HO cycle in 1997 and 1998 over the southern Indian Ocean derived from CO, radon, and hydrocarbon measurements made at Amsterdam Island - Archive ouverte HAL Accéder directement au contenu
Article Dans Une Revue Journal of Geophysical Research: Atmospheres Année : 2001

HO cycle in 1997 and 1998 over the southern Indian Ocean derived from CO, radon, and hydrocarbon measurements made at Amsterdam Island

Résumé

A new empirical method for the derivation of average HO radical concentrations is presented. The method is based on estimation of CO lifetime through the relative variability of CO and Rn measurements, and hydrocarbon measurements are used to independently determine the relative effects of chemistry and dynamics. Data from Amsterdam Island (37øS, 77øE), a remote site in the southern Indian Ocean, are used to calculate annual and daily HO levels for 1997 and 1998. A seasonal variation in calculated daily HO, consistent with seasonally changing photolysis rates, with maxima in summer and minima in winter is also derived which is comparable but slightly lower than the most recent zonal mean HO estimates of Spivakovs&v et al. [2000]. The calculated annual HO shows a decrease from 2.7 x 10 • molecule cm-'3 in 1997 to 0.8 x l0 s molecule cm-3 in 1998, possibly as a result of E1 Nifio related meteorological changes. The empirically calculated HO correlates with temperature and relative humidity measured at the island but anticorrelates strongly with CO and to a lesser extent with O3. The limitations and improvements to this method are discussed. The method has potential for long-term monitoring of HO changes over areas upwind from remote sites. 1.
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Dates et versions

hal-03117188 , version 1 (21-01-2021)

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J. Williams, V. Gros, B. Bonsang, V. Kazan. HO cycle in 1997 and 1998 over the southern Indian Ocean derived from CO, radon, and hydrocarbon measurements made at Amsterdam Island. Journal of Geophysical Research: Atmospheres, 2001, 106 (D12), pp.12719-12725. ⟨10.1029/2001JD900116⟩. ⟨hal-03117188⟩
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