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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 235 records · Page 13
All sourcesNASA NTRSDOE OSTI
NASA NTRS1975

Sasaki's variational optimization analysis of temperature and moisture advection in a severe storm environment

Temperature and moisture advection patterns of dry air intrusion were analyzed by a variational optimization method to relate mesoscale advection to a severe thunderstorm environment. The analysis results presented here were obtained from a case study, May 26, 1973, when a tornado squall line developed in Oklahoma in conjunction with a clearly delineated dry air intrusion. Observations from the synoptic upper air network were used for inputs of horizontal wind components, potential temperature, and mixing ratio at each 50 mb increment from 950 to 100 mb. An objective analysis was performed to assign values of the variables to grid points of a 15 x 14 horizontal grid with approximate 125 km grid spacing at each pressure level. After the analysis the data fields were smoothed using a variational formalism.

Mcfarland, M. J.↗
NASA NTRS1976

An equivalent potential vorticity theory applied to the analysis and prediction of severe storm dynamics

Potential vorticity theory is developed in a description of an equivalent potential temperature topography, and a new theory suited to the description of scale interaction is elaborated. Macroscale triggering of ageostrophic flow fields at the mesoscale, in turn leading to release of convective instability along narrow zones at the microscale, is examined. Correlation of appreciable decrease in potential vorticity with such phenomena as cumulonimbi, tornados, and duststorms is examined. The relevance of a multiscale energy-momentum cascade in numerical prediction of severe mesoscale and microscale phenomena from radiosonde data is reviewed. Hypotheses for mesoscale dynamics are constructed.

Paine, D. A.↗
NASA NTRS1977

Laser Doppler dust devil measurements

A scanning laser doppler velocimeter (SLDV) system was used to detect, track, and measure the velocity flow field of naturally occurring tornado-like flows (dust devils) in the atmosphere. A general description of the dust devil phenomenon is given along with a description of the test program, measurement system, and data processing techniques used to collect information on the dust devil flow field. The general meteorological conditions occurring during the test program are also described, and the information collected on two selected dust devils are discussed in detail to show the type of information which can be obtained with a SLDV system. The results from these measurements agree well with those of other investigators and illustrate the potential for the SLDV in future endeavors.

Bilbro, J. W.↗
NASA NTRS1975

Urban construction and safety project

The purpose and functions of NASA technology applications temas (TAT) are described, with emphasis on the activities of the Urban and Construction and Safety Project. The transfer and implementation of technology is discussed in five activities. Topics include: flat conductor cable, NASA house and compendium, flood insurance studies, tornado studies, and the controller for stationary diesels.

Source record↗
NASA NTRS1977

Analytic studies of local-severe-storm observables by satellites

Attention is concentrated on the exceptionally violet whirlwind, often characterized by a fairly vertical axis of rotation. For a cylindrical polar coordinate system with axis coincident with the axis of rotation, the secondary flow involves the radial and axial velocity components. The thesis advanced is, first, that a violent whirlwind is characterized by swirl speeds relative to the axis of rotation on the order of 90 m/s, with 100 m/s being close to an upper bound. This estimate is based on interpretation of funnel-cloud shape (which also suggests properties of the radial profile of swirl, as well as the maximum magnitude); an error assessment of the funnel-cloud interpretation procedure is developed. Second, computation of ground-level pressure deficits achievable from typical tornado-spawning ambients by idealized thermohydrostatic processes suggests that a two-cell structure is required to sustain such large speeds.

Dergarabedian, P.↗
NASA NTRS1977

Towards a theory of stochastic vorticity-augmentation

A new hypothesis to account for the formation of tornadoes is presented. An elementary one-dimensional theory is formulated for vorticity transfer between an ambient sheared wind and a transverse penetrating jet. The theory points out the relevant quantities to be determined in describing the present stochastic mode of vorticity augmentation.

Liu, V. C.↗
NASA NTRS1977

Landsat - Current and future capabilities for agriculture

The potential of the Landsat spacecraft in applications related to agriculture is demonstrated by the examples of assessing the damage to the Brazilian coffee crop due to freezing temperatures on July 17-18, 1975; and damage assessment in the state of Iowa, following a tornado which struck a corn and soybean producing region on June 13, 1976. Some techniques which have been used to measure snow covers on the basis of Landsat data are also noted. The advantages that are expected to accrue from the installation of sophisticated equipment on the third and fourth Landsat spacecraft, scheduled to be launched in 1978 and 1981, respectively, are reviewed.

Walter, L. S.↗
NASA NTRS1977

Operational utilization of remotely sensed data

The use of data from environmental satellites and other remote sensing platforms in some of NOAA's operational services are described. Topics discussed include: hurricanes; severe local storms and tornadoes; forest guidance; weather forecasting; hydrology; space program support; oceanography; search and rescue; and wildlife management. Applications which have become routine, and those which are in advanced field test are included. Some applications yield a clear cut economic benefit. In other cases, benefits -- if any -- are obscure. In yet other cases, benefits in one sector may be offset by detriments in another. Illustrative examples are given.

Jones, J. B.↗
NASA NTRS1976

Classification and machine recognition of severe weather patterns

Forecasting and warning of severe weather conditions are treated from the vantage point of pattern recognition by machine. Pictorial patterns and waveform patterns are distinguished. Time series data on sferics are dealt with by considering waveform patterns. A severe storm patterns recognition machine is described, along with schemes for detection via cross-correlation of time series (same channel or different channels). Syntactic and decision-theoretic approaches to feature extraction are discussed. Active and decayed tornados and thunderstorms, lightning discharges, and funnels and their related time series data are studied.

Wang, P. P.↗
NASA NTRS1977

Variational analysis of temperature and moisture advection in a severe storm environment

Horizontal wind components, potential temperature, and mixing ratio fields associated with a severe storm environment in the south central United States were objectively analyzed from synoptic upper air observations with a nonhomogeneous anisotropic weighting function. The particular case study discussed here is the tornado producting squall line which moved through eastern Oklahoma 26 May 1973. The synoptic situation which preceded squall line development was cyclogenesis and frontogenesis in the lee-of-mountain trough, which produced a well-defined surface dry line (or dew point front) and a pronounced mid-level dry air intrusion. It is shown that the intrusion was also characterized by warm air, with a lapse rate approaching the dry adiabatic.

Mcfarland, M. J.↗
NASA NTRS1977

Satellite-based thunderstorm intensity parameters

Thunderstorm growth rates are investigated through use of infrared data furnished by the Synchronous Meteorological Satellite. Blackbody temperature isotherms provide an accurate method of delineating the areal expansion of cold areas; the blackbody temperature isotherms are valuable analytical tools even in cases when there is very little decrease with time of the minimum cloud top temperature. In an application of the severe storm monitoring technique, the origin of tornadoes is found to be closely linked to a rapid expansion of cold areas in seven out of eight cases.

Adler, R. F.↗
NASA NTRS1977

Thunderstorm-associated cloud motions as computed from 5-minute SMS pictures

The five-minute rapid-scan imagery from the Synchronous Meteorological Satellite is employed to study cloud motions associated with the Omaha tornado of May 6, 1975. Cloud-motion vectors derived from automated and man-machine interactive systems provide an account of the mesoscale phenomena. In addition to the geostationary satellite data, aerial photography obtained during a cloud-truth mission is used in the severe storm investigation. For tracking overland cumuli with short half-lives, a three-minute scan interval appears necessary for the satellite imagery.

Tecson, J. J.↗
NASA NTRS1977

Relationships between convective storms and their environment in AVE IV determined from a three-dimensional subsynoptic-scale, trajectory model

The paper describes interrelationships between synoptic-scale and convective-scale systems obtained by following individual air parcels as they traveled within the convective storm environment of AVE IV. (NASA's fourth Atmospheric Variability Experiment, AVE IV, was a 36-hour study in April 1975 of the atmospheric variability and structure in regions of convective storms.) A three-dimensional trajectory model was used to calculate parcel paths, and manually digitized radar was employed to locate convective activity of various intensities and to determine those trajectories that traversed the storm environment. Spatial and temporal interrelationships are demonstrated by reference to selected time periods of AVE IV which contain the development and movement of the squall line in which the Neosho tornado was created.

Wilson, G. S.↗
NASA NTRS1977

A Landsat Agricultural Monitoring Program

The paper discusses the Landsat Agricultural Monitoring Program which was developed to identify, observe, and evaluate alarm conditions influencing Iowa corn production in 1976. Used in conjunction with climatic and field reports, studies were made of crop development, crop alarms (such as heavy rainfall, hail, tornadoes, and drought) and estimated crop yield.

Aaronson, A. C.↗
NASA NTRS1977

The multiple nesting of mesoscale, submesoscale, and nonhydrostatic microscale numerical models for a case of mesocyclogenesis and severe storm development

A fundamental approach involving the integration of two different numerical models over several different spatial mesh lengths is considered. Model I is a hydrostatic, incompressible, and adiabatic primitive (Newtonian) equation set with no boundary layer forcing, i.e., surface heat or moisture flux or external frictional stresses. Typically this model is initialized from conventional radiosonde data and run for a 12-15 hour forecast period over a 40 km horizontal mesh. If phase I of the tornado developmental processes develops, the data is 'frozen' in space and time, interpolated to a 20 km mesh, and integrated for a shorter time period (3 hours) with a shorter time step. Model II is a nonhydrostatic compressible 18-level complement of model I. If model II indicates the development of the intensification of phase V dynamical processes, the data is frozen and interpolated to finer mesh lengths until the tornadic circulation system is approximated

Kaplan, M. L.↗
NASA NTRS1977

Severe weather prediction studies

A numerical forecast model is described which uses three-dimensional primitive equations to predict the evolution of the wind, temperature and moisture fields along with the subsynoptic-scale convective activity. There are 15 vertical levels set on a longitude-latitude horizontal grid. In this study, the horizontal grid distance is 70 km (0.625 deg latitude and 0.816 deg longitude at 40 deg N) and the time step is 90 sec. Orography is included and terrain coordinates are adopted. The forecast model is used to test two tornado-producing storms with very different synoptic structures. A 12 hr forecast is carried out for both cases. The rms errors of the forecast indicate much smaller errors in the middle troposphere than in the lower troposphere. The results demonstrate that a rather fine-mesh limited-area numerical model is capable of providing a valuable short-range forecast of the circulation and the mesoscale precipitation features.

Chang, C.-B.↗
NASA NTRS1978

NASA's AVE 7 experiment: 25-mb sounding data

The AVE 7 Experiment is described and tabulated rawinsonde data at 25 mb internals from the surface to 25 mb for the 24 stations participating in the experiment are presented. Soundings were taken between 0000GMT May 2 and 1200 GMT May 3, 1978. The methods of data processing and the accuracy are briefly discussed. Selected synoptic charts prepared from the data are presented as well as an example of contact data. A tabulation of adverse weather events that occured during the AVE 7 period, including freezing temperature, snow, tornadoes, damaging winds, and flooding, is presented.

Davis, J. G.↗
NASA NTRS1977

Detection of severe storms through a tropospheric-ionospheric coupling mechanism

Acoustic-gravity waves were detected by a ground-based ionospheric sounding array, and the location of the wave generation source was determined by a reverse group ray path computation. Computed sources of these waves were located near locations where tornadoes touched down from 2 to 4 hours later. It is suggested that the overshooting and ensuing collapse of convective turrets may be responsible for generating the acoustic-gravity waves observed.

Hung, R. J.↗