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Lecture on atmospheric remote sensing [email protected]
Remote sensing in 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]
moleculesaerosols
Cloud droplets
rain droplets
Remote sensing in IR spectral range
Wavelengths from ~1 to 1000μm
-vibrational + rotational transitions
Lecture on atmospheric remote sensing [email protected]
In the IR spectral range, typically emission spectra are analysed
In some cases also absorption spectra of the solar radiation are measured
Lecture on atmospheric remote sensing [email protected]
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)
Lecture on atmospheric remote sensing [email protected]
The observed Intensity is:
= 0if only emission is observed Optical depth
-emission and absorption plays a role
-typically no simple inversion (like in the UV/vis) is possible
-complex radiative transfer modelling has to be applied
Lecture on atmospheric remote sensing [email protected]
( ) ( ) ),,(,,,, TpSTNNTp ijijij νννσνα −⋅⋅=
N: Number density
T: Temperature
p: Pressure
σ: absorption cross section
S: Line width
α: absorption coefficient
gl is the degeneracy and El the energy for state l,μis the overall dipole (or other) moment coupling to the radiation fieldQ(T)= Σgl exp (- El /kT) is the partition functionφij² is the transition matrix element
Lecture on atmospheric remote sensing [email protected]
Scheme of rotational-vibrational transitions
Lecture on atmospheric remote sensing [email protected]
Zu sehen sind die Rotationsschwingungsspektren von HCl (2800 cm-1) und DCl (2200 cm-1) sowie deren erste Obertöne (HCl bei 5600 cm-1 und DCl bei 4400 cm-1) sowie Wasserbanden (3600 cm-1) und CO2-Banden (2600 cm-1).
Lecture on atmospheric remote sensing [email protected]
Example of an absorption FTIR- measurement
Lecture on atmospheric remote sensing [email protected]
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)
Lecture on atmospheric remote sensing [email protected]
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
Lecture on atmospheric remote sensing [email protected]
MIPAS-HNO3-observation
Lecture on atmospheric remote sensing [email protected]
Natural line width:
It can be ignored compared to collision (pressure) broadening at lower altitudes and Doppler (thermal motion) broadening at higher altitudes.
Collision (pressure) broadening:
-collission between molecules shortens lifetimes for specific states-for increasing pressure towards lower altitudes the probability to be scattered increases-the line shape for pressure broadening can be approximated by a Lorentzianline shape:
(Δν: line width for pressure broadening)
The Lorentian line shpae can be retrievd from the *van Vleck and Weisskopf* line shape assuming that the duration of a collision is much shorter than the time between two collisions (impact-approximation)
Lecture on atmospheric remote sensing [email protected]
Lorentian line width:
The Lorentian line width is temperature dependent
Typical value: 2.5 MHz Typical value: 0.75p0: 1hPaT0: 300K
Lecture on atmospheric remote sensing [email protected]
Doppler broadening
-is caused by thermal motion of molecules. The Maxwell distribution depends on temperature and the molecular mass:
According to the Doppler-effect, the line width becomes:
With line width:
By convolution of the Lorentian and Doppler line shape one gets the so called Voigt line shape:
Lecture on atmospheric remote sensing [email protected]
www2.nict.go.jp/kk/e414/shuppan/ kihou-journal/journal-vol49no2/4-06.pdf
Lecture on atmospheric remote sensing [email protected]
Lecture on atmospheric remote sensing [email protected]
Different types of spectrometers:
-Grating spectrometer: simple setup, medium spectral resolution, typical for early measurements, today satellite instrument CRISTA
-FTIR, 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)
Lecture on atmospheric remote sensing [email protected]
Michelson-Interferometer
Lecture on atmospheric remote sensing [email protected]
cν
λν =≡
1
)2cos(1 xAa ⋅⋅⋅= νπ ))(2cos(2 xxAa Δ−⋅⋅⋅= νπ
))2/(2cos()2cos(221 xxxAaaa Δ+⋅⋅⋅Δ⋅⋅⋅=+= νπνπ
[ ])2cos(12)2(cos4 222 xIxAaI in Δ⋅⋅+⋅⋅=Δ⋅⋅⋅⋅== νπνπ
0 1 2 3 4
-1.0
-0.5
0.0
0.5
1.0a2
a1
Δx
Am
plitu
de
Phase in W ellenlängen
Wellenzahl:
Überlagerung zweier monochromatischer Wellen mit Phasenverschiebung Δx:
Intensität:
Prinzip des Michelson- Interferometers
Lecture on atmospheric remote sensing [email protected]
Polychromatische InterferenzDa Spektrometer Licht vieler Wellenlängen verarbeiten, entsteht die oben beschriebene Interferenz für jede Wellenlänge. Entsprechend überlagern sich die Interferenz-Intensitäten der einzelnen Wellenlängen zusätzlich.
Lecture on atmospheric remote sensing [email protected]
Fourier Transformation
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
-balloon-borne observations of IR emission
-satellite observations of scattered sun light (NIR)
-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]
Atmospheric observations
-ground based measurements
-balloon-borne observations of IR emission
-satellite observations of scattered sun light (NIR)
-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]
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).
Lecture on atmospheric remote sensing [email protected]
Lecture on atmospheric remote sensing [email protected]
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
reolution spectrometer
Lecture on atmospheric remote sensing [email protected]
CO and CH4 column above the Jungfraujoch station
1985 - 1996Mahieu et al., 1997
Lecture on atmospheric remote sensing [email protected]
Total column CO abundance over Zvenigorod (right scale) and corresponding mean tropospheric mixing ratio (left scale). Regression lines for 1970-1984 and for 1985-1997 are shown.
http://www.igac.noaa.gov/newsletter/igac21/trends.html
Lecture on atmospheric remote sensing [email protected]
Seasonal cycle of free tropospheric CO from 1950/51 and 1985-87
(ISSJ Jungfraujoch)
Lecture on atmospheric remote sensing [email protected]
www.ifjungo.ch/reports/1999_2000/pdf/09.pdf
Increase of several species from 1951 to 2000 (ISSJ Jungfraujoch)
Early measurements were carried out witha grating spectrometer; the spectral resolution was limited
A spectrum from 2000 mathematically degraded to the resolution from 1951
Original spectrum from 2000 measured with a FTIR high reolution spectrometer
Lecture on atmospheric remote sensing [email protected]
Lecture on atmospheric remote sensing [email protected]
1951 1988 2000 1951 1988 2000
Lecture on atmospheric remote sensing [email protected]
Total column densities of HCl, measured in Spitsbergen between 1992 and 2000.
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.
Lecture on atmospheric remote sensing [email protected]
Atmospheric observations
-ground based measurements
-balloon-borne observations of IR emission
-satellite observations of scattered sun light (NIR)
-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]
MIPAS Balloon
Lecture on atmospheric remote sensing [email protected]
Lecture on atmospheric remote sensing [email protected]
MIPAS ClONO2-Messung
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
-balloon-borne observations of IR emission
-satellite observations of scattered sun light (NIR)
-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]
SCIAMACHY-Spectral regions
Lecture on atmospheric remote sensing [email protected]
How does the earth look like in the NIR spectral region?
SCIAMACHY on ENVISAT measures backscattered sunlight in the near-IR
Lecture on atmospheric remote sensing [email protected] nm
Unterer Häufungspunkt der Reflektivität als Maß für wolkenfreie Messungen M. Grezeorski
Lecture on atmospheric remote sensing [email protected] nm
Unterer Häufungspunkt der Reflektivität als Maß für wolkenfreie Messungen M. Grezeorski
Lecture on atmospheric remote sensing [email protected]
Lecture on atmospheric remote sensing [email protected]
Panel (a) shows the spectrally fully resolved total optical densities for a vertical path for CH4 (V = 3.6 · 1019molec/cm-2) and H2O (V = 6.5 · 1022molec/cm-2) while panel (b) depicts the vertical optical densities of CH4 for different height layers in the atmosphere. The expected total slant optical density (here for A=2.41) is now shown in panel c). Shown is the high resolution optical density and the convolved one that is seen by the instrument, i.e. convolved with I (here: SCIAMACHY slit function in channel 8: Gaussian,FWHM=0.24nm). Starting from this linearisation point, the effect of a change in the vertical column density of CH4 of +1018molec/cm2(i.e. 3% of the total column) in different height layers is shown in panel (d). Panel (e) shows the derivatives (also with respect to CH4perturbations) for different linearisation points, viz. for different water vapour columns (1.3, 6.5 and 32.5 1022molec/cm-2, respectively).The optical densities in (a) and (b) are not convolved.
Lecture on atmospheric remote sensing [email protected]
Typical modelled and measured differential slant optical densities (DSOD) in the CO2 (a)
and CH4 (b) fit windows are shown. In panel (a), CO2 contributes most to the depicted total
DSOD, while there are also very weak absorptions by water vapour. In panel (b),
absorptions by CO2 and H2O marginally add to the strong CH4 signal. In both panels, all
species are fitted simultaneously and make up the total DSOD using a gaussian slit function
with 1.35 nm full width at half maximum.
Lecture on atmospheric remote sensing [email protected]
Lecture on atmospheric remote sensing [email protected]
Example of a CO fit. The upper panel shows the differential slant optical density of all absorbers (CH4, H2O and CO), the middle panelthat of CO. The lower panel shows the residual of the fit.
C. Frankenberg, IUP Heidelberg
CO absorption detected in SCIAMACHY spectra
Lecture on atmospheric remote sensing [email protected]
CO maps correlate well with maps of fire countsC. Frankenberg, IUP Heidelberg
Fire counts measured by MODIS aboard Terra.
Lecture on atmospheric remote sensing [email protected]
C. Frankenberg, IUP HeidelbergCH4 maps from SCIAMACHY
CH4 columns are normalised with respect to CO2 columns
CH4CO2
Aug-Nov 2003
Lecture on atmospheric remote sensing [email protected]
C. Frankenberg, IUP Heidelberg
J.F. Meirink, KNMI, Utrecht
Comparison with model results
Aug-Nov 2003
Aug-Nov 2003
Lecture on atmospheric remote sensing [email protected]
MODIS Enhanced Vegetation Index
The largest differences can be seen in tropical broadleaf evergreen forests
Science, March 2005
C. Frankenberg, IUP Heidelberg
In agreement with recent findings of a new CH4source from plants under aerobic conditions
Keppler et al., Nature 2006
Difference SCIAMACHY – Model, Aug-Nov 2003
Lecture on atmospheric remote sensing [email protected]
Atmospheric observations
-ground based measurements
-balloon-borne observations of IR emission
-satellite observations of scattered sun light (NIR)
-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]
Different viewing geometries and wavelength ranges:
Direct sun observations provide a high signal to noise ratio
The light path is well defined
High requirements on telescope adjustement
Only special parts of the earth can be monitored
Lecture on atmospheric remote sensing [email protected]
The platform for SAGE II is the Earth Radiation Budget Satellite (ERBS). Nominal orbit parameters for ERBS are:
•Launch Date: October 5, 1984•Planned Duration: 2 years•Actual Duration: ongoing•Orbit: non-sun synchronous, circular at 650 km•Inclination: 57 degrees•Nodal Period: 96.8 minutes
http://www-sage2.larc.nasa.gov/instrument/
Channel Wavelength (nm)
1 1020 2 935 3 600 4 525 5 452 6 448 (nominal) 7 386
SAGE II Channels
Lecture on atmospheric remote sensing [email protected]
Channels Species ApproximateAltitude Range (km)
3-6 O3, NO2 45-60 1, 3-6 O3, NO2, Aerosol (3) 15-45 1, 3-5 O3, Aerosol(3) 10-151, 3 ,4 O3, Aerosol (2) 5-10 1 Aerosol (1) 1-5 Table 2. Algorithm Species and Altitude Range. (3) 1020, 525, and 452-nm extinction profiles; (2) 1020 and 525 nm; (1) 1020 nm only.
Lecture on atmospheric remote sensing [email protected]
http://www-sage2.larc.nasa.gov/data/v6_data/
Lecture on atmospheric remote sensing [email protected]
Lecture on atmospheric remote sensing [email protected]
Atmospheric observations
-ground based measurements
-balloon-borne observations of IR emission
-satellite observations of scattered sun light (NIR)
-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]
Limb-Beobachtung
Lecture on atmospheric remote sensing [email protected]
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
Lecture on atmospheric remote sensing [email protected]
Lecture on atmospheric remote sensing [email protected]
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.] )
Lecture on atmospheric remote sensing [email protected]
http://www.crista.uni-wuppertal.de/images/space.png
Lecture on atmospheric remote sensing [email protected]
Measured CRISTA spectra of a single altitude scan in the tropical upper troposphere. Shaded spectral signatures originate from H2O emissions of weak lines.
Lecture on atmospheric remote sensing [email protected]
CRISTA ist in der Ladebucht desSpace Shuttles eingebaut
Lecture on atmospheric remote sensing [email protected]
N20-Karte am 06. November 1994 in 30 km Höhe
Lecture on atmospheric remote sensing [email protected]
Assimilated water vapor field at 215 hPa on August 12, 1997.
Lecture on atmospheric remote sensing [email protected]
MIPAS/ENVISAT
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MIPAS on Envisat
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
Lecture on atmospheric remote sensing [email protected]
Model simulation O3 GOME O3 GOME NO2 GOME OClO
(TM3-DAM, KNMI) (IUP Bremen) (IUP Heidelberg) (IUP Heidelberg)
21.09.
22.09.
23.09.
Walburga Wilms-Grabe
Lecture on atmospheric remote sensing [email protected]
Model simulation O3 GOME O3 GOME NO2 GOME OClO
(TM3-DAM, KNMI) (IUP Bremen) (IUP Heidelberg) (IUP Heidelberg)
24.09.
25.09.
26.09.
Walburga Wilms-Grabe
Lecture on atmospheric remote sensing [email protected]
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]
Lecture on atmospheric remote sensing [email protected]
Atmospheric observations
-ground based measurements
-balloon-borne observations of IR emission
-satellite observations of scattered sun light (NIR)
-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]
http://www.atmosp.physics.utoronto.ca/MOPITT/MATR.pdf
MOPITT measures emitted (4.6 μm) and and reflected (2.3 μm) radiation
Lecture on atmospheric remote sensing [email protected]
MOPITT instrument
LMC: length modulated gas correlation cell
PMC: pressure modulated gas correlation cell
Transmission convolved with the detector sensitivity (4.6 μm) for different CO absorptions
Lecture on atmospheric remote sensing [email protected]
Global CO on 23 March 2000
Global CO distribution from SCIAMACHY (top) and MOPITT (bottom)
Averaging kernels
Buchwitz et al., 2004
Remedios et al., 2005
Lecture on atmospheric remote sensing [email protected]
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.
Clerbaux et al., 2003
Lecture on atmospheric remote sensing [email protected]
Detection of HNO3 from IMG data.
Lecture on atmospheric remote sensing [email protected]
Surface temperature retrieved from IMG at 976.75 cm−1
Lecture on atmospheric remote sensing [email protected]
(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 se 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
Lecture on atmospheric remote sensing [email protected]
Global distributions of IMG O3 total and partial columns for theApril 1–10, 1997 IMG
period, filtered and averaged over a 5 5 grid and the time period.
Turquety et al., ACP, 2004
Lecture on atmospheric remote sensing [email protected]
Global distributions of IMG CH4 and CO total columns for the April 1–10, 1997 IMGperiod. The data are averaged over the time period and a 55 grid. The corresponding available NDSCmeasurements are represented by colored circles on each map.
Lecture on atmospheric remote sensing [email protected]
Lecture on atmospheric remote sensing [email protected]
From Beer, 2005
TroposphericEmissionSpectrometer (TES)
Lecture on atmospheric remote sensing [email protected]
First TES global map oftropospheric O3 (9/21/2004)
GEOS-CHEM modelfor 9/21/2004
Lecture on atmospheric remote sensing [email protected]
CO Column from TES, 9-20-04
Lecture on atmospheric remote sensing [email protected]
CO Column from MOPITT, 9-20-04
Lecture on atmospheric remote sensing [email protected]
Atmospheric observations
-ground based measurements
-balloon-borne observations of IR emission
-satellite observations of scattered sun light (NIR)
-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-1 High Resolution InfraredRadiometer (HRIR) image, taken at nightover western Europe - note the distortion that enlarges Germany and Sweden relative tosouthern countries - the Italians might be aggrieved by the shrinking of the "boot".
Nimbus-1Launch Date August 28, 1964
Operational Period Operational until September 23, 1964
Lecture on atmospheric remote sensing [email protected]
Nimbus-4Launch Date April 8, 1970
Operational Period
Over 10 years until it was deactivated on September 30, 1980
700-mile Long Thermometer. Nimbus-4 took temperature readings of three continents (Africa, Europe andAsia) from 700 statute miles with an infrared camera. The temperature data were reconstructed into aphotograph. White dots on the photo are grid marks which provide scientists with precise latitude andlongitude information. Since the images were measured in heat emitted from Earth, dark areas are land,grey are water and white are clouds.
Lecture on atmospheric remote sensing [email protected]
visible, 0.58-0.68µm
AVHRR 23 Jan 2005 at 1245 UTC
near infra-red, 0.725-1.10µm
short wave infra-red, 1.58-1.64 or3.55-3.93µm
thermal infra-red, 10.3-11.3µm
thermal infra-red, 11.5-12.5µm
Dundee Satellite Receiving Stationhttp://www.sat.dundee.ac.uk/abin/browse/avhrr/2005/1/23/1245
Lecture on atmospheric remote sensing [email protected]
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
Lecture on atmospheric remote sensing [email protected]
Engelen and Graeme, 2002
Retrieved water vapor between 1000 - 700 mb, 700 - 500 mb, and 500 - 300 mb for CSUalgorithm, NVAP algorithm, and Susskind's algorithm.
Lecture on atmospheric remote sensing [email protected]
Monochromatic interference
Set up of an interferometer