A new fast stratospheric ozone chemistry scheme in an intermediate general-circulation model. II: Application to effects of future increases in greenhouse gases

2005 ◽  
Vol 131 (610) ◽  
pp. 2243-2261 ◽  
Author(s):  
M. S. Bourqui ◽  
C. P. Taylor ◽  
K. P. Shine
Keyword(s):  
Greenhouse Gases ◽  
General Circulation Model ◽  
General Circulation ◽  
Stratospheric Ozone ◽  
Circulation Model

Regional Tropical Precipitation Change Mechanisms in ECHAM4/OPYC3 under Global Warming*

2006 ◽  
Vol 19 (17) ◽  
pp. 4207-4223 ◽  
Author(s):  
Chia Chou ◽  
J. David Neelin ◽  
Jien-Yi Tu ◽  
Cheng-Ta Chen
Keyword(s):  
Global Warming ◽  
Greenhouse Gases ◽  
General Circulation Model ◽  
General Circulation ◽  
Vertical Motion ◽  
Circulation Model ◽  
Ocean General Circulation Model ◽  
Additional Contribution ◽  
Tropical Precipitation ◽  
Precipitation Anomalies

Abstract Mechanisms of global warming impacts on regional tropical precipitation are examined in a coupled atmosphere–ocean general circulation model (ECHAM4/OPYC3). The pattern of the regional tropical precipitation changes, once established, tends to persist, growing in magnitude as greenhouse gases increase. The sulfate aerosol induces regional tropical precipitation anomalies similar to the greenhouse gases but with opposite sign, thus reducing the early signal. Evidence for two main mechanisms, the upped-ante and the anomalous gross moist stability (M′) mechanisms (previously proposed in an intermediate complexity model), is found in this more comprehensive coupled general circulation model. Preferential moisture increase occurs in convection zones. The upped-ante mechanism signature of dry advection from nonconvective regions is found in tropical drought regions on the margins of convection zones. Here advection in both the atmospheric boundary layer and lower free troposphere are found to be important, with an additional contribution from horizontal temperature transport in some locations. The signature of the M′ mechanism—moisture convergence due to increased moisture in regions of large mean vertical motion—enhances precipitation within strong convective regions. Ocean dynamical feedbacks can be assessed by net surface flux, the main example being the El Niño–like shift of the equatorial Pacific convection zone. Cloud–radiative feedbacks are found to oppose precipitation anomalies over ocean regions.

scholarly journals Development of the global atmospheric chemistry general circulation model BCC-GEOS-Chem v1.0: model description and evaluation

2020 ◽  
Vol 13 (9) ◽  
pp. 3817-3838
Author(s):  
Xiao Lu ◽  
Lin Zhang ◽  
Tongwen Wu ◽  
Michael S. Long ◽  
Jun Wang ◽  
...  
Keyword(s):  
General Circulation Model ◽  
Atmospheric Chemistry ◽  
Tropospheric Ozone ◽  
General Circulation ◽  
Climate Models ◽  
Transport Model ◽  
Stratospheric Ozone ◽  
Circulation Model ◽  
Satellite Observations ◽  
Model Description

Abstract. Chemistry plays an indispensable role in investigations of the atmosphere; however, many climate models either ignore or greatly simplify atmospheric chemistry, limiting both their accuracy and their scope. We present the development and evaluation of the online global atmospheric chemical model BCC-GEOS-Chem v1.0, coupling the GEOS-Chem chemical transport model (CTM) as an atmospheric chemistry component in the Beijing Climate Center atmospheric general circulation model (BCC-AGCM). The GEOS-Chem atmospheric chemistry component includes detailed tropospheric HOx–NOx–volatile organic compounds–ozone–bromine–aerosol chemistry and online dry and wet deposition schemes. We then demonstrate the new capabilities of BCC-GEOS-Chem v1.0 relative to the base BCC-AGCM model through a 3-year (2012–2014) simulation with anthropogenic emissions from the Community Emissions Data System (CEDS) used in the Coupled Model Intercomparison Project Phase 6 (CMIP6). The model captures well the spatial distributions and seasonal variations in tropospheric ozone, with seasonal mean biases of 0.4–2.2 ppbv at 700–400 hPa compared to satellite observations and within 10 ppbv at the surface to 500 hPa compared to global ozonesonde observations. The model has larger high-ozone biases over the tropics which we attribute to an overestimate of ozone chemical production. It underestimates ozone in the upper troposphere which is likely due either to the use of a simplified stratospheric ozone scheme or to biases in estimated stratosphere–troposphere exchange dynamics. The model diagnoses the global tropospheric ozone burden, OH concentration, and methane chemical lifetime to be 336 Tg, 1.16×106 molecule cm−3, and 8.3 years, respectively, which is consistent with recent multimodel assessments. The spatiotemporal distributions of NO2, CO, SO2, CH2O, and aerosol optical depth are generally in agreement with satellite observations. The development of BCC-GEOS-Chem v1.0 represents an important step for the development of fully coupled earth system models (ESMs) in China.

Forest fires in Russia: carbon dioxide emissions to the atmosphere

1993 ◽  
Vol 23 (4) ◽  
pp. 700-705 ◽  
Author(s):  
Robert K. Dixon ◽  
Olga N. Krankina
Keyword(s):  
Greenhouse Gases ◽  
General Circulation Model ◽  
Forest Fire ◽  
Forest Fires ◽  
General Circulation ◽  
Vegetation Change ◽  
Circulation Model ◽  
Fire Control ◽  
Fire Emissions ◽  
Biogenic Carbon

Boreal forests of Russia play a prominent role in the global carbon cycle and the flux of greenhouse gases to the atmosphere. Large areas of Russian forest burn annually, and contributions to the net flux of carbon to the atmosphere may be significant. Forest fire emissions were calculated for the years 1971–1991 using fire frequency and distribution data and fuel and carbon density for different forest ecoregions of Russia. Both direct carbon release and indirect post-fire biogenic carbon flux were estimated. From 1971 to 1991 the annual total forest area burned by wildfire ranged from 1.41 × 106 to 10.0 × 106 ha. Approximately 15 000–25 000 forest fires occurred annually during this period. Mean annual direct CO2-C emissions from wildfire was approximately 0.05 Pg over this 21-year period. Total post-fire biogenic CO2-C emissions for 1971–1991 ranged from 2.5 to 5.9 Pg (0.12–0.28 Pg annually). Forest fires and other disturbances are expected to be a primary mechanism driving vegetation change associated with projected global climate change. Future forest fire scenarios in Russia based on general circulation model projections suggest that up to 30–50% of the land surface area, or 334 × 106 to 631 × 106 ha of forest, will be affected. An additional 6.7 × 106 to 12.6 × 106 ha of Russian boreal forest are projected to burn annually if general circulation model based vegetation-change scenarios are achieved within the next 50 years. The direct flux of CO2-C from future forest fires is estimated to total 6.1–10.7 Pg over a 50-year period. Indirect post-fire biogenic release of greenhouse gases in the future is expected to be two to six times greater than direct emissions. Forest management and fire-control activities may help reduce wildfire severity and mitigate the associated pulse of greenhouse gases into the atmosphere.

Assimilation of stratospheric ozone from MIPAS into a global general-circulation model: The September 2002 vortex split

2006 ◽  
Vol 132 (614) ◽  
pp. 231-257 ◽  
Author(s):  
A. J. Geer ◽  
C. Peubey ◽  
R. N. Bannister ◽  
R. Brugge ◽  
D. R. Jackson ◽  
...  
Keyword(s):  
General Circulation Model ◽  
General Circulation ◽  
Stratospheric Ozone ◽  
Circulation Model ◽  
Vortex Split

Numerical model studies of the effect of injected nitrogen oxides on stratospheric ozone

1977 ◽  
Vol 355 (1681) ◽  
pp. 267-299 ◽  
Keyword(s):  
Nitrogen Oxides ◽  
General Circulation Model ◽  
General Circulation ◽  
Stratospheric Ozone ◽  
Three Dimensional ◽  
Circulation Model ◽  
Reaction Rates ◽  
Transport Processes ◽  
One Dimensional ◽  
Dimensional Models

The work reported here has employed one-dimensional models, in which atmospheric transport is represented in combination with chemical kinetic mechanisms, to compute average vertical distributions of the minor constituents of the stratosphere as a function of time. Perturbation experiments simulating the effects of exhaust emissions, particularly nitrogen oxides and water vapour, from supersonic and subsonic aircraft fleets have been performed. The effect on stratospheric ozone of a possible four year variation in tropospheric N 2 O levels from 1966 to 1969 has also been investigated. Inert tracer studies from a three-dimensional tropospheric and stratospheric general circulation model have been used to examine specific limitations of the representation of transport processes in one-dimensional models. The inability of current one-dimensional models to represent counter gradient transport of minor gaseous constituents by the mean global circulation is a serious shortcoming in their use for studies of this type; the importance of mean motions in the general circulation is demonstrated by diagnostic data from a three-dimensional general circulation model, and by reference to the production of nitrogen oxides in thunderstorms. Further subjects studied were the effects on the calculated ozone reductions of using different profiles of vertical eddy diffusivity, diurnal and seasonal time dependence of the solar zenith angle in the photochemistry and temperature dependence of the chemical reaction rates. It was also found that the effects of injections from the supersonic and subsonic fleets were not linearly additive in the one-dimensional diffusive models used in this study. The optimum latitude at which to operate a one-dimensional model is discussed; for injected species with long atmospheric lifetimes a value of 34° is recommended for the Northern Hemisphere.

scholarly journals Results of an interactively coupled atmospheric chemistry – general circulation model: Comparison with observations

2001 ◽  
Vol 19 (4) ◽  
pp. 435-457 ◽  
Author(s):  
R. Hein ◽  
M. Dameris ◽  
C. Schnadt ◽  
C. Land ◽  
V. Grewe ◽  
...  
Keyword(s):  
General Circulation Model ◽  
Atmospheric Chemistry ◽  
General Circulation ◽  
Middle Atmosphere ◽  
Stratospheric Ozone ◽  
Circulation Model ◽  
Ozone Layer ◽  
The Arctic ◽  
Time Step ◽  
Stratospheric Dynamics

Abstract. The coupled climate-chemistry model ECHAM4.L39(DLR)/CHEM is presented which enables a simultaneous treatment of meteorology and atmospheric chemistry and their feedbacks. This is the first model which interactively combines a general circulation model with a chemical model, employing most of the important reactions and species necessary to describe the stratospheric and upper tropospheric ozone chemistry, and which is computationally fast enough to allow long-term integrations with currently available computer resources. This is possible as the model time-step used for the chemistry can be chosen as large as the integration time-step for the dynamics. Vertically the atmosphere is discretized by 39 levels from the surface up to the top layer which is centred at 10 hPa, with a relatively high vertical resolution of approximately 700 m near the extra-tropical tropopause. We present the results of a control simulation representing recent conditions (1990) and compare it to available observations. The focus is on investigations of stratospheric dynamics and chemistry relevant to describe the stratospheric ozone layer. ECHAM4.L39(DLR)/CHEM reproduces main features of stratospheric dynamics in the arctic vortex region, including stratospheric warming events. This constitutes a major improvement compared to earlier model versions. However, apparent shortcomings in Antarctic circulation and temperatures persist. The seasonal and interannual variability of the ozone layer is simulated in accordance with observations. Activation and deactivation of chlorine in the polar stratospheric vortices and their inter-hemispheric differences are reproduced. Considering methane oxidation as part of the dynamic-chemistry feedback results in an improved representation of the spatial distribution of stratospheric water vapour concentrations. The current model constitutes a powerful tool to investigate, for instance, the combined direct and indirect effects of anthropogenic trace gas emissions.Key words. Atmospheric composition and structure (middle atmosphere – composition and chemistry) – Meteorology and atmospheric dynamics (general circulation; middle atmosphere dynamics)

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