stratospheric and mesospheric applications of sciamachy limb observations
DESCRIPTION
Stratospheric and Mesospheric Applications of SCIAMACHY Limb Observations. 5th German SCIAMACHY Validation Team Meeting. C. von Savigny, A. Rozanov, G. Rohen, K.-U. Eichmann, E. J. Llewellyn * , J. W. Kaiser + , M. Sinnhuber, M. Scharringhausen, P. Ulasi, H. Bovensmann, and J. P. Burrows - PowerPoint PPT PresentationTRANSCRIPT
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Stratospheric and Mesospheric Applications of SCIAMACHY Limb Observations C. von Savigny, A. Rozanov, G. Rohen, K.-U. Eichmann, E. J. Llewellyn*, J. W. Kaiser+, M. Sinnhuber, M. Scharringhausen, P. Ulasi, H. Bovensmann, and J. P. Burrows
Institute of Environmental Physics/Remote Sensing, University of Bremen, Bremen, Germany* Department of Physics and Physics Engineering, University of Saskatchewan, Saskatoon, Canada+ Remote Sensing Laboratories, University of Zurich, Zurich, Switzerland5th German SCIAMACHY Validation Team Meeting
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Outline
Stratospheric applicationsPolar stratospheric cloudsMinor constituent profiles
Mesospheric applicationsMesospheric ozone profilesOH* (3-1) rotational temperature retrievalsNoctilucent clouds
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SCIAMACHY Limb GeometryTangent 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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Polar Stratospheric Clouds
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Step I: Determine colour index profiles
Step II: Determine vertical gradient of CI(TH):
with TH = 3.3 km
Theoretical maximum (TH) values for 15-30 km altitude range:
a) 1.05 for pure Rayleigh atmosphere b) 1.1 for stratospheric background aerosol c) 1.16 for moderate volcanic aerosol d) 1.55 for extreme volcanic aerosol
Detection threshold chosen: (TH) = 1.3
detection is somewhat biased towards optically thicker PSCsPSC detection with limb measurements
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Maps of detected PSCs (open circles: detected PSCs) superimposed to UKMO temperature field at 550 K potential temperature (about 22 km) for August 7-12, 2003. PSC maps
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Temporal variation of PSC altitudesPSC descent rates for 2003:
Santacesaria et al. [2001] : 2.5 km / monthat 66 S / 140 E based on a 9-year Lidar climatologyFromm et al. [1997] :2.0 km / month derived from POAM II
50 S - 60 S 2.5 km / month60 S - 70 S 2.0 km / month70 S - 80 S 1.2 km / month
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Histograms of temperature at PSC altitude
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Stratospheric Minor Constituents
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The scia-arc website The scia-arc website provides value-added scientific data products
Presently available limb data products: stratospheric profiles of O3, NO2 and BrO
In preparation: - mesospheric O3 profiles - maps of NLCs and PSCs - OH rotational temperatures at the mesopausehttp://www.iup.physik.uni-bremen.de/scia-arc
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One week before the major stratospheric warming: September 12, 2002Savigny et al. [2004]
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The ozone hole split: September 27, 2002
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At mid-latitudes typical BrO mixing ratios are about 10 pptv, corresponding to about 50 % of the available inorganic bromine (20 pptv). The rest is almost exclusively BrONO2 .[e.g., Sinnhuber et al., 2002] Within the vortex BrO mixing ratios are most likely enhanced due to the reduced NO2, therefore reduced formation of BrONO2.
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OH rotational temperature retrievals
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OH* produced and vibrationally-rotationally excited at mesopause altitudes by: H + O3 OH* (v 9) + O2 + 3.3 eVAirglow emission centered around 87 km with about 8 km FWHM
Relative population of rotational levels governed by Boltzmanns distributionMeasurements of relative intensities of rotational emission lines makes retrieval of OH rotational temperature possible
OH*(v = 3) is in local thermodynamical equilibrium (LTE) for lower rotational quantum numbers because:- collisional frequency at 86 km is 3 104 s-1- lifetime of OH at v = 3 is about 0.014 s rotational temperatures are equal to kinetic temperature of ambient air
Retrieval of OH* (3-1) rotational temperatures
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EJ J(J+1)J=0J=2J=3J=4J=5Selection rule: J = 0,+1,-1=3=1J=1J=0J=2J=3J=4J=5J=1Q-branchP-branch
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Impact of different Einstein coefficients used:Kovacs [1969], Mies [1974], Goldman et al. [1998]TKovacs TMies = 1.1 K and TKovacs TGoldman = 3.2 KSample OH spectral fitIterative retrieval approach:
linear fit with 2nd order polynomial
(2) non-linear fit (Levenberg-Marquard) driving OH model, including -shift
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CalibrationmeasurementsCalibrationmeasurementsLimbmeasurementsLimbmeasurementsCalibrationmeasurementsCoverage of Limb eclipse measurements
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Replacement of nighttime Nadir observations by limb observations
Implemented on September 6, 2004SCIAMACHY Operations Change Request 19
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GRound-based Infrared P-branch Spectrometer (GRIPS) I at Hohenpeissenberg (47 N / 11 E)
GRIPS-I data provided by Michael Bittner and Kathrin Hppner (DLR)First validation results Mesospheric Temperature Mapper (MTM) at Hawaii (21 N / 204 E)
MTM data provided by Mike Taylor and Yucheng Zhao (Utah State University)
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OH-Temperatures 2003 Temperatures: for latitudes from 20 to 70 deg from July 2002 up to now.
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Mesospheric Ozone
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Weighting functionsAveraging kernels
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Ozone depletion during the Oct. / Nov. 2003 SPEsHOx production by ionization:
O2+ + O2 + M O2+O2 + MO2+O2 + H2O O2+H2O + O2 O2+H2O + H2O H3O+OH + O2H3O+OH + H2O H3O+ H2O + OHH3O+ H2O + e- 2 H2O + HO2+ + H2O + e- O2 + H + OH(Courtesy M.-B. Kallenrode and M. Sinnhuber )NOx is formed as well
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Ozone depletion during the Oct. / Nov. 2003 SPEsOzone loss at 55 km and north of magnetic 60 N relative to October 20 24 reference period 40 MeV protons penetrate the atmosphere Down to about 45 km altitude
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Observations vs. ModelSCIAMACHYmeasurementsModel simulations(M. Sinnhuber)Percent ozone loss north of 60 N magnetic latitudeReference period:October 20 24, 2003
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Noctilucent Clouds
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UV limb radiance profileswith NLCs and without NLCs
Detection of Noctilucent Clouds (NLCs)
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I. In single scattering approximation the PMC backscatter is given by:q(,): Differential scattering cross sectionS(): Solar irradiance spectrumII. The sun-normalized PMC backscatter spectrum:with spectral exponent NLC particle size determination I
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Ambiguity: spectral exponent does not monotonically increase with increasing radius
Use several and significantly different wavelengths to determine r and [von Cossart et al, 1999].Assumptions:
Mie theory, i.e., homogeneous dielectric spheres
Refractive index of ice [Warren, 1984]
Log-normal distribution The spectral exponent is related to the PMC particle sizes by Mie-calculationsSimulated spectral exponents for log-normal distribution with = 1.4 NLC particle size determination II
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NLC particle size determination January 2003
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ConclusionsSCIAMACHY limb observations with their broad spectral coverage and extended altitude range both on the day and nightside allows a wide range of stratospheric and mesospheric to be studied:
Optically thin aerosols like NLCs and PSCs
Minor constituent profiles (O3, NO2, BrO; soon H2O, CH4)
Mesopause temperature (soon Rayeigh temperatures)