Download or read book The AFGL Global Spectral Model written by Stephen Brenner and published by . This book was released on 1984 with total page 84 pages. Available in PDF, EPUB and Kindle. Book excerpt: The flexible resolution/truncation baseline version of the AFGL global spectral model as adapted to the CRAY-1 is described. A series of low-resolution (6 layer, rhomboidal 15) and high-resolution (12 layer, rhomboidal 30) forecasts were run and compared to test the performance of the model. In general, higher resolution resulted in improved forecast skill in the 24-to-96-hour range. The only exception to this is the humidity forecast, which shows minimal skill. This characteristic is rather insensitive to the resolution partly because of the poor quality of analyzed humidity fields used for initial data and verification. The original gridded (2.5 X 2.5 deg) topography has been replaced by a smoothed terrain field that has been passed through a nine-point smoother, interpolated to the model's Gaussian grid, and then spectrally truncated. Finally, the effects of initialization have been studied by comparing a series of forecasts subjected to several initialization methods. For forecasts beyond 24 hours, the model is able to supress spurious gravity waves through the combined effects of the semi-implicit time scheme and the subgrid scale diffusion. The impact of normal mode initialization is seen mainly in the very short-range forecasts (less than 24 hours) and is thus important for providing smooth first-guess fields for the analysis/data assimilation cycle. Keywords: Atmospheric models; Spectral models; Weather forecasting; Numerical weather prediction; Global atmospheric circulation.
Download or read book THE AFGL GLOBAL SPECTRAL MODEL written by Stephen Brenner and published by . This book was released on 1984 with total page 72 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Adiabatic and Diabatic Initialization of the AFGL Global Spectral Model Using Dynamic Normal Mode and Nonlinear Normal Mode Methods written by Larry Knowlton and published by . This book was released on 1989 with total page 50 pages. Available in PDF, EPUB and Kindle. Book excerpt: Dynamic normal mode initialization (DNI) is applied to low and high resolution versions of the AFGL global spectral mode. This scheme is tested against the operational nonlinear normal mode initialization (NMI) procedure using both adiabatic and diabatic forms of the model tendencies. The DNI-based forecasts are comparable in accuracy to the NMI-based forecasts, with small differences between the adiabatic and diabatic versions of each. DNI initial conditions were somewhat more damped in the divergence fields than were the NMI fields. This is believed to be due to the frequency response characteristics of the DNI's forward-backward time scheme, which tended to partially damp resolvable wavelengths.
Download or read book The AFGL Global Spectral Model written by and published by . This book was released on 1984 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book The AFGL Spectral Model of the Moist Global Atmosphere written by Stephen Brenner and published by . This book was released on 1982 with total page 70 pages. Available in PDF, EPUB and Kindle. Book excerpt: The baseline version of the AFGL model of the moist global atmosphere is described in detail. The numerical methods include spectral representation in the horizontal, the Arakawa vertical differencing scheme, and the semi-implicit time scheme. For this version, the pre- and postprocessing, the nonlinear normal mode initialization and the parameterized boundary layer processes and moisture physics are adapted from the NMC spectral model. A series of test forecasts indicate that the model performance is comparable to that of similar large-scale models.
Download or read book Boundary Layer Parameterization for a Global Spectral Model written by Larry Mahrt and published by . This book was released on 1987 with total page 192 pages. Available in PDF, EPUB and Kindle. Book excerpt: Much of the work has concentrated on interactions between the soil model and the model of the atmospheric boundary layer and the behavior of the boundary-layer package within the Air Force Global Spectral Model. Such studies have underscored the importance of the formulation of surface properties and transport within the underlying soil. Work during the contract period also focussed on elimination of several inadequacies of boundary-layer modelling. The inclusion of the statistical impact of subgrid variations of surface properties leads to a surface exchange coefficient which varies more smoothly with stability and does not decrease as rapidly with very stable conditions. Such modifications reduce the nocturnal cooling which is usually overestimated in boundary-layer models. Other improvements of the boundary-layer model in stable conditions have resulted from increasing the critical Richardson number in the boundary-layer depth formulation and adopting the Kondo formulation for the eddy diffusivity. The development of a formulation for boundary-layer cumulus has allowed inclusion of cloud-induced drying. Although this formulation leads to significant improvement of the boundary-layer predictions in cloudy situations, the general problem is far from solved. Keywords: Atmospheric boundary layer; Surface energy balance; Soil model; Stable layer parameterization; Surface fluxes. (jhd).
Download or read book The AFGL Spectral Model of the Moist Global Atmosphere written by Stephen Brenner and published by . This book was released on 1982 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: The baseline version of the AFGL model of the moist global atmosphere is described in detail. The numerical methods include spectral representation in the horizontal, the Arakawa vertical differencing scheme, and the semi-implicit time scheme. For this version, the pre- and postprocessing, the nonlinear normal mode initialization and the parameterized boundary layer processes and moisture physics are adapted from the NMC spectral model. A series of test forecasts indicate that the model performance is comparable to that of similar large-scale models.
Download or read book Phillips Laboratory Global Spectral Numerical Weather Prediction Model written by Donald C. Norquist and published by . This book was released on 1992 with total page 168 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book The AFGL Air Force Geophysics Laboratory Spectral Model of the Moist Global Atmosphere Documentation of the Baseline Version written by Stephen Brenner and published by . This book was released on 1982 with total page 63 pages. Available in PDF, EPUB and Kindle. Book excerpt: The baseline version of the AFGL model of the moist global atmosphere is described in detail. The numerical methods include spectral representation in the horizontal, the Arakawa vertical differencing scheme, and the semi-implicit time scheme. For this version, the pre- and postprocessing, the nonlinear normal mode initialization and the parameterized boundary layer processes and moisture physics are adapted from the NMC spectral model. A series of test forecasts indicate that the model performance is comparable to that of similar large-scale models.
Download or read book Adiabatic and Diabatic Initialization of the AFGL Global Spectral Model Using Dynamic Normal Mode and Nonlinear Normal Mode Methods written by Larry Knowlton and published by . This book was released on 1989 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Dynamic normal mode initialization (DNI) is applied to low and high resolution versions of the AFGL global spectral mode. This scheme is tested against the operational nonlinear normal mode initialization (NMI) procedure using both adiabatic and diabatic forms of the model tendencies. The DNI-based forecasts are comparable in accuracy to the NMI-based forecasts, with small differences between the adiabatic and diabatic versions of each. DNI initial conditions were somewhat more damped in the divergence fields than were the NMI fields. This is believed to be due to the frequency response characteristics of the DNI's forward-backward time scheme, which tended to partially damp resolvable wavelengths.
Download or read book Development of a Cloud Forecast Scheme for the GL Baseline Global Spectral Model written by Kenneth E. Mitchell and published by . This book was released on 1989 with total page 166 pages. Available in PDF, EPUB and Kindle. Book excerpt: Using forecast relative humidity (RH) from a global model, several pre-existing diagnostic RH-to-cloud schemes were tested to forecast global fractional cloud cover in a postprocessor format. Since none of the schemes tested provided a superior cloud forecast when compared to Air Force Global Weather Central's (AFGWC) operational 5LAYER cloud forecasts, a new RH-to-cloud scheme was developed by relating cumulative frequencies of forecast RH to cumulative frequencies of analyzed cloud cover from the AFGWC RTNEPH cloud analysis. This scheme creates a series of forecast time-dependent RH-to-cloud curves that can be temporally updated to account for changes in season, cloud analysis, or forecast model, The global model used was a spectral-type developed by the Geophysics Laboratory (GL) using parameterized diabatic physics presently incorporated in the operational GSM (global spectral model) at AFGWC.
Download or read book Diagnostics for and Evaluations of New Physical Parameterization Schemes for Global NWP Models written by Chien-Hsiung Yang and published by . This book was released on 1990 with total page 284 pages. Available in PDF, EPUB and Kindle. Book excerpt: The procedures and results of a study undertaken to evaluate and assess the impacts of three new parameterization schemes for the GL global spectral model as a 3-4 day range forecast model are described. The tree parameterization schemes are one each for the boundary-layer physics, moist convection and heating due to solar and terrestrial radiations. These schemes are incorporated either singly or jointly into a rhomboidal-30, 12-layer global spectral model for four-day simulations using FGGE III- a data as input. Evaluation and assessment are made on the basis of two kinds of global statistics: mean and root-mean-square errors, and on their magnitudes and distributions. The statistics are generated for both the primary, that is, prognostic, variables, and supplementary variables such as zonal-mean and zonal-eddies energy densities. The new moist convection scheme has been found to increase convective activity significantly and maintain it throughout the four-day period. It also warms and dries the middle troposphere, but produces rainfall far in excess of the climatology. The radiation parameterization has been found to cool the atmosphere and reduce its specific humidity. It counterbalances enhanced heating and moistening brought about by the new boundary-layer and moist convection schemes and eliminates the systematic warming of the old model.
Download or read book An Introduction to Global Spectral Modeling written by T.N. Krishnamurti and published by Springer Science & Business Media. This book was released on 2006-07-11 with total page 328 pages. Available in PDF, EPUB and Kindle. Book excerpt: This is an introductory textbook on global spectral modeling designed for senior-level undergraduates and possibly for first-year graduate students. This text starts with an introduction to elementary finite-difference methods and moves on towards the gradual description of sophisticated dynamical and physical models in spherical coordinates. Computational aspects of the spectral transform method, the planetary boundary layer physics, the physics of precipitation processes in large-scale models, the radiative transfer including effects of diagnostic clouds and diurnal cycle, the surface energy balance over land and ocean, and the treatment of mountains are some issues that are addressed. The topic of model initialization includes the treatment of normal modes and physical processes. A concluding chapter covers the spectral energetics as a diagnostic tool for model evaluation. This revised second edition of the text also includes three additional chapters. Chapter 11 deals with the formulation of a regional spectral model for mesoscale modeling which uses a double Fourier expansion of data and model equations for its transform. Chapter 12 deals with ensemble modeling. This is a new and important area for numerical weather and climate prediction. Finally, yet another new area that has to do with adaptive observational strategies is included as Chapter 13. It foretells where data deficiencies may reside in model from an exploratory ensemble run of experiments and the spread of such forecasts.
Download or read book Refinement and Testing of the Radiative Transfer Parameterization in the PL Global Spectral Model written by John Louis Schattel and published by . This book was released on 1992 with total page 38 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Diagnostics for and Evaluations of New Physical Parameterization Schemes for Global NWP Models written by and published by . This book was released on 1990 with total page 282 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Scientific and Technical Aerospace Reports written by and published by . This book was released on 1991 with total page 308 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Monthly Catalog of United States Government Publications written by and published by . This book was released on 1988 with total page 644 pages. Available in PDF, EPUB and Kindle. Book excerpt:
