In Situ Ozone and Carbon
Dioxide Measurements From the NASA DC-8 and P3-B Aircraft
Melody
A. Avery, Stephanie A. Vay
Description of Ozone Instrument Features and Capabilities
Our in situ ozone sensors are capable of fast,
sensitive ozone measurements over a large dynamic range and a wide
variety of atmospheric conditions. The
measurements are performed by combining pure reagent nitric oxide
(NO) with incoming sample air in a small
volume reaction chamber, and by measuring light from the
resulting NO2 chemiluminescence. The
reaction chamber is maintained at constant temperature and pressure
(25 Torr) by buffering ambient pressure changes with a larger-volume
prechamber maintained at 125 Torr. The
technique, as adapted for use on aircraft, is described in detail
in the references listed below. Sampled
air enters the aircraft through a forward-facing, J-shaped probe
that has been shown to be insensitive to aircraft attitude. Approximately
2 standard liters/minute of air is pulled from RAM flow through
the probe into the instrument prechamber. Finally,
sample flow into the reaction chamber is 500 standard cc/minute. The
instruments are calibrated by reference to the NIST standard ozone
photometer. Corrections
for water vapor quenching are applied, post-flight, using in flight
pressure, temperature and water vapor data. These corrections are largest (up to 13% of the measured ozone)
in the marine boundary layer, and are negligible at altitudes above
3 km. Final data from
the TRACE-P mission are available from the GTE ftp site. Some
instrument specifications are listed below.
Ozone Instrument Specifications
Technique: Chemluminescent
reaction of ozone with nitric oxide
Dynamic Range: 0.8 – 1500
ppb
Accuracy: 5%
or 2 ppb
Precision: 2%
or 0.8 ppb
Response: 2-3
Hz
Spatial Resolution: 50
m vertical, 200 m horizontal
Data Coverage: 96.2%
DC-8, 98.9% P3-B
References
Eastman,
J.A. and D.H. Stedman, A fast response sensor for ozone eddy-correlation
flux measurements, Atmos. Environ., 11, 1209-1211,
1977.
Gregory,
G.L., C.H. Hudgins, J. Ritter and M. Lawrence, In situ ozone
instrumentation for 10-Hz measurements: Development and evaluation,
Proceedings of sixth symposium on Meteorological Observations
and Instrumentation, New Orleans, LA, Jan 12-16, 136-139, 1987.
Pearson
R.W. and D.H. Stedman, Instrumentation for fast response ozone measurements from aircraft, Atmos Tech, 12,
1980.
|
Carbon
dioxide
|
Dynamic
Range
|
0 to
3000 ppmv
|
Accuracy
|
0.25
ppmv
|
Precision
|
0.07
ppmv (1s)
|
Data
Rate
|
Recorded
at 5 Hz (DC-8); 66 Hz (P-3B)
|
Data
Reporting
|
1 Hz
|
References:
Anderson,
B. E., G. L. Gregory, J. E. Collins, Jr., G. W. Sachse, T. J.
Conway, and G. P. Whiting, Airborne Observations of the Spatial
and Temporal Variability of Tropospheric Carbon Dioxide, J. Geophys.
Res., 101(D1), 1985-1997, 1996.
Vay,
S. A., B. E. Anderson, T. J. Conway, G. W. Sachse, J. E. Collins,
Jr., D. R. Blake, and D. J. Westberg, Airborne observations of
the tropospheric CO2 distribution and its controlling
factors over the South Pacific Basin, J. Geophys. Res., 104(D5),
5663-5676, 1999.
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