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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 289 records · Page 16
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NASA NTRS1984

Development of the Centralized Storm Information System (CSIS) for use in severe weather prediction

The centralized storm information system is now capable of ingesting and remapping radar scope presentations on a satellite projection. This can be color enhanced and superposed on other data types. Presentations from more than one radar can be composited on a single image. As with most other data sources, a simple macro establishes the loops and scheduling of the radar ingestions as well as the autodialing. There are approximately 60 NWS network 10 cm radars that can be interrogated. NSSFC forecasters have found this data source to be extremely helpful in severe weather situations. The capability to access lightning frequency data stored in a National Weather Service computer was added. Plans call for an interface with the National Meteorological Center to receive and display prognostic fields from operational computer forecast models. Programs are to be developed to plot and display locations of reported severe local storm events.

Mosher, F. R.↗
NASA NTRS1983

A nested-grid limited-area model for short term weather forecasting

The present investigation is concerned with a mesoscale atmospheric simulation system (MASS), incorporating the sigma-coordinate primitive equations. The present version of this model (MASS 3.0) has 14 vertical layers, with the upper boundary at 100 mb. There are 128 x 96 grid points in each layer. The earlier version of this model (MASS 2.0) has been described by Kaplan et al. (1982). The current investigation provides a summary of major revisions to that version and a description of the parameterization schemes which are presently included in the model. The planetary boundary layer (PBL) is considered, taking into account aspects of generalized similarity theory and free convection, the surface energy budget, the surface moisture budget, and prognostic equations for the depth h of the PBL. A cloud model is discussed, giving attention to stable precipitation, and cumulus convection.

Wong, V. C.↗
NASA NTRS1984

Observational-numerical Study of Maritime Extratropical Cyclones Using FGGE Data

The accomplishments, current research, and future plans of a study investigating the development, maturation, and decay of maritime extratropical cyclones are reported. Three cases of explosive cyclogenesis during the first GARP global experiment (FGGE) DOP-1 were studied diagnostically using storm-following budgets derived from the ECMWF and GLAS level III-b analyses. Mass, vorticity and angular momentum budgets for the moving storm environment were computed for each case. Key results from these studies include: (1) demonstration that the FGGE analyses can be used to explore oceanic circulations; (2) isolation of the role of upper level jet streaks in the initiation of the explosive period in all three cases; and (3) illustration of the lower tropospheric destabilization during each rapid deepening period, which is primarily due to sensible heating of the cold air by the warmer ocean surface. The physics package of the Navy global forecast model was successfully utilized in a semi-prognostic mode to estimate diabatic components of oceanic cyclone systems. Fields of sensible and latent heat fluxes, radiational heating and inferred cloud structures were also computed.

Wash, C. H.↗
NASA NTRS1985

Parameterization of Surface Fluxes in the VVR Fourth Order GCM

The Variable Vertical Resolution (VVR) option of the GLAS Fourth Order General Circulation Model (GCM) allows one to enhance the vertical resolution of the region of the atmosphere adjacent to the Earth's surface. This, in turn, makes it possible to compute turbulent surface fluxes of heat, momentum and moisture directly from the prognosticated properties of the lowest model layer by use of the Monin-Obukhov surface layer similarity theory. The similarity theory applies formally only to the constant flux surface layer which is but a few tens of meters deep. It is not practically feasible to work with a lowest GCM layer thin enough to satisfy these formal constraints. It is shown that at least under conditions of neutral stratification, the similarity theory can be extended beyond its formal limits. The theory still gives reasonable looking results, when the distance from the ground becomes as large as 150 m. It is not infeasible to run the VVR model with a lowest layer thickness on the order of 300 m (the center of the layer would then be 150 m above the Earth's surface), and so if one can prescribe similarity functions phi sub m (zeta) and phi sub h (zeta) to adequately describe the entire extended surface layer, the problem of surface flux parameterization is solved.

Helfand, H. M.↗
NASA NTRS1985

Response of cumulus clouds to large-scale forcing and cumulus parameterization

Using the cumulus ensemble model (Soong and Ogura, 1980), statistical properties of cumulus clouds that occur in response to the imposed large scale forcing were investigated both in the tropical and midlatitude situtations. A strong drying process was found to occur in the boundary layer in association with deep convection in a midlatitude case. The Arakawa-Schubert (1974) cumulus parameterization scheme was tested semi-prognostically against both the model result and the observation in a tropical rain event that occurred in GATE. The Cloud heating and drying effects predicted by the Arakawa-Schubert scheme were found to agree well both with the observation and the model result. However, it was also found that the Arakawa-Schuber scheme underestimates both condensation and evaporation rates substantially. An inclusion of the downdraft effect, as formulated by Johnson (1976), appears to alleviate this deficiency. This downdraft effect may be important in predicting the behavior of the boundary accurately.

Ogura, Y.↗
NASA NTRS1985

Mixing line analysis of clouds and cloudy boundary layers

The diagnostic study of the thermodynamic structure of nonprecipitating clouds and cloudy boundary layers is formulated using a mixing line and saturation point approach. A parametric model for the mean structure is developed as a tool for diagnostic and prognostic modeling. Cloud-scale mixing processes are analyzed in the same framework, together with the energies of the evaporative instability in cumulus clouds. A velocity scale emerges for this evaporative instability. The statistical study of saturation level distribution in partially cloudy boundary layers is proposed to related cloud fraction to the mean thermodynamic mixing processes.

Betts, A. K.↗
NASA NTRS1986

Synoptic impacts of NOAA 6/Tiros N data on numerical circulation forecasts

Profiles of retrieved satellite observed temperatures provided to the Israel Meteorological Service (IMS) by the National Environmental Satellite Data and Information Service were used to enhance the specification of atmospheric conditions during three winter periods. Introduction of the satellite data was via three alternative schemes, and the enhanced specifications were used to initialize 48-hour numerical forecasts with the IMS five-layer primitive equation model; control forecasts were run in parallel from initial conditions without the satellite data. The study selects one forecast from each period for which discernible impacts on forecast synoptic fields can be attributed to the different initializations. The first two case studies examine the results of only one assimilation scheme and the third relates to all three schemes. Verification of the prognostics show the positive impact of including satellite temperatures in the initialization, but there were also examples of negative impact.

Druyan, L. M.↗
NASA NTRS1985

Validation of mesocale number sea breeze thunderstorm forecasts over Florida using LPATS - The Lightning Position and Tracking System

The research reported in the present paper has the objective to develop improved operational techniques for sea breeze (SB) initiated convective storms. It is pointed out that the sea breeze is a relatively simple mesoscale circulation. The considered studies are mainly concerned with detailed thunderstorm potential forecasts during the next several hours, taking into account real-time predictions using new supercomputer technology. Thunderstorm and coastal mesoscale circulations are discussed along with the P3DM model sea. The considered code represents the result of a further development of the NOAA Florida sea breeze model which was introduced by Pielke (1974). After its modificataion, the model was renamed the Prognostic Three Dimensional Mesoscale (P3DM) Model, with its 2-D connterpart the P2DM. Attention is also given to real time climatology, and a case study concerned with developments occurring on 5 May 1984 over the Florida Peninsula.

Lyons, W. A.↗
NASA NTRS1986

A brief description of the simple biosphere model (SiB)

A biosphere model for calculating the transfer of energy, mass, and momentum between the atmosphere and the vegetated surface of the Earth was designed for atmospheric general circulation models. An upper vegetation layer represents the perennial canopy of trees or shrubs, a lower layer represents the annual ground cover of grasses and other herbacious species. The local coverage of each vegetation layer may be fractional or complete but as the individual vegetation elements are considered to be evenly spaced, their root systems are assumed to extend uniformly throughout the entire grid-area. The biosphere has seven prognostic physical-state variables: two temperatures (one for the canopy and one for the ground cover and soil surface); two interception water stores (one for the canopy and one for the ground cover); and three soil moisture stores (two of which can be reached by the vegetation root systems and one underlying recharge layer into and out of which moisture is transferred only by hydraulic diffusion).

Sellers, P. J.↗
NASA NTRS1987

The terminal area simulation system. Volume 1: Theoretical formulation

A three-dimensional numerical cloud model was developed for the general purpose of studying convective phenomena. The model utilizes a time splitting integration procedure in the numerical solution of the compressible nonhydrostatic primitive equations. Turbulence closure is achieved by a conventional first-order diagnostic approximation. Open lateral boundaries are incorporated which minimize wave reflection and which do not induce domain-wide mass trends. Microphysical processes are governed by prognostic equations for potential temperature water vapor, cloud droplets, ice crystals, rain, snow, and hail. Microphysical interactions are computed by numerous Orville-type parameterizations. A diagnostic surface boundary layer is parameterized assuming Monin-Obukhov similarity theory. The governing equation set is approximated on a staggered three-dimensional grid with quadratic-conservative central space differencing. Time differencing is approximated by the second-order Adams-Bashforth method. The vertical grid spacing may be either linear or stretched. The model domain may translate along with a convective cell, even at variable speeds.

Proctor, F. H.↗
NASA NTRS1985

High-latitude filtering in a global grid-point model using model normal modes

A normal modes expansion technique is applied to perform high latitude filtering in the GLAS fourth order global shallow water model with orography. The maximum permissible time step in the solution code is controlled by the frequency of the fastest propagating mode, which can be a gravity wave. Numerical methods are defined for filtering the data to identify the number of gravity modes to be included in the computations in order to obtain the appropriate zonal wavenumbers. The performances of the model with and without the filter, and with a time tendency and a prognostic field filter are tested with simulations of the Northern Hemisphere winter. The normal modes expansion technique is shown to leave the Rossby modes intact and permit 3-5 day predictions, a range not possible with the other high-latitude filters.

Takacs, L. L.↗
NASA NTRS1986

Prediction of monthly 700 mb heights using simulated medium-range numerical forecasts

Standardized 700 mb heights at 126 grid points over the Northern Hemisphere during 1948-80 were used to quantify the persistence of the heights from one month to the next (using various antecedent period lengths) and to determine predictive skill for calendar-month 700 mb heights using antecedent and simulated prognostic height information. The calculations showed that optimum period length and its corresponding average pattern correlation vary widely over the course of the year, being largest in summer and winter. The skill of models using simulated prog heights was found to be much superior to those using antecedent heights.

Harnack, R.↗
NASA NTRS1987

Short range forecasting of sea breeze generated thunderstorms at the Kennedy Space Center: A real-time experiment using a primitive equation mesoscale numerical model

The operational efficiency of using guidance from a mesoscale numerical model to improve sea breeze thunderstorm forecasts at and around the Shuttle landing strip was assessed. The Prognostic Three-Dimensional Mesoscale (P3DM) model, developed as a sea breeze model, reveals a strong correlation between regions of mesoscale convergence and the triggering of sea breeze convection thunderstorms. The P3DM was modified to generate stability parameters familiar to the operational forecaster. In addition to the mesoscale fields of wind, vertical motion, moisture, temperature, a stability indicator, a combination of model-predicted K and Lifted Indices and the maximum grid cell vertical motion, were proposed and tested. Results of blind tests indicate that a forecaster, provided with guidance derived from model output, could improve local thunderstorm forecasts.

Lyons, Walter A.↗
NASA NTRS1988

Rotorcraft technology at Boeing Vertol: Recent advances

An overview is presented of key accomplishments in the rotorcraft development at Boeing Vertol. Projects of particular significance: high speed rotor development and the Model 360 Advanced Technology Helicopter. Areas addressed in the overview are: advanced rotors with reduced noise and vibration, 3-D aerodynamic modeling, flight control and avionics, active control, automated diagnostics and prognostics, composite structures, and drive systems.

Shaw, John↗
NASA NTRS1988

An expert system approach to turbopump health monitoring

A preliminary report is presented on the development of a system for monitoring the High Pressure Oxidizer Turbopump of the SSME. System development will proceed by defining the degradation mechanism of the turbopump, identifying those conventional and advanced sensor measurements that can monitor these mechanisms, and determining the digital processing requirements for these measurements. Once the failures and associated measurements have been defined, an expert system will be developed that can make both diagnostic and prognostic inferences about the condition and performance of the turbopump.

Perry, John G.↗
NASA NTRS1988

An assessment model for atmospheric composition

Predicting future perturbations to global air quality and climate requires, as a prerequisite, prognostic models for the composition of the Earth's atmosphere. Such assessment models are needed to evaluate the impact on our environment of different social choices that affect emissions of the photochemically and radiatively important trace gases. Our presentation here of a prototype assessment model is intended to encourage public scientific discussions of the necessary components of the model and their interactions, with the recognition that models similar to this will likely be used by the Environmental Protection Agency and other regulatory agencies in order to assess the effect of changes in atmospheric composition on climate over the next century.

Prather, Michael J.↗
NASA NTRS1989

Assessment of surface turbulent fluxes using geostationary satellite surface skin temperatures and a mixed layer planetary boundary layer scheme

A method is presented for evaluating the fluxes of sensible and latent heating at the land surface, using satellite-measured surface temperature changes in a composite surface layer-mixed layer representation of the planetary boundary layer. The basic prognostic model is tested by comparison with synoptic station information at sites where surface evaporation climatology is well known. The remote sensing version of the model, using satellite-measured surface temperature changes, is then used to quantify the sharp spatial gradient in surface heating/evaporation across the central United States. An error analysis indicates that perhaps five levels of evaporation are recognizable by these methods and that the chief cause of error is the interaction of errors in the measurement of surface temperature change with errors in the assigment of surface roughness character. Finally, two new potential methods for remote sensing of the land-surface energy balance are suggested which will relay on space-borne instrumentation planned for the 1990s.

Diak, George R.↗