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At least 307 records · Page 17

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NASA NTRS1975

Annual review of earth observations from space

An overview is given of the present state of satellites making observations of the earth. Satellite systems discussed include the NOAA series of Synchronous Meteorological Satellites (SMS) and sun-synchronous satellites, the two LANDSATS (formerly called ERTS), and the NIMBUS series. Examples are presented of the types of observations being made as well as their purposes. These include observations of synoptic and mesoscale atmospheric processes for daily weather forecasting, global atmospheric processes for long-range weather forecasting, planetary radiation budget and ocean circulation for monitoring climatic trends, earth dynamics and tectonic structure for mineral exploration and assessing earthquake hazards, atmospheric composition and water quality for environment monitoring, and thematic mapping for monitoring land use, managing crops and water resources, and assessing environmental impacts.

Nordberg, W.↗

NASA NTRS1974

Civil and scientific applications of the geoid

SEASAT-A can be used for determining the geoid to much higher accuracy on a world wide basis and in a relatively short time. Two basic objectives can be considered: (1) determination of the geoid to at least 1 meter. This accuracy will satisfy most geodetic requirements for applications purposes; and (2) determination of the geoid to better than 1-meter an oceanographic objective required for measurement of sea surface topography and sea slope, quasi-stationary departure from the geoid, ocean circulation, air and sea interaction, etc. The geodesy objective in this case will be to define a reference equipotential surface as a means by which the oceanographic requirements can be achieved.

Mourad, A. G.↗

NASA NTRS1978

The earth's gravity field and ocean dynamics

An analysis of the signal-to-noise ratio of the best gravity field available shows that a basis exists for the recovery of the dominant parameters of the quasi-stationary sea surface topography. Results obtained from the analysis of GEOS-3 show that it is feasible to recover the quasi-stationary dynamic sea surface topography as a function of wavelength. The gravity field models required for synoptic ocean circulation modeling are less exacting in that constituents affecting radial components of orbital position need not be known through shorter wavelengths.

Mather, R. S.↗

NASA NTRS1979

The response of an equatorial ocean to simple wind stress patterns. I - Model formulation and analytic results. II - Numerical results

A time-dependent, primitive equation, beta plane model that is two-dimensional in the horizontal has been developed to model wind-driven equatorial ocean circulation. A simple vertical structure consisting of two layers above the thermocline with the same constant density permits a steady-state undercurrent in the model. An analytical study of the linear dynamics of the model suggests that the addition of inertial effects is needed to simulate the undercurrent properly. Also, both linear and nonlinear dynamics of the model are investigated numerically. Such nonlinear response to wind stress as a strong eastward equatorial undercurrent and an intense eastward 'countercurrent' at three deg N are noted in the numerical results.

Cane, M. A.↗

NASA NTRS1980

Phytoplankton pigments from the Nimbus-7 Coastal Zone Color Scanner - Comparisons with surface measurements

Algorithms are developed for removing aerosol effects in visual data from the Nimbus-7 Coastal Zone Color Scanner (CZCS). The corrected imagery reveals eddy-like ocean circulation patterns. Pigment concentrations from CZCS are compared with surface determinations. CZCS imagery estimates pigment concentration to within 0.5 log C, where C is the sum of the concentrations of chlorophyll a and phaeopigments a

Gordon, H. R.↗

NASA NTRS1980

Atmospheric and oceanographic research review, 1979

Papers generated by atmospheric, oceanographic, and climatological research performed during 1979 at the Goddard Laboratory for Atmospheric Sciences are presented. The GARP/global weather research is aimed at developing techniques for the utilization and analysis of the FGGE data sets. Observing system studies were aimed at developing a GLAS TIROS N sounding retrieval system and preparing for the joint NOAA/NASA AMTS simulation study. The climate research objective is to support the development and effective utilization of space acquired data systems by developing the GLAS GCM for short range climate predictions, studies of the sensitivity of climate to boundary conditions, and predictability studies. Ocean/air interaction studies concentrated on the development of models for the prediction of upper ocean currents, temperatures, sea state, mixed layer depths, and upwelling zones, and on studies of the interactions of the atmospheric and oceanic circulation systems on time scales of a month or more.

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NASA NTRS1981

A four-dimensional primitive equation model for coupled coastal-deep ocean studies

A prototype four dimensional continental shelf/deep ocean model is described. In its present form, the model incorporates the effects of finite amplitude topography, advective nonlinearities, and variable stratification and rotation. The model can be forced either directly by imposed atmospheric windstress and surface pressure distributions, and energetic mean currents imposed by the exterior oceanic circulation; or indirectly by initial distributions of shoreward propagation mesoscale waves and eddies. To avoid concerns over the appropriate specification of 'open' boundary conditions on the cross-shelf and seaward model boundaries, a periodic channel geometry (oriented along-coast) is used. The model employs a traditional finite difference expansion in the cross-shelf direction, and a Fourier (periodic) representation in the long-shelf coordinate.

Haidvogel, D. B.↗

NASA NTRS1982

The TOPEX satellite option study

The applicability of an existing spacecraft bus and subsystems to the requirements of ocean circulation measurements are assessed. The operational meteorological satellite family TIROS and DMSP are recommended. These programs utilize a common bus to satisfy their Earth observation missions. Note that although the instrument complements were different, the pointing accuracies were different, and, initially, the boosters were different, a high degree of commonality was achieved.

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NASA NTRS1983

Satellite altimetry

Progress in satellite altimetry accuracy, together with geoid surface measurements, is reviewed, and future programs are outlined. The Skylab, Geos-3, and Seasat spacecraft all carried altimeters for observing ocean topography, wind speed, and wave height from space. Data were gathered on the geoid and gravity anomalies over ocean areas, leading to determinations of the mesoscale variability of the oceans and a preliminary data base on ocean circulation. Satellite altimeters are currently accurate to 2 cm over a period of several years, and radial errors have been reduced to 50 cm with Seasat. Mean sea surfaces are measured with decimeter accuracy, a level of precision expected for altimetry when improved Doppler tracking, laser tracking, and the introduction of a GPS-based tracking system are implemented. The Shuttle is regarded as a prime vehicle for testing new altimetry techniques.

Marsh, J. G.↗

NASA NTRS1984

Ocean fluxes simulated by the GLAS GCM

A two year run with the GLAS climate model with prescribed but seasonally varying boundary conditions provided mean monthly fluxes of sensible heat, latent heat, and radiative energy. These fluxes were analyzed to examine the energy exchange processes between the atmosphere and the ice-free ocean. A mean annual plot of monthly zonal fuxes of sensible heat, latent heat, and net radiation was produced. From these, northward transport of heat flux that would follow if the GCM simulated fluxes were consistent with oceanic circulation were produced. These results are compared with observations.

Sud, Y. C.↗

NASA NTRS1982

Topex: Observing the Oceans from Space

Measurement of global ocean topography by a radar altimeter aboard the TOPEX satellite is discussed. Technical aspects of satellite altimetry as they pertain to the measurement of ocean circulation are described. The TOPEX mission is explained and a general history of oceanography is included.

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NASA NTRS1984

Global mean sea surface based upon SEASAT altimeter data

A global mean sea surface based upon the SEASAT altimeter data was derived. A combination of crossing arc techniques, accurate SEASAT reference orbits, and a previously computed GOES-3/SEASAT mean sea surface were used in the computation process. This mean sea surface provides a basis for the determination of global ocean circulation patterns and for detailed analysis of the Earth's internal structure. A contour map of the global mean sea surface is presented.

Marsh, J. G.↗

NASA NTRS1984

Theoretical and experimental studies in support of the geophysical fluid flow experiment

Computer programming was completed for digital acquisition of temperature and velocity data generated by the Geophysical Fluid Flow Cell (GFFC) during the upcoming Spacelab 3 mission. A set of scenarios was developed which covers basic electro-hydrodynamic instability, highly supercritical convection with isothermal boundaries, convection with imposed thermal forcing, and some stably stratified runs to look at large-scale thermohaline ocean circulations. The extent to which the GFFC experimental results apply to more complicated circumstances within the Sun or giant planets was assessed.

Hart, J.↗

NASA NTRS1984

Integrated remote sensing of the earth from low earth orbit in the 1990's

Trends in the areas of science, data systems, instruments and space technologies and their related infrastructures that will be experienced in earth remote sensing activities from LEO in the 1990s are discussed. Interdisciplinary studies will examine the flow of energy through the earth system, encompassing surveys of atmospheric and ocean circulations, the hydrologic cycle, and biogeochemical cycles. Mainframe computer assimilation of large data inputs will be associated with distributed microcomputer processing and analyses. Single satellite antennas will scan several microwave frequencies simultaneously, e.g., taking data on vegetation, water, and ice. Broadening the range of simultaneous observations will require multiinstrumented free-flying platforms, placed in orbit, repaired and/or retrieved by the Shuttle. Future instrumentation will include visible/IR imagers and the multifrequency microwave sounders with capabilities mainly limited by the availability of sufficient data-handling facilities.

Butler, D. M.↗

NASA NTRS1984

TOPEX - Observing the oceans from space

Born, G. H.↗

NASA NTRS1984

The potential of satellite-based radar altimeters

The benefits of satellite-based radar altimetry for oceanographic research are discussed in connection with the Seasat Altimeter Data Seminar. After a general review of the oceanographic data collected by the Seasat and GEOS-3 satellites, a number of criteria are proposed for the successful operation of a satellite-based radar altimeter for oceanographic remote sensing applications. It is shown how the interpretation of altimeter return power waveforms can be used to calculate wind speed, ocean circulation and variability in wind, waves, and tides. A number of recommendations for improving the accuracy of radar altimeter data are given which may be incorporated in the design of the GEOSAT and TOPEX research satellites.

Mooers, C. N. K.↗

NASA NTRS1985

Observing large-scale temporal variability of ocean currents by satellite altimetry - With application to the Antarctic circumpolar current

A new method is developed for studying large-scale temporal variability of ocean currents from satellite altimetric sea level measurements at intersections (crossovers) of ascending and descending orbit ground tracks. Using this method, sea level time series can be constructed from crossover sea level differences in small sample areas where altimetric crossovers are clustered. The method is applied to Seasat altimeter data to study the temporal evolution of the Antarctic Circumpolar Current (ACC) over the 3-month Seasat mission (July-October 1978). The results reveal a generally eastward acceleration of the ACC around the Southern Ocean with meridional disturbances which appear to be associated with bottom topographic features. This is the first direct observational evidence for large-scale coherence in the temporal variability of the ACC. It demonstrates the great potential of satellite altimetry for synoptic observation of temporal variability of the world ocean circulation.

Fu, L.-L.↗

NASA NTRS1985

On the geographical correlation of orbit error

The orbit accuracies needed to support the global crustal dynamics project and recent satellite altimeter missions have placed unique demands on the data analysis and orbit analysis systems. These demands include accurate and well distributed observations, improved computational techniques and substantial enhancements in the force models which represent the satellite's motion. For example, the satellite altimeter mission (TOPEX), whose objectives will be: (1) to measure the time variable ocean surface topography, and (2) to demonstrate the ability to map the general ocean circulation, requires that the radial component of the satellite's orbit be known with an rms accuracy of 13 cm for the three year mission lifetime. The primary force model uncertainty which limits the contemporary orbit computation accuracy is the inaccuracy in the values assigned to the spherical harmonic coefficients used to model the Earth's gravity field.

Tapley, B. D.↗