Impact of Solar Spectral Irradiance Variability on Middle Atmospheric Ozone
September 12, 2011
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Solar spectral irradiance variability in NRL SSI
Sunspot
Case:
04/30/2005
FaculaPlage:
08/29/2005
Solar Min
Ref:
11/09/2007
J. Lean,
GRL., vol. 27,
pp 2425, 2000.
SORCE Meeting, Sedona Arizona
The Impact of Solar Spectral Irradiance Variability on Middle Atmospheric Ozone
September 12, 2011
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Solar forcing and Earth atmospheric response
Solar forcing and response mechanisms are wavelength dependent
Chemistry climate models require
SSI to determine the role of solar
forcing
Ultraviolet (UV) radiation drives
many atmospheric processes
Solar input to models
• Historically solar input spectra scaled
by long-term proxies such as sunspot
index,F10.7 or Mg II index.
• Now GCM use NRLSSISSI reconstructions based on combined
sunspot and facular proxy indicators
[Lean, 2000].
• NRLSSI employed as solar input
for climate model inter-comparison
studies, so represents the de facto
standard for comparison.
[SPARC CCMVAL, Eyring et al., 2010]
Altitude contour for attenuation
by a factor of 1/e
SORCE Meeting, Sedona Arizona
The Impact of Solar Spectral Irradiance Variability on Middle Atmospheric Ozone
September 12, 2011
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Haigh et al. 2010 ozone study: model comparisons with MLS
Haigh et al., Nature, 2010
•
Results from 2-d modeling in accord with ozone observations from AURA-MLS
• 0.68-0.32 hPa ozone change of -1.7% (2004-2007)
• 10.0- 6.8 hPa ozone change of +4.5%
• Cross over from negative to positive at ~45 km
• Merkel et al. 2011 extends this study with the following enhancements:
•
•
•
Utilizes a 3‐d GCM (WACCM) with chemistry rather than a static 2‐d stratospheric model
Uses 9 years (2002-2011) of TIMED SABER ozone data to covers the full descending
phase of SC23 with independent instrumental observation
Segregates by day and night to isolate photochemical effects.
SORCE Meeting, Sedona Arizona
The Impact of Solar Spectral Irradiance Variability on Middle Atmospheric Ozone
September 12, 2011
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Trends of Annual TIMED-SABER Ozone
Lower Mesosphere
 Out-of-phase with solar cycle
 Trend in day, absent at night
 O3 loss due to HOx cycles and O2
photolysis ceases at night
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Stratosphere
 In-phase with solar cycle
 Trend similar for day and night
Less driven by photochemistry
 Very little diurnal variation
The Impact of Solar Spectral Irradiance Variability on Middle Atmospheric Ozone
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SABER Compared to WACCM Simulations for Upper Atmospheric Ozone
NRLSSI
SABER
SORCE
O3 Difference (%)
Active 2004-Quiet 2007
O3 Difference (%)
(2002/3) - (2008/9)
O3 Difference (%)
Active 2004-Quiet 2007
O3 Difference (%)
Avg. 15ºN-15ºS
Latitude
•
•
•
•
Panel on right shows equatorial response of all three
The comparisons imply that the higher SORCE UV variability improves the model/data
agreement of daytime mesospheric ozone.
Suggests enhanced HOx photochemistry with greater SORCE solar variability
Regression of SABER data commensurate with MLS regression in Haigh et al., 2010:
• Mesosphere: 0.3-0.03 hPa ⇒ 2.8% 1.4%
• Stratosphere: 5.0-1.2 hPa ⇒ 2.6% 0.63%
SORCE Meeting, Sedona Arizona
The Impact of Solar Spectral Irradiance Variability on Middle Atmospheric Ozone
September 12, 2011
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SABER compared to HALOE & SBUV
SBUV
HALOE
Halogen Occultation Experiment
(Remsberg et al., 2008)
SABER
Solar Backscatter Ultraviolet
(Soukharev and Hood, 2006)
Near 0% at 50km
1991-2005
O3 % (Max-min)
Figure 9
➨SABER stratospheric ozone congruent with previous observations.
➨SABER able to resolve lower mesospheric ozone response to solar forcing.
SORCE Meeting, Sedona Arizona
The Impact of Solar Spectral Irradiance Variability on Middle Atmospheric Ozone
September 12, 2011
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Conclusions
• The combined SIM, SRPM, and PSPT image analysis provide
a effective method to analyze solar variability
– SIM indicates irradiance trends that are larger than solar modulation
that compensate to produce the TSI trend.
– SRPM analysis is able to capture offsetting trends observed by SIM,
but refinements are still needed.
– Active region evolution by itself is not sufficient to account for the
observations – suggestive of changes in the internetwork/network
radiance.
• In-depth Earth atmospheric modeling is progressing
– Solar forcing in WACCM from SORCE spectra produces a very
different response in O3 from semi-empirical models of SSI: a
reduction in mesospheric ozone at higher solar activity and a
increase in mid- to upper stratosphere.
– We don’t know if our results are specific to this minimum because
we only have SSI and ozone measurements for the descending phase
of SC23. Continued observations are needed.
SORCE Meeting, Sedona Arizona
The Impact of Solar Spectral Irradiance Variability on Middle Atmospheric Ozone
September 12, 2011
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Extras
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The Impact of Solar Spectral Irradiance Variability on Middle Atmospheric Ozone
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Fundamental Equations
For a single wavelength, λ. At two separate times 0 and 1.
ln( I A0 ) =
ln( E0 ) − τ A0 , ln( I A0 ) =
ln( E0 ) − τ A0
ln( I B 0 ) =
ln( E0 ) − τ B 0 , ln( I B 0 ) =
ln( E0 ) − τ B 0
 I A1 
 E1 
ln=
ln


  − F ∆Χ A0→1
I
 A0 
 E0 
F is time dependent degradation factor
∆Χ A0→1 is the exposure time for SIM A between times t=0 and t=1
 I B1 
 E1 
 teB 
ln=
ln
F
−


 

 ∆Χ A0→1
I
E
te
 A
 B0 
 0
te = relative exposure time difference between SIM A & SIM B for same clock time
Account for difference in intensity due to solar distance change:
1au
F ′ ( λ , t ) = F (λ , t )
solDist 2
τ (λ
, t1 − t0 )
=
∫
t
t0
F ′ ( λ , t )∆Χ A0→1 dt degradation accumulates with time and
must be determined for each wavelength.
τ ( λ , t1 − t0 ) can be decomposed for computational convenience into a purely
wavelength component (κ ( λ )) and a time dependent part C ( λ , t1 − t0 ) .
But τ ( λ , t1 − t0 ) is the only physically accessible quantity.
SORCE Meeting, Sedona Arizona
The Impact of Solar Spectral Irradiance Variability on Middle Atmospheric Ozone
September 12, 2011
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SIM degradation correction and long-term uncertainty
∆κ
κ
SORCE Meeting, Sedona Arizona
The Impact of Solar Spectral Irradiance Variability on Middle Atmospheric Ozone
September 12, 2011
≤ .02
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WACCM ozone differences 2004-2007
NRLSSI
forcing
SORCE
forcing
SORCE Meeting, Sedona Arizona
The Impact of Solar Spectral Irradiance Variability on Middle Atmospheric Ozone
September 12, 2011
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SABER regression, equatorial average 15o N -to- 15o S
Day
Night
Lower
Mesosphere
Stratosphere
All regression fits are
significant at 95% level
SORCE Meeting, Sedona Arizona
The Impact of Solar Spectral Irradiance Variability on Middle Atmospheric Ozone
September 12, 2011
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