 |
| Titel |
Airborne intercomparison of HOx measurements using laser-induced fluorescence and chemical ionization mass spectrometry during ARCTAS |
| VerfasserIn |
X. Ren, J. Mao, W. H. Brune, C. A. Cantrell, R. L. Mauldin III, R. S. Hornbrook, E. Kosciuch, J. R. Olson, J. H. Crawford, G. Chen, H. B. Singh |
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| ISSN |
1867-1381
|
| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Measurement Techniques ; 5, no. 8 ; Nr. 5, no. 8 (2012-08-21), S.2025-2037 |
| Datensatznummer |
250003054
|
| Publikation (Nr.) |
 copernicus.org/amt-5-2025-2012.pdf |
|
|
|
|
|
| Zusammenfassung |
| The hydroxyl (OH) and hydroperoxyl (HO2) radicals, collectively called
HOx, play central roles in tropospheric chemistry. Accurate
measurements of OH and HO2 are critical to examine our understanding of
atmospheric chemistry. Intercomparisons of different techniques for
detecting OH and HO2 are vital to evaluate their measurement
capabilities. Three instruments that measured OH and/or HO2 radicals
were deployed on the NASA DC-8 aircraft throughout Arctic Research of the
Composition of the Troposphere from Aircraft and Satellites (ARCTAS) in the
spring and summer of 2008. One instrument was the Penn State Airborne
Tropospheric Hydrogen Oxides Sensor (ATHOS) for OH and HO2 measurements
based on Laser-Induced Fluorescence (LIF) spectroscopy. A second instrument
was the NCAR Selected-Ion Chemical Ionization Mass Spectrometer (SI-CIMS)
for OH measurement. A third instrument was the NCAR Peroxy Radical Chemical
Ionization Mass Spectrometer (PeRCIMS) for HO2 measurement. Formal
intercomparison of LIF and CIMS was conducted for the first time on a same
aircraft platform. The three instruments were calibrated by quantitative
photolysis of water vapor by ultraviolet (UV) light at 184.9 nm with three different
calibration systems. The absolute accuracies were ±32% (2σ)
for the LIF instrument, ±65% (2σ) for the SI-CIMS
instrument, and ±50% (2σ) for the PeRCIMS instrument. In
general, good agreement was obtained between the CIMS and LIF measurements
of both OH and HO2 measurements. Linear regression of the entire data
set yields [OH]CIMS = 0.89 × [OH]LIF + 2.8 × 104 cm−3
with a correlation coefficient r2 = 0.72 for OH,
and [HO2]CIMS = 0.86 × [HO2]LIF + 3.9 parts
per trillion by volume (pptv, equivalent to pmol mol−1) with a
correlation coefficient r2 = 0.72 for HO2. In general, the
difference between CIMS and LIF instruments for OH and HO2 measurements
can be explained by their combined measurement uncertainties. Comparison
with box model results shows some similarities for both the CIMS and LIF
measurements. First, the observed-to-modeled HO2 ratio increases
greatly for higher NO mixing ratios, indicating that the model may not
properly account for HOx sources that correlate with NO. Second, the
observed-to-modeled OH ratio increases with increasing isoprene mixing
ratios, suggesting either incomplete understanding of isoprene chemistry in
the model or interferences in the measurements in environments where
biogenic emissions dominate ambient volatile organic compounds. |
| |
|
| Teil von |
|
|
|
|
|
|
|
|