The atmospheric hydrologic cycle in the ACME v0.3 model

Journal Article · 28 July 2017 · Climate Dynamics

DOI: https://doi.org/10.1007/s00382-017-3803-x · OSTI ID:1468074

Terai, Christopher R.  ^[1]; Caldwell, Peter M. ^[1]; Klein, Stephen A. ^[1]; Tang, Qi ^[1]; Branstetter, Marcia L.  ^[2]

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1. Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States). Cloud Processes Research Group
2. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

In this paper, we examine the global water cycle characteristics in the Accelerated Climate Modeling for Energy v0.3 model (a close relative to version 5.3 of the Community Atmosphere Model) in atmosphere-only simulations spanning the years 1980–2005. We evaluate the simulations using a broad range of observational and reanalysis datasets, examine how the simulations change when the horizontal resolution is increased from 1° to 0.25°, and compare the simulations against models participating in the the Atmosphere Model Intercomparison Project of the 5th Coupled Model Intercomparison Project (CMIP5). Particular effort has been made to evaluate the model using the best available observational estimates and verifying model biases with additional datasets when differences are known to exist among the observations. Regardless of resolution, the model exhibits several biases: global-mean precipitation, evaporation, and precipitable water are too high, light precipitation occurs too frequently, and the atmospheric residence time of water is too short. Many of these biases are shared by the multi-model mean climate of models participating in CMIP5. The reasons behind regional biases in precipitation are discussed by examining how different fields, such as local evaporation and transport of water vapor, contribute to the bias. Although increasing the horizontal resolution does not drastically change the water cycle, it does lead to a few differences: an increase in global mean precipitation rate, an increase in the fraction of total precipitation that falls over land, more frequent heavy precipitation (>30 mm day^-1), and a decrease in precipitable water. One of the most notable changes is the shift of precipitation produced by the convective parameterization to that produced by the large-scale microphysics parameterization. We analyze how changes in moisture and circulation with resolution contribute to this shift in the precipitation partitioning. Because changing horizontal resolution requires some re-tuning, the effect of that tuning was evaluated by performing an additional simulation at 1° but using the tunings from the 0.25° simulation. Lastly, the evaluation shows that the more frequent heavy precipitation, the decrease in precipitable water, and the shift from convective to large-scale precipitation are predominantly due to resolution changes, while tuning changes have a major influence on the global mean precipitation and the land/ocean partitioning of precipitation.

• Research Organization: Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States). Oak Ridge Leadership Computing Facility (OLCF); Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA (United States). National Energy Research Scientific Computing Center (NERSC)
• Sponsoring Organization: USDOE Office of Science (SC), Biological and Environmental Research (BER); USDOE Office of Science (SC), Advanced Scientific Computing Research (ASCR)
• Grant/Contract Number: AC05-00OR22725; AC02-06CH11357; AC02-05CH11231; AC52-07NA27344
• OSTI ID: 1468074
• Alternate ID(s): OSTI ID: 1461872
• Journal Information: Climate Dynamics, Vol. 50, Issue 9-10; ISSN 0930-7575
• Publisher: Springer-VerlagCopyright Statement
• Country of Publication: United States
• Language: English