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

Outline

Stratospheric applicationsPolar stratospheric cloudsMinor constituent profiles

Mesospheric applicationsMesospheric ozone profilesOH* (3-1) rotational temperature retrievalsNoctilucent clouds

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.

Polar Stratospheric Clouds

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

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

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

Histograms of temperature at PSC altitude

Stratospheric Minor Constituents

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

One week before the major stratospheric warming: September 12, 2002Savigny et al. [2004]

The ozone hole split: September 27, 2002

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.

OH rotational temperature retrievals

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

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

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

CalibrationmeasurementsCalibrationmeasurementsLimbmeasurementsLimbmeasurementsCalibrationmeasurementsCoverage of Limb eclipse measurements

Replacement of nighttime Nadir observations by limb observations

Implemented on September 6, 2004SCIAMACHY Operations Change Request 19

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)

OH-Temperatures 2003 Temperatures: for latitudes from 20 to 70 deg from July 2002 up to now.

Mesospheric Ozone

Weighting functionsAveraging kernels

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

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

Observations vs. ModelSCIAMACHYmeasurementsModel simulations(M. Sinnhuber)Percent ozone loss north of 60 N magnetic latitudeReference period:October 20 24, 2003

Noctilucent Clouds

UV limb radiance profileswith NLCs and without NLCs

Detection of Noctilucent Clouds (NLCs)

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

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

NLC particle size determination January 2003

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)