Lecture on atmospheric remote sensing [email protected] Remote sensing in the IR spectral range • Overview • Trace gas spectra • Spectrometer concepts • Trace gas measurements from different platforms • Imaging satellite instruments
Lecture on atmospheric remote sensing [email protected]
Remote sensing in the IR spectral range
• Overview
• Trace gas spectra
• Spectrometer concepts
• Trace gas measurements from different platforms
• Imaging satellite instruments
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moleculesaerosols
Cloud droplets
rain droplets
Remote sensing in IR spectral range
Wavelengths from ~1 to 1000m
-vibrational + rotational transitions
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In the IR spectral range, typically emission spectra are analysed
In some cases also absorption spectra of the solar radiation are measured
SWIR
NearIR
ThermalIR
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Usually IR spectra are given as function of wavenumberWavenumber = 1 / Wavenumber is usually given in 1 / cm
3.3 m5 m10 m20 m
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Infrared emission spectrum of the Earth atmosphere in the mid-infrared region (700–2250 cm−1) calculated with the radiative transfer model LBLRTM for mid-latitude conditions (summer, unpolluted scenario). The most important absorption bands of different trace gases (O3, CO, CO2, H2O, CH4, N2O) are indicated.
(Orphal et al., 2005)
~4.4m~15.3m
300K
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The observed Intensity is:
= 0if only emission is observed Optical depth
-emission and absorption have to be considered
-typically no simple inversion (like in the UV/vis) is possible
-complex radiative transfer modelling has to be applied
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dsdWithout the surface term and with :
for
For small optical depth the observed signal becomes proportional to the optical depth
=
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),,(,,,, TpSTNNTp ijijij
N: Number densityT: Temperaturep: Pressure: absorption cross sectionS: Line width
: absorption coefficient
Optical depth
From the measured optical depth, the absorption coefficient, or finally the number density of a trace gas can be derived.
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Als Auswahlregeln bei der RotationsAls Auswahlregeln bei der Rotations--Schwingungsspektroskopie erhält man:Schwingungsspektroskopie erhält man:
1v 1J ,0
01Rotations-Schwingungsterme: S(v, J) v BJ J 12
Rotations-Schwingungspektroskopie
linear in quadratisch in J
Vibrationsquantenzahl Rotationsquantenzahl J
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Termschema:Termschema:
Eine Linie Eine Linie steht für einen steht für einen kombinierten kombinierten RotationsRotations--SchwingungsSchwingungs--übergang!übergang!
Rotations-Schwingungspektroskopie
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Man erhält ein Spektrum der folgenden Art:Man erhält ein Spektrum der folgenden Art:
Rotations-Schwingungspektroskopie
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The rotational-vibrational spectra are determined by the molecules symmetry and complexity
Methyl ethyl ketone (13 atoms, nonsymmetric)
Benzene(12 atoms, symmetric)
Formaldehyde(4 atoms, non-linear)
Acetylene(4 atoms, linear)
Nitric oxide(heteronuclear, diatomic)
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Example of an absorption FTIR- measurement
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Subtraction sequence of an absorption measurement
Lecture on atmospheric remote sensing [email protected]://www-imk.fzk.de:8080/imk2/mipas-b/bestfit.gif
Example of an emission FTIR- measurement
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MIPAS-HNO3-observation
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Example: N2O-Isotopes
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www2.nict.go.jp/kk/e414/shuppan/ kihou-journal/journal-vol49no2/4-06.pdf
From pressure broadening information on vertical profiles can be obtained
(but often (only) total columns are determined)
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Information content and the sensitivity of a remote sensing measurement can be described by so called averaging kernels. They are determined during the retrieval process:
The measured spectra are simulated using a) assumed atmospheric profilesb) a radiative transfer modelc) an instrument simulation modelThe atmospheric profile is varied until measured and simulated spectra agree.
For the comparison with other data sets (e.g. model results) theaveraging kernels have to be applied:
')',,(',,,),,(0
dzzyxModelzzyxAKzyxtMeasuremenTOA
ztmeasuremen
e.g. concentrationor total or partialcolumn density
e.g. concentrationor partial column density
Can be extended to 3 dimensions
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Averaging kernels: indicate height-dependent sensitivity
Lecture on atmospheric remote sensing [email protected]://www.ifac.cnr.it/retrieval/documents/AK_report.pdf
HNO3 from MIPAS
Thermal IR
Averaging kernel for limb observations
Narrow kernels are ‚good‘
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Comparison to ozone sonde
Segers et al., ACP 2005
O3 from SCIAMACHY
(UV)
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Different types of spectrometers:
-Grating spectrometer: simple setup, medium spectral resolution, typical for early measurements, today: satellite instrument CRISTA
-Fourier Transform IR, e.g. MIPAS: complex system with moving parts, high spectral resolution (typical instruments today)
-Etalon spectrometers (e.g. CLAES): high spectral resolution in selected wavelength windows
-gas correlation filter radiometer (e.g. satellite instrument MOPITT)
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Michelson-Interferometer
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Monochromatic interference
Set up of an interferometer
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Fourier Transformation
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Atmospheric observations
-ground based measurements
-air-borne observations of IR emission
-satellite observations of direct sun light
-satellite observations of IR emission (limb)
-satellite observations of IR emission (nadir)
-satellite observations imagers (IR emission nadir)
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Schematic illustration of theinstrumental setup used. Thesolar/lunar tracker follows the course of the sun/moon and feeds a parallel light beam into the spectrometer. In the interferometer the light beam is splitted into the two rays by the beamsplitter.Several detectors are mounted which allow to record the whole spectral region from the IR at 700/cm (14 µm) up to the UV at 33000/cm (300 nm).
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Increase of free tropospheric CO from 1951 to 1985(ISSJ Jungfraujoch)
Early measurements were carried out with a grating spectrometer; the
spectral resolution was limited
A spectrum from 1985 mathematically degraded to the
resolution from 1951
Original spectrum from 1985 measured with a FTIR high
resolution spectrometer
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CO and CH4 column above the Jungfraujoch station
1985 - 1996Mahieu et al., 1997
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Seasonal cycle of freetropospheric CO from 1950/51 and 1985-87
(ISSJ Jungfraujoch)
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www.ifjungo.ch/reports/1999_2000/pdf/09.pdf
Original spectrum from 2000 measured with a FTIR high resolution spectrometer
Increase of several species from 1951 to 2000 (ISSJ Jungfraujoch)
Early measurements were carried outwith a grating spectrometer; the spectral resolution was limited
A spectrum from 2000 mathematically degraded to the resolution from 1951
H2OH2O H2O
CO2 CO2
arrows: CFC-12 (CCl2F2)
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www.ifjungo.ch/reports/1999_2000/pdf/09.pdf
Lecture on atmospheric remote sensing [email protected]
www.ifjungo.ch/reports/1999_2000/pdf/09.pdf
Lecture on atmospheric remote sensing [email protected]
www.ifjungo.ch/reports/1999_2000/pdf/09.pdf
Lecture on atmospheric remote sensing [email protected]
Lecture on atmospheric remote sensing [email protected]
Griesfeller, A.: Validierung von ENVISAT-Daten mit Hilfe von bodengebundenen FTIR-Messungen, Dissertation, FZK Report No. 7072, Forschungszentrum Karlsruhe, Germany, 2004.
During polar night NOx is converted into HNO3
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Atmospheric observations
-ground based measurements
-air-borne observations of IR emission
-satellite observations of direct sun light
-satellite observations of IR emission (limb)
-satellite observations of IR emission (nadir)
-satellite observations imagers (IR emission nadir)
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MIPAS Balloon
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MIPAS ClONO2-Messung
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MIPAS Balloon
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K. Weigel et al., CRISTA-NF measurements during AMMA, AMT 2010
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K. Weigel et al., CRISTA-NF measurements during AMMA, AMT 2010
Measurements contaminated by clouds
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K. Weigel et al., CRISTA-NF measurements during AMMA, AMT 2010
Measurements contaminated by clouds
Lecture on atmospheric remote sensing [email protected]. Weigel et al., CRISTA-NF measurements during AMMA, AMT 2010
Lecture on atmospheric remote sensing [email protected]
Atmospheric observations
-ground based measurements
-air-borne observations of IR emission
-satellite observations of direct sun light
-satellite observations of IR emission (limb)
-satellite observations of IR emission (nadir)
-satellite observations imagers (IR emission nadir)
Lecture on atmospheric remote sensing [email protected]
ATMOS instrument on the space shuttle
Atmospheric Trace Molecule Spectroscopy (ATMOS)
Four Missions:
-Spacelab: 1985-ATLAS-1: 1992-ATLAS-2: 1993-ATLAS-3: 1994
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Key profiles from ATMOS Spacelab 3 sunset occultation data.
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The ACE satellite: IR sun occultation measurementshttp://www.ace.uwaterloo.ca/images/ACE_occultation.jpg
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Lecture on atmospheric remote sensing [email protected]
http://www.ace.uwaterloo.ca/images/ACE_occultation.jpg
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Bernath, Peter (2006), Atmospheric Chemistry Experiment (ACE): Analytical Chemistry from Orbit, Trends in Analytical Chemistry, Vol. 25, No. 7., pp. 647-654
Lecture on atmospheric remote sensing [email protected]
Bernath, Peter (2006), Atmospheric Chemistry Experiment (ACE): Analytical Chemistry from Orbit, Trends in Analytical Chemistry, Vol. 25, No. 7., pp. 647-654
Lecture on atmospheric remote sensing [email protected]
Lecture on atmospheric remote sensing [email protected]
Carleer, M.R., et al. (2008), Validation of water vapour profiles from the Atmospheric Chemistry Experiment (ACE), Atmos. Chem. Phys.Discuss., 8, 4499-4559, 2008 (PDF)
Lecture on atmospheric remote sensing [email protected]
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From ACE, also high resolution solar spectra were generated
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Limb-Beobachtung
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THE (Cryogenic Limb Array Etalon Spectrometer ) CLAES INSTRUMENTCLAES infers the amounts of gases in the stratosphere from the measurement of the unique infrared emission features by combining a telescope with an infrared spectrometer and solid state detectors, and cryogenically cooling the whole instrument below 150 Kelvin to minimise its own thermal infrared emissions. The spectrometer operates over the wavelength range 3.5 to 12.9 microns.Spectroscopy is performed by tilt scanning one of the four solid etalons between one or more of the nine blocking filters. The nine filters are centered at 2843, 1897, 1605, 1257, 925, 879, 843, 792 and 780 cm-1.
http://www.lmsal.com/9120/CLAES/mission.html
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24 hours of ClONO2 (top) and HNO3 (bottom)data at 21 km as measured by CLAES in theArctic stratosphere for individual days between July 1992 and May 1993. (Roche et al., J. Atmos. Sci., 51, 2877-2902, Oct. 15, 1994.] )
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http://www.crista.uni-wuppertal.de/images/space.png
Lecture on atmospheric remote sensing [email protected]
CRISTA ist in der Ladebucht desSpace Shuttles eingebaut
CRISTA-SPAS has successfully completed two missions:
CRISTA 1 was launched on November 3, 1994 with STS-66 Atlantis.On November 12 the satellite was retrieved and two days later returned to Earth. The STS-66 payload alsoincluded the SSBUV experiment and the ATLAS-3instrument package.
CRISTA 2 was launched on August 7, 1997 with STS-85 Discovery.The Space Shuttle landed on August 19, 11:08 UT at NASA Kennedy Space Center, Florida.
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Measured CRISTA spectra of a single altitude scan in the tropical upper troposphere. Shaded spectral signatures originate from H2O emissions of weak lines.
Fig. 1 Viewing geometry of CRISTA
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N20-Karte am 06. November 1994 in 30 km Höhe
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Assimilated water vapor field at 215 hPa on August 12, 1997.
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MIPAS/ENVISAT
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MIPAS on Envisat
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Lecture on atmospheric remote sensing [email protected]
http://www-imk.fzk.de/asf/ame/ClosedProjects/assfts/P_III_12_Glatthor_N.pdf
13.5km
16.4km
19.4km
40.3km
ClO emission
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www.copernicus.org/EGU/acp/acpd/4/6283/acpd-4-6283.pdf
Lecture on atmospheric remote sensing [email protected]
Lecture on atmospheric remote sensing [email protected]
Lecture on atmospheric remote sensing [email protected]
Atmospheric observations
-ground based measurements
-air-borne observations of IR emission
-satellite observations of direct sun light
-satellite observations of IR emission (limb)
-satellite observations of IR emission/absorption (nadir)
-satellite observations imagers (IR emission nadir)
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IR / MW: ideal case 1: surface is warmer than atmosphere:
=> only absorption has to be considered
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IR / MW: ideal case 2: surface is colder than atmosphere:
=> only emission has to be considered
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IR / MW: typical case: Tsurface and Tatmosphere are similar:
emission and absorption have to be considered
Clouds and aerosols further complicate the measurement
Radiative transfer simulations are needed
Typically the thermal contrast between the surface and the air directly above is small
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High Resolution Infrared Radiation Sounder Version 2 (HIRS/2) on he TIROS Operational Vertical Sounder (TOVS)
Sensitivity of TOVS H2O observation for different IR wavelengths
Soden and Bretherton, 1996
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Engelen and Graeme, 2002
Retrieved water vapor between 1000 - 700 mb, 700 - 500 mb, and 500 - 300 mb from TOVS
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http://www.atmosp.physics.utoronto.ca/MOPITT/MATR.pdf
MOPITT measures emitted (4.6 m) and and reflected (2.3 m) radiation
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MOPITT instrument: Gas correlation technique
Transmission is varied
Gas cell Broad band radiometer
Signal =
emission
x
transmission
atmospheric emission
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MOPITT instrument: Gas correlation technique
atmospheric emission: 0 atmospheric emission: x
Instrument transmission: 0
Instrument transmission: 0.5
Difference signal: 0
Difference signal: 0.5x
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MOPITT instrument
LMC: length modulated gas correlation cell
PMC: pressure modulated gas correlation cell
Transmission convolved with the detector sensitivity (4.6 m) for different CO absorptions
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Global CO distribution from SCIAMACHY (bottom) and MOPITT (top)
Averaging kernels
Remedios et al., 2005
Buchwitz et al., 2004
20.09.2004
Lecture on atmospheric remote sensing [email protected]://suzaku.eorc.jaxa.jp/GLI2/adeos/Project/Img.html
IMG Main Characteristics
Spectral Range ofMeasurement
714-303 cm (14 -3.3um)
Wave number resolution 0.1cm (apodized) Absolute accuracy ofmeasurement < = 1k
Stability of measurement <= 0.1k
Interferogram scan time <= 10sec Sampling perintergerogram <= 100,000
Mass < 115kg
Power consumption < 150w
Approximate Size within1000x800x500mm
Interferometric Monitor for Greenhouse Gases (IMG)(1996 – 1997)
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IMG spectrum (in transmittance units) in the 600–2500 cm−1 spectral range recorded over South Pacific (−75.24, −28.82) on 4 April 1997, 04:00:42GMT (top). Radiative transfer simulations for absorption contributions due to strong (middle) and weak (bottom) absorbers are also provided.
Zoom next slide
Clerbaux et al., 2003
IMG:InterferometricMonitor for GreenhouseGases
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Detection of HNO3 from IMG data.
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(a) Best ozone spectral fits for IMG observations above the Uccle (left plot) and Ny-Alesund (rightplot) sites. The selected scenes correspond to surface temperatures of 280 and 255 K, respectively. The dashed lines at ±107 W/(cm2 sr cm1) correspond to the value selected to constrain the retrievals.
(b) Retrieved ozone profiles in number density units and relative differences calculated with respect to the smoothed ozone sonde profiles at the two locations. The a priori profile is also shown.
Coheur et al., JGR 2005
IMGUccle Ny Alesund
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Global distributions of IMG CH4 and CO total columns for the April 1–10, 1997 IMG period. The data are averaged over the time periodand a 5° x 5° grid. The corresponding available NDSCmeasurements are represented by colored circles on each map.
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AIRS:
Atmospheric IR Sounder
http://airs.jpl.nasa.gov
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AIRS measures upwelling radiances in 2378 spectral channels in the infrared (IR) from 3.74 µm to 15.4 µm.
650 – 2700 cm^-1 wavenumbers, spectral resolution: 0.5 – 2cm-1
AIRS is a grating spectrometer
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Atmospheric Infrared Sounder (AIRS) originally designed to measure atmospheric water vapor and temperature for weather forecasting Also atmospheric CO and CO2 can be retrieved for the mid-troposphere(about 8 km above the surface)
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TES observes atmospheric emissions in both limb and nadir geometry
http://tes.jpl.nasa.gov/
TES is a high-resolution,infrared, imaging Fourier-transform spectrometer with spectral coverage of 650 to 2250 cm-1 at a spectral resolution of 0.1 cm-1 (low resolution) or 0.025 cm--1
(high resolution)
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Lecture on atmospheric remote sensing [email protected]
From Beer, 2005
Tropospheric EmissionSpectrometer (TES)
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First TES global map oftropospheric O3 (9/21/2004)
GEOS-CHEM modelfor 9/21/2004
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CO Column from TES, 9-20-04
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CO Column from MOPITT, 9-20-04
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Zhang et al., 2006
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Zhang et al., 2006
Lecture on atmospheric remote sensing [email protected]
Launched in 2006 on METOP-A.
A second and third instrument will be mounted on the METOP-B and C satellites with launches scheduled in August 2012 andOctober-November 2016.
Infrared Atmospheric Sounding Interferometer (IASI)
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Infrared Atmospheric Sounding Interferometer
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Lecture on atmospheric remote sensing [email protected]
Clarisse et al., ACP 2008
Spectrum outside volcanic plume
Spectrum inside volcanic plume
Ratio spectrum
Detection of SO2 in volcanic plumes
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Detection of SO2 in volcanic plumes
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Clerbaux et al., ACP 2008
Detection of several trace gases in biomass burning plumes
Fires in east Siberia, May 2007
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(Tropospheric) Ozone from IASI
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Lecture on atmospheric remote sensing [email protected]
Atmospheric observations
-ground based measurements
-air-borne observations of IR emission
-satellite observations of direct sun light
-satellite observations of IR emission (limb)
-satellite observations of IR emission (nadir)
-satellite observations imagers (IR emission nadir)
Lecture on atmospheric remote sensing [email protected]
Nimbus-1Launch Date August 28, 1964
Operational Period Operational until September 23, 1964
Nimbus-1 High Resolution Infrared Radiometer (HRIR) image, taken at night over western Europe - note the distortion that enlarges Germany and Sweden relative to southern countries.
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0.58-0.68µm 1.58 - 1.64µm 10.3 - 11.3µm
AVHRR, chan. 1
29 Apr 2006 at 1330 UTC
Dundee Satellite Receiving Station (http://www.sat.dundee.ac.uk)
AVHRR, chan. 3 AVHRR, chan. 4
Measurements of radiometers: Clouds are bright
Thermal IRVisible Near IR
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Short summary for IR atmospheric remote sensing:
-in the thermal infrared a large number of molecules can be measured
-instruments at different platforms and with different viewing geometries
-pressure broadening allows to retrieve height information (for stratosphere)
-instrumentation is often very complex (deep temperatures, interferrometers)
-from satellite, usually the sensitivity for trace gases in the boundary layer is low