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33 results on '"Bacmeister, J. T."'

3. Reconciling and Improving Formulations for Thermodynamics and Conservation Principles in Earth System Models (ESMs)

Author

Lauritzen, P. H., primary, Kevlahan, N. K.‐R., additional, Toniazzo, T., additional, Eldred, C., additional, Dubos, T., additional, Gassmann, A., additional, Larson, V. E., additional, Jablonowski, C., additional, Guba, O., additional, Shipway, B., additional, Harrop, B. E., additional, Lemarié, F., additional, Tailleux, R., additional, Herrington, A. R., additional, Large, W., additional, Rasch, P. J., additional, Donahue, A. S., additional, Wan, H., additional, Conley, A., additional, and Bacmeister, J. T., additional

Published
2022
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4. Reconciling and Improving Formulations for Thermodynamics and Conservation Principles in Earth System Models (ESMs)

Author

Lauritzen, P. H., Kevlahan, N. K. R., Toniazzo, Thomas, Eldred, C., Dubos, T., Gassmann, A., Larson, V. E., Jablonowski, C., Guba, O., Shipway, B., Harrop, B. E., Lemarié, F., Tailleux, R., Herrington, A. R., Large, W., Rasch, P. J., Donahue, A. S., Wan, H., Conley, A., Bacmeister, J. T., Lauritzen, P. H., Kevlahan, N. K. R., Toniazzo, Thomas, Eldred, C., Dubos, T., Gassmann, A., Larson, V. E., Jablonowski, C., Guba, O., Shipway, B., Harrop, B. E., Lemarié, F., Tailleux, R., Herrington, A. R., Large, W., Rasch, P. J., Donahue, A. S., Wan, H., Conley, A., and Bacmeister, J. T.

Abstract

This paper provides a comprehensive derivation of the total energy equations for the atmospheric components of Earth System Models (ESMs). The assumptions and approximations made in this derivation are motivated and discussed. In particular, it is emphasized that closing the energy budget is conceptually challenging and hard to achieve in practice without resorting to ad hoc fixers. As a concrete example, the energy budget terms are diagnosed in a realistic climate simulation using a global atmosphere model. The largest total energy errors in this example are spurious dynamical core energy dissipation, thermodynamic inconsistencies (e.g., coupling parameterizations with the host model) and missing processes/terms associated with falling precipitation and evaporation (e.g., enthalpy flux between components). The latter two errors are not, in general, reduced by increasing horizontal resolution. They are due to incomplete thermodynamic and dynamic formulations. Future research directions are proposed to reconcile and improve thermodynamics formulations and conservation principles.

Published
2022
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6. The Whole Atmosphere Community Climate Model Version 6 (WACCM6)

Author

Gettelman, A., primary, Mills, M. J., additional, Kinnison, D. E., additional, Garcia, R. R., additional, Smith, A. K., additional, Marsh, D. R., additional, Tilmes, S., additional, Vitt, F., additional, Bardeen, C. G., additional, McInerny, J., additional, Liu, H.‐L., additional, Solomon, S. C., additional, Polvani, L. M., additional, Emmons, L. K., additional, Lamarque, J.‐F., additional, Richter, J. H., additional, Glanville, A. S., additional, Bacmeister, J. T., additional, Phillips, A. S., additional, Neale, R. B., additional, Simpson, I. R., additional, DuVivier, A. K., additional, Hodzic, A., additional, and Randel, W. J., additional

Published
2019
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7. The Origin of Systematic Errors in the GCM Simulation of ITCZ Precipitation

Author

Chao, Winston C, Suarez, M. J, Bacmeister, J. T, Chen, B, and Takacs, L. L

Subjects
Meteorology And Climatology
Abstract

Previous GCM studies have found that the systematic errors in the GCM simulation of the seasonal mean ITCZ intensity and location could be substantially corrected by adding suitable amount of rain re-evaporation or cumulus momentum transport. However, the reason(s) for these systematic errors and solutions has remained a puzzle. In this work the knowledge gained from previous studies of the ITCZ in an aqua-planet model with zonally uniform SST is applied to solve this puzzle. The solution is supported by further aqua-planet and full model experiments using the latest version of the Goddard Earth Observing System GCM.

Published
2006

11. CO 2 Increase Experiments Using the CESM: Relationship to Climate Sensitivity and Comparison of CESM1 to CESM2.

Author

Bacmeister, J. T., Hannay, C., Medeiros, B., Gettelman, A., Neale, R., Fredriksen, H. B., Lipscomb, W. H., Simpson, I., Bailey, D. A., Holland, M., Lindsay, K., and Otto‐Bliesner, B.

Subjects
*CLIMATE sensitivity, *CARBON dioxide, *DEFORESTATION, *GREENHOUSE gases, *ATMOSPHERIC models, *ATMOSPHERIC carbon dioxide
Abstract

We examine the response of the Community Earth System Model Versions 1 and 2 (CESM1 and CESM2) to abrupt quadrupling of atmospheric CO2 concentrations (4xCO2) and to 1% annually increasing CO2 concentrations (1%CO2). Different estimates of equilibrium climate sensitivity (ECS) for CESM1 and CESM2 are presented. All estimates show that the sensitivity of CESM2 has increased by 1.5 K or more over that of CESM1. At the same time the transient climate response (TCR) of CESM1 and CESM2 derived from 1%CO2 experiments has not changed significantly—2.1 K in CESM1 and 2.0 K in CESM2. Increased initial forcing as well as stronger shortwave radiation feedbacks are responsible for the increase in ECS seen in CESM2. A decomposition of regional radiation feedbacks and their contribution to global feedbacks shows that the Southern Ocean plays a key role in the overall behavior of 4xCO2 experiments, accounting for about 50% of the total shortwave feedback in both CESM1 and CESM2. The Southern Ocean is also responsible for around half of the increase in shortwave feedback between CESM1 and CESM2, with a comparable contribution arising over tropical ocean. Experiments using a thermodynamic slab‐ocean model (SOM) yield estimates of ECS that are in remarkable agreement with those from fully coupled Earth system model (ESM) experiments for the same level of CO2 increase. Finally, we show that the similarity of TCR in CESM1 and CESM2 masks significant regional differences in warming that occur in the 1%CO2 experiments for each model. Plain Language Summary: Computer models of the Earth's climate system are complex. Our best guess scenarios for how the climate system will change due to human activity over the next century are also complex. They include estimates of changing greenhouse gas (e.g., CO2) levels in the atmosphere, aerosol (e.g., smog and haze) emissions, and land use changes (e.g., deforestation and urbanization). To help understand this complex system, the climate modeling community has designed two simplified experiments: abrupt CO2 quadrupling (4xCO2) and 1% annual CO2 increase (1%CO2). In these experiments all human‐induced factors in the climate system are held constant (at preindustrial levels) except for CO2 in the atmosphere. Results of these experiments from different climate models can be compared to gain insight into the climate system. We look at two versions of the Community Earth System Model (CESM1 and CESM2). The warming simulated in the 4xCO2 experiment (climate sensitivity) has increased substantially in CESM2. This is related to changes in clouds over the Southern Ocean and tropics. At the same time warming in in the 1%CO2 experiment has not increased. This is related to differences in how CESM1 and CESM2 simulate northern oceans (Arctic, North Atlantic, and North Pacific). Key Points: Climate sensitivity has increased from 4 K to over 5 K in CESM2 compared to CESM1Shortwave radiation feedbacks over the Southern Ocean play a key role in determining the response of CESM to increasing CO2Various measures of climate response, including equilibrium climate sensitivity (ECS) and transient climate response (TCR), are not simply related in CESM [ABSTRACT FROM AUTHOR]

Published
2020
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12. NCAR Release of CAM‐SE in CESM2.0: A Reformulation of the Spectral Element Dynamical Core in Dry‐Mass Vertical Coordinates With Comprehensive Treatment of Condensates and Energy

Author

Lauritzen, P. H., primary, Nair, R. D., additional, Herrington, A. R., additional, Callaghan, P., additional, Goldhaber, S., additional, Dennis, J. M., additional, Bacmeister, J. T., additional, Eaton, B. E., additional, Zarzycki, C. M., additional, Taylor, Mark A., additional, Ullrich, P. A., additional, Dubos, T., additional, Gettelman, A., additional, Neale, R. B., additional, Dobbins, B., additional, Reed, K. A., additional, Hannay, C., additional, Medeiros, B., additional, Benedict, J. J., additional, and Tribbia, J. J., additional

Published
2018
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20. Mountain Waves in the Stratosphere

Author

NAVAL RESEARCH LAB WASHINGTON DC SPACE SCIENCE DIV, Eckermann, S. D., Broutman, D., Tan, K. A., Preusse, P., Bacmeister, J. T., NAVAL RESEARCH LAB WASHINGTON DC SPACE SCIENCE DIV, Eckermann, S. D., Broutman, D., Tan, K. A., Preusse, P., and Bacmeister, J. T.

Abstract

This article describes recent progress in our efforts to model, forecast, and observe mountain waves in the stratosphere. We have developed a numerical model that globally forecasts stratospheric mountain wave effects. Recent improvements to that model are outlined briefly. We illustrate the potential usefulness of these model forecasts by successfully "hindcasting" some cases where unexpected severe turbulence was encountered by aircraft at stratospheric cruise altitudes. We also show the model's usefulness in forecasting mountain-wave-induced polar stratospheric clouds. which play a crucial role in stratospheric ozone depletion. Finally, we describe some recent satellite observations that have provided us with global data on stratospheric mountain wave distributions, allowing us to benchmark our global mountain wave predictions against data for the first time., Reprinted from 2000 NRL Review. Prepared in collaboration with Computational Physics, the University of New South Wales, the University of Wuppertal, and Universities Space Research Association. Sponsored by Office of Naval Research and the National Aeronautics and Space Adminstration. The original document contains color images.

Published
2000

21. NCAR global model topography generation software for unstructured grids.

Author

Lauritzen, P. H., Bacmeister, J. T., Callaghan, P. F., and Taylor, M. A.

Subjects
*TOPOGRAPHY, *ATMOSPHERIC models, *TURBULENT flow, *PARAMETERIZATION, *COMPUTER software, *NUMERICAL grid generation (Numerical analysis)
Abstract

It is the purpose of this paper to document the NCAR global model topography generation software for unstructured grids. Given a model grid, the software computes the fraction of the grid box covered by land, the gridbox mean elevation, and associated sub-grid scale variances commonly used for gravity wave and turbulent mountain stress parameterizations. The software supports regular latitude-longitude grids as well as unstructured grids; e.g. icosahedral, Voronoi, cubed-sphere and variable resolution grids. As an example application and in the spirit of documenting model development, exploratory simulations illustrating the impacts of topographic smoothing with the NCARDOE CESM (Community Earth System Model) CAM5.2-SE (Community Atmosphere Model version 5.2 - Spectral Elements dynamical core) are shown. [ABSTRACT FROM AUTHOR]

Published
2015
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