Analysis of residual mean transport in the stratosphere: 1. Model description and comparison with satellite data

Schneider, Hans R.; Jones, Dylan B. A.; Chen, Xinyu; Shi, Guangyu

doi:10.1029/2000jd900213

Cited by 23 publications

(24 citation statements)

References 36 publications

(9 reference statements)

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“…This is within the range constrained by the methylchloroform observations, which imply a 25% uncertainty in global mean OH concentrations [ Intergovernmental Panel on Climate Change ( IPCC ), 2001]. Stratospheric loss of methanol is computed using OH concentrations archived from a global 2‐D stratospheric chemistry model [ Schneider et al , 2000] and amounts to only 2% of the loss in the troposphere. Our computed lifetime of methanol against oxidation by OH is 11 days.…”

Section: Model Descriptionmentioning

confidence: 86%

Global budget of methanol: Constraints from atmospheric observations

et al. 2005

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[1] We use a global three-dimensional model simulation of atmospheric methanol to examine the consistency between observed atmospheric concentrations and current understanding of sources and sinks. Global sources in the model include 128 Tg yr À1 from plant growth, 38 Tg yr À1 from atmospheric reactions of CH 3 O 2 with itself and other organic peroxy radicals, 23 Tg yr À1 from plant decay, 13 Tg yr À1 from biomass burning and biofuels, and 4 Tg yr À1 from vehicles and industry. The plant growth source is a factor of 3 higher for young than from mature leaves. The atmospheric lifetime of methanol in the model is 7 days; gas-phase oxidation by OH accounts for 63% of the global sink, dry deposition to land 26%, wet deposition 6%, uptake by the ocean 5%, and aqueous-phase oxidation in clouds less than 1%. The resulting simulation of atmospheric concentrations is generally unbiased in the Northern Hemisphere and reproduces the observed correlations of methanol with acetone, HCN, and CO in Asian outflow. Accounting for decreasing emission from leaves as they age is necessary to reproduce the observed seasonal variation of methanol concentrations at northern midlatitudes. The main model discrepancy is over the South Pacific, where simulated concentrations are a factor of 2 too low. Atmospheric production from the CH 3 O 2 self-reaction is the dominant model source in this region. A factor of 2 increase in this source (to 50-100 Tg yr À1 ) would largely correct the discrepancy and appears consistent with independent constraints on CH 3 O 2 concentrations. Our resulting best estimate of the global source of methanol is 240 Tg yr À1. More observations of methanol concentrations and fluxes are needed over tropical continents. Better knowledge is needed of CH 3 O 2 concentrations in the remote troposphere and of the underlying organic chemistry.

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Section: Model Descriptionmentioning

confidence: 86%

Global budget of methanol: Constraints from atmospheric observations

et al. 2005

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“…For simulation years before December 1995, the model has 20 vertical levels, for December 1995, 1996 and 1997, 26 levels, and for 2000 and 2001, 48 levels. To calculate the chemical loss of CH 3 Cl, the tropospheric OH field was taken from the GEOS‐CHEM full‐chemistry simulation by Martin et al [2003] and the stratospheric OH field taken from a 2‐D stratosphere/mesosphere model was used [ Schneider et al , 2000]. The tropospheric OH field yields a global mean methyl chloroform (CH 3 CCl 3 ) lifetime of 5.6 years in good agreement with the observations [ Spivakovsky et al , 2000; Prinn et al , 2001; Martin et al , 2003].…”

Section: Model Descriptionmentioning

confidence: 92%

A three‐dimensional global model study of atmospheric methyl chloride budget and distributions

et al. 2004

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[1] Global simulations of atmospheric methyl chloride (CH 3 Cl) are conducted using the GEOS-CHEM model in order to understand better its sources and sinks. Observations from 7 surface sites and 9 aircraft field experiments are used to evaluate the model simulations with assimilated meteorology fields for 7 years. The model simulates CH 3 Cl observations at northern mid and high latitudes reasonably well. The seasonal variation of CH 3 Cl at southern mid and high latitudes is severely overestimated, however. Simulated vertical profiles of CH 3 Cl are in general agreement with the observations in most regions; the disagreement occurs in the vicinities of major sources, principally reflecting the uncertainties in the estimated distributions of our added pseudobiogenic and the biomass burning sources. Our estimate of known sources (1.5 Tg yr À1 ) from ocean, biomass burning, incineration/industry, salt marshes, and wetlands accounts for only 34% of the total source (4.4 Tg yr À1 ). We hypothesize that the missing source of 2.9 Tg yr À1 is likely of biogenic origin. On the basis of the observed CH 3 Cl seasonality at northern mid and high latitudes, we find that this pseudobiogenic source is located at 30°N-30°S, not at mid and high latitudes. If so, the observed CH 3 Cl latitudinal distribution indicates that the annual hemispheric mean OH ratio is within the range of 0.8-1.3. The net uptake regions by ocean are located at high latitudes. A relatively small loss of 150 Gg yr À1 over these regions is critical for the model to reproduce the observed annual mean latitudinal gradient of CH 3 Cl in the southern hemisphere. The large overestimate of the seasonal variation of CH 3 Cl at southern mid and high latitudes likely implies that the seasonality of simulated oceanic uptake is incorrect as a result of defects in the parameterization of this loss in the model.

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“…The parameterized chemistry decreases the model run time as compared to the kinetic solver used by Bey et al [2001a] by over a factor of 10, allowing us to perform sensitivity studies with decade‐long simulations. Removal of CO by OH in the stratosphere is calculated using loss frequencies from a 2‐d stratospheric model [ Schneider et al , 2000; D. Jones, personal communication, 2000]; the production rate of CO from CH 4 oxidation in the stratosphere is taken from the same model. About 3% of CO loss occurs in the stratosphere.…”

Section: Model Frameworkmentioning

confidence: 99%

Global budget of CO, 1988–1997: Source estimates and validation with a global model

Duncan¹,

Logan²,

Bey³

et al. 2007

J. Geophys. Res.

353

486

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[1] We present a model study of carbon monoxide for 1988-1997 using the GEOS-Chem 3-D model driven by assimilated meteorological data, with time-varying emissions from biomass burning and from fossil fuel and industry, overhead ozone columns, and methane. The hydroxyl radical is calculated interactively using a chemical parameterization to capture chemical feedbacks. We document the inventory for fossil fuels/industry and discuss major uncertainties and the causes of differences with other inventories that give significantly lower emissions. We find that emissions hardly change from 1988 to 1997, as increases in Asia are offset by decreases elsewhere. The model reproduces the 20% decrease in CO at high northern latitudes and the 10% decrease in the North Pacific, caused primarily by the decrease in European emissions. The model compares well with observations at sites impacted by fossil fuel emissions from North America, Europe, and east Asia suggesting that the emissions from this source are reliable to 25%, and we argue that bottom-up emission estimates are likely to be too low rather than too high. The model is too low at the seasonal maximum in spring in the southern tropics, except for locations in the Atlantic Ocean. This problem may be caused by an overestimate of the frequency of tropical deep convection, a common problem in models that use assimilated meteorological data. We argue that the yield of CO from methane oxidation is near unity, contrary to some other studies, based on removal rates of intermediate species.

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Analysis of residual mean transport in the stratosphere: 1. Model description and comparison with satellite data

Abstract: Abstract. A coupled two-dimensional model of the dynamics, chemistry, and radiation of the stratosphere is described. The effects of Rossby wave mixing are parameterized by externally specified coefficients Kyy, which are used consistently

Cited by 23 publications

References 36 publications

Global budget of methanol: Constraints from atmospheric observations

Global budget of methanol: Constraints from atmospheric observations

A three‐dimensional global model study of atmospheric methyl chloride budget and distributions

Global budget of CO, 1988–1997: Source estimates and validation with a global model

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