Simulation of the Global Hydrological Cycle in the CCSM Community Atmosphere Model Version 3 (CAM3): Mean Features

Hack, James J.; Caron, Julie M.; Yeager, Stephen; Oleson, Keith W.; Holland, Marika M.; Truesdale, John; Rasch, Philip J.

doi:10.1175/jcli3755.1

Cited by 148 publications

(125 citation statements)

References 60 publications

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“…Horizontal resolution in the model thus does not seem to be the primary culprit for reduced blocking frequency in atmospheric models, consistent with earlier findings (e.g., Scaife et al 2010). This is despite the fact that the low-level dynamical circulation features in CAM3 at T85 horizontal resolution are improved relative to those at T42 when compared to observations (Hack et al 2006a).…”

Section: Model Resolution and Topographysupporting

confidence: 86%

“…A detailed description of CAM3 can be found in Collins et al (2006a) and Hurrell et al (2006). Other model-specific aspects relevant to this study are described in Hack et al (2006b) in relation to the model's simulation of the hydrological cycle, tropical Pacific variability (Zelle et al 2005;Deser et al 2006), and specifically the climate of the Australian region (Ummenhofer et al , 2009.…”

Section: B Agcm Experimentsmentioning

confidence: 99%

“…For further details on more general aspects of SH climate in CAM3, we refer the reader to Collins et al (2006a,b), Hack et al (2006b), and Hurrell et al (2006).…”

Section: Model Mean Statementioning

confidence: 99%

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Impact of Surface Forcing on Southern Hemisphere Atmospheric Blocking in the Australia–New Zealand Sector

et al. 2013

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Characteristics of atmospheric blocking in the Southern Hemisphere (SH) are explored in atmospheric general circulation model (AGCM) simulations with the Community Atmosphere Model, version 3, with a particular focus on the Australia-New Zealand sector. Preferred locations of blocking in SH observations and the associated seasonal cycle are well represented in the AGCM simulations, but the observed magnitude of blocking is underestimated throughout the year, particularly in late winter and spring. This is related to overly zonal flow due to an enhanced meridional pressure gradient in the model, which results in a decreased amplitude of the longwave trough/ridge pattern. A range of AGCM sensitivity experiments explores the effect on SH blocking of tropical heating, midlatitude sea surface temperatures, and land-sea temperature gradients created over the Australian continent during austral winter. The combined effects of tropical heating and extratropical temperature gradients are further explored in a configuration that is favorable for blocking in the Australia-New Zealand sector with warm SST anomalies to the north of Australia, cold to the southwest of Australia, warm to the southeast, and cool Australian land temperatures. The blockingfavorable configuration indicates a significant strengthening of the subtropical jet and a reduction in midlatitude flow, which results from changes in the thermal wind. While these overall changes in mean climate, predominantly forced by the tropical heating, enhance blocking activity, the magnitude of atmospheric blocking compared to observations is still underestimated. The blocking-unfavorable configuration with surface forcing anomalies of opposite sign results in a weakening subtropical jet, enhanced midlatitude flow, and significantly reduced blocking.

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Section: Model Resolution and Topographysupporting

confidence: 86%

Section: B Agcm Experimentsmentioning

confidence: 99%

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Impact of Surface Forcing on Southern Hemisphere Atmospheric Blocking in the Australia–New Zealand Sector

et al. 2013

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“…Similar to the ERA-40 data, CMAP does not extend the NPST P as far into North America as does CAM3. Hack et al (2006b, their Fig. 19) compare annual mean P between CAM3 and CCSM3 and find similar P bias over Europe and adjacent Atlantic waters.…”

Section: Bias In Diabatic Heating Fieldsmentioning

confidence: 79%

Sources of CAM3 temperature bias during northern winter from diagnostic study of the temperature bias equation

2009

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The Community Atmosphere Model version 3 (CAM3) temperature simulation bias is examined in this paper. We compare CAM3 output with European Centre for Medium-Range Weather Forecasts (ECMWF) 40 year reanalysis (ERA-40) data. We formulate a time mean temperature bias equation then evaluate each term in the equation. Our focus is on the Northern Hemisphere winter time. We group the temperature equation terms into these categories: linear advection terms, nonlinear advection terms, transient eddy terms and diabatic heating, and find that linear advection and diabatic bias are the largest. The nonlinear terms (velocity bias advection of temperature bias) are much smaller than each of the other groups of terms at all levels except near the surface. Linear advection terms have dipolar pattern in the Atlantic (negative NW of positive) which reflects the shift of the CAM3 model North Atlantic storm track (NAST) into Europe, especially in the upper troposphere; opposite sign dipolar structure occurs over Alaska (positive) and the north Pacific storm track (negative). The transient advection terms in middle latitudes are larger in the upper troposphere and generally positive along the Atlantic storm track. Along the north Pacific storm track (NPST), the transient terms are negative in the mid and lower troposphere over much of the NPST (positive in upper troposphere). The diabatic heating bias has large values in the tropics along the Intertropical Convergence Zone (ICZ) and along the midlatitude storm tracks. During this time of year the ICZ is mainly in the Southern Hemisphere, but CAM3 emphasizes an ICZ-like heating in the northern hemisphere of the Atlantic and Pacific Oceans. CAM3 tends to have a weaker ICZ, especially in the Atlantic. In midlatitudes, we find large bias in heating by precipitation and vertically averaged net radiation over the NAST, Europe, and the Middle East.

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“…In the model, these two maxima are clearly separated by a local minimum in H 2 O mix at the Equator. This is connected to the model having a tendency to produce a double intertropical convergence zone (ITCZ) (Hack et al 2006). The transport time to higher altitudes in the model seems to be fairly realistic but the amount of water vapor transported from tropics to higher latitudes is underestimated.…”

Section: Stratospheric Transportmentioning

confidence: 99%

Modeling Water Vapor in the Upper Troposphere and Lower Stratosphere

Gulstad¹,

Isaksen²

2007

Terr. Atmos. Ocean. Sci.

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Simulation of the Global Hydrological Cycle in the CCSM Community Atmosphere Model Version 3 (CAM3): Mean Features

Cited by 148 publications

References 60 publications

Impact of Surface Forcing on Southern Hemisphere Atmospheric Blocking in the Australia–New Zealand Sector

Impact of Surface Forcing on Southern Hemisphere Atmospheric Blocking in the Australia–New Zealand Sector

Sources of CAM3 temperature bias during northern winter from diagnostic study of the temperature bias equation

Modeling Water Vapor in the Upper Troposphere and Lower Stratosphere

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