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- Author or Editor: FRANCIS J. WINNINGHOFF x
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Abstract
A restorative-iterative procedure is tested in initializing the height and wind fields for a global, barotropic prediction model. Real 500-mb data are used as the basis of initial height values in the midlatitudes and as the basis of the initial stream function values in the Tropics. The procedure is tested for the case of frictionless and adiabatic flow and for the case where friction and a simulated heating function are included. Experiments were also performed in which an “observed” divergent wind was added in the Tropics. Results are encouraging in the sense that use of the procedure substantially reduces the amplitudes of the external inertia-gravity motions excited by the initial imbalance between the mass and wind fields.
Abstract
A restorative-iterative procedure is tested in initializing the height and wind fields for a global, barotropic prediction model. Real 500-mb data are used as the basis of initial height values in the midlatitudes and as the basis of the initial stream function values in the Tropics. The procedure is tested for the case of frictionless and adiabatic flow and for the case where friction and a simulated heating function are included. Experiments were also performed in which an “observed” divergent wind was added in the Tropics. Results are encouraging in the sense that use of the procedure substantially reduces the amplitudes of the external inertia-gravity motions excited by the initial imbalance between the mass and wind fields.
Abstract
The U.S. Navy Fleet Numerical Weather Central (FNWC), Monterey, Calif., five-layer, primitive-equation, atmospheric prediction model has been under development since late 1968 and became operational in September 1970. Seventy-two-hour prognoses are generated twice daily, requiring 2 hr per run.
The conservation forms of the difference equations are based on the Arakawa technique and are integrated, using a 381-km space step (at 60°N) and a 10-min time step, on sigma surfaces. Realistic mountains are used. Pressure-force terms are replaced by a single geopotential gradient on pressure surfaces synthesized locally to reduce inconsistent truncation error. Lateral diffusion is performed on forecast difference fields to prevent systematic distortions of sigma-surface state parameter distributions. Stress is applied at the lowest level. Restoration boundaries and centered time differencing are used. The integrations are restarted each 6 hr with a Euler-backward step to reduce solution separation.
The moisture and heat source and sink terms are modeled in a similar manner to those in the Mintz and Arakawa general circulation model. Terms representing evaporation and large-scale condensation, sensible heat exchange, a parameterization of cumulus convection and precipitation, and solar and terrestrial radiation are included. Dry convective adjustment precludes hydrostatic instability.
Initialization of the model is based on FNWCs Northern Hemisphere objective analyses of the state parameter structure from the surface to 50 mb. Nondivergent initial wind fields are obtained from solution of a linear balance equation.
The verification results are encouraging. The 36-hr sea-level pressure prognoses exhibit considerable skill. The model's ability to simulate the generation of new storms in the winter is noteworthy. Problems included the slow movement of small-scale features (truncation problem), need for improvement in description of the heating and friction, and a need for improved initialization.
Abstract
The U.S. Navy Fleet Numerical Weather Central (FNWC), Monterey, Calif., five-layer, primitive-equation, atmospheric prediction model has been under development since late 1968 and became operational in September 1970. Seventy-two-hour prognoses are generated twice daily, requiring 2 hr per run.
The conservation forms of the difference equations are based on the Arakawa technique and are integrated, using a 381-km space step (at 60°N) and a 10-min time step, on sigma surfaces. Realistic mountains are used. Pressure-force terms are replaced by a single geopotential gradient on pressure surfaces synthesized locally to reduce inconsistent truncation error. Lateral diffusion is performed on forecast difference fields to prevent systematic distortions of sigma-surface state parameter distributions. Stress is applied at the lowest level. Restoration boundaries and centered time differencing are used. The integrations are restarted each 6 hr with a Euler-backward step to reduce solution separation.
The moisture and heat source and sink terms are modeled in a similar manner to those in the Mintz and Arakawa general circulation model. Terms representing evaporation and large-scale condensation, sensible heat exchange, a parameterization of cumulus convection and precipitation, and solar and terrestrial radiation are included. Dry convective adjustment precludes hydrostatic instability.
Initialization of the model is based on FNWCs Northern Hemisphere objective analyses of the state parameter structure from the surface to 50 mb. Nondivergent initial wind fields are obtained from solution of a linear balance equation.
The verification results are encouraging. The 36-hr sea-level pressure prognoses exhibit considerable skill. The model's ability to simulate the generation of new storms in the winter is noteworthy. Problems included the slow movement of small-scale features (truncation problem), need for improvement in description of the heating and friction, and a need for improved initialization.
Abstract
Estimates of atmospheric heating in the troposphere at Washington, D.C., for each successive 12 hr. during June and July 1961, were used to study the relation between local heating and the large-scale features of the circulation, to determine the local production of available potential energy, and to assist in interpreting cloud and radiation data from meteorological satellites.
Some interesting inter-connections are found between heating and the circulation: e.g., it is shown that there is a very critical phase relation between heating and the temperature field which is important in determining the generation or destruction of the atmosphere's potential energy. This suggests that special care is needed in designing numerical computations of diabatic heating.
A major effort should be directed to interpreting satellite data in terms of the atmospheric heat budget, because such global estimates may be useful (using a procedure suggested in this paper) in determining the world-wide distribution of regions of maintenance or destruction of potential energy.
Abstract
Estimates of atmospheric heating in the troposphere at Washington, D.C., for each successive 12 hr. during June and July 1961, were used to study the relation between local heating and the large-scale features of the circulation, to determine the local production of available potential energy, and to assist in interpreting cloud and radiation data from meteorological satellites.
Some interesting inter-connections are found between heating and the circulation: e.g., it is shown that there is a very critical phase relation between heating and the temperature field which is important in determining the generation or destruction of the atmosphere's potential energy. This suggests that special care is needed in designing numerical computations of diabatic heating.
A major effort should be directed to interpreting satellite data in terms of the atmospheric heat budget, because such global estimates may be useful (using a procedure suggested in this paper) in determining the world-wide distribution of regions of maintenance or destruction of potential energy.
