Results from the Intergovernmental Panel on Climatic Change Photochemical Model Intercomparison (PhotoComp) (original) (raw)
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Journal of Geophysical Research, 1999
A model of atmospheric photochemistry and transport has been developed and applied toward investigating global tropospheric chemistry. The Model of Atmospheric Transport and Chemistry - Max-Planck-Institute for Chemistry version (MATCH-MPIC) is described and key characteristics of its global simulation are presented and compared to available observations. MATCH-MPIC is an "offline" model which reads in gridded time-dependent values for the most basic meteorological parameters (e.g., temperature, surface pressure, horizontal winds), then uses these to compute further meteorological parameters required for atmospheric chemistry simulations (convective transport, cloud microphysics, etc.). The meteorology component of MATCH-MPIC simulates transport by advection, convection, and dry turbulent mixing, as well as the full tropospheric hydrological cycle (water vapor transport, condensation, evaporation, and precipitation). The photochemistry component of MATCH-MPIC represents the major known sources (e.g., industry, biomass burning), transformations (chemical reactions and photolysis), and sinks (e.g., wet and dry deposition) which affect the O3hyphen;HOx-NOy-CH4-CO photochemical framework of the "background" troposphere. The results of two versions of the model are considered, focusing on the more recent version. O3 is in relatively good agreement with observed soundings, although it is generally underestimated at low levels and overestimated at high levels, particularly for the more recent version of the model. We conclude that the simulated stratosphere-troposphere flux of O3 is too large, despite the fact that the total flux is 1100 Tg(O3)/yr, whereas the upper limit estimated in recent literature is over 1400 Tg(O3)/yr. The OH distribution yields a tropospheric CH4 lifetime of 10.1 years, in contrast to the lifetime of 7.8 years in the earlier model version, which nearly spans the range of current estimates in the literature (7.5-10.2 years). Surface CO mixing ratios are in good agreement with observations. NO is generally underestimated, a problem similar to what has also been found in several other recent model studies. HNO3 is also considerably underestimated. H2O2 and CH3OOH, on the other hand, are in relatively good agreement with available observations, though both tend to be underestimated at high concentrations and overestimated at low concentrations. Possible reasons for these differences are considered.
Quantifying the causes of differences in tropospheric OH within global models
Journal of Geophysical Research: Atmospheres
- Factors responsible for OH and CH 4 lifetime differences between eight models are quantified using neural networks 2) O 3 , the photolysis frequency (J) of O 3 O( 1 D), CO, and chemical mechanism differences are main drivers of OH variations 3) H 2 O & NO x differences drive moderate OH variation on regional scale; isoprene & J(NO 2 ) differences have small role in driving OH variations warming potential (GWP) of this compound [Table TS.2, IPCC, 2013]. Furthermore, models disagree on how CH4 will evolve over the next century due to variations in atmospheric composition. found a multi-model mean change in CH4 of +8.5±10.4% between year 2000 and 2100, for simulations conducted using 14 models driven by the Representative Concentration Pathway (RCP) 8.5 greenhouse gas emissions scenario.
Atmospheric Chemistry and Physics Discussions, 2006
We present a systematic comparison of tropospheric NO 2 from 17 global atmospheric chemistry models with three state-of-the-art retrievals from the Global Ozone Monitoring Experiment (GOME) for the year 2000. The models used constant anthropogenic emissions from IIASA/EDGAR3.2 and monthly emissions from biomass burning based 5 20 over eastern China and over the Highveld region of South Africa, and overestimate the retrievals in regions dominated by biomass burning during the dry season. The discrepancy over South America south of the Amazon disappears when we use the GFED emissions specific to the year 2000. The seasonal cycle is analyzed in detail for eight different continental regions. Over regions dominated by biomass burning, 25 the timing of the seasonal cycle is generally well reproduced by the models. However, over Central Africa south of the Equator the models peak one to two months earlier than the retrievals. We further evaluate a recent proposal to reduce the NO x emission 2967 ACPD Abstract Introduction Conclusions References Tables Figures Back Close Full Screen / Esc Printer-friendly Version Interactive Discussion
Measurements of tropospheric OH concentrations: A comparison of field data with model predictions
Journal of Atmospheric Chemistry, 1987
Using long path UV absorption spectroscopy we have measured OH concentrations close to the earth's surface. The OH values observed at two locations in Germany during 1980 through 1983 range from 0.7 x 1()6 to 3.2 x 10" cm-3 • Simultaneously we measured the concentrations of 03, H20, NO, N02, CH 4 , CO, and the light non methane hydrocarbons. We also determined the photolysis rates of 0 3 and N0 2 • This allows calculations of OH using a zero dimensional time dependent model. The modelled OH concentrations significantly exceed the measured values for low NO," concentrations. It is argued that additional, so far unidentified, HO x loss reactions must be responsible for that discrepancy.
An updated tropospheric chemistry reanalysis and emission estimates, TCR-2, for 2005–2018
2020
This study presents the results from the Tropospheric Chemistry Reanalysis version 2 (TCR-2) for the period 2005-2018 at 1.1 • horizontal resolution obtained from the assimilation of multiple updated satellite measurements of ozone, CO, NO 2 , HNO 3 , and SO 2 from the OMI, SCIAMACHY, GOME-2, TES, MLS, and MOPITT satellite instruments. The reanalysis calculation was conducted using a global chemical transport model MIROC-CHASER and an ensemble Kalman filter technique that optimizes both chemical concentrations of various species and emissions of several precursors, which was efficient for the correction of the entire tropospheric profile of various species and its year-to-year variations. Comparisons against independent aircraft, satellite, and ozonesonde observations demonstrate the quality of the reanalysis fields for numerous key species on regional and global scales, as well as for seasonal, yearly, and decadal scales, from the surface to the lower stratosphere. The multi-constituent data assimilation brought the model vertical profiles and interhemispheric gradient of OH closer to observational estimates, which was important in improving the description of the oxidation capacity of the atmosphere and thus vertical profiles of various species. The evaluation results demonstrate the capability of the chemical reanalysis to improve understanding of the processes controlling variations in atmospheric composition, including long-term changes in near-surface air quality and emissions. The estimated emissions can be employed for the elucidation of detailed distributions of the anthropogenic and biomass burning emissions of co-emitted species (NO x , CO, SO 2) in all major regions, as well as their seasonal and decadal variabilities. The data sets are available at https://doi.org/10.25966/9qgv-fe81 (Miyazaki et al., 2019a).
Journal of Geophysical Research, 1995
We present results of global tropospheric chemistry simulations with the coupled chemistry/atmospheric general circulation model ECHAM. Ultimately, the model will be used to study climate changes induced by anthropogenic influences on the chemistry of the atmosphere; meteorological parameters that are important for the chemistry, such as temperature, humidity, air motions, cloud and rain characteristics, and mixing processes are calculated on-line. The chemical part of the model describes background tropospheric CH4-CO-NOx-HOx photochemistry. Emissions of NO and CO, surface concentrations of CH4, and stratospheric concentrations of 03 and NOy are prescribed as boundary conditions. Calculations of the tropospheric 03 budget indicate that seasonal variabilities of the photochemical production and of injection from the stratosphere are represented realistically, although some aspects of the model still need improvement. Comparisons of calculated 03 surface concentrations and 03 profiles with available measurements show that the model reproduces 03 distributions in remote tropical and midlatitudinal sites. Also, the model matches typical profiles connected with deep convection in the Intertropical Convergence Zone (ITCZ). However, the model tends to underestimate 0 3 concentrations at the poles and in relatively polluted regions. These underestimates are caused by the poor representation of tropopause foldings in midlatitudes, which form a significant source of tropospheric 03 from the stratosphere, too weak transport to the poles, and the neglect of higher hydrocarbon chemistry. Also, mixing of polluted continental boundary layer air into the free troposphere may be underestimated. We discuss how these model deficiencies will be improved in the future. 20,983 20,984 ROELOFS AND LELIEVELD: TROPOSPHERIC O3 IN A CHEMISTRY GCM Institute for Meteorology in Hamburg, Germany [Roeckner et al. , 1992]. All meteorological data needed to evaluate chemical tracer concentrations in the atmosphere are calculated on-line by ECHAM with a time resolution of 40 min. As a result of the meteorology calculations, more CPU time is required than with an off-line model with the same spatial resolution and chemistry. In our model the calculations associated with chemical species (i.e., the processes described in section 2 and transport in the atmosphere) need approximately the same amount of CPU time as the meteorology calculations. However, the use of an off-line model requires substantial CPU time and memory to read and store data for the calculation of transport and the complex interactions between meteorological and chemical processes, whereas a large amount of data may be needed to cover different model resolutions. Further, a chemistry GCM interactively calculates concentrations of radiatively active species such as 03 that directly drive the radiation scheme and the GCM meteorology. When fully developed and tested, a coupled chemistry GCM is a powerful tool in the study of the intricate interactions between atmospheric chemistry and global climate.
MODELLED OZONE BIAS NEAR THE STRATOPAUSE USING ESA CCI OZONE DATA
Photochemical models are known to underestimate the ozone in the upper stratosphere and lower mesosphere (USLM), i.e. above 45 km of altitude. In the present study, we evaluate this issue within the state-of-the-art BASCOE model. A reference BASCOE model underestimates the ozone in USLM by 30-50%. First, we dicuss the impact of the vertical model grid and the corresponding temperature forcing. Second, we investigate the impact on ozone of the gas-phase chemical reaction rates and photo-dissociation cross-sections of the latest Jet Propulson Laboratory (JPL) recommendations published in 2011. Third, methods of computing the photodissociation rates (J-tables) are evaluated. Fourth, a sensitivity test to the solar irradiance spectrum is performed. Finally, the impact of the temperature field on the modeled ozone is studied. To this end, we compare the temperature field used in our model with temperature profiles provided by limb and occultation satellite data. The results of our experiments are evaluated using the ESA CCI level 2 ozone data as well as MLS, MIPAS and ACE-FTS to document the ozone underestimation issue. As a result, the BASCOE model provides essentially less biased ozone in the USLM. The mean model bias decreases to 0 -15%.
Why are there large differences between models in global budgets of tropospheric ozone?
Journal of Geophysical Research, 2007
Global 3-D tropospheric chemistry models in the literature show large differences in global budget terms for tropospheric ozone. The ozone production rate in the troposphere, P(O x ), varies from 2300 to 5300 Tg yr -1 across models describing the present-day atmosphere. The ensemble mean of P(O x ) in models from the post-2000 literature is 35% higher than that compiled in the Intergovernmental Panel on Climate Change (IPCC) Third Assessment Report (TAR). Simulations conducted with the GEOS-Chem model using two different assimilated meteorological data sets for 2001 (GEOS-3 and GEOS-4), as well as 3 years of GISS GCM meteorology, show P(O x ) values in the range 4250 -4700 Tg yr -1 ; the differences appear mostly due to clouds. Examination of the evolution of P(O x ) over the GEOS-Chem model history shows major effects from changes in heterogeneous chemistry, the lightning NO x source, and the yield of organic nitrates from isoprene oxidation. Multivariate statistical analysis of model budgets in the literature indicates that 74% of the variance in P(O x ) across models can be explained by differences in NO x emissions, inclusion of non-methane volatile organic compounds (NMVOCs, mostly biogenic isoprene), and ozone influx from stratosphere-troposphere exchange (STE).