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At least 19 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1972

An investigation of relationships between meso- and synoptic-scale phenomena

Methods based on the vorticity equation, the adiabatic method, the curvature of the vertical wind profile, and the structure of synoptic waves are used to determine areas of positive vertical motion in the mid-troposphere for a period in each season. Parameters indicative of low-level moisture and conditional instability are areas in which mesoscale systems may be present. The best association between mesoscale and synoptic-scale phenomena was found for a period during December when synoptic-scale systems were well developed. A good association between meso- and synoptic-scale events also was found for a period during March, while the poorest association was found for a June period. Daytime surface heating apparently is an important factor in the formation of mesoscale systems during the summer. It is concluded that the formation of mesoscale phenomena may be determined essentially from synoptic-scale conditions during winter, late fall, and early spring.

Scoggins, J. R.↗
NASA NTRS1975

Barotropic instability in relation to the generation of synoptic-scale atmospheric vortices

At mid-latitudes, where baroclinicity predominates, barotropic instability cannot account for the development of a cyclone. Barotropic models rarely predict the formation of extratropical cyclones. However, after large-scale disturbances have developed due to baroclinic instability, further development may be aided by barotropic instability. In the present paper, an attempt is made to relate barotropic instability to the generation of synoptic-scale atmospheric vortices, using the synoptic data of the tornado outbreak over the area of the United States on April 3, 1974. A barotropic instability analysis of wind profiles shows that the atmosphere above the area hit by the tornado was barotropically most unstable during the outbreak. This indicates that barotropic instability may have been synoptically associated with the outbreak. The need to study additional cases is pointed out

Tseng, C.-Y.↗
NASA NTRS1982

The measurement of the synoptic scale wind over the ocean

Mesoscale and microscale features of the turbulent winds over the ocean are related to the synoptic scale winds in terms of published spectral forms for the microscale, a mesoscale valley and published values of U*, VAR u', VAR v' and z/L, as defined in the text and as obtained for moderate to gale force winds. The frequencies involved correspond to periods longer than 1 hour and extend to the microscale, which starts at a period near 2 minutes, or so, and continues to the Kolmogorov inertial range. Nondimensional spectra that span both the mesoscale and the microscale are derived as a function of u, f(= n z/u) and z/L, where z is 10 meters, L is the Monin Obukov stability length and u is evaluated at 10 meters. For the same u, different values of z/L produce a range of values of u which in turn result in variations of the eddy structure of the mesoscale and microscale spectra. Both conventional anemometer averages and remotely sensed winds contain a random component of the mesoscale wind in their values. These components are differnces and not errors when winds are compared, and quantitative values for these differences are given. Ways to improve the measurement of the synoptic scale wind by transient ships, data buoys and scatterometers on future spacecraft are described. These ways are loner averaging times for ships and data buoys, depending on the synoptic conditions, and pooling spacecraft to form super observations. Design considerations for future remote sensing systems are given.

Pierson, W. J.↗
NASA NTRS1982

Sampling theory for asynoptic satellite observations. I Space-time spectra, resolution, and aliasing. II - Fast Fourier synoptic mapping

An evaluation of the information content of asynoptic data taken in the form of nadir sonde and limb scan observations is presented, and a one-to-one correspondence is established between the alias-free data and twice-daily synoptic maps. Attention is given to space and time limitations of sampling and the orbital geometry is discussed. The sampling pattern is demonstrated to determine unique space-time spectra at all wavenumbers and frequencies. Spectral resolution and aliasing are explored, while restrictions on sampling and information content are defined. It is noted that irregular sampling at high latitudes produces spurious contamination effects. An Asynoptic Sampling Theorem is thereby formulated, as is a Synoptic Retrieval Theorem, in the second part of the article. In the latter, a procedure is developed for retrieving the unique correspondence between the asymptotic data and the synoptic maps. Applications examples are provided using data from the Nimbus-6 satellite.

Salby, M. L.↗
NASA NTRS1974

Synoptic planetary imaging with the LST high-resolution camera

The value of synoptic imaging of the planets is illustrated. Advantages of the large space telescope, as compared with ground based telescopes, planetary orbiters, and flybys are discussed. Desirable LST camera parameters and observing strategies are considered from the standpoint of synoptic imaging.

Baum, W. A.↗
NASA NTRS1978

Synoptic analysis of interplanetary radio scintillation spectra observed at 34 MHz

Synoptic observations of the temporal power spectrum of interplanetary scintillations were made in the summer of 1976 on the University of Iowa's Cocoa Cross radio telescope and the University of Maryland's TPT array. Most of the observations were at large (larger than 40 deg) solar elongations. It was found that the power spectrum broadens when enhanced turbulence at the front of a high-speed solar wind stream sweeps over the earth. In the case with sufficient synoptic coverage, the broadening appeared to result from the relative closeness of the enhanced scattering region rather than from an increase in velocity. A small percentage of the spectra displayed two power law components with a plateau between them. These may result from a flattening in the spatial turbulence spectrum such as has been observed by spacecraft.

Gotwols, B. L.↗