Transcript OzoneOSU05.ppt

AIR-BROADENED LINE WIDTHS AND
SHIFTS IN THE ν3 BAND OF 16O3 AT
TEMPERATURES BETWEEN 160 AND 300 K
M. A. H. SMITH and C. P. RINSLAND
NASA Langley Research Center, Hampton, VA 23681-2199 U.S.A.
V. MALATHY DEVI and D. CHRIS BENNER
The College of William and Mary, Williamsburg, VA 23187-8795 U.S.A.
A. M. COX
New Horizons Governor’s School for Science and Technology,
Hampton, VA 23666 and Poquoson High School, Poquoson, VA 23662
U.S.A.
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Good vs. Bad Ozone
 “Good” Ozone in the Stratosphere (10 – 40 km)




Produced from photodissociation of O2 molecules
Peak O3 concentrations at ~ 25 km
Protects life from harmful shortwave UV radiation
Destroyed by compounds such as CFCs released into the
atmosphere
 Significant depletion contributes to cooling of the stratosphere
 “Bad” Ozone in the Troposphere (0 – 10 km)





Produced in photochemical smog
Toxic to animals (including humans) when inhaled
Causes damage to plants
A greenhouse gas in the upper troposphere
Reacts to cleanse the troposphere of some pollutants
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Tropospheric Ozone Measured from Space
•
Since 1978 the Total Ozone Mapping Spectrometer (TOMS) instruments have been
measuring global ozone levels from a variety of satellites. Instruments aboard the
Aura satellite launched in 2004 are continuing the long term monitoring of ozone.
•
Learn more about tropospheric ozone at http://earthobservatory.nasa.gov/
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Global Average Temperature Profile
Tropopause temperatures vary with latitude and season, and are
typically below 195 K in the tropics.
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Hurricanes and Ozone
Ozone column measurements collected
over Hurricane Erin on September 12,
2001 by the TOMS instrument on
NASA’s Earth Probe satellite
In the eye, where air from the stratosphere
is transported downward, ozone
concentrations are elevated (yellow and
green).
The core is surrounded by an area of much
lower ozone concentrations (purple and
blue) due to ozone-poor surface air
being transported upward by strong
thunderstorms.
Dropping ozone levels around the eye may
be sign that a storm is strengthening.
From http://earthobservatory.nasa.gov/
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Spectra Used for Ozone Fits in the ν3 Band
NO. OF
DATE
SAMPLE
SPECTRA
2
2
4
1
2
3
3
3
5
1
3
1
1
VMR
(%)
10-Nov-94 O3 + Air
10-Nov-94 O3 + Air
7-Feb-96 O3
29-Apr-97 O3
30-Apr-97 O3 + Air
1-May-97 O3 + Air
2-May-97 O3 + Air
4-May-97 O3 + Air
6-May-97 O3 + Air
21-May-98 O3
21-May-98 O3 + Air
22-May-98 O3 + Air
22-May-98 O3 + Air
4.7
3.6
81 - 90
30.3
0.6
0.5
0.4
0.3
0.3
13
1.5
1.9
1.9
TEMPERATURE PRESSURE
(K)
(TORR)
300
300
300
298
297
272
254
233
213
170
186
160
168
101, 204
76, 153
0.3 - 0.5
1.3
110, 201
101 - 220
107 - 216
104 - 220
86 - 201
2.2
94 - 193
203
134
PATH
BAND
RES.
(m)
PASS
(cm-1)
0.0998
0.0998
0.0998
0.500
0.500
0.500
0.500
0.500
0.500
0.095
0.095
0.095
0.095
2
2
2
2
2
1
1
1
1
1
1
2
2
0.0027
0.0027
0.0027
0.0052
0.0052
0.0052
0.0052
0.0052
0.0052
0.005
0.005
0.005
0.005
Band pass 1 = 500-1400 cm-1; Band pass 2 = 800-1400 cm-1
All spectra were recorded using the McMath-Pierce FTS with KCl beam splitter, 8 mm
aperture, and He-cooled As:Si detectors.
February 1996 spectra were used in the intensity study published in JGR (Smith et al., 2001).
May 1998 spectra were recorded using a single detector.
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Example of a Measured Spectrum
Ozone Spectrum 818
1.0
0.8
Transmittance
50-cm cell
0.3 % O3 in air
p = 86.2 torr
T = 213 K
Resolution =
0.0052 cm-1
▲ Red triangles mark
lines for which
parameters were
determined.
0.6
0.4
0.2
0.0
1021
1022
1023
Wavenumber
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1024
1025
Multispectrum Fitting Strategy
1) Four low-pressure spectra for which concentrations were
determined by UV absorption (254 nm) were fit together first to
obtain absolute line intensities.
2) Intensities were fixed to these retrieved values for subsequent
fitting of air-broadened spectra.
3) Room-temperature air-broadened spectra were added to the fit
first, followed by the lower-temperature spectra down to 213 K.
4) Noisy spectra from 186 to 160K were added to the fit with low
weights due to relatively poor Signal-to-Noise.
5) Parameters have been determined for 41 P-branch lines in the
spectral region 1016 – 1025 cm-1 (J˝ = 15 – 26, Ka˝ = 0 – 11).
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Results: Intensities
1.10
1.08
Intensity Ratio
1.06
1.04
1.02
1.00
0.98
0.96
0.94
14
16
18
20
22
24
26
J"
Present Work / HITRAN 2004, Mean = 1.041, SD = 0.013
Present Work / HITRAN 2000, Mean = 1.008, SD = 0.013
Present Work / Smith et al. (2001), Mean = 1.003, SD = 0.003
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28
Results: Broadening Coefficients
0.088
HITRAN 2004 (air)
HITRAN 2000 (air)
Spencer et al., 1992 (N2)
Present Work (air)
0.080
-1
bL (cm atm ) at 296K
0.084
-1
0.076
0
0.072
0.068
0.064
14
16
18
20
22
J"
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24
26
28
Results: Broadening Temperature
Dependence Exponents
1.1
1.0
HITRAN 2004 (air)
HITRAN 2000 (air)
Spencer et al., 1992 (N2)
0.9
Present Work (air)
n
0.8
0.7
0.6
0.5
0.4
14
16
18
20
22
J"
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24
26
b = b (T0/T)n
0
28
Results: Pressure-Induced Line Shifts
0.004
0.000
-0.002
-1
-0.004
-0.006
 (Present Work)
-0.008
 (Malathy Devi et al., 1997)
0
-1
 (cm atm ) at 296 K
0.002
-0.010
HITRAN 2004
-0.012
14
 1 (Smith et al., 1997)
16
18
20
22
J"
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24
26
28
Results: Temperature Dependences of
Pressure-Induced Line Shifts
8e-5
3
6e-5
2
1
4e-5
-1
-1
-1
' (cm atm K )
1e-4
2e-5
0
-2e-5
-4e-5
-6e-5
-8e-5
14
0(T) = 0(T0) + ' (T-T0)
16
18
20
22
J"
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24
26
28
Comparison with the Other Fundamental Bands
Broadening Coefficients
Temperature Dependence Exponents
0.9
3
0.8

0.085

0.7
Calc  3
-1
Calc  1
0.6
0
-1
0.080
n
bL (cm atm ) at 296 K
0.090
0.5
0.075
0.4
0.070
14
16
18
20
22
J"
24
26
28
0.3
14
16
18
20
22
24
26
J"
Measured values are from Present Work, Malathy Devi et al. (1997) and Smith et al. (1997).
Calculated values are based on empirical formulas given by Wagner et al. (2002).
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28
Comparison with Overtone Band
Air-Shift Coefficients
0.004
0.084
0.000
 (cm atm ) at 296 K
0.088
0.080
-1
-0.004
-0.008
-1
0.076
-0.012
 3 (Present Work)
0
0
-1
-1
bL (cm atm ) at 296 K
Air-Broadening Coefficients
0.072
3 3 (Smith et al., 1994)
-0.016
0.068
14
16
18
20
22
J"
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24
26
28
14
16
18
20
22
J"
24
26
28
Summary
•
Intensities, air-broadening and shift parameters have been determined for 41 ν3
P-branch lines with J˝ = 15 – 26 from spectra recorded at temperatures from
160 K to 300 K.
•
Intensities retrieved with 2005 version of the multispectrum fitting program are
identical to those retrieved from the same spectra for the 2001 study.
•
Air-broadening coefficients agree within 5% or better with measurements in the
ν1, ν2, and 3ν3 bands and with HITRAN 2004.
•
Air-shift coefficients agree within error bars with measurements in the ν1 and ν2
bands and with HITRAN 2004.
•
Vibrational dependence of the air-shift coefficients is apparent between the ν3
and 3ν3 bands.
•
Temperature dependence exponents for air-broadening are 5 to 25% smaller
than HITRAN 2004 values. The measured values generally decrease with J˝,
while the HITRAN values increase with J˝.
•
More research is needed!
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