Infrared Spectroscopy of the Atmosphere using the FTIR Spectrometer
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Infrared Spectroscopy of the Atmosphere
using the FTIR Spectrometer
Brian EchevarriaJennifer Link
Introduction to Atmospheric Instrumentation (ATMS 360)
University of Nevada Reno
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FTIRFourier Transform InfraRed
The FTIR Spectrometer is an optical instrument used to measure infrared spectra from 5 microns to 20 microns. Interested in the window region from about 13 microns to 8 microns (800cm-1 – 1300cm1)
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Applications• Obtains Infrared spectrum of absorption,
emission, and photoconductivity of:– Solids, liquids and gases
• Identification of Cloud base temperatures
• Identification of inorganic compounds and organic compounds
• Measures solar irradiance• In Remote sensing
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How the FTIR works• The FTIR spectrometer uses a Michelson
Interferometer setup that consists of:– A beam splitter, a fixed mirror, and a mirror
that translates back and forth.
Cold and hot black Bodies are for calibrationIn order to get correct cloud Radiance and BrightnessMeasurements.
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Calibration
Thermistor Probe
Circulation Water Out
Circulation Water In
Cone
Black Paint
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Calibration
• j
Detector
Cold Black Body
Hot Black Body
Mirror
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Cold Black Body
0
0.002
0.004
0.006
0.008
0.01
0.012Cold Black Body Radiance
Wavenumber (cm-1)
Radi
ance
(Wm
/m2
Sr c
m-1
)
266.6266.7266.8266.9267
267.1267.2267.3267.4267.5267.6
Cold Black Body Brightness Temperature
Wavenumber (cm-1)
Brig
htne
ss T
empe
ratu
re (K
)
Entered Cold BBT: -6C
Generated Cold BBT: -5.9C
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Hot Black Body
Entered Hot BBT: 44.16C
Generated Hot BBT: 44.19C
0.0000.0020.0040.0060.0080.0100.0120.0140.0160.0180.020 Hot Black Body Radiance
Wavenumber (cm-1)
Radi
ance
(Wm
/m2
Sr c
m-1
)
317317.05317.1
317.15317.2
317.25317.3
317.35317.4
317.45317.5
Hot Black Body Brightness Temperature
Wavenumber (cm-1)
Brig
htne
ss T
empe
ratu
re (K
)
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Data CollectionRadiance:
H2O
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Data CollectionBrightness Temperature:
• Cloud Base Temperatures• Comparing surface
temperature/moisture conditions
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500.491670.207839.9231009.631179.341349.051518.751688.461858.160
50
100
150
200
250
300
350
Brightness Temperature
Wavenumber (cm-1)
Brig
htne
ss T
empe
ratu
re (K
)
500.491 674.064 847.637 1021.21 1194.77 1368.33 1541.89 1715.45 1889.020
0.002
0.004
0.006
0.008
0.01
0.012
0.014
0.016
Radiance
Wavenumber (cm-1)
Radi
ance
(mW
/m2
Sr c
m-1
)
Cirrus- April 10, 17:00
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.
Lidar Cloud height@ 1700: 5300m
Sounding LCLH@1700: 5610m
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“Mostly Clear”- April 12, 1648
1510.070
0.002
0.004
0.006
0.008
0.01
0.012
0.014
Radiance
Wavenumber (cm-1)
Radi
ance
(mW
/m2S
r cm
-1)
1510.070
50
100
150
200
250
300
Brightness Temperatures
Wavenumber (cm-1)
Brig
htne
ss T
empe
ratu
re (K
)
Surface Temperature@ 1648: 9C
Sounding Surface Temp@ 1700: 10C
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No significant clouds detected byThe Lidar for 1648.
Generally clear from 1645 to 1700
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Altostratus- April 17, 16:36
1510.070
0.002
0.004
0.006
0.008
0.01
0.012
0.014
0.016
Radiance
Wavenumber (cm-1)
Radi
ance
(Wm
/m2
Sr cm
-1)
1510.07230
240
250
260
270
280
290
300
Brightness Temperature
Wavenumber (cm-1)
Brig
htne
ss T
empe
ratu
re (K
)
Base Cloud Temperature@ 1636: -15C
Sounding LCLT @ 1700: -11C
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Compare the Cloud Height with theLidar and the Cloud temperature withThe brightness temperature
Lidar Cloud height@ 1636 : 4800mLidar Cloud height@ 1700: 4300m
Sounding LCLH@1700: 4400m
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1510.07255
260
265
270
275
280
285
290
295
300
305
Wavenumber (cm-1)
Brig
htne
ss T
empe
ratu
re (K
)
Stratocumulus- April 19, 16:58
Cloud Base Temperature@ 1658: -2C
Sounding LCLT @ 1700: -1C
Brightness Temperature
1510.070
0.002
0.004
0.006
0.008
0.01
0.012
0.014
0.016
Radiance
Wavenumber (cm-1)
Radi
ance
(Wm
/m2
Sr c
m-1
)
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Lidar Cloud height@ 1658 : 2400m
Sounding LCLH@1700: 3800m
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1510.070
0.002
0.004
0.006
0.008
0.01
0.012
0.014
0.016
Clear Vs. Cloudy Ra-diance
Clear
Cloudy
Wavenumber (cm-1)
Radi
ance
(m
W/m
2Sr
cm-1
)
Lowered values of N2O
CH4 still present
Increased CO2
Increased H2O
Little to no CFC detection
No Ozone detection
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1510.070
50
100
150
200
250
300
350
Clear Vs. Cloudy Brightness Temperatures
ClearCloudy
Wavenumber (cm-1)
Brig
htne
ss T
empe
ratu
re (K
)
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Errors in Data• Cold and Hot black body
temperatures.• Quickly fluctuating hot and cold
black body temperatures.• Not a completely clear day for
comparison. • Sounding Location.
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Conclusion• Evidence of stratospheric
greenhouse gases and surface gases.• Determine cloud base temperature
and height and compare with Lidar and sounding data.
• Further analyze unknown gases in data.
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Questions?