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Report on GRIPS

March 14-17, Toronto, Canada

Diane Pendlebury, SPARC IPO, University of Toronto, Canada (diane@atmosp.physics.utoronto.ca)
Steven Pawson, NASA Goddard Space Flight Center, USA (pawson@gmao.gsfc.nasa.gov)

Introduction

The tenth and final workshop for the GCM-Reality Intercomparison Project for SPARC (GRIPS) was held in Toronto. For about a decade, GRIPS
has been the modelling focus for SPARC, and has had the role of evaluating and comparing different dynamical models of the stratosphere from the international community. A number of tasks have been defined, ranging from basic evaluation and validation of GCMs, through studies that aimed to understand the realism and limitations of processes in the models, to longer model simulations designed to examine the consistency of how models
respond to changes in forcing. Following the tradition of past GRIPS workshops, the programme included elements related to the formal tasks, alongside other presentations, ranging from developments in individual models to broader scientific questions of relevance to the community.

In order to meet the evolving demands on SPARC, the modelling strategy has been revised, to the extent that the Chemistry- Climate Model Validation (CCMVal) project will become the main focus. CCMVal has a broader mandate than GRIPS, with the intention of addressing issues of relevance to the topics of all three of SPARC’s major themes (Stratospheric Chemistry and Climate, Stratosphere-Troposphere Coupling, and Detection and Attribution of Stratospheric Change). Many of the issues are directly related to some of the GRIPS tasks in explicit relationships (e.g., model climate and the factors that influence it), and indirect relationships (e.g., impact of parameterizations on climate and climate change). However, in order to answer these questions, SPARC needs to have a much broader scope for model evaluation and validation with formal tasks on details of chemistry and radiation. CCMVal will encompass detailed analyses of the chemistry (e.g., photolysis) and transport, as well as the dynamics and radiation. To this end, CCMVal will likely involve detailed study of the radiative, chemical and dynamical aspects of current models, not necessarily restricting attention to GCMs. Because of the relevance of many GRIPS activities to CCMVal, a main aspect of the 2005 Workshop was on how any unfinished tasks may be carried forward. It should be stressed that, even though no formal GRIPS tasks involving chemistry-climate models have been defined, much discussion at this and previous workshops has been devoted to such models. As these models reach a level of maturity that justifies cross-comparison, it is natural that SPARC’s modelling activities should look for suitable tests of these models, just as GRIPS has explored the performance of the dynamical- radiative components of the full CCMs.

WCRP has led numerous modelling efforts with the Working Group on Coupled Models (WGCM) and the Working Group on Numerical Experimentation (WGNE). Projects such as AMIP, CMIP among others have fulfilled the needs of the community, with substantial investment in infrastructure. WCRP’s objective is to unify these efforts into a common framework under the Coordinated Observation and Prediction of the Earth System (COPES), with two panels that will report directly to the Joint Scientific Committee (JSC): the WCRP Modelling Panel (WMP) and the WCRP Observations and Assimilation Panel (WOAP). The COPES WMP will consist of representatives from all WCRP programmes (S. Pawson will represent SPARC) and from all WCRP working groups.

Model Developments

Several presentations discussed recent developments in climate models. Discussion of these model developments enabled speakers and audience to share common experiences with the various models.

J. Scinocca from CCCma and B. Morel from LMDz gave presentations on the ongoing development and application of global coupled climate models aimed at understanding climate change and variability. The focus at CCCma is primarily on improved representation of physical processes, but a major undertaking over the past year has been the set-up and execution of a large number of scenario runs for use in the upcoming IPCC Fourth Assessment Report. The CCCma global model is used operationally to produce seasonal forecasts, and because the model computes ‘weather’ at 20-minute time steps, one can use the model to say something about extreme events and their changing probabilities. The LMDz-Reprobus CCM has been evaluated with a 10-year climatology and compares well with observations. Sensitivity studies for the orographic gravity wave forcing have been performed, and imply that the introduction of the stratosphere has led to an increase in the surface AO persistence and predictability.

A. Bushell presented the efforts in extending the Met Office HadGAM1 ‘New Dynamics’ Climate Model. The model has changed from non-hydrostatic to quasihydrostatic, and to a hybrid sigma-pressure grid, and includes new dynamics (e.g. mass flux convection, statistical cloud scheme, prognostic ice microphysics, non-local boundary layer), extra middle atmosphere physics such as methane oxidation (photolysis of water vapour at higher levels),
spectral gravity wave parameterization (new dissipation and launch spectra, and a transparent upper boundary, hydrostatic non-rotating dispersion relation), and new added input data. The group is also looking to incorporate satellite data assimilation, increasing predictability at seasonal timescales and improving process representation, such as the QBO.

R. Stolarski and M. Gupta reported on results of the Goddard stratospheric chemical transport model (CTM) and on updating the NASA Goddard Coupled Chemistry- Climate model (GEOS-GCM). The credible performance of the CTM driven by GEOSGCM meteorology in simulating the age of air, the life-cycle of the polar vortex and the observed ozone trends is the basis for development of a coupled model. The CTM transports source molecules, (e.g. CFCs,
Halons, methyl bromide, methane, nitrous oxide) with specified surface mixing ratios, and chemical families (e.g. NOx, ClOx).

Additionally, GEOS-GCM simulations using different scenarios of SST and CTM produced ozone distributions that have shown reasonable behaviour. Chemistry and radiation in GEOS-CCM are presently coupled only through stratospheric and mesospheric ozone. Future plans include invoking the radiative coupling of chemically modified water vapour between 380K surface and top of the model domain, extensive evaluation of the model with UARS and AURA observations, introducing a combined tropospheric-stratosphericmesospheric photochemical mechanism, and coupling with an ocean-ice model.

Stratospheric Forecasting

G. Roff presented the study from WGNE on stratospheric prediction. Better skill in the stratosphere is expected since the dynamics is dominated by a quasi-stationary polar vortex, unlike the troposphere, which is influenced by transient and synoptic scale waves. Therefore, it is to better test our skill in predicting
“stratospheric weather” when the polar vortex is undergoing strong changes over a short period of time, such as sudden warmings. The results show that stratospheric forecasting in the Northern Hemisphere (NH) and Southern Hemisphere (SH) shows similar characteristics. The stratospheric forecasting performance at six days is comparable to three days in the troposphere, but there exists large variability in the forecast skill at six days, often depending on how active the planetary waves are and thus how quickly the vortex distorts. Skill is increased by increasing stratospheric vertical resolution and by raising the lid.

T. Hirooka showed results from a study examining the predictability of Stratospheric Sudden Warmings (SSWs) in the NH inferred from ensemble forecast data. Two case studies (Mukougawa and Hirooka (2004, Mon. Wea. Rev.), Mukougawa et al. (2005, GRL, submitted)) found predictability times of two weeks to one month for SSW events in December of 1998 and 2001. It was found that different ensemble members showed a high sensitivity of the prediction skill to the initial conditions. This case study looks at SSWs in 2002/03 and 2003/04. It was found that the predictability of SSWs in
these cases was approximately two to three weeks, and that the predictability is dependent on occurrences of SSW events.

While stratospheric forecasting has been peripheral to the main aims of GRIPS, several presentations have addressed it at various workshops. This issue has been addressed by the WGNE group, but with the reorganization of SPARC’s modelling activities and the attempts by the WCRP to unify their modelling work through COPES, the topic remains relevant to SPARC. Discussions of stratospheric forecasting were thus based on this premise. It was noted that various groups are now using the same models for analysis/forecasting as for climate studies. This means that study of model performance when constrained by atmospheric data will likely emerge as an important diagnostic for the climate models. Such activities will likely be coordinated through SPARC’s data
assimilation group, in conjunction with CCMVal and the WCRP-COPES panels.

Polar Vortices, Warmings and Annular Modes

G.Roff presented the results from the comparison of polar vortices between models and analyses (GRIPS task 1i). The NMC dataset indicates that the typical characteristics for the SH polar vortex are; a rapid and deep onset throughout the depth of the atmosphere, a high correlation between its size and the maximum wind speed, it is generally polar centred and symmetric, and during its demise there is gradual decay from aloft. All the models tend to capture the main features of the vortex, but the vertical extent is greatly affected by model characteristics (e.g. those models with a sponge layer are forced to close the
polar vortex near the top levels, and those with no gravity wave parameterization tend to have very strong, deep vortices). Elliptical diagnostics show that models that do not extend high enough have polar vortices that are artificially curtailed aloft.

L. Polvani presented a new climatology of SSWs. From observations we can determine their frequency, amplitude, type and distribution, and from models we can learn about their dynamical behaviour. Using the WMO definition (easterly winds at 60N and 10hPa), SSWs can be classified into two main groups according to their evolution: vortex displacement and vortex splitting. In the NCAR/NCEP and ERA-40 analyses, it was found that about three SSW
events occurred every four years, and that vortex displacements accounted for two thirds of these events. These numbers should serve as benchmarks for models. Other results are that the largest variability is in January-March, splitting events are concentrated in January and February, and there is little evidence of trends in the number of warmings. He also noted that the Baldwin and Dunkerton picture of downward propagation of the AO signal might be misleading in that the weak vortex events are actually SSWs, and the strong vortex events are really non-events.

Aspects of the circulation that have received much attention are the annular modes in the two hemispheres. In a study using the MRI Chemical GCM, Y. Kuroda examined the impacts of solar variability on the annular mode in the SH and compared the model response to observations. Regarding the Northern Annular Mode (NAM), an important question remains: what drives the daily variability of the NAM? There is no ‘NAM tendency’ equation. A. Haklander
presented an analysis of mid-latitude stratospheric wind variations, using the zonalmean momentum equation, to investigate changes in normalized cross-covariances of eddy forcing terms with the zonal mean wind tendency. Using the Transformed Eulerian Mean formulation, the resulting daily absolute angular momentum changes yield both a change in relative and planetary angular momentum, each of similar magnitude. There is a downward propagation of low-frequency variations of the wind tendency not visible in the resolved eddy forcing terms, suggesting that gravity wave drag may play a role in the downward propagation of variations in the upper stratosphere and lower mesosphere.

Kodera (2002, 2003) found that the signal associated with the NAO in winter extends to hemispheric scale and into the upper stratosphere in High Solar (HS) years (Kphenomenon). Ogi et al. (2003) also found that the signal associated with the winter NAO tends to persist until next summer in HS years (O-phenomenon). K. Kodera presented a study using ERA-40 data, to determine whether the Southern Annular Mode (SAM) exhibits similar behaviour. A
correlation analysis was performed on the October-November mean SAM index separately on HS and LS years. Both phenomena were found in SAM, and SAM is very persistent in HS years. Observations, and model runs with and without chemistry suggest that ozone plays a key role for persistence of SAM signal. The high extension of the SAM signal toward the upper stratosphere in late winter (K-phenomenon) is important factor for the driving of ozone
to polar-lower stratosphere for the persistence of the AM (O-phenomenon).

J. Perlwitz presented a study on the impact of stratospheric climate change on the troposphere by stratosphere-troposphere dynamical coupling. The key processes in stratosphere-troposphere dynamical coupling are the upward propagation of planetary Rossby waves from the troposphere to the stratosphere, and the absorption of wave activity in the stratosphere which changes the mean flow, which in turn changes the region of strongest interaction of the waves
due to these changes in the basic state. The zonal mean flow perturbation progresses downward and poleward.Wave activity may also be reflected back down into the troposphere such that the structure of tropospheric waves is modified, but there is little effect on the zonal mean.

To study the downward propagation of the Northern Annular Mode (NAM), the leading EOFs were calculated of the daily zonal mean height, and the time-lagged correlation coefficients for DJF relative to 10 hPa. It was found that the downward progression of the NAM was captured in all models studied, except in the GISS model, but that the relationship between the stratospheric and near-surface NAM fields is stronger in models than in reanalysis. Models also show a stronger persistence of NAM in the stratosphere.

Discussion on stratospheric variability and its coupling to the troposphere was lively. While early GRIPS tasks studied warmings and interannual variability of the coupled troposphere-stratosphere system, these model evaluations were limited by the lack of long runs. Since it is now becoming possible to run multi-decadal simulations (even with interactive chemistry), it is timely to revisit these questions. Reviving the early GRIPS Tasks, in the context of examing 20- 50 year simulations with present models, is thus possible. The presentations by G. Roff and J. Perlwitz, as well as many ideas raised in discussion, pointed to the continued value of such evaluations, for both fundamental understanding of GCMs (or CCMs) and for insight into how changes in the circulation into the 21st century may be impacted by the baseline circulation statistics of the models. Such work is encouraged in the GRIPS-CCMVal transition period.

Gravity Wave Drag

A realistic simulation of the climate of the middle atmosphere requires the transfer of angular momentum by unresolved gravity waves (GW). Without a gravity wave drag (GWD) parameterization scheme most GCMs will not produce many of the basic features of the middle atmosphere (e.g., cold
summer mesopause, zonal wind reversal of the mesosphere,QBO). A number of parameterizations are currently used in GCMs, with the fundamental difference between them being how the waves “break” and deposit their momentum to the background flow. However, due to the lack of observational
evidence, the parameters of a GWD parameterization are typically “tuned” to obtain a reasonable mean climate.

While gravity wave properties at source level are the greatest uncertainty, typically they are specified so that a reasonable middle atmosphere results from numerical simulations. However, this feature does not allow for changes of source properties in different climate change scenarios. Using the WACCM, F. Sassi tested three GW generation schemes: the base case (with a zonally uniform GW source that operates continuously with an intermittency factor), the Charron and Manzini (2002) scheme for GW production due to frontal development, and the Beres (2004) scheme for production of GW by convection.
The results show that model consistent GW schemes are in general preferable to ad hoc solutions. Frontogenesis and convection introduce realistic seasonal
and spatial variability, however, these schemes introduce a new level of tuning that can be arbitrary and model dependent, and needs further exploration.

C. McLandress addressed the question of how the differences in the parameterization of wave breaking actually affect climate simulations. Gravity wave dissipation can occur in two ways: nonlinear dissipation, and critical level (CL) dissipation. It is the nonlinear dissipation that is different in each of the GWD parameterizations. Using the standard settings from Hines, Warner-McInytre (WM) and Alexander- Dunkerton (AD) will produce large differences
in the GCM responses. However, by modifying the saturation threshold for WM and AD, it is possible for all three parametrizations to deposit their momentum at the same height. The wind response is nearly identical. This suggests that it is height at which the GWs are dissipated, and not the details of the nonlinear dissipation mechanisms, that is the crucial factor in determining the GCM response.

T. Shaw addressed the question of spurious downward influence of the mesosphere on the stratosphere due to using GWD parametrizations that are not constrained by momentum conservation, either in principle or in the way in which they are implemented. Momentum conservation implies that GWD induced downwelling (and heating) at a given altitude depends only on the gravity wave momentum flux through that altitude (Haynes et al., 1991),
such that GWD feedbacks from changes in the zonal wind above a given level are restricted to the region above. Therefore, zonal wind changes above a level cannot affect the circulation below it via GWD feedbacks. To respect the momentum constraint and avoid spurious downward influence, any nonzero parameterized momentum flux at the model lid must be deposited in the model domain. Dynamical feedbacks from parameterizations could be falsely interpreted as stratospheric and mesospheric effects on climate.

S. Pawson showed runs from the GEOS-4 GCM that were capable of producing a QBO. The AD GWD parametrization was used and the control run produced a reasonable SAO and a low-frequency oscillation in the tropical stratosphere, with some resemblance to the QBO with a period of about 20 months. GWD by a “convective spectrum” in the AD scheme does the work, however, the spectral parameters need to be quite different from those recommended by Alexander and Rosenlof (AR). It was found that in order to produce the QBO shorter wavelengths (100 km vs. 4000 km) were used than in the standard AR scheme, a much narrower spectral width was needed, and a stronger momentum flux at launch level was needed. It was also found that the QBO period increased with slightly weaker GW forcing and there was a better downward extent of the QBO, especially in the easterly anomalies.
Increasing the vertical resolution also led to tighter shear zones and perhaps better downward propagation into the lowest part of the stratosphere.

Issues in Chemistry- Climate Modelling

R. Stolarski gave a presentation on the need for, and the problems with producing, highquality, long-term datasets. Long-term datasets, such as the total ozone data from TOMS and SBUV, enable us to test how processes act together to give decadal-scale responses. The ultimate prediction test is our hindcast capability so that decadal scale hindcasts compared to long-term data sets provide additional evaluations of models beyond process-oriented evaluation.
A long-term dataset is comprised of data from many satellites, and each instrument has calibration and drift issues. It is necessary to estimate trend uncertainty due to instrument drift and to remove known systematic errors from long-term datasets. However, residual errors could remain that lead to drift uncertainty. In addition, the introduction of a new instrument into a dataset introduces a new uncertainty, so it is important to have enough overlap to properly calibrate instruments and improve uncertainties. Ground stations are useful in that they may be calibrated as needed, but statistical uncertainty dominates the trend
uncertainty, and there are still drift uncertainties in individual ground stations. Using a combination of both satellite and ground-based measurements is better.

Extratropical ozone builds up in winter/spring due to transport from the tropics, and decreases in late-spring/summer due to photochemistry (more so in
NH than in SH). It tends to be that years that are high/low in spring are high/low in summer. T. Shepherd showed that the correlation coefficient (of detrended data) between different months from 35° to 60° shows a remarkable seasonal persistence of ozone anomalies until fall. In both hemispheres,
35°-80° springtime ozone is a good predictor for both 35°-60° and 60°-80° summertime ozone. In fact it is a better predictor of 60°-80° summertime ozone
than is 60°-80° springtime ozone. Once the vortex breaks down, the correlations become coherent throughout the extratropics (Fioletov and Shepherd, 2005). The SH midlatitude ozone variability seems to be slaved to NH variability. This memory could be in tropical zonal winds, i.e. the “flywheel” (Scott and Haynes, 1998).

V. Fomichev presented the result from an ongoing study to diagnose the impact of increasing greenhouse gas (GHG) concentrations
in the Canadian Middle Atmosphere Model (CMAM). A series of multi-year runs has been performed with double CO2, with and without interactive
chemistry, and with sea surface temperatures (SSTs) prescribed for both 1xCO2 and 2xCO2 climate. In response to CO2 doubling, the middle atmosphere cools ~10K with maximum impact near the stratopause. The ozone radiative feedback (through both solar and IR heating) reduces the CO2 induced cooling by up to ~4.5K. The main impacts of SST changes on the middle atmosphere are a higher and warmer tropopause, cooling just above the tropopause (in both the tropics and extratropics), and a decrease in ozone near the tropopause, both possibly related to the “tropopause shift”. However, the winter polar regions can be highly variable, so long runs are required to increase confidence in the results.

On behalf of A. Scaife and N. Butchart, A. Bushell presented the results from the Level 4 GRIPS task on how climate change affects the Brewer-Dobson circulation. The troposphere-stratosphere mass exchange determines the lifetimes of key trace gases, and transports ozone down into the troposphere. Therefore, changes in the mass circulation will affect both ozone and climate predictions. The Unified Model predicts that an increase in GHGs will cause a systematic increase in troposphere-stratosphere exchange (Butchart and Scaife, 2001), and this study is an attempt to assess the robustness of this predicted change in mass exchange and the role of planetary wave driving using 14 different model runs from 11 different groups.

The results of the study are that all models have a Brewer Dobson circulation with upwelling in a “tropical pipe” extending to about ±30° (annual mean), and the pipe is displaced by 10°-20° toward the summer pole. However, at 70 hPa, the upwelling mass flux varies by up to a factor of 2 between models. The maximum upwelling is in DJF and is often 50% larger than in JJA. All models confirm a positive trend in the mass flux across the tropopause due to
climate change. This occurs throughout the year and is consistent with an increase in planetary wave driving at upper levels. The increase is about 2% per decade. This feedback could amount to a ~20% decrease in the lifetime of N2O and CFCs, for example, by 2100 and is not included in standard climate models.

J.Austin presented a study on the age of air and the meridional circulation in a GFDL coupled chemistry-climate model. Two 21- year runs were used: one with 1960 forcings and one with 1980 forcings. In timeslice simulations water vapour increased by 4% per decade from 1960 to 2000, entirely consistent with CH4 oxidation. The tropical upwelling increased at the equivalent rate of 1.7% per decade. The decrease is approximately balanced by a 2.7% per
decade decrease in the age of air. Model results are in reasonable agreement with observations for tropical upwelling, but underpredict age of air by over 30%, implying that there is too much mixing. A summary of GFDL’s strategy for chemistry- climate evolution was also outlined.

J. de Grandpré presented a 20 year run from the CMAM including heterogeneous chemistry, interactive ozone, and current chlorine loading. The findings
indicate that CMAM has a realistic representation of the residual circulation, but that the homogeneity of temperature, and that of long-lived constituents is too strong in the NH winter period. Ozone flux from the stratosphere to the troposphere has an upper limit of 750 Tg/year, and methane and nitrogen loss in the stratosphere is 13.6 Tg/year and 16.1 Tg/year respectively.

Discussion of chemistry-climate simulations tackled several aspects. There is a need to balance between studies that address the mechanisms of interaction and the necessity of producing multi-decadal integrations that span the period of around
1950-2100, in order to meet requirements for the forthcoming ozone assessment. Key scientific questions for CCM evaluation are the detection, attribution and prediction of trends in atmospheric ozone in the interactive chemistry-climate environment, the future recovery of stratospheric ozone within the context of human-induced and natural variabilities, the effects of changing chemical composition on the coupled tropospheric- stratospheric dynamics and radiation budget and vice-versa, and the effects of natural perturbations (e.g. volcanic) on the interactive chemistry-climate environment. All of these are priorities in
SPARC research.

Cross-evaluation of multiple CCMs has not progressed substantially since the previous ozone assessment, and this is a task that will be undertaken within CCMVal. Many aspects of the validation may draw from GRIPS studies, but chemical evaluation will require different diagnostics and a different set of expertise than has been available for GRIPS.

In many ways, interpretation of chemistryclimate prediction studies is not a fully mature field. The discussions showed that the various research groups have different levels of accountability to funding agencies and, on this basis, have different priorities for model experiments. While the baseline scientific questions are essentially well defined, neither the strategy for numerical experimentation nor the analysis methods are well established. This means that more
basic research is required, which may contradict the perceived requirement that all groups run their simulations under identical, controlled conditions.While there was consensus that emission scenarios for anthropogenic “climate” and “chemistry” gases will be adopted from established scenarios (from 3-D climate models and 2-D chemistry models), there is less agreement on issues such as: which scenarios would be used; what boundary conditions should be used (e.g., future sea-surface temperatures); whether or not to impose solar cycles in incoming irradiance. The treatment of aerosols remains quite primitive,
with models run with low aerosol loading at the moment, although this is a very important climate issue. In the prediction context, it is necessary to understand how major eruptions at different times will affect climate response and the detection of ozone changes. The role of bromine gases was also the focus of interesting discussion, motivated by the cameo appearance of R. Salawich at the meeting. This discussion especially underscored the importance of
scientific experimentation, in order to better understand the fundamental issues in chemistry-climate change.

The lack of agreement on these issues is somewhat contradictory to the need for SPARC to contribute to the next WMO/UNEP ozone assessment. A major point raised was the time needed for groups to complete useful climate runs, and the fact that IPCC scenarios were not set in time for groups to respond.While the timeline allowed for 2-D runs to be performed, it will not be adequate for most groups to complete full 3-D CCM runs. The need to lead the science in defining acceptable scenarios, rather than lag behind many groups running different scenarios is desirable. This implies the need to quickly agree on scenarios for the upcoming assessements. Even then, some groups are already well into their simulations and these groups have not coordinated their scenarios.

Discussion on GRIPS Tasks and Other Issues

The GRIPS tasks are in various stages of completion; some tasks can be brought to closure, and others should carry forward into CCMVal. A summary of the tasks and their status is given in Table 1. Plans to update the model evaluation (Tasks 1a,b) will essentially be superseded by CCMVal. Studies of troposphere-stratosphere connections are ongoing and will be part of the transition from GRIPS to CCMVal, and although task 1d (Sudden Warmings) was completed, it may be revived. Level-2 tasks, aimed at understanding the parameterizations used in models and their impacts on the simulated climate, are mostly complete.P. Forster has almost completed the comparison stage of the radiation codes (Task 2a) and the results were presented at the SPARC General Assembly 2004.

Level-3 tasks are aimed at understanding how the climate models respond to different physical forcing mechanisms. The PINMIP experiments (Task 3a) will likely evolve into CCMVal tasks, along with task 3d. The solar forcing task (3b) is complete and will be reported on in this meeting. Substantial progress has also been made with the “1980 – 2000” ozone project, and it is almost complete (U. Langematz could unfortunately not attend the workshop). GRIPS had one Level-4 task, an examination of the changes in residual circulation in a changing climate, which was discussed.

While GRIPS is now ending, many of the remaining questions in “meteorological” modelling of the middle atmosphere will carry forward into CCMVal, where they will be complemented by questions of relevance to transport, chemistry and radiation. CCMVal should draw from the experiences of GRIPS, but will face new challenges. One of these concerns data management. Because of the possibilities for longer model runs, with chemical as well as meteorological output, CCMVal will require more resources. The SPARC Data Centre has already made some plans to cope with the amount of data that will be necessary to handle for some of the planned projects. Another challenge for CCMVal will be community involvement, so that the tasks do not fall on certain individuals. CCMVal is taking an “open conference” approach to many of its activites, but there will remain a need for focused, workshopstyle activities within SPARC. The key will be to effectively combine COPES and CCMVal activities and procure funding.

Acknowledgements

We are grateful to David Sankey (U. Toronto) for organizing the meeting and to Norm McFarlane (SPARC Office) and Ted Shepherd (U. Toronto) for their invaluable contributions to its success.

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