scholarly journals Three-dimensional parameterizations of the synoptic scale kinetic energy and momentum flux in the Earth's atmosphere

2011 ◽  
Vol 18 (6) ◽  
pp. 807-827 ◽  
Author(s):  
D. Coumou ◽  
V. Petoukhov ◽  
A. V. Eliseev
Keyword(s):  
Kinetic Energy ◽  
Momentum Flux ◽  
General Circulation ◽  
Three Dimensional ◽  
Circulation Model ◽  
Storm Tracks ◽  
Synoptic Scale ◽  
Dynamical Equations ◽  
Turbulent Diffusion Coefficient ◽  
Energy And Momentum

Abstract. We present a new set of statistical-dynamical equations (SDEs) which can accurately reproduce the three-dimensional atmospheric fields of synoptic scale kinetic energy and momentum flux. The set of equations is closed by finding proper parameterizations for the vertical macro-turbulent diffusion coefficient and ageostrophic terms. The equations have been implemented in a new SD atmosphere model, named Aeolus. We show that the synoptic scale kinetic energy and momentum fluxes generated by the model are in good agreement with empirical data, which were derived from bandpass-filtered ERA-40 data. In addition to present-day climate, the model is tested for substantially colder (last glacial maximum) and warmer (2×CO2) climates, and shown to be in agreement with general circulation model (GCM) results. With the derived equations, one can efficiently study the position and strength of storm tracks under different climate scenarios with calculation time a fraction of those of GCMs. This work prepares ground for the development of a new generation of fast Earth System Models of Intermediate Complexity which are able to perform multi-millennia simulations in a reasonable time frame while appropriately accounting for the climatic effect of storm tracks.

Barotropic Impacts of Surface Friction on Eddy Kinetic Energy and Momentum Fluxes: An Alternative to the Barotropic Governor

2012 ◽  
Vol 69 (10) ◽  
pp. 3028-3039 ◽  
Author(s):  
Elizabeth A. Barnes ◽  
Chaim I. Garfinkel
Keyword(s):  
Kinetic Energy ◽  
Momentum Flux ◽  
General Circulation ◽  
Circulation Model ◽  
Surface Friction ◽  
Eddy Kinetic Energy ◽  
Surface Drag ◽  
Momentum Fluxes ◽  
Upper Level ◽  
Energy And Momentum

Abstract As the surface drag is increased in a comprehensive general circulation model (GCM), the upper-level zonal winds decrease and eddy momentum flux convergence into the jet core increases. Globally averaged eddy kinetic energy decreases, a response that is inconsistent with the conventional barotropic governor mechanism whereby decreased barotropic shears encourage baroclinic wave growth. As the conventional barotropic governor appears insufficient to explain the entire response in the comprehensive GCM, the nondivergent barotropic model on the sphere is used to demonstrate an additional mechanism for the effect of surface drag on eddy momentum fluxes and eddy kinetic energy. Analysis of the pseudomomentum budget shows that increased drag modifies the background meridional vorticity gradient, which allows for enhanced eddy momentum flux convergence and decreased eddy kinetic energy in the presence of a constant eddy source. This additional feedback may explain the changes in eddy momentum fluxes observed in the comprehensive GCM and was likely present in previous work on the barotropic governor.

scholarly journals Downstream Self-Destruction of Storm Tracks

2011 ◽  
Vol 68 (10) ◽  
pp. 2459-2464 ◽  
Author(s):  
Yohai Kaspi ◽  
Tapio Schneider
Keyword(s):  
Kinetic Energy ◽  
Rotation Rate ◽  
General Circulation ◽  
Energy Transport ◽  
Circulation Model ◽  
Eddy Kinetic Energy ◽  
Storm Tracks ◽  
Planetary Rotation ◽  
The Pacific ◽  
Longitudinal Length

Abstract The Northern Hemisphere storm tracks have maximum intensity over the Pacific and Atlantic basins; their intensity is reduced over the continents downstream. Here, simulations with an idealized aquaplanet general circulation model are used to demonstrate that even without continents, storm tracks have a self-determined longitudinal length scale. Their length is controlled primarily by the planetary rotation rate and is similar to that of Earth’s storm tracks for Earth’s rotation rate. Downstream, storm tracks self-destruct: the downstream eddy kinetic energy is lower than it would be without the zonal asymmetries that cause localized storm tracks. Likely involved in the downstream self-destruction of storm tracks are the energy fluxes associated with them. The zonal asymmetries that cause localized storm tracks enhance the energy transport through the generation of stationary eddies, and this leads to a reduced baroclinicity that persists far downstream of the eddy kinetic energy maxima.

scholarly journals Operational ocean models in the Adriatic Sea: a skill assessment

Ocean Science ◽  
2008 ◽  
Vol 4 (1) ◽  
pp. 61-71 ◽  
Author(s):  
J. Chiggiato ◽  
P. Oddo
Keyword(s):  
General Circulation ◽  
Mean Squared Error ◽  
Three Dimensional ◽  
Circulation Model ◽  
Remote Sensing Data ◽  
Skill Assessment ◽  
Regional Models ◽  
Operational Systems ◽  
Forecasting System ◽  
The Mediterranean

Abstract. In the framework of the Mediterranean Forecasting System (MFS) project, the performance of regional numerical ocean forecasting systems is assessed by means of model-model and model-data comparison. Three different operational systems considered in this study are: the Adriatic REGional Model (AREG); the Adriatic Regional Ocean Modelling System (AdriaROMS) and the Mediterranean Forecasting System General Circulation Model (MFS-GCM). AREG and AdriaROMS are regional implementations (with some dedicated variations) of POM and ROMS, respectively, while MFS-GCM is an OPA based system. The assessment is done through standard scores. In situ and remote sensing data are used to evaluate the system performance. In particular, a set of CTD measurements collected in the whole western Adriatic during January 2006 and one year of satellite derived sea surface temperature measurements (SST) allow to asses a full three-dimensional picture of the operational forecasting systems quality during January 2006 and to draw some preliminary considerations on the temporal fluctuation of scores estimated on surface quantities between summer 2005 and summer 2006. The regional systems share a negative bias in simulated temperature and salinity. Nonetheless, they outperform the MFS-GCM in the shallowest locations. Results on amplitude and phase errors are improved in areas shallower than 50 m, while degraded in deeper locations, where major models deficiencies are related to vertical mixing overestimation. In a basin-wide overview, the two regional models show differences in the local displacement of errors. In addition, in locations where the regional models are mutually correlated, the aggregated mean squared error was found to be smaller, that is a useful outcome of having several operational systems in the same region.

scholarly journals Simulation of satellite lidar and radiometer retrievals of a general circulation model three-dimensional cloud data set

1998 ◽  
Vol 103 (D20) ◽  
pp. 26025-26039 ◽  
Author(s):  
M. Doutriaux-Boucher ◽  
J. Pelon ◽  
V. Trouillet ◽  
G. Sèze ◽  
H. Le Treut ◽  
...  
Keyword(s):  
General Circulation Model ◽  
General Circulation ◽  
Three Dimensional ◽  
Circulation Model ◽  
Data Set ◽  
Cloud Data

scholarly journals The Steady-State Atmospheric Circulation Response to Climate Change–like Thermal Forcings in a Simple General Circulation Model

2010 ◽  
Vol 23 (13) ◽  
pp. 3474-3496 ◽  
Author(s):  
Amy H. Butler ◽  
David W. J. Thompson ◽  
Ross Heikes
Keyword(s):  
Climate Change ◽  
Steady State ◽  
General Circulation Model ◽  
General Circulation ◽  
Storm Track ◽  
Circulation Model ◽  
Storm Tracks ◽  
Polar Surface ◽  
Tropical Troposphere ◽  
Polar Stratosphere

Abstract The steady-state extratropical atmospheric response to thermal forcing is investigated in a simple atmospheric general circulation model. The thermal forcings qualitatively mimic three key aspects of anthropogenic climate change: warming in the tropical troposphere, cooling in the polar stratosphere, and warming at the polar surface. The principal novel findings are the following: 1) Warming in the tropical troposphere drives two robust responses in the model extratropical circulation: poleward shifts in the extratropical tropospheric storm tracks and a weakened stratospheric Brewer–Dobson circulation. The former result suggests heating in the tropical troposphere plays a fundamental role in the poleward contraction of the storm tracks found in Intergovernmental Panel on Climate Change (IPCC)-class climate change simulations; the latter result is in the opposite sense of the trends in the Brewer–Dobson circulation found in most previous climate change experiments. 2) Cooling in the polar stratosphere also drives a poleward shift in the extratropical storm tracks. The tropospheric response is largely consistent with that found in previous studies, but it is shown to be very sensitive to the level and depth of the forcing. In the stratosphere, the Brewer–Dobson circulation weakens at midlatitudes, but it strengthens at high latitudes because of anomalously poleward heat fluxes on the flank of the polar vortex. 3) Warming at the polar surface drives an equatorward shift of the storm tracks. The storm-track response to polar warming is in the opposite sense of the response to tropical tropospheric heating; hence large warming over the Arctic may act to attenuate the response of the Northern Hemisphere storm track to tropical heating. 4) The signs of the tropospheric and stratospheric responses to all thermal forcings considered here are robust to seasonal changes in the basic state, but the amplitude and details of the responses exhibit noticeable differences between equinoctial and wintertime conditions. Additionally, the responses exhibit marked nonlinearity in the sense that the response to multiple thermal forcings applied simultaneously is quantitatively different from the sum of the responses to the same forcings applied independently. Thus the response of the model to a given thermal forcing is demonstrably dependent on the other thermal forcings applied to the model.

The role of drift mass in the kinetic energy and momentum of periodic water waves and sound waves

1997 ◽  
Vol 331 ◽  
pp. 429-438 ◽  
Author(s):  
CHIA-SHUN YIH
Keyword(s):  
Kinetic Energy ◽  
Water Waves ◽  
Three Dimensional ◽  
Periodic Waves ◽  
Sound Waves ◽  
Linear Waves ◽  
Energy And Momentum ◽  
Linear Water Waves ◽  
Wave Momentum

For two-dimensional periodic water waves or sound waves, the kinetic energy per wavelength is ½mdc2, and the momentum per wavelength is ±mdc, where c is the wave velocity, and md is the drift mass per wavelength. These results also hold for three-dimensional periodic waves, for which the kinetic energy, momentum, and drift mass are all for one wave cell, the area of which is the product of the wavelengths in two perpendicular directions.The results obtained are rigorous, and not restricted to linear waves or even to nonlinear symmetric waves. For linear water waves, in particular, the kinetic energy can be shown to be equal to the sum of the potential energy and the surface energy (due to surface tension), so that the total energy E is twice the kinetic energy, andformula hereMcIntyre's (1981) contention that wave momentum is a myth is discussed at length for both water waves and sound waves.

scholarly journals Energy of Midlatitude Transient Eddies in Idealized Simulations of Changed Climates

2008 ◽  
Vol 21 (22) ◽  
pp. 5797-5806 ◽  
Author(s):  
Paul A. O’Gorman ◽  
Tapio Schneider
Keyword(s):  
Kinetic Energy ◽  
Potential Energy ◽  
Radiative Forcing ◽  
General Circulation ◽  
Thermal Structure ◽  
Circulation Model ◽  
Static Stability ◽  
Eddy Kinetic Energy ◽  
Available Potential Energy ◽  
Wide Range

Abstract As the climate changes, changes in static stability, meridional temperature gradients, and availability of moisture for latent heat release may exert competing effects on the energy of midlatitude transient eddies. This paper examines how the eddy kinetic energy in midlatitude baroclinic zones responds to changes in radiative forcing in simulations with an idealized moist general circulation model. In a series of simulations in which the optical thickness of the longwave absorber is varied over a wide range, the eddy kinetic energy has a maximum for a climate with mean temperature similar to that of present-day earth, with significantly smaller values both for warmer and for colder climates. In a series of simulations in which the meridional insolation gradient is varied, the eddy kinetic energy increases monotonically with insolation gradient. In both series of simulations, the eddy kinetic energy scales approximately linearly with the dry mean available potential energy averaged over the baroclinic zones. Changes in eddy kinetic energy can therefore be related to the changes in the atmospheric thermal structure that affect the mean available potential energy.

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