Using enthalpy as a prognostic variable in atmospheric modelling with variable composition

Akmaev, R. A.; Juang, Hann‐Ming Henry

doi:10.1002/qj.345

Cited by 15 publications

(16 citation statements)

References 20 publications

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“…The Whole Atmosphere Model (WAM) has been developed to study dynamical links between the lower atmosphere and the upper atmosphere and ionosphere [ Akmaev , 2011; Akmaev et al , 2008; Akmaev and Juang , 2008; Fuller‐Rowell et al , 2008]. WAM is a general circulation model of the neutral atmosphere from 0 to 600 km altitude built on an existing operational Global Forecast System (GFS) model used by the U.S. National Weather Service (NWS) for medium‐range weather prediction.…”

Section: Models and Simulationsmentioning

confidence: 99%

“…The current version of WAM uses a spectral resolution T62, corresponding to 1.8° × 1.8° in latitude‐longitude. The vertical extension of the model domain required the additional physical processes (e.g., ion drag, Joule heating, eddy mixing; details are given by Akmaev et al [2008]), and also substantial changes in the dynamical core [ Akmaev , 2011; Akmaev and Juang , 2008]. Simulation results of the diurnal tide with zonal wave number one (DW1), the semidiurnal tide with zonal wave number two (SW2), and the non‐migrating diurnal wave number three (DE3) from WAM have shown good agreement with data [e.g., Akmaev et al , 2008].…”

Section: Models and Simulationsmentioning

confidence: 99%

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Longitudinal variation of ionospheric vertical drifts during the 2009 sudden stratospheric warming

et al. 2012

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[1] The Whole Atmospheric Model (WAM) initialized with a data assimilation scheme is capable of simulating real sudden stratospheric warming (SSW) events. The electrodynamics in the Coupled Thermosphere Ionosphere and Plasmasphere with Electrodynamics model (CTIPe) was driven by the WAM thermospheric winds in January 2009 to study the response of ionospheric drifts during the SSW. Simulation results are compared with observations of the vertical drift at Jicamarca and the equatorial electrojet (EEJ) in the Asian sectors. Early morning upward drift and afternoon downward drift are reproduced in all longitudes in the simulations, and are consistent with the available observations. Results also show that the occurrence time of the early morning upward drift and afternoon downward drift have significant phase differences between different longitudes. Simulations suggest that during the SSW the longitude dependence of the amplitude and phase of the equatorial vertical plasma drift is caused by the changing magnitudes of the migrating tides modulated by the geometry of the geomagnetic field. Some additional day-to-day variability and modulation of the phase structures at different longitudes in ionospheric vertical drifts during the SSW are possibly produced by the short-term changes in the non-migrating tides and by planetary waves.

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Section: Models and Simulationsmentioning

confidence: 99%

Section: Models and Simulationsmentioning

confidence: 99%

Longitudinal variation of ionospheric vertical drifts during the 2009 sudden stratospheric warming

et al. 2012

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“…The Whole Atmosphere Model (WAM) is being developed under the Integrated Dynamics in the Earth's Atmosphere (IDEA) project to study dynamical links between the lower atmosphere and the upper atmosphere and ionosphere [ Akmaev et al , 2008; Akmaev and Juang , 2008; Fuller‐Rowell et al , 2008]. It represents a neutral‐atmosphere component of the coupled IDEA model and is an extension of the medium‐range weather prediction Global Forecast System (GFS) model to the top of the atmosphere [ Akmaev et al , 2008].…”

Section: Modelmentioning

confidence: 99%

Midnight temperature maximum (MTM) in Whole Atmosphere Model (WAM) simulations

Akmaev

Fuller‐Rowell

et al. 2009

Geophysical Research Letters

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[1] Discovered almost four decades ago, the midnight temperature maximum (MTM) with typical magnitudes of 50-100 K has been regularly observed by satellite and ground-based instruments in the tropical upper thermosphere. Although several mechanisms have been suggested to explain the phenomenon, previous attempts to reproduce it with comprehensive thermosphere-ionosphere models have been unsuccessful. First long-term simulations with the Whole Atmosphere Model (WAM) reveal the presence of a realistically prominent MTM and reproduce the salient features of its daily, seasonal, and latitudinal variability. Preliminary analysis indicates that the feature may be traced down to the lower thermosphere, where it is manifested primarily in the form of an upward propagating terdiurnal tidal wave. Its spectrum expands to higher-order zonal wavenumbers and frequencies and its phase advances to near midnight higher up in the thermosphere. Possible mechanisms generating this wave may involve nonlinear interactions between other tidal harmonics originating in the middle and lower atmosphere. Our results thus suggest that the MTM is yet another phenomenon driven by dynamical links between the lower and upper atmosphere and ionosphere. Citation: Akmaev, R. A., F. Wu, T. J.

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“…As mentioned in Akmaev and Juang (2008), from Hirschfelder et al (1964), the IEE for gas-type compositions, while the external forcing acting on each molecule is proportional to its mass, can be written as…”

Section: B Internal Energy Equationmentioning

confidence: 99%

“…Any gas-form tracer, such as ozone, has its own heat contribution to the environment through the internal energy equation (IEE). To collaborate with SWPC, all gases are considered in thermodynamic equation and enthalpy is used as a thermodynamic variable (Akmaev and Juang 2008) to reduce the computation while all gases are included in thermodynamic equations, as derived from IEE without further approximation and assumptions.…”

Section: Introductionmentioning

confidence: 99%

A Multiconserving Discretization with Enthalpy as a Thermodynamic Prognostic Variable in Generalized Hybrid Vertical Coordinates for the NCEP Global Forecast System

Juang

2011

Mon. Wea. Rev.

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A new vertical discretization used in the atmospheric dynamics of the National Centers for Environmental Prediction (NCEP) Global Forecast System (GFS) is illustrated, with enthalpy as the thermodynamic prognostic variable to reduce computation in thermodynamic equations while concerning all gas tracers in the model. Mass, energy, entropy, and angular momentum conservations are utilized as constraints to discretize the vertical integration with a finite-difference scheme. A specific definition of a generalized hybrid vertical coordinate, including sigma, isobaric, and isentropic surfaces, is introduced to define pressure at the model levels. Vertical fluxes are obtained by the equation of local changes in variables defined for vertical coordinates at all model layers. The forward-weighting semi-implicit time scheme is utilized to eliminate computational noise for stable integration. Because of time splitting between the dynamic and physics processes, the vertical advection is required both in the model dynamics and model physics, and the semi-implicit time scheme is used both in dynamics and after physics computation.Three configurations-sigma, sigma pressure, and sigma entropy-from the specific hybrid vertical coordinates with layer definition similar to NCEP operational GFS have been implemented in the NCEP GFS. Results from the sigma-isentropic coordinate show the largest anomaly correlation and the smallest rootmean-square error in tropical wind among all results at all layers, especially the upper layers. The scores from a period of daily forecast up to 5 days with the sigma-isentropic coordinate show the same level of skill as compared to the NCEP operational GFS. The results from the hurricane tracks for the fall of 2005 with sigmaisentropic coordinates show better scores compared with the operational GFS.

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Using enthalpy as a prognostic variable in atmospheric modelling with variable composition

Cited by 15 publications

References 20 publications

Longitudinal variation of ionospheric vertical drifts during the 2009 sudden stratospheric warming

Longitudinal variation of ionospheric vertical drifts during the 2009 sudden stratospheric warming

Midnight temperature maximum (MTM) in Whole Atmosphere Model (WAM) simulations

A Multiconserving Discretization with Enthalpy as a Thermodynamic Prognostic Variable in Generalized Hybrid Vertical Coordinates for the NCEP Global Forecast System

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