Stratospheric trace constituents simulated by a three-dimensional general circulation model: Comparison with UARS data (original) (raw)
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Journal of Geophysical Research, 1999
A new middle-atmosphere general circulation model that includes the photochemistry for ozone and other chemical species (19 photolysis and 52 chemical reactions) has been constructed. The horizontal spectral resolution is T21 (about a 600 km horizontal grid spacing) with 30 layers in the vertical. Preliminary results from over 10 years of model integration are presented. The distributions of longlived species, such as N20, are rather similar to those of satellite observations in a climatological sense, although the sharp meridional gradient around 30 ø latitude is not well simulated in the model stratosphere. Neither is the double peak structure that occurs during equinox periods well reproduced. This result is consistent with the fact that the westerly phase of the semiannual oscillation is weak in this model. This may be due to the coarse resolution of the model. The seasonal evolution of the ozone column abundance is quite realistic, although the model slightly underestimates total tropical ozone. The model also underestimates ozone amounts around the equatorial tropopause. The February midlatitude number density of OH in the model upper stratosphere is about 1.8 x 107 cm -3, which is slightly less than that observed. The horizontal distributions of short-lived species, such as NO, suggest a reasonable model diurnal variation. The model has a cold bias of about 25 K in the lower stratospheric Northern Hemisphere winter and 5 K in the Southern Hemisphere winter. The model residual mean vertical velocity in the equatorial lower stratosphere is too weak (about 0.1 mm/s) during the Northern Hemisphere winter, compared with the observed (about 0.4 mm/s), while the model temperature around the equatorial tropopause is cooler than that observed.
A domain-filling, forward trajectory model originally developed for simulating stratospheric water vapor is used to simulate ozone (O 3 ) and carbon monoxide (CO) in the upper troposphere and lower stratosphere (UTLS). Trajectories are initialized in the upper troposphere, and the circulation is based on reanalysis wind fields. In addi-5 tion, chemical production and loss rates along trajectories are included using calculations from the Whole Atmosphere Community Climate Model (WACCM). The trajectory model results show good overall agreement with satellite observations from the Aura Microwave Limb Sounder (MLS) and the Atmospheric Chemistry Experiment Fourier Transform Spectrometer (ACE-FTS) in terms of spatial structure and seasonal variabil-10 ity. The trajectory model results also agree well with the Eulerian WACCM simulations. Analysis of the simulated tracers shows that seasonal variations in tropical upwelling exerts strong influence on O 3 and CO in the tropical lower stratosphere, and the coupled seasonal cycles provide a useful test of the transport simulations. Interannual variations in the tracers are also closely coupled to changes in upwelling, and the 15 trajectory model can accurately capture and explain observed changes during 2005-2011. This demonstrates the importance of variability in tropical upwelling in forcing chemical changes in the tropical UTLS. 25 1998; Wang and Dessler, 2012) all support this understanding. Back trajectory models 5992 ACPD 14, 5991-6025, 2014
Journal of Geophysical Research, 2010
1] The goal of the Chemistry-Climate Model Validation (CCMVal) activity is to improve understanding of chemistry-climate models (CCMs) through process-oriented evaluation and to provide reliable projections of stratospheric ozone and its impact on climate. An appreciation of the details of model formulations is essential for understanding how models respond to the changing external forcings of greenhouse gases and ozonedepleting substances, and hence for understanding the ozone and climate forecasts produced by the models participating in this activity. Here we introduce and review the models used for the second round (CCMVal-2) of this intercomparison, regarding the implementation of chemical, transport, radiative, and dynamical processes in these models. In particular, we review the advantages and problems associated with approaches used to model processes of relevance to stratospheric dynamics and chemistry. Furthermore, we state the definitions of the reference simulations performed, and describe the forcing data used in these simulations. We identify some developments in chemistry-climate modeling that make models more physically based or more comprehensive, including the introduction of an interactive ocean, online photolysis, troposphere-stratosphere chemistry, and non-orographic gravity-wave deposition as linked to tropospheric convection. The relatively new developments indicate that stratospheric CCM modeling is becoming more consistent with our physically based understanding of the atmosphere. Citation: Morgenstern, O., et al. (2010), Review of the formulation of present-generation stratospheric chemistry-climate models and associated external forcings,
Atmospheric Chemistry and Physics, 2006
The new Modular Earth Submodel System (MESSy) describes atmospheric chemistry and meteorological processes in a modular framework, following strict coding standards. It has been coupled to the ECHAM5 general circulation model, which has been slightly modified for this purpose. A 90-layer model version up to 0.01 hPa was used 5 at T42 resolution (≈2.8 • latitude and longitude) to simulate the lower and middle atmosphere. The model meteorology has been tested to check the influence of the changes to ECHAM5 and the radiation interactions with the new representation of atmospheric composition. A Newtonian relaxation technique was applied in the tropospheric part of the domain to weakly nudge the model towards the analysed meteorology during the 10 period 1998-2005. It is shown that the tropospheric wave forcing of the stratosphere in the model suffices to reproduce the Quasi-Biennial Oscillation and major stratospheric warming events leading e.g. to the vortex split over Antarctica in 2002. Characteristic features such as dehydration and denitrification caused by the sedimentation of polar stratospheric cloud particles and ozone depletion during winter and spring are 15 simulated accurately, although ozone loss in the lower polar stratosphere is slightly underestimated. The model realistically simulates stratosphere-troposphere exchange processes as indicated by comparisons with satellite and in situ measurements. The evaluation of tropospheric chemistry presented here focuses on the distributions of ozone, hydroxyl radicals, carbon monoxide and reactive nitrogen compounds. In spite 20 of minor shortcomings, mostly related to the relatively coarse T42 resolution and the neglect of interannual changes in biomass burning emissions, the main characteristics of the trace gas distributions are generally reproduced well. The MESSy submodels and the ECHAM5/MESSy1 model output are available through the internet on request. 6, 2006 EGU 20 5th generation European Centre Hamburg GCM, ECHAM5 (Roeckner et al., 2003. We pursue a rigorous modularisation and apply coding standards to face the challenges associated with increasing model complexity . The resulting Modular Earth Submodel System (MESSy) is portable, user-friendly and flexible, well-documented and easily expandable (see http://www.messy-interface.org).
Trajectory model simulations of ozone (O 3) and carbon monoxide (CO) in the lower stratosphere
A domain-filling, forward trajectory model originally developed for simulating stratospheric water vapor is used to simulate ozone (O 3 ) and carbon monoxide (CO) in the lower stratosphere. Trajectories are initialized in the upper troposphere, and the circulation is based on reanalysis wind fields. In addition, chemical production and loss rates along trajectories are included using calculations from the Whole Atmosphere Community Climate Model (WACCM). The trajectory model results show good overall agreement with satellite observations from the Aura Microwave Limb Sounder (MLS) and the Atmospheric Chemistry Experiment Fourier Transform Spectrometer (ACE-FTS) in terms of spatial structure and seasonal variability. The trajectory model results also agree well with the Eulerian WACCM simulations. Analysis of the simulated tracers shows that seasonal variations in tropical upwelling exerts strong influence on O 3 and CO in the tropical lower stratosphere, and the coupled seasonal cycles provide a useful test of the transport simulations. Interannual variations in the tracers are also closely coupled to changes in upwelling, and the trajectory model can accurately capture and explain observed changes during 2005-2011. This demonstrates the importance of variability in tropical upwelling in forcing chemical changes in the tropical lower stratosphere.
C HAPTE R 6 Model Simulations of Stratospheric Ozone
2012
Model Simulations of Stratospheric Ozone Multi-dimensional models are designed to provide simulations of the large-scale transport in the stratosphere. This transport rate is combined with the local chemical production and removal rates of ozone to determine the distribution of ozone as a fu nction of longitude, latitude, height, and season. • There is strong observational evidence that heterogeneous chemistry (hydrolysis of N20s and ClON02) is oper ating on surfaces of the aerosol particles in the stratospheric sulfate layer. There is a general agreement on how this should be represented in the models. Models that include these reactions produce calculated ozone decreases (between 1980 and 1990) that are larger and in better agreement with the observed trend than those produced by models that include only gas-phase reactions. All model simulations reported here include these two reactions.
Journal of Geophysical Research, 2006
1] Simulations of the stratosphere from thirteen coupled chemistry-climate models (CCMs) are evaluated to provide guidance for the interpretation of ozone predictions made by the same CCMs. The focus of the evaluation is on how well the fields and processes that are important for determining the ozone distribution are represented in the simulations of the recent past. The core period of the evaluation is from 1980 to 1999 but long-term trends are compared for an extended period . Comparisons of polar high-latitude temperatures show that most CCMs have only small biases in the Northern Hemisphere in winter and spring, but still have cold biases in the Southern Hemisphere spring below 10 hPa. Most CCMs display the correct stratospheric response of polar temperatures to wave forcing in the Northern, but not in the Southern Hemisphere. Global long-term stratospheric temperature trends are in reasonable agreement with satellite and radiosonde observations. Comparisons of simulations of methane, mean age of air, and propagation of the annual cycle in water vapor show a wide spread in the results, indicating differences in transport. However, for around half the models there is reasonable agreement with observations. In these models the mean age of air and the water vapor tape recorder signal are generally better than reported in previous model intercomparisons. Comparisons of the water vapor and inorganic chlorine (Cl y ) fields also show a large intermodel spread. Differences in tropical water vapor mixing ratios in the lower stratosphere are primarily related to biases in the simulated tropical tropopause temperatures and not transport. The spread in Cl y , which is largest in the polar lower stratosphere, appears to be primarily related to transport differences. In general the amplitude and phase of the annual cycle in total ozone is well simulated apart from the southern high latitudes. Most CCMs show reasonable agreement with observed total ozone trends and variability on a global scale, but a greater spread in the ozone trends in polar regions in spring, especially in the Arctic. In conclusion, despite the wide range of skills in representing different processes assessed here, there is sufficient agreement between the majority of the CCMs and the observations that some confidence can be placed in their predictions. Citation: Eyring, V., et al. (2006), Assessment of temperature, trace species, and ozone in chemistry-climate model simulations of the recent past,
Trajectory model simulations of ozone (O3) and carbon monoxide (CO) in the lower stratosphere
Atmospheric Chemistry and Physics, 2014
A domain-filling, forward trajectory model originally developed for simulating stratospheric water vapor is used to simulate ozone (O<sub>3</sub>) and carbon monoxide (CO) in the lower stratosphere. Trajectories are initialized in the upper troposphere, and the circulation is based on reanalysis wind fields. In addition, chemical production and loss rates along trajectories are included using calculations from the Whole Atmosphere Community Climate Model (WACCM). The trajectory model results show good overall agreement with satellite observations from the Aura Microwave Limb Sounder (MLS) and the Atmospheric Chemistry Experiment Fourier Transform Spectrometer (ACE-FTS) in terms of spatial structure and seasonal variability. The trajectory model results also agree well with the Eulerian WACCM simulations. Analysis of the simulated tracers shows that seasonal variations in tropical upwelling exerts strong influence on O<sub>3</sub> and CO in the tropical lower ...
Effects of stratosphere-troposphere chemistry coupling on tropospheric ozone
Journal of Geophysical Research, 2010
1] A new, computationally efficient coupled stratosphere-troposphere chemistry-climate model (S/T-CCM) has been developed based on three well-documented components: a 64-level general circulation model from the UK Met Office Unified Model, the tropospheric chemistry transport model (STOCHEM), and the UMSLIMCAT stratospheric chemistry module. This newly developed S/T-CCM has been evaluated with various observations, and it shows good performance in simulating important chemical species and their interdependence in both the troposphere and stratosphere. The modeled total column ozone agrees well with Total Ozone Mapping Spectrometer observations. Modeled ozone profiles in the upper troposphere and lower stratosphere are significantly improved compared to runs with the stratospheric chemistry and tropospheric chemistry models alone, and they are in good agreement with Michelson Interferometer for Passive Atmospheric Sounding satellite ozone profiles. The observed CO tape recorder is also successfully captured by the new CCM, and ozone-CO correlations are in accordance with Atmospheric Chemistry Experiment observations. However, because of limitations in vertical resolution, intrusion of CO-rich air in the stratosphere from the mesosphere could not be simulated in the current version of S/T-CCM. Additionally, the simulated stratosphere-to-troposphere ozone flux, which controls upper tropospheric OH and O 3 concentrations, is found to be more realistic in the new coupled model compared to STOCHEM.
Three-dimensional simulations of wintertime ozone variability in the lower stratosphere
Journal of Geophysical Research, 1991
The evolution of ozone has been calculated for the winters of 1979 and 1989 using winds derived from our stratospheric data assimilation system (STRATAN). The ozone fields calculated using this technique are found to compare well with satellite-measured fields for simulations of 2-3 months. Here we present comparisons of model fields with both satellite and sonde measurements to verify that stratospheric transport processes are properly represented by this modeling technique. Attention is focussed on the northern hemisphere middle and high latitudes at the 10-hPa level and below, where transport processes are most important to the ozone distribution. First-order quantities and derived budgets from both the model and satellite data are presented. By sampling the model with a limb-viewing satellite and then Kalman filtering the "observations" of the model, it is shown that transient subplanetary-scale features that are essential to the ozone budget are missed by the satellite system.