On the ozone minimum over the equatorial Pacific Ocean

Piotrowicz, Stephen R.; Bezdek, H. F.; Harvey, George R.; Springer-Young, M.; Hanson, Karen L.

doi:10.1029/91jd01809

Cited by 38 publications

(21 citation statements)

References 18 publications

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“…Over biomass burning regions with enhanced lower tropospheric ozone, the TOMS retrieval algorithm underestimates the ozone column by 3–5 DU. Over oceanic regions with ozone‐depleted air, the TOMS retrieval algorithm overestimates the ozone column by 2–5 DU; the largest overestimate occurs over the western Pacific where surface ozone concentrations are typically less than 20 ppbv (Figure 2c) [ Piotrowicz et al , 1991; Oltmans et al , 1998]. Efficiency corrections calculated from the simulation with reduced lightning emissions do not differ significantly from the values presented here.…”

Section: Correction To Toms Retrieval In the Lower Tropospherementioning

confidence: 67%

Interpretation of TOMS observations of tropical tropospheric ozone with a global model and in situ observations

et al. 2002

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[1] We interpret the distribution of tropical tropospheric ozone columns (TTOCs) from the Total Ozone Mapping Spectrometer (TOMS) by using a global three-dimensional model of tropospheric chemistry (GEOS-CHEM) and additional information from in situ observations. The GEOS-CHEM TTOCs capture 44% of the variance of monthly mean TOMS TTOCs from the convective cloud differential method (CCD) with no global bias. Major discrepancies are found over northern Africa and south Asia where the TOMS TTOCs do not capture the seasonal enhancements from biomass burning found in the model and in aircraft observations. A characteristic feature of these northern tropical enhancements, in contrast to southern tropical enhancements, is that they are driven by the lower troposphere where the sensitivity of TOMS is poor due to Rayleigh scattering. We develop an efficiency correction to the TOMS retrieval algorithm that accounts for the variability of ozone in the lower troposphere. This efficiency correction increases TTOCs over biomass burning regions by 3-5 Dobson units (DU) and decreases them by 2-5 DU over oceanic regions, improving the agreement between CCD TTOCs and in situ observations. Applying the correction to CCD TTOCs reduces by $5 DU the magnitude of the ''tropical Atlantic paradox '' [Thompson et al., 2000], i.e. the presence of a TTOC enhancement over the southern tropical Atlantic during the northern African biomass burning season in December-February. We reproduce the remainder of the paradox in the model and explain it by the combination of upper tropospheric ozone production from lightning NO x , persistent subsidence over the southern tropical Atlantic as part of the Walker circulation, and cross-equatorial transport of upper tropospheric ozone from northern midlatitudes in the African ''westerly duct.'' These processes in the model can also account for the observed 13-17 DU persistent wave-1 pattern in TTOCs with a maximum over the tropical Atlantic and a minimum over the tropical Pacific during all seasons. The photochemical effects of mineral dust have only a minor role on the modeled distribution of TTOCs, including over northern Africa, due to multiple competing effects. The photochemical effects of mineral dust globally decrease annual mean OH concentrations by 9%. A global lightning NO x source of 6 Tg N yr À1 in the model produces a simulation that is most consistent with TOMS and in situ observations. INDEX TERMS: 0343 Atmospheric Composition and Structure: Planetary atmospheres (5405, 5407, 5409, 5704, 5705, 5707); 0365 Atmospheric Composition and Structure: Troposphere-composition and chemistry; JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 107, NO. D18, 4351, doi:10.1029/2001JD001480, 2002

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Section: Correction To Toms Retrieval In the Lower Tropospherementioning

confidence: 67%

Interpretation of TOMS observations of tropical tropospheric ozone with a global model and in situ observations

et al. 2002

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“…Thompson and Lenschow [1984] demonstrated that these low NO levels, given the high moisture and solar insolation of the equatorial Pacific (with appreciable production of OH), are consistent with a diurnal cycle of 03 increasing at night and decreasing during daytime. This diurnal pattern of surface 0 3 has been confirmed on a number of oceanographic expeditions in the remote Pacific since the mid-1980s [Piotrowicz et al, 1986[Piotrowicz et al, , 1991Johnson et al, 1990]. …”

Section: Introductionmentioning

confidence: 81%

“…Evidence for this picture of remote marine chemistry has been collected through trace gas measurements on a number of oceanographic cruises. Examples include the 1980 R/V Meteor cruise [Lowe and Schmidt, 1982], the 1987 Polarstern cruise [Rudolph and Johnen, 1990;Platt et al, 1992], and several NOAA/RITS (radiative!y important trace species) cruises [see Piotrowicz et al, 1986Piotrowicz et al, , 1991Johnson et al, 1990]. However, a comprehensive set of photochemically reactive trace gas measurements with sensitive instruments required for low concentrations has not been possible until recently.…”

Section: Introductionmentioning

confidence: 99%

Ozone observations and a model of marine boundary layer photochemistry during SAGA 3

Thompson¹,

Johnson²,

Torres³

et al. 1993

J. Geophys. Res.

119

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A major purpose of the third joint Soviet‐American Gases and Aerosols (SAGA 3) oceanographic cruise was to examine remote tropical marine O3 and photochemical cycles in detail. On leg 1, which took place between Hilo, Hawaii, and Pago‐Pago, American Samoa, in February and March 1990, shipboard measurements were made of O3, CO, CH4, nonmethane hydrocarbons (NMHC), NO, dimethyl sulfide (DMS), H2S, H2O2, organic peroxides, and total column O3. Postcruise analysis was performed for alkyl nitrates and a second set of nonmethane hydrocarbons. A latitudinal gradient in O3 was observed on SAGA 3, with O3 north of the intertropical convergence zone (ITCZ) at 15–20 parts per billion by volume (ppbv) and less than 12 ppbv south of the ITCZ but never ≤3 ppbv as observed on some previous equatorial Pacific cruises (Piotrowicz et al., 1986; Johnson et al., 1990). Total column O3 (230–250 Dobson units (DU)) measured from the Akademik Korolev was within 8% of the corresponding total ozone mapping spectrometer (TOMS) satellite observations and confirmed the equatorial Pacific as a low O3 region. In terms of number of constituents measured, SAGA 3 may be the most photochemically complete at‐sea experiment to date. A one‐dimensional photochemical model gives a self‐consistent picture of O3‐NO‐CO‐hydrocarbon interactions taking place during SAGA 3. At typical equatorial conditions, mean O3 is 10 ppbv with a 10–15% diurnal variation and maximum near sunrise. Measurements of O3, CO, CH4, NMHC, and H2O constrain model‐calculated OH to 9 × 105 cm−3 for 10 ppbv O3 at the equator. For DMS (300–400 parts per trillion by volume (pptv)) this OH abundance requires a sea‐to‐air flux of 6–8 × 109 cm−2 s−1, which is within the uncertainty range of the flux deduced from SAGA 3 measurements of DMS in seawater (Bates et al., this issue). The concentrations of alkyl nitrates on SAGA 3 (5–15 pptv total alkyl nitrates) were up to 6 times higher than expected from currently accepted kinetics, suggesting a largely continental source for these species. However, maxima in isopropyl nitrate and bromoform near the equator (Atlas et al., this issue) as well as for nitric oxide (Torres and Thompson, this issue) may signify photochemical and biological sources of these species.

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“…Net photochemical destruction of ozone over the Pacific (Thompson et al 1993) leads to very low surface ozone (< 5 ppbv). Convective mixing of lowozone surface air can lead to low ozone concentrations aloft (Piotrowicz et al 1991) and a low-tropospheric ozone column.…”

mentioning

confidence: 99%