부산대학교 도서관

To support remote sensing of carbon dioxide in the troposphere, H2O pressure-broadened half-widths were obtained for 182 lines of C[O.sub.2] in the 2250-2390 [cm.sup.-1] region. For this, six spectra of C[O.sub.2] were recorded at 0.003 89 [cm.sup.-1] resolution using a Bruker IFS-125HR at the Jet Propulsion Laboratory. The absorption cell length was 6.14 cm, and the water pressures ranged from 20.1 to 26.5 torr (1 torr = 133.322 4 Pa) near room temperatures. Partial pressures of the species in the mixtures were determined by measuring selected line intensities in the [v.sub.3] band of C[O.sub.2] and the [v.sub.2] band of [H.sub.2]O. Sample temperatures were validated by deriving rotational temperature from the [v.sub.3] and [v.sub.2] + [v.sub.3] - [v.sub.2] intensities of [sup.12][CO.sup.2] and those of CO (1-0). Positions, intensities, and half-widths were retrieved spectrum by spectrum using a nonlinear least-squares line-fitting algorithm, employing a standard Voigt line shape profile and an instrumental line shape consisting of a sinc function with aperture correction. Half-widths obtained for both the fundamental and the hot band of [sup.12]C[O.sub.2] and the fundamental [v.sub.3] band of [sup.13]C[O.sub.2] had similar values. While half-widths of CO2 broadened by other atmospheric gases (such as [N.sub.2], [O.sub.2], C[O.sub.2], and air) tend to decrease with increasing rotational quantum number J', the [H.sub.2]O-broadened half-widths were observed to increase for intermediate J' (8 ≤ J' ≤ 42): ~ 0.127 [cm.sup.-1] [atm.sup.-1] near J' = 8, and increasing to ~ 0.143 [cm.sup.-1] [atm.sup.-1] (1 atm = 101.325 kPa) towards J' = 42. Moreover, for 10 ≤ J' ≤ 40, the empirical widths were within ~2%-3% of theoretical calculations. Since water vapor could reach up to 5% of ambient atmospheric surface pressure in the tropical regions, water broadened half-widths are required to model tropospheric C[O.sub.2], particularly for high-precision remote sensing, to achieve a sub-percent precision in the measurements of C[O.sub.2] column averaged mixing ratio. Since little vibrational dependence in line broadening has been seen, these results at 4.3 µm can be used for other bands of C[O.sub.2]. PACS Nos: 33.20.Ea, 33.70.Jg Pour reussir la mesure a distance du C[O.sub.2] dans la troposphere, nous avons obtenu les valeurs de demi-largeurs, etalees par pression partielle de [H.sub.2]O, pour 182 lignes dans la region 2250-2390 [cm.sup.-1]. A cette fin, nous avons enregistre six spectres de C[O.sub.2] avec une resolution de 0,003 89 [cm.sup.-1] en utilisant un spectrometre Bruker IFS-125HR au Jet Propulsion Laboratory. La longueur de la cellule d'absorption etait 6,14 cm et la pression de [H.sub.2]O a varie de 20,1 a 26,5 torr (1 torr = 133.322 4 Pa) a la tempe rature de la piece. Les pressions partielles des composantes du melange ont ete determinees en mesurant l'intensite de lignes choisies dans la bande [v.sub.3] du C[O.sub.2] et dans la bande [v.sub.2] de [H.sub.2]O. Nous avons valide la temperature des echantillons en obtenant leur temperature rotationnelle a partir des intensites [v.sub.3] et [v.sub.2] + [v.sub.3] - [v.sub.2] du C[O.sub.2] et celles du CO (1,0). Les positions, intensites et demilargeurs des lignes ont ete extraites spectre par spectre via un algorithme aux moindres carres non lineaire utilisant un profil de Voigt pour la forme de la ligne et une forme experimentale faite d'une fonction sinc avec une correction d'ouverture. Les demilargeurs obtenues pour a la fois le fondamental et la bande chaude du [sup.12]C[O.sub.2] et la bande fondamentale [v.sub.3] du [sup.13]C[O.sub.2] ont des valeurs similaires. Alors que les demi-largeurs etalees par des gaz atmospheriques (comme [N.sub.2], [O.sub.2], C[O.sub.2] et l'air) tendent a diminuer avec l'augmentation du nombre quantique rotationnel J', l'elargissement cause par [H.sub.2]O augmente avec J' pour les valeurs interme diaires (8 ≤ J' ≤ 42) par ~0,127 [cm.sup.-1] atm-1 (1 atm = 101.325 kPa) pres de J' = 8 et jusqu'a ~0,143 [cm.sup.-1] [atm.sup.-1] vers J' = 42. De plus, pour 10 ≤ J' 40, les valeurs empiriques sont a 2%-3 % pres des valeurs calculees. Puisque la vapeur d'eau peut atteindre 5 % de la pression atmospherique a la surface dans les regions tropicales, nous devons atteindre des valeurs d'etalement de ligne capables de modeliser le C[O.sub.2] tropospherique, specialement pour faire des mesures a distance de haute precision, de fac on a atteindre des precisions de mesure sous le 1 %. Puisque nous n'avons observe qu'une faible dependance vibrationnelle dans l'elargissement de ligne, ces resultats a 4,3 mm peuvent etre utilises pour d'autres bandes du C[O.sub.2]. [Traduit par la Redaction]
Introduction C[O.sub.2] is the second most abundant greenhouse gas following [H.sub.2]O and the most important anthropogenic gas impacting long-term climate change. However, only about half the amount of the C[O.sub.2] [...]