first monitoring

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Identification of the 5-day wave in
Envisat/SCIAMACHY NLC measurements and
simultaneous Aura/MLS temperature
measurements Christian von Savigny1 and Michael
Schwartz2, and John P. Burrows1 1 Institute
of Environmental Physics and Remote
Sensing University of Bremen, Otto-Hahn-Allee
1 28334 Bremen, Germany 2 Jet Propulsion
Laboratory, Pasadena, U.S.
2
SCIAMACHY on Envisat
SCIAMACHY Scanning Imaging Absorption
Spectrometer for Atmospheric CartograpHY

• Features
• UV/Vis/NIR grating spectrometers
• 220 - 2380 nm
• Moderate spectral resolution
• 0.2 1.5 nm
• Measurement Geometries

• Polar, sun-synchronous orbit
• Descending node 1000 LST
• Global coverage within 6 days
• During eclipse calibration and limb measurements

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SCIAMACHY Limb scattering / emission observations

• Tangent height range 0 to 100 km
• Tangent height step size 3.3 km
• Vertical FOV 2.6 km
• Observation optimised for limb-nadir matching
• Duration of Limb sequence 60 s
• Observed is limb scattered solar radiation and
  terrestrial airglow emissions
• On the Earths night side limb emissions are
  observed in a dedicated mesosphere/ thermosphere
  observation mode with tangent height between 75
  and 150 km.

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Conditions near the polar summer mesopause
Adapted from Rapp and Thomas 2005
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NLC signatures in SCIAMACHY limb radiance profiles
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NLC particle size determination I
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NLC particle size determination II
??? The retrieval is performed with a
Levenberg-Marquard algorithm driving the Mie-code
by Michenko
Modeled spectral exponent (265-300 nm range) as a
function of scattering angle and mode radius r0
assuming a log-Normal PSD with ? 1.4 following
von Cossart et al. 1999
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Latitudinal dependence of NLC radii for July 2005
Previous NLC size retrievals Reference Techniq
ue Radii / width Size distribution Carbary et
al. 1996 limb-scatter r0 ? 70 nm, ? ?
1.2 Log-normal Debrestian et al. 1997 solar
occultation r0 lt 70 nm, ? ? 1.4 Log-normal Gumbel
and Witt 1998 rocket photometry r ? 50
nm ?-function Rusch et al. 1991 limb-scatter
Log-normal von Cossart et al. 1999 ground-based
Lidar r0? 50 nm, ? ? 1.4 Log-normal von Savigny
et al. 2005 limb-scatter r0? 30 50
nm, Log-normal ? 1.4 Model
simulations Berger and von Zahn 2002 r0 ?
40 50 nm Normal Rapp and Thomas 2002 r0 ?
40 nm Normal
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Dynamic control of the geographic NLC distribution
The geographical distribution of NLCs is also
influenced by dynamic modulations of the
temperature field
(a) Gravity waves
(b) Tidal variations (semi-diurnal tide
dominates von Zahn et al., 1998)
(c) Planetary waves (5-day wave in NLC
brightnesses Merkel et al., 2003)
(a) and (b) cannot be investigated with
Envisat/SCIAMACHY, yet (c) can be
First simultaneous observations of the 5-day wave
in NLC characteristics (sizes, occurrence rates
and brightnesses) and mesopause temperatures
(measured with Aura/MLS)
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The physical-space picture of the 5-day wave
White Lines Temperature contours at 83 km
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MLS temperatures at 83 km averaged over 60 N -
80 N
NLC radii for latitudes between 60 N 80 N
June 11, 2005
NLC relative brightness INLC / Ibackground
between 60 N 80 N
Coverage of SCIAMACHY Limb measurements between
60 N 80 N
NLC occurrence rate NNLC / Nmeas between 60 N
80 N
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MLS temperatures at 83 km averaged over 60 N -
80 N
NLC radii for latitudes between 60 N 80 N
June 12, 2005
NLC relative brightness INLC / Ibackground
between 60 N 80 N
Coverage of SCIAMACHY Limb measurements between
60 N 80 N
NLC occurrence rate NNLC / Nmeas between 60 N
80 N
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MLS temperatures at 83 km averaged over 60 N -
80 N
NLC radii for latitudes between 60 N 80 N
June 13, 2005
NLC relative brightness INLC / Ibackground
between 60 N 80 N
Coverage of SCIAMACHY Limb measurements between
60 N 80 N
NLC occurrence rate NNLC / Nmeas between 60 N
80 N
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MLS temperatures at 83 km averaged over 60 N -
80 N
NLC radii for latitudes between 60 N 80 N
June 14, 2005
NLC relative brightness INLC / Ibackground
between 60 N 80 N
Coverage of SCIAMACHY Limb measurements between
60 N 80 N
NLC occurrence rate NNLC / Nmeas between 60 N
80 N
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MLS temperatures at 83 km averaged over 60 N -
80 N
NLC radii for latitudes between 60 N 80 N
June 15, 2005
NLC relative brightness INLC / Ibackground
between 60 N 80 N
Coverage of SCIAMACHY Limb measurements between
60 N 80 N
NLC occurrence rate NNLC / Nmeas between 60 N
80 N
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MLS temperatures at 83 km averaged over 60 N -
80 N
NLC radii for latitudes between 60 N 80 N
June 16, 2005
NLC relative brightness INLC / Ibackground
between 60 N 80 N
Coverage of SCIAMACHY Limb measurements between
60 N 80 N
NLC occurrence rate NNLC / Nmeas between 60 N
80 N
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MLS temperatures at 83 km averaged over 60 N -
80 N
NLC radii for latitudes between 60 N 80 N
June 17, 2005
NLC relative brightness INLC / Ibackground
between 60 N 80 N
Coverage of SCIAMACHY Limb measurements between
60 N 80 N
NLC occurrence rate NNLC / Nmeas between 60 N
80 N
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MLS temperatures at 83 km averaged over 60 N -
80 N
NLC radii for latitudes between 60 N 80 N
June 18, 2005
NLC relative brightness INLC / Ibackground
between 60 N 80 N
Coverage of SCIAMACHY Limb measurements between
60 N 80 N
NLC occurrence rate NNLC / Nmeas between 60 N
80 N
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MLS temperatures at 83 km averaged over 60 N -
80 N
NLC radii for latitudes between 60 N 80 N
June 19, 2005
NLC relative brightness INLC / Ibackground
between 60 N 80 N
Coverage of SCIAMACHY Limb measurements between
60 N 80 N
NLC occurrence rate NNLC / Nmeas between 60 N
80 N
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MLS temperatures at 83 km averaged over 60 N -
80 N
NLC radii for latitudes between 60 N 80 N
June 20, 2005
NLC relative brightness INLC / Ibackground
between 60 N 80 N
Coverage of SCIAMACHY Limb measurements between
60 N 80 N
NLC occurrence rate NNLC / Nmeas between 60 N
80 N
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MLS temperatures at 83 km averaged over 60 N -
80 N
NLC radii for latitudes between 60 N 80 N
June 21, 2005
NLC relative brightness INLC / Ibackground
between 60 N 80 N
Coverage of SCIAMACHY Limb measurements between
60 N 80 N
NLC occurrence rate NNLC / Nmeas between 60 N
80 N
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The 5-day wave in NLC occurrence frequency and
temperatures
June 25
June 20
June 15
June 10
Determination of T-fluctuations by subtraction of
20-day sliding mean
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The Fourier-space picture of the 5-day wave
2004
2005
Data from May to August used
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FT transform of NLC occurrence rate and
Temperature fluctuations
August 8
July 21
June 30
June 10
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Comparison of NLC occurrence rates in 2004 / 2005
2004
2005
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FT transform of NLC occurrence rate and
Temperature fluctuations
2005
2004
2005
Day relative to summer solstice
Day relative to summer solstice
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Solar cycle dependence of 5-day activity periods ?

• Indications for a solar cycle variations of the
  periods with maximum 5-day wave activity Merkel
  et al., 2003
• In 2001 a single maximum in 5-day wave activity
  near the middle of the NLC season
• In 1998 two maxima in 5-day wave activity near
  the beginning and the end of the NLC season

MgII Fraunhofer solar proxy M. Weber, IUP
Bremen
??? SCIAMACHY NLC observations during 2004 and
2005 consistent with Merkel et al. findings
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Do solar proton events affect the occurrence of
NLCs ?
Solar proton event in January 2005 SH NLC season
Ionisation rate profiles
Ionisation rate profiles kindly provided by M.-B.
Kallenrode (University of Osnabrück)
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Correlation of NLC occurrence frequency and
ionisation rates
Right y-axis flipped and x-axis shifted by 4 days
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NLC occurrence frequencies for the NH NLC season
NLC occurrence frequencies smoothed with 3-day
boxcar
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Can SCIAMACHY confirm the Carbary hump at 265
nm?
Carbary et al., GRL, 2004 reported a bump in
the Rayleigh-corrected NLC limb-spectra measured
with UVISI on MSX-6 Explained by bi-modal NLC
size distribution with mode around 220 nm
Carbary et al. 2004
Carbary et al. 2004
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Evidence for larger NLC particles ?
Do we find the hump also in SCIAMACHY limb
observations ?
SCIAMACHY also provides high precision
measurements of solar irradiance
Sample SCIAMACHY sun-normalized NLC spectra
Skupin et al., ASR, 2005
Several hundred cases viewed, and NONE showed the
hump at 260 nm !!
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Conclusions

• First simultaneous observation of the
  westward-propagating 5-day wave in NLC
  occurrence rates and mesopause temperatures
• Indications for a solar-cycle dependence of the
  periods (during the NLC season) with enhanced
  5-day wave activity
• Impact of planetary wave perturbations on NLC
  distribution and microphysical characteristics
  has to be investigated further in order to
  understand long-term changes in NLC properties

Acknowlegdements We are indebted to all members
of the SCIAMACHY team whose efforts made this
analysis possible. Funding for the present
investigations is provided by the University of
Bremen, the German Ministry of Education and
Research BMBF and the German Aerospace Center
DLR. Some of the retrievals were performed at the
HLRN (High Performance Computing Center North),
whose service and support is gratefully
acknowledged. We thank SPARC for financial
support to attend this meeting!