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Apel, J. R.

Publications and source records attributed to Apel, J. R..

11 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1986

Hydrodynamics of internal solitons and a comparison of SIR-A and SIR-B data with ocean measurements

Large internal solitary waves have been observed by Shuttle SIR-A and SIR-B at locations in the Andaman Sea and the New York Bight. Satellite imagery and oceanographic measurements are used in conjunction with hydrodynamic interaction and electromagnetic scattering models to estimate the expected SAR image intensity modulations associated with the internal waves. There is reasonable agreement between the predicted and observed internal wave signatures.

Apel, J. R.↗
NASA NTRS1985

Surface and internal ocean wave observations

The physical characteristics of the ocean surface waves are discussed, together with the prinicples behind altimetry measurements of the wave height and SAR measurements of surface wave direction and length. In addition, theoretical aspects of oceanic internal gravity waves are presented, and the measurements of oceanic internal wave fields, using the 'surface signatures' accompanying the underlying oscillations, are described. Results of the surface wave measurements obtained by the Seasat altimeter and SAR are presented along with inferred internal wave results obtained by SAR.

Rufenach, C. L.↗
NASA NTRS1984

SAR internal wave signature experiment

Internal wave and surface wave observations by research vessels will be conducted in conjunction with aircraft SAR images. Synthetic Aperture Radar Internal Wave Signature Experiment (SARSEX) provides an opportunity to acquire aircraft and spacecraft SAR imagery of internal waves with appropriate sea truth data. Objectives are to investigate basic mechanisms (both hydrodynamic and electromagnetic) responsible for internal wave signatures and quantitatively test theories and models for predicting internal wave signatures from given ocean and radar parameters.

Winokur, R. S.↗
NASA NTRS1976

Internal wave observations made with an airborne synthetic aperture imaging radar

Synthetic aperture L-band radar flown aboard the NASA CV-990 has observed periodic striations on the ocean surface off the coast of Alaska which have been interpreted as tidally excited oceanic internal waves of less than 500 m length. These radar images are compared to photographic imagery of similar waves taken from Landsat 1. Both the radar and Landsat images reveal variations in reflectivity across each wave in a packet that range from low to high to normal. The variations point to the simultaneous existence of two mechanisms for the surface signatures of internal waves: roughening due to wave-current interactions, and smoothing due to slick formation.

Elachi, C.↗
NASA NTRS1974

A synopsis of Seasat-A scientific contributions

SEASAT-A satellite data processing and modelling capabilities address scientific and applications problems in the domains of oceanic, atmospheric, and solid earth geophysics studies by the use of active radar, and passive microwave and infrared instruments. A data flow map depicts the interrelationship between SEASAT-A instruments and other sources of information and the geophysical parameters to be determined.

Apel, J. R.↗
NASA NTRS1974

The Earth and Ocean Physics Applications Program (EOPAP). Ocean dynamics program

SEASAT-A is a research oriented program consisting of a spacecraft, precision ground tracking systems, and data processing and modelling capabilities that address both scientific and application programs problems in ocean surface dynamics for the EOPAP program. An array of active radar and passive microwave and infrared instruments allows for quantitative measurements of oceanic, atmospheric, and geodetic parameters under stormy wind and wave conditions, as well as over regions lying under a cloud cover.

Apel, J. R.↗
NASA NTRS1974

Ocean internal waves off the North American and African coasts from ERTS-1

Periodic features observed in the ocean portions of certain ERTS-1 images have been identified with reasonable certainty as surface manifestations of oceanic internal gravity waves. A series of images taken over the New York Bight, commencing with the 16 July 1972 overpass and continuing on into autumn of 1973, has shown the internal waves to be present when summer solar heating stratifies the water sufficiently well to support such oscillations. When fall and winter wind action mixes the shelf water down to the bottom, the waves no longer appear. In the Bight, the wavelengths range from approximately 400 to 1000 m, with the wave field being most sharply delineated near the edges of the continental shelf, at the mouth of the Hudson Canyon. They appear in packets consisting of several waves separated by 10-15 km, which propagate up on the shelf and disappear.

Apel, J. R.↗
NASA NTRS1967

Beam-plasma interactions

Wavelength, frequency, and growth rate dependence on density, stream velocity, and magnetic field strength

STREAM FUNCTION↗