Subject: Update on CAM Intercomparison Activity Date: Thu, 17 Aug 2000 16:05:25 -0600 From: Paula Fisher To: paulad@bearmtn-e0.cgd.ucar.edu To members of the CSM AMWG, We now have a complete list of participants for the first round of the CAM configuration intercomparison. Based on feedback from several of the participants, and the relatively limited number of proposed changes, we have decided to eliminate the workshop which was tentatively scheduled for 27-29 September 2000. We will conduct this initial selection process electronically, via the web and e-mail. This will provide some additional time to the participants to complete and submit the initial simulations associated with their proposed modifications to the CAM0.1 model. We will require that all simulation materials be available for evaluation by no later than Friday, 29 September 2000. As before, participants are also expected to provide CAM developers in the NCAR Climate Modeling Section with access to the computer code to facilitate discussion of coding and code maintenance issues. We will accept comments on the various configuration options until 10 October 2000, at which point the viable configurations will be moved forward for the next round of evaluation. The AMWG will convene a workshop in Boulder on 12-14 December 2000 to evaluate and discuss the configurations that survive the initial cut in early October. One of these configurations will be selected for the next version of the CCSM atmospheric component model. Invitations to attend this meeting will be extended to the broader CSM community with the expectation that other working groups will be able to provide additional diagnostic insights into the important strengths and weaknesses of the various configuration options. Presently, the candidate configurations include the following: Collins longwave changes to include up-to-date H2O absorption Boville vertical diffusion of dry static energy Khairoutdinov CSU Version of Arakawa-Schubert convection Rasch Zhang-McFarlane convection - physical triggers Zhang Zhang-McFarlane convection - modified closure Hack/Tribbia Relaxed Arakawa-Schubert convection Williamson Semi-Lagrangian Dynamical (SLD) core Lin finite-volume (Lin-Rood) dynamical core Kristjansson Ice crystal optics These proposals will be posted on the web as simulation results become available. All participants should notify Dr. Mark Stevens (stevens@ucar.edu) as soon as their simulation results are available. Mark will coordinate access to the simulation data to interested CSM working group members, and will see that a common set of analysis metrics are made available via the web. When simulation data becomes available, Mark will provide the investigator with access to a standard analysis package of mean climate metrics. Mark will see that the graphical results produced by this package are posted on an AMWG web page for comment from the CCSM community. Results from control simulations of the standard (i.e., distributed) physics package for all three dynamical cores currently under consideration should begin to appear over the next few weeks. As before, working group members should contact Jim Hack or Dave Randall with any questions, concerns, or suggestions about the current plan. J. J. Hack D. A. Randall ----------------------------------------------------------------------------------------------------------- Subject: CAM-1 Candidate Evaluation Project Participation Request Date: Thu, 03 Aug 2000 10:31:58 -0600 From: Lydia Harper CAM-1 Candidate Evaluation Project Participation Request The CCSM Climate Variability Working Group (CVWG) is coordinating an evaluation of the candidates for CAM-1 (Community Atmospheric Model version 1). Volunteer participants are needed to examine and comment on results from the various configurations being tested by the Atmospheric Model Working Group (AMWG). The CVWG will collect the comments and transmit them to the AMWG and to the Scientific Steering Committee (SSC). The CVWG will also provide information on access to the model results. This project provides an opportunity for consumers of model data as well as model developers to contribute their expertise to the development of CAM-1. If you are interested in participating, please provide your name, email address, and aspects of the model results that you wish to examine to either Jim Hurrell (jhurrell@cgd.ucar.edu) or Ed Schneider (schneide@cola.iges.org). Jim Hurrell and Ed Schneider Co-chairs, Climate Variability Working Group ------------------------------------------------------------------------------------------------------------------ Subject: Message to the AMWG Date: Fri, 13 Oct 2000 12:34:11 -0600 From: Paula Fisher To: paulad@bearmtn-e0.cgd.ucar.edu To members of the CCSM AMWG, We now have passed the initial due date for submission of simulation results for proposed configurations of the CAM 1.0 and it's time for an update. At the moment a subset of the candidate configurations are complete where plots have been (or will soon be) posted on the CAM developer's password protected web page http://www.cgd.ucar.edu/cms/amwg/ All submitted configurations have been adequately tuned from a global surface energy budget point of view. They include: Boville vertical diffusion of dry static energy Khairoutdinov CSU Version of Arakawa-Schubert convection Hack Relaxed Arakawa-Schubert convection Williamson Semi-Lagrangian Dynamical (SLD) core Williamson Eulerian, T42, 30 level, 1 digit reduced grid The last entry was inadvertently omitted from the August list of candidate configurations. It is the same as the standard development control configuration except that it employs a reduced-grid for the evaluation of the physics and non-linear terms. This configuration is aimed at improving the model's computational efficiency. The remaining candidate configurations include: Collins longwave changes to include up-to-date H2O absorption Rasch Zhang-McFarlane convection - physical triggers Zhang (Guang) Zhang-McFarlane convection - modified closure Lin finite-volume (Lin-Rood) dynamical core Kristjansson Ice crystal optics Most of these configurations have been delayed because of unanticipated complexity, coupled with recent constraints in the availability of computer resources. Despite the delay, it is still extremely important that most of them are given full consideration. Therefore, we are extending the deadline by a few more weeks for completion of the initial 5-year simulation using climatological annually-repeating sea surface temperatures. In the meanwhile, we will begin the process of defining the second experimental phase for the intercomparison. We will be conducting a 15+ year AMIP simulation to begin to assess aspects of model variability in an uncoupled mode. With this email we are soliciting the community for input on sampling requirements for the AMIP simulation. We anticipate requiring daily sampling of these simulations for some subset of the fields carried by the developmental model. We would like to develop a consensus on what this list should include. We are also interested in any special sampling requirements. For example, one variability analysis package requires 3 hour sampling of a selected number of fields over a period of a few months. We need to assemble detailed information along these lines over the next few weeks so that the AMIP simulations can be started. Please send your comments to both Jim Hack (jhack@ncar.ucar.edu) and Dave Randall (randall@redfish.atmos.colostate.edu) as soon as possible. And keep watching the AMWG Diagnostics Archive page for new submissions. Finally, we wish to emphasize that the AMWG meeting currently planned for December is aimed at facilitating detailed discussion of the simulation strengths and weaknesses for the various candidate model configurations now under consideration. The objective for this meeting will be to select a model configuration to serve as the next official release for CCSM's atmospheric component model (designated CAM 1.0). This discussion must include aspects of atmospheric variability for each of the proposed configurations. In several weeks we will evaluate where this intercomparison activity stands to determine whether a December workshop will be worthwhile, or whether it will be necessary to postpone this discussion until early January. We will also be soliciting guidance from the SSC on how much longer to wait versus moving forward with what has already been submitted. So, please keep this in mind the when making plans. We will continue to strive for holding the December 12-14 workshop, but do not want to hold a workshop if there is insufficient basis for discussion. Although a postponement of the December meeting is a possibility, those involved in development activities should know that a final decision on a model configuration cannot take place any later than mid January. We will advise the working group of any schedule changes as soon as we have more definitive information on when the remaining model configurations will complete their initial simulations so that they are ready for additional testing. J. J. Hack D. A. Randall ----------------------------------------------------------------------------------------------------- Subject: PCMDI Diagnostic Website Now Available Date: Fri, 10 Nov 2000 11:44:08 -0700 From: Paula Fisher To: paulad@bearmtn-e0.cgd.ucar.edu To: Members of the CCSM Atmospheric and Climate Variability Working Groups From: Michael Wehner, Program for Climate Model Diagnosis and Intercomparison The PCMDI is undertaking an independent assessment of the candidate models for the atmospheric component of the next version of the Community Climate System Model (CCSM). Extensive intercomparison results are posted at http://www-pcmdi.llnl.gov/CAM . Currently, analysis is restricted to those models available on the AMWG web site, http://www.cgd.ucar.edu/cms/amwg/ . As additional candidate models are released, we can process them in a three to four day time frame. As the raw data is considered proprietary by NCAR, these results and interpretations should be considered in the same vein. Hence, this web site is password protected with the user name "pcmdi" and password "!ncar". The PCMDI welcomes comment on these findings. Correspondence should be directed to Michael Wehner, mwehner@llnl.gov . -------------------------------------------------------------------------------------------------------------- Subject: Message to AMWG and CCSM Working Group Chairs Date: Mon, 27 Nov 2000 11:16:25 -0700 From: Paula Fisher To: paulad@bearmtn-e0.cgd.ucar.edu CC: joannem@bearmtn-e0.cgd.ucar.edu To members of the CSM AMWG: Attached is a draft agenda for the upcoming AMWG Workshop in Boulder on 12-14 December 2000. Please regard this agenda to be one that will evolve right up until the start of the workshop. Up-to-date versions will be posted via a link from the CCSM AMWG web page http://www.cesm.ucar.edu/working_groups/Atmosphere/ Note that the first day of the workshop will focus on presentations and open discussion of the nine configuration options under consideration. The bulk of the time will be spent on the dynamical core and convection parameterization options. The second day will be devoted to presentations and discussion of analyses completed by the at-large CCSM community. As we indicated in an earlier mail message, our expectation is that members of the AMWG, along with interested members from other CCSM working groups, will subject the simulation data to analyses of both the mean climate and it's variability on a wide range of time scales. We hope that there will be extensive participation in this activity from members of other CCSM working groups. At this time the entire afternoon on Wednesday is reserved for presentations of analyses that may be currently underway by members of the CCSM community. PLEASE LET US KNOW IF YOU INTEND TO MAKE A PRESENTATION ON YOUR ANALYSIS OF THE CURRENT SUITE OF MODEL CONFIGURATIONS SO WE CAN PLAN FOR IT. These presentations need not be highly polished, but should serve as a basis for discussion. We are encouraging as much community participation in this part of the workshop as possible. The morning of the third day will be devoted to an open discussion of what the AMWG should propose to the CCSM SSC as the configuration of the next CCSM atmospheric component. In addition to the current simulation data (a 5-year climatological SST forced simulation, and a 16-year AMIP II simulation), we will soon be providing information on the location of a one year simulation sampled at three hour intervals for several of the proposed configurations. This latest simulation is intended to facilitate limited analysis of variability down to diurnal time scales. As before, for planning purposes we are interested in determining how many people will be attending the meeting. PLEASE LET US KNOW IF YOU WILL BE ATTENDING THE WORKSHOP BY SENDING MAIL TO paulad@ucar.edu. If you need any help with your travel plans, feel free contact Paula Fisher at paulad@ucar.edu. J. J. Hack D. A. Randall ============= Draft AMWG Workshop Agenda - December 12-14, 2000 Tuesday, 12 December 8:00 am Coffee 8:30 am Welcome and update on model development activity (Hack/Randall) Presentations and Discussion of Candidate Configurations 9:00 am Vertical Diffusion of Dry Static Energy B. A. Boville 9:20 am Eulerian, 1-Digit Reduced Grid D. L. Williamson 9:40 am Longwave changes to H2O absorption W. Collins 10:00 am BREAK 10:20 am Semi-Lagrangian Dynamical Core D. L. Williamson 11:10 am Finite-Volume Dynamical Core S. J. Lin 12:00 noon Lunch 1:10 pm CSU Arakawa-Schubert Cumulus Parameterization M. Khairoutdinov 2:00 pm Relaxed Arakawa-Schubert Cumulus Parameterization J. J. Hack 2:50 pm Zhang-McFarlane Cumulus Parameterization - physical triggers P. J. Rasch 3:40 pm BREAK 4:00 pm Zhang-McFarlane Cumulus Parameterization - modified closure G. J. Zhang 4:50 pm General Discussion of Candidate Configurations 5:30 pm RECEPTION Wednesday, 13 December 8:30 am Coffee Diagnostic Analyses and Discussion of Candidate Configurations 9:00 am PCMDI Analyses of Candidate Configurations M. Wehner 10:30 am BREAK 10:50 am Intraseasonal Variability C. Demott 11:20 am Convective Variability: Diurnal through Intraseasonal L. Ricciarduli 11:50 am LUNCH 1:00 pm Reserved for other CCSM working group diagnostic analyses 5:00 pm Adjourn for the day Thursday, 14 December 8:30 am Coffee Discussion of Configuration Options 9:00 am Comments on Candidate Configurations CCSM Working Group Chairs 10:00 am Discussion of atmospheric component recommendations to SSC 12:00 noon ADJOURN ---------------------------------------------------------------------------------------------------------------- Subject: Message to the AMWG Date: Fri, 22 Dec 2000 13:23:43 -0700 From: Paula Fisher To: paulad@ucar.edu To members of the CSM AMWG: The next AMWG workshop will be held in Boulder, at the NCAR Mesa Laboratory in the Main Seminar Room on Monday, 22 January 2001. We will convene the meeting at 8:30 am and anticipate that the workshop will require most, if not all, of the day. Please plan your travel accordingly. The next version of the CCSM atmospheric model will be determined at this workshop. We hope to see as many of you as possible. Happy holidays ... -- Jim Hack Dave Randall ------------------------------------------------------------------------------------------------------------- Subject: Message from PCMDI Date: Wed, 17 Jan 2001 13:36:19 -0700 From: Paula Fisher To: paulad@bearmtn-e0.cgd.ucar.edu The PCMDI analysis of the Phase II of the AMWG intercomparison is now complete. As before, results are posted at www-pcmdi.llnl.gov/CAM The user name is pcmdi, the password is !ncar. The analysis is as in Phase I, except that polar projection plots have been added. ----------------------------------------------------------------------------------------------------------------- Subject: convergence toward an atmospheric model Date: Thu, 15 Feb 2001 09:10:57 -0700 (MST) From: James Hack Reply-To: jhack@ncar.ucar.edu To: wmson@ncar.ucar.edu (Dave Williamson), pjr@renegade.cgd.ucar.edu (Phil Rasch), wcollins@renegade.cgd.ucar.edu (William Collins), boville@ncar.ucar.edu (Byron Boville), arat@inferno.atmos.colostate.edu (Marat Khairoutdinov) CC: jhack@ncar.ucar.edu (James J. Hack), randall@redfish.atmos.colostate.edu (Dave Randall), jtkon@renegade.cgd.ucar.edu (Jeff Kiehl), blackmon@renegade.cgd.ucar.edu (Maurice Blackmon) Hello all, Well, it's February 15th, and we still have not completed the final configuration of the atmospheric model we proposed to the SSC. As many of you know, the work we knew about has taken longer, and there are even some new things that have cropped up along the way. It's appropriate to review where we stand, and where I would hope this activity can be in the next couple of weeks. First, Phil and Marat have done all that can be done in the way of tuning the clouds and convection in the SLD/CSU configuration. Unfortunately, one of the main difficulties with this tuning exercise is a clear-sky longwave bias introduced by the CSU convection scheme via the cold tropopause, and possibly deficient distribution of water vapor. The representation of the cloud field is also highly problematical. The consequences are that the both the longwave and shortwave cloud forcing is poorly represented, although the all-sky fluxes balance (to within 0.5 w/m2) at the top of the model. In my opinion, the overall quality of the simulation looks quite bad, but the remaining biases are well outside the bounds of what any cloud tuning exercise could hope to address. I feel Phil has done his best at adjusting the basic radiation budget so as to make the model suitable for coupling to an ocean. Any other simulation deficiencies are a consequence of the configuration adopted by the AMWG community. Bill is still working on final touches to the LW water vapor absorption scheme. This, too, has taken longer, and has been more involved than first anticipated. My understanding is that this work should be completed by no later than the end of next week. So, the configuration tuned by Phil and Marat is on hold until we can incorporate the final changes that will be recommended by Bill. In the meantime, two other potential changes have been discussed. Dave has indicated that he has a final SLD configuration that introduces changes to the diffusion in the stratosphere, making for an improved simulation of things like the polar night jet. Byron has also been toying with a change to the gravity-wave drag scheme to correct a minor problem with the implementation over places like open ocean. I would like to suggest, while we're waiting on the final longwave changes, that Byron and Dave conduct a simulation of the new SLD and modified gravity wave drag schemes to demonstrate that there are no undesirable surprises. Once this configuration has been demonstrated, the next step would be to combine it with the cloud tuning and convection changes recently completed by Phil and Marat. Some additional minor tuning may be necessary, which could be completed while waiting on the longwave. Finally, this configuration should then incorporate Bill's longwave absorption update. My expectation is that additional tuning, perhaps significant additional tuning, may be required. However, at that point we will have completed the exercise we agreed to on 22 January, and should be in a position to couple the model to an interactive ocean (at least in terms of global annual energy balance). Hopefully, the oceanographers will have something for us to couple to at that time, probably a couple of weeks from now. Given the nature of the physical changes we are likely to be dealing with, partially based on the continued degradation of the model with the newly revised CSU convection scheme, I strongly recommend that Bill completes his initial tests of the new longwave code in the 26-level baseline Eulerian model we used for Phase II of this development process. We have a long control to compare against, and it will provide a clean 1-off experimental test. In addition to completing a long simulation of the recommended configuration (SLD/CSU convection) I will see that an SLD/ZM simulation is tuned and conducted. All of these simulations will be subjected to as comprehensive a diagnostic analysis as possible, and the results will be placed on the web for comment. Hopefully, all this makes sense to everyone. If there's something that doesn't make sense, or if, for example, anyone wants to withdraw any additional changes so that a specific stage in this process is no longer necessary, please let me know immediately. This process has dragged on far too long already, and I am determined to see that we achieve closure on the AMWG's promise of a new model by no later than the first full week in March. Jim ------------------------------------------------------------------------------------------------------------ >Dear Jim and Dave: > >We have spent some time at COLA looking at the results from the models >that are candidates for the next generation CCSM AGCM. Given the results >of the AMIP runs and the differences in the execution time of the candidate >dynamical cores, the recommendation made by the AMWG seems inevitable. We >have some additional comments made in the spirit of constructive >criticism. > >There are several aspects of the recommended SLD dynamics/CSU >convection configuration that stand out as potentially serious problems. >These may argue for not releasing this model as the new official CCSM AGCM, >and instead extending the research/model comparison phase until a >satisfactory model can be assembled. These problems are: > 1) Poor simulation of arctic surface winds, which will make the work put >into the development of the new sea ice model irrelevant in the context of >the coupled model. > 2) A precipitation bomb in the Pacific near the coast of Central America >in JJA (error off scale relative to Xie Arkin, as Jim Hurrell pointed out >at the January SSG/WG chairmen meeting). > 3) Extreme errors in the 200 mb JJA zonal winds over tropical Africa and >the Atlantic (larger than 29m/sec!). > 4) Poor DJF and JJA simulations of precipitation in the tropical western >Pacific, with maximum values on the opposite side of the equator from >observations. > >Additionally there were some procedural problems with the model selection >process. In particular: > 1) A completely new closure that is in part not physically justifiable >was introduced into the CSM convection scheme between the December and >January AMWG meetings. Some effort needs to be made to clean this up. > 2) No coupled simulations were made with the candidate AGCM >configurations. The coupled simulation of tropical SST in the current CSM >is not satisfactory. Whatever happens in this area in the new >coupled model will be a surprise, and there is little reason to suspect >that it will be a pleasant one. > >However, we also recognize the sociological need to release a new model. >Therefore, we feel that a reasonable course of action at this point is to >release the new version, but also to continue research with the 4 (+1) >candidate models until the above problems can be satisfactorily addressed. > >COLA is prepared to help with evaluation of the simulations of the coupled >tropical climate with the different research AGCMs. Our proposal is to make >one to two decade "quick and dirty" simulations with each of the candidate >AGCMs coupled to our intermediate resolution (nominal horizontal resolution >1.5 degree, 25 levels) non-polar version of MOM3 ("IRI" physics). The COLA >coupling procedure (using the coupler built into MOM rather than the flux >coupler) would be used. We could do this under the auspices of either the >AMWG or the CVWG, using the CCSM CSL computer time. We would also need >access to the research version of the AGCM. We would appreciate your >response to this proposal. > >Best regards, >Ed > >Edwin K. Schneider >Senior Research Scientist >Center for Ocean-Land-Atmosphere Studies >4041 Powder Mill Rd., Suite 302 >Calverton, MD 20705-3106 >telephone: (301)-595-7000 > (301)-902-1250 >fax: (301)-595-9793 >email: schneide@cola.iges.org >www: http://www.iges.org ------------------------------------------------------------------------------------------------------------------- Subject: Re: Choice of new CCSM AGCM Date: Tue, 20 Feb 2001 10:52:28 -0700 (MST) From: James Hack Reply-To: jhack@ncar.ucar.edu To: schneide@cola.iges.org (Edwin Schneider) CC: jhack@ncar.ucar.edu, randall@redfish.atmos.colostate.edu, blackmon@ncar.ucar.edu, jfein@nsf.gov, shukla@cola.iges.org, jhurrell@cgd.ucar.edu Dear Ed, Thanks for the comments you sent last Friday. As you know, having participated in the working group deliberations on 22 January, every one of the problems you note were explicitly discussed. They were also discussed at the SSC meeting that followed our working group meeting. My reading of Maurice Blackmon's summary of the SSC meeting was that the SSC is not entirely comfortable with the recommendation because of these simulation biases. They may also be reluctant to embrace the recommendation until after we have some experience coupling the proposed atmosphere to an ocean model. As you may also recall, although coupled simulations were a part of the AMWG selection strategy, we are still unable to conduct coupled simulations for technical and other reasons. I hope we will be able to begin coupled simulations by the end of the month. At that point we will be in a better position to quantify the effects of the uncoupled biases on the coupled configuration. We hope that you will continue to play a role in this phase of the evaluation process. Frankly, I am also extremely uncomfortable with the recommended configuration for many of the same reasons you have expressed. I was also dissatisfied with certain aspects of the process that got us to where we are, but this is a learning process and I'm certain that the next time will be better. Overall, I believe we have managed to establish a process by which the community can come together to contribute to the development of the atmospheric model, and critically evaluate its performance. I'm happy to consider the extension of our procedures as proposed in your message. However, before responding I would like to discuss the proposal with Dave Randall, and other members of the working group who have contributed unpublished components to the experimental configurations. In the meantime, we will keep all working groups updated on our progress, and hope that we will continue to get constructive feedback on the performance of the proposed model configuration. Best wishes ... Jim ------------------------------------------------------------------------------------------------------------------- Subject: Message to the AMWG Date: Thu, 26 Apr 2001 16:11:15 -0600 From: Paula Fisher To: paulad@bearmtn-e0.cgd.ucar.edu To members of the CCSM AMWG, The core development team has now completed what the working group proposed to the SSC in January. A configuration of the development model we adopted in January, CSU Arakawa-Schubert convection with Semi-Lagrangian dynamics (CSU/SLD), along with the proposed additions has been tuned and run with climatological and AMIP II SST forcing. The additions include: Modified SLD algorithm: a change to the horizontal diffusion formulation in the stratosphere Modified cloud water: changes to allow the cloud water to work in a middle-atmosphere configuration, along with additional algorithmic changes to address newly identified problems Modified gravity wave drag scheme: elimination of all orographic gravity wave drag over ocean surfaces Modified hydrostatic equation Minor correction to the hydrostatic calculation in the physics Modified CSU convection scheme subcycling of convection, along with other necessary changes Modified longwave water vapor absorption scheme: Extension of the H2O path range; consistent treatment of line and continuum absorption dependence on RH; plus other miscellaneous updates Simulation results (along with pointers to the data archive) can be found on the AMWG diagnostics web page http://www.cgd.ucar.edu/cms/amwg/phase3.html The web page is password protected and available to working group members engaged in the evaluation of the atmospheric model configuration options. The user name is amwg_archive and password is postmortem. My evaluation of this model configuration is that it will be judged to be inadequate for coupling purposes. There are large systematic errors in both the tropics and extratropics. We have made an attempt to identify the sources of some of these errors, and include two additional climatological SST forced simulations. They include the old CCM3 convection configuration in both Eulerian and semi-Lagrangian dynamical cores. There are strong signals in these simulations that are highly consistent with the conclusions drawn from Phase II of this AMWG intercomparison. For example, the stationary wave error appears to be associated with the SLD dynamical core. The double ITCZ and excessive precipitation features appear to be associated with the CSU convection scheme. Even though some features of these simulations are clearly improved over the CSU/SLD simulation, each of them contain their own set of problems, such as the extreme dry bias present in both simulations. At the moment, the only alternatives to the CSU/SLD configuration are the two Zhang-McFarlane simulations linked at the bottom of this Phase III web page, and the original CCM3. The down side of adopting the original CCM3 is that the incorporation into CCSM2 of many of the improvements included in the current development model would be indefinitely delayed. At NCAR, we are currently exploring one final configuration for consideration by the working group. We hope to have extended simulations available by early next week, linked to the Phase III web page. The AMWG been asked to make a formal and final recommendation to the SSC on an atmospheric configuration for CCSM2. They would like this recommendation within two weeks, so coupled simulations can be started in advance of the June workshop. Please have a look at this web page and send me your comments by no later than Wednesday, May 9, 2001. We will attempt to assemble a consensus on a working group recommendation based on the comments we receive. Jim Hack ------------------------------------------------------------------------------------------------------------------ Subject: More on AMWG Intercomparison Date: Mon, 30 Apr 2001 14:51:11 -0600 From: Paula Fisher To: paulad@bearmtn-e0.cgd.ucar.edu To members of the CSM AMWG, As mentioned in an earlier mail message, several members of the NCAR staff have been exploring one final atmospheric configuration for consideration by the AMWG. This configuration allows for the evaporation of precipitation condensate from the Zhang-McFarlane convection scheme. A five-year simulation completed over the weekend and has been linked to the Phase III web page. The case name is zm31139evap06. A second experiment, using AMIP II SSTs, is currently a little more than halfway complete. We are in the process of conducting an intermediate analysis of this simulation using the first ten years (1979-1988), and will link these results to the Phase III web page. We will update these diagnostics as soon as the simulation completes, hopefully by sometime late tomorrow. To reiterate our goal, the working group will need to make a final recommendation to the SSC on an atmospheric configuration for CCSM2 by the end of next week. Dave Randall and I will collect your comments on the available configurations through Wednesday, May 9. Please send your comments to me (jhack@ncar.ucar.edu). Dave and I will attempt to assemble a consensus on a working group recommendation based on the comments we receive. Jim Hack -------------------------------------------------------------------------------------------------------------- Subject: Message to the AMWG Date: Fri, 11 May 2001 12:02:46 -0600 From: Paula Fisher To: paulad@bearmtn-e0.cgd.ucar.edu To members of the AMWG: We have formally recommended a new CCSM2 atmospheric model configuration to the SSC. Our recommendation to them is attached. Thanks to all of you who have either participated in the development of the atmospheric model over the last few years, or contributed to the diagnostic evaluation of the many competing configurations. We look forward to seeing you at the June workshop in Breckenridge. Jim Hack Dave Randall ---------------------- To our SSC colleagues: We have collected and reviewed comments on the atmospheric configurations currently available to the AMWG. Based on these comments, and our own evaluation of the simulations, we are formally recommending a configuration for the new CCSM-2 atmospheric component that includes the major improvements to the CCM3 physical parameterizations previously discussed at SSC and CAB meetings (e.g., prognostic cloud water, longwave radiative transfer improvements, generalized cloud overlap), along with a modified version of the CCM3 Zhang-McFarlane convection scheme, using the spectral Eulerian dynamical core. The uncoupled simulations for this configuration are shown on the AMWG Phase III web page as cases zm31139evap06 and amipevap06. In addition to providing a much improved modeling framework, we believe this configuration provides a number of significant simulation improvements, most notably in the eastern equatorial Pacific. The model we are proposing will initially be configured to use a standard T42 Gaussian grid so that coupled modeling work in advance of the CCSM June workshop will not be delayed. After the workshop, we will provide a reduced-grid version of the model, which may require some modifications to the coupler, but which will also significantly improve simulation turnaround without introducing changes to the simulated climate. Although we have been forced to select a single model configuration for coupling purposes, many of the competing approaches have shown great promise for addressing remaining systematic biases. We believe there is merit to continued exploration of these approaches, such as the finite-volume and semi-Lagrangian dynamical cores, as well as physical parameterization packages, such as the new CSU Arakawa-Schubert cumulus scheme. We would like to reiterate our desire to maintain the existing AMWG research infrastructure for the immediate future, so that we can continue to build on the valuable work that has been completed in the process of defining the new atmospheric model. We hope the SSC will endorse this objective by committing the necessary technical resources so that a viable AMWG research framework can be maintained as the CCSM continues to evolve. Jim Hack Dave Randall Co-Chairs, CCSM Atmospheric Model Working Group