3 rd international limb workshop, montreal, canada, 25 - 28 april, 2006 retrieval of bro vertical...
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33rdrd International Limb Workshop, Montreal, Canada, 25 - 28 April, 2006 International Limb Workshop, Montreal, Canada, 25 - 28 April, 2006
Retrieval of BrO vertical distributions from Retrieval of BrO vertical distributions from SCIAMACHY limb measurements: SCIAMACHY limb measurements:
Data quality assessment and algorithm improvementsData quality assessment and algorithm improvements
A. Rozanov1, S. Kühl2, C. Sioris3, H. Bovensmann1, J. P. Burrows1, M. Chipperfield9, F. Goutail7, F. Hendrick4, M. von Hobe8, S. Hrechanyy8,
C. McLinden5, K. Pfeilsticker2, J. Pukite2, M. van Roozendael4, R. Salawitch6, B.-M. Sinnhuber1, F. Stroh8, T. Wagner2
1Instutute of Environmental Physics, University of Bremen, Germany2 Instutute of Environmental Physics, University of Heidelberg, Germany
3Harvard-Smithsonian Center for Astrophysics, Cambridge, USA
4Belgian Institute for Space Aeronomy, IASB-BIRA, Belgium 5Meteorological Service of Canada, Toronto, Canada
6Jet Propulsion Laboratory, Pasadena, California, USA 7Service d’Aeronomie - CNRS, France
8Juelich Research Center, Germany 9University of Leeds, UK
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BOOST: A joint intercomparison projectBOOST: A joint intercomparison project
Bromine Oxide in the lOwer STratosphere (BOOST)Bromine Oxide in the lOwer STratosphere (BOOST)
Project objectivesProject objectives
Comparison of BrO vertical distributions retrieved from SCIAMACHY limb measurements using different retrieval algorithms
Investigation of possible reasons for the disagreement between the retrievals identified in previous studies
Improvement of the existing retrieval algorithms (especially w.r.t. the retrieval quality in the lower stratosphere and the upper troposphere)
Investigation of the sensitivity of the retrieved profiles to the retrieval parameters such as spectral range, initial profiles, cross sections, spectral corrections
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BOOSTBOOST: participating groups: participating groupsSCIAMACHY retrieval groups:SCIAMACHY retrieval groups:
IUP, University of Bremen: Alexei Rozanov IUP, University of Heidelberg: Sven Kühl Harvard-Smithsonian Center for Astrophysics (SAO): Chris Sioris
Balloon-borne and ground-based measurements:Balloon-borne and ground-based measurements: IUP, University of Heidelberg: DOAS, Klaus Pfeilsticker Juelich Research Center: TRIPLE, Serhiy Hrechanyy Service d’Aeronomie – CNRS: SAOZ, Florence Goutail Belgian Institute for Space Aeronomy: ground-based, François Hendrick
Modeling groups:Modeling groups: IUP, University of Bremen: Björn-Martin Sinnhuber Jet Propulsion Laboratory: Ross Salawitch Meteorological Service of Canada: Chris McLinden University of Leeds: Martyn Chipperfield
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Main inversion procedure:• Solution: Information Operator
or Optimal Estimation• Measurement vector: differential
signal in all spectral points at all selected tangent heights
• State vector: trace gas number densities at altitude levels
Retrieval algorithm of the University of BremenRetrieval algorithm of the University of Bremen
Simulated limb spectra Weighting functions w.r.t. concentrations
Forward modeling (SCIATRAN) :• Fully spherical treatment for SS• Approximation for MS
Measured and simulated limb spectra Vertically integrated WF
Correction parameters
Pre-processing (DOAS-like fit) at each tangent height:
•Shift and squeeze correction•Spectral corrections
Vertical distributions of trace gas number densities
Measured and simulated limb spectra with all corrections appliedWeighting functionsA priori constraints
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Retrieval algorithm of the University of HeidelbergRetrieval algorithm of the University of HeidelbergO
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Block Air Mass FactorsForward modeling (TRACY) :
•Fully spherical Monte Carlo
Measured limb spectra Cross sections
Slant columns as a function of tangent height
DOAS fit for both measured and simulated spectra at each tangent height:
•Shift•Spectral corrections
Vertical distributions of trace gas number densities
Fitted slant columnsBlock Air Mass FactorsA priori constraints
Inversion procedure:• Solution: Optimal Estimation
(maximum a posteriori)• Measurement vector: fitted
slant columns• State vector: trace gas number
densities at altitude levels
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Inversion procedure (Chahine-like):
Retrieval algorithm of SAORetrieval algorithm of SAO
Simulated limb spectra
Measured or simulated limb spectra Cross sections
Slant columns as a function of tangent height
DOAS fit for both measured and simulated spectra at each tangent height for a set of temperatures:
•No shift/squeeze correction•Spectral corrections
Vertical distributions of trace gas number densities
Measured slant columnsSimulated slant columns interpolated to an appropriate temperature
Forward modeling (VECTOR) :• Fully spherical treatment for SS• Approximation for MS
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Subsequent iterations:
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Retrieval settingsRetrieval settings
Uni BremenUni Bremen Uni HeidelbergUni Heidelberg SAOSAO
Spectral range 337 – 357 nm 337 – 357 nm 344 – 360 nm
Reference tangent height
~ 35 km ~ 35 km 33 – 70 kmco-addition
Spectral corrections
shift, 1/I0, eta,
I0-correction for
O3, ring
shift, ring, 1/I0, /I0, I0-corrected O3 cross section, eta, zeta
tilt, I0-corrected O3 cross section
Temperature dependence
full O3 cross sections at 223 K and 243 K fitted
series of fits with O3 and NO2 cross sections at different temperatures
Regularizationweak statistical, smoothness
statistical sharp gradients are not permitted
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Initial set of the limb states to be comparedInitial set of the limb states to be compared
Selection criteria (based on results from Selection criteria (based on results from Dorf at al., 2006):):
At the current stage of the project comparisons will be performed for the limb states collocated with:
Three balloon-borne DOAS measurements (photochemically corrected)
Three balloon-borne TRIPLE measurements (uncorrected)
Selected ground-based zenith-sky twilight measurements (photochemically corrected)
For each balloon flight air mass trajectory calculations were done identifying the forward (being in the future w.r.t. the balloon flight) and the backward (being in the past w.r.t. the balloon flight) match with SCIAMACHY limb observations
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Selected balloon flightsSelected balloon flights
List of DOAS flights:List of DOAS flights:
March 23rd, 2003; Kiruna (67.9oN, 21.1oE); 15:19 - 16:09
October 9th, 2003; Air sur l’Adour (43.7oN, 0.3oW); 15:39 - 17:09
March 24th, 2004; Kiruna (67.9oN, 21.1oE); 13:55 - 17:35
List of TRIPLE flights:List of TRIPLE flights:
September 24th, 2002; Air sur l'Adour (43.7oN, 0.3oW); balloon ascent: 8:20 - 9:18 UTC
March 6th, 2003; Kiruna (67.9oN, 21.1oE); balloon ascent: 6:30 - 7:56 UTC; balloon descent: 8:33 - 9:44 UTC
June 9th, 2003; Kiruna (67.9oN, 21.1oE); balloon descent: 7:56 - 9:09 UTC
Ground-based zenith-sky twilight measurements :Ground-based zenith-sky twilight measurements :
Selected days, Harestua, Sweden Harestua, Sweden (60.2(60.2ooN, 10.8N, 10.8ooE)E)
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Comparisons to balloon-born DOAS (1)Comparisons to balloon-born DOAS (1)
Balloon flight: Balloon flight: March 23rd, 2003; Kiruna (67.9oN, 21.1oE); 15:19 - 16:09Ground based:Ground based: same day sunrise at Harestua, Sweden (60.2oN, 10.8oE)
Backward match:Backward match: March 23rd, 2003; 11:07 UT; Orbit 5545; State 7; 75oN,16oE
Forward match:Forward match: March 24th, 2003; 9:01 UT; Orbit 5558; State 10; 56oN, 26oE
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Comparisons to balloon-born DOAS (2)Comparisons to balloon-born DOAS (2)
Balloon flight: Balloon flight: October 9th, 2003; Air sur l’Adour (43.7oN, 0.3oW); 15:39 - 17:09
Backward match:Backward match: October 9th, 2003; 9:51 UT; Orbit 8407; State 9; 41oN,8oE
Forward match:Forward match: October 10th, 2003; 9:20 UT; Orbit 8421; State 9; 41oN, 16oE
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Comparisons to balloon-born DOAS (3)Comparisons to balloon-born DOAS (3)
Balloon flight: Balloon flight: March 24th, 2004; Kiruna (67.9oN, 21.1oE); 13:55 - 17:35Ground based:Ground based: March 24th, 2004 sunset at Harestua, Sweden (60.2oN, 10.8oE)
Backward match:Backward match: March 24th, 2004; 10:36 UT; Orbit 10798; State 9; 66oN,9oE
Forward match:Forward match: March 25th, 2004; 8:25 UT; Orbit 10811; State 9; 62oN, 38oE
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Convolved cross sections Convolved cross sections (FWHM = 0.2 nm)(FWHM = 0.2 nm)
Absolute difference after Absolute difference after scaling, shift and squeezescaling, shift and squeeze
Scaling factors (Wimouth/Fleischmann): 1.03 @ 298 K, 1.11 @ 228/223 KScaling factors (Wimouth/Fleischmann): 1.03 @ 298 K, 1.11 @ 228/223 K
Relative shift: 0.004 – 0.006 nm @298 K 0.009 nm – 0.02 nm @ 228/223 KRelative shift: 0.004 – 0.006 nm @298 K 0.009 nm – 0.02 nm @ 228/223 K
Cross sections comparison: Fleischmann vs. WilmouthCross sections comparison: Fleischmann vs. Wilmouth
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Balloon flight: Balloon flight: March 24th, 2004; Kiruna (67.9oN, 21.1oE); 13:55 - 17:35
Backward match:Backward match: March 24th, 2004; 10:36 UT; Orbit 10798; State 9; 66oN,9oE
Forward match:Forward match: March 25th, 2004; 8:25 UT; Orbit 10811; State 9; 62oN, 38oE
Effect of BrO cross section: Fleischmann vs. WilmouthEffect of BrO cross section: Fleischmann vs. Wilmouth
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Comparisons to TRIPLE (1)Comparisons to TRIPLE (1)
Balloon flight: Balloon flight: September 24th, 2002; Air sur l'Adour (43.7oN, 0.3oW); balloon ascent: 8:20 - 9:18 UTC; SZA = 65o - 56o
Backward match: Backward match: SZA = 44.5o;; September 23rd, 2002; 11:06 UT; Orbit 2954; State 11; 40oN,10oW
Forward match:Forward match: SZA = 50o; September 24th, 2002; 10:32 UT; Orbit 2968; State 10; 47oN, 2oE
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Comparisons to TRIPLE (2)Comparisons to TRIPLE (2)Balloon flight: Balloon flight: March 6th, 2003; Kiruna (67.9oN, 21.1oE); balloon ascent: 6:30 - 7:56 UTC; SZA = 85o - 78o; balloon descent: 8:33 - 9:44 UTC; SZA = 76o – 73o
Backward match: Backward match: SZA = 82.6o; March 5th, 2003; 12:13 UT; Orbit 5288; State 6; 76.5oN,4oE
Forward match:Forward match: SZA = 72.5o; March 6th, 2003; 10:04 UT; Orbit 5301; State 8; 66oN, 17oE
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Comparisons to TRIPLE (3)Comparisons to TRIPLE (3)Balloon flight: Balloon flight: June 9th, 2003; Kiruna (67.9oN, 21.1oE);
balloon descent: 7:56 - 9:09 UTC; SZA = 49o - 45o
Backward match: Backward match: SZA = 81.5o; June 8th, 2003; 19:01 UT; Orbit 6652; State 5; 68oN,21oE
Forward match:Forward match: SZA = 45.6o; June 9th, 2003; 10:18 UT; Orbit 6661; State 11; 68oN, 16oE
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Comparison to ground-based measurementsComparison to ground-based measurements
Zenith-sky twilight measurements at Harestua, Sweden Zenith-sky twilight measurements at Harestua, Sweden (60.2(60.2ooN, 10.8N, 10.8ooE)E)
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Dependence on a priori informationDependence on a priori information
Balloon flight: Balloon flight: October 9th, 200315:39 - 17:09Air sur l’Adour 43.7oN, 0.3oW
SCIAMACHY limb:SCIAMACHY limb: October 10th, 20039:20 UTOrbit 8421, State 941oN, 15oE
University of Bremen retrievals:University of Bremen retrievals:
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Dependence on a priori informationDependence on a priori information
University of HeidelbergUniversity of Heidelberg SAOSAO
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Conclusions (1)Conclusions (1)
All retrievals agree within error barsAll retrievals agree within error bars Error bars of SAO retrievals are very large in the lower layers: 60 %
at 17 km increasing downwards, often about 100% below 16 km
Below 20 km SAO retrieval tend to produce higher values as compared to Bremen and Heidelberg results
Good agreement between Uni Bremen and SAO retrievals in the upper layers above 22 – 25 km
Retrievals of Uni Heidelberg result in slightly higher values compared to Uni Bremen and SAO retrievals in the upper layers above 20 - 22 km, which is in a better agreement with ground-based measurements but in worse agreement with balloon-born DOAS results
Mostly good agreement between Bremen and Heidelberg in the lower layers below 20 - 22 km.
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Conclusions (2)Conclusions (2)
Overall good agreement with balloon-born DOASOverall good agreement with balloon-born DOAS
Variable degree of agreement with TRIPLEVariable degree of agreement with TRIPLE Reasonable agreement with exception of the lowest point for the
flight on September 24th, 2002 Very good agreement for the forward match on June 9th, 2003, a
photochemical correction is required for the backward match
Disagreement for the flight on March 6th, 2003, further investigations necessary
More comparisons needed to draw any conclusion for More comparisons needed to draw any conclusion for ground-based measurementsground-based measurements
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Conclusions (3)Conclusions (3)
Dependence on a priori informationDependence on a priori information Uni Heidelberg retrievals are independent of a priori profiles
down to 20 km and show a clear dependence below. Although retrieval results obtained using different a priori profiles are still agree within error bars.
Uni Bremen retrievals are independent of a priori information down to 17 km and show a weak dependence of the form of a priori profile below. Similar to Heidelberg retrievals the deviations between results obtained using different a priori profiles are always below the error bars.
SAO retrievals are found to be independent of the initial profile
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OutlookOutlook
Additional comparisons are needed Additional comparisons are needed Additional DOAS flight: June 17th, 2005 Photochemical correction of the backward match for TRIPLE flight
on March 6th, 2003 Balloon born SAOZ measurements Ground-based measurements
Model simulations and retrievalsModel simulations and retrievals SCIATRAN (Uni Bremen) VECTOR (SAO) TRACY (Uni Heidelberg)
Further investigation of the influence of the spectral region, Further investigation of the influence of the spectral region, reference tangent height, and retrieval initialisation parametersreference tangent height, and retrieval initialisation parameters
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