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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 55 records · Page 3
All sourcesNASA NTRSDOE OSTI
NASA NTRS1993

Observing Global Ocean Circulation From Space: The First Year's Results From the TOPEX/POSEIDON Mission

The joint U.S./France TOPEX/Poseidon satellite was launched on August 10, 1992, and became operational 42 days later. The major goal of the mission is to use a radar altimeter system for making precise measurements of the height of the sea surface for the study of the dynamics of large-scale ocean circulation, which is a key to understanding global climate change. Additionally, the data are used for studying ocean tides and marine geophysics. The radar altimeter also measures wave height and wind speed. The mission is being conducted to optimize the sea surface height measurements for a minimum of three years. The primary objective of the first six months of the mission was to calibrate and validate the mission's measurements. The verification results indicate that all the measurement objectives have been met...

Fu, L. -L.↗
NASA NTRS1993

Observing Global Ocean Circulation From Space: The First Year's Results From the TOPEX/POSEIDON Mission

The joint U.S./France TOPEX/Poseidon satellite was launched on August 10, 1992, and became operational 43 days later. The major goal of the mission is to use a radar altimeter system for making precise measurements of the height of the sea surface for the study of the dynamics of large-scale ocean circulation, which is a key to understanding global climate change. Additionally, the data are used for studying ocean tides and marine geophysics. The radar altimeter also measures wave height and wind speed. The mission is being conducted to optimize the sea surface height measurements for a minimum of three years. The primary objective of the first six months of the mission was to calibrate and validate the mission's measurements...

Fu, L. -L.↗
NASA NTRS1995

Observation of the Global Ocean Circulation From the TOPEX/POSEIDON Mission

Since 1992, the TOPEX/POSEIDON satellite has been making altimetric sea surface observations with a sea level accuracy of 4.4 cm. This data can be used for studying regional and seasonal differences in sea level and for evaluating oceanic circulation models and tidal models. Longer term changes can also be studied, such as El Nino and overall sea level rising (although the latter is still within the margin of error).

sea level oceanography TOPEX POSEIDONsea surface t↗
NASA NTRS1990

Determination of the ocean circulation using Geosat altimetry

A spherical harmonic model of the sea surface topography complete to degree and order 10 and a model of the earth's geopotential field complete to degree and order 50 have been obtained in a simultaneous solution using Geosat altimeter data and tracking data from 14 different satellites. The sea surface topography model compares well with oceanographic models computed using hydrographic data and ship drift data. Currently, errors in the estimated gravity field model limit the determination of the spherical harmonic coefficients of the general ocean circulation to degrees 10 and lower, corresponding to a minimum wavelength of 4000 km. Error analysis indicates that the correlation between the geoid and the sea surface topography model is less than 0.2, indicating good separation of the geoid and the sea surface topography at wavelengths of 4000 km or longer. Estimates of the scale factor for the significant wave height (H1/3), which is used to compute the electromagnetic bias correction and the bias for the Geosat altimeter, are obtained. The estimate of the H1/3 correction is 3.6 + or - 1.5 percent, and the height bias estimate is zero.

Nerem, R. S.↗
NASA NTRS1988

On estimating the basin-scale ocean circulation from satellite altimetry. Part 1: Straightforward spherical harmonic expansion

Direct estimation of the absolute dynamic topography from satellite altimetry has been confined to the largest scales (basically the basin-scale) owing to the fact that the signal-to-noise ratio is more unfavorable everywhere else. But even for the largest scales, the results are contaminated by the orbit error and geoid uncertainties. Recently a more accurate Earth gravity model (GEM-T1) became available, providing the opportunity to examine the whole question of direct estimation under a more critical limelight. It is found that our knowledge of the Earth's gravity field has indeed improved a great deal. However, it is not yet possible to claim definitively that our knowledge of the ocean circulation has improved through direct estimation. Yet, the improvement in the gravity model has come to the point that it is no longer possible to attribute the discrepancy at the basin scales between altimetric and hydrographic results as mostly due to geoid uncertainties. A substantial part of the difference must be due to other factors; i.e., the orbit error, or the uncertainty of the hydrographically derived dynamic topography.

Tai, Chang-Kou↗
NASA NTRS1981

Regional eddy vorticity transport and the equilibrium vorticity budgets of a numerical model ocean circulation

A mean vorticity budget analysis is presented of Holland's (1978) numerical ocean general circulation experiment. The stable budgets are compared with classical circulation theory to emphasize the ways in which the mesoscale motions of the model alter (or leave unaltered) classical vorticity balances. The basinwide meridional transports of vorticity by the mean flow and by the mesoscale flow in the mean are evaluated to establish the role(s) of the mesoscale in the larger scale equilibrium vorticity transports. The vorticity equation for this model fluid system is presented and the budget analysis method is described. Vorticity budgets over the selected regions and on a larger scale are given, and a summary of budget results is provided along with remarks about the utility of this type of analysis.

Harrison, D. E.↗
NASA NTRSDate not supplied

Ocean Circulation and Biogeochemistry

Dr. Whitt will give an oral presentation on his work on the impact of the ocean’s meridional overturning circulation on North Atlantic Ocean biogeochemical tracer budgets, including nutrients and carbon. The results are derived from two versions of the Estimating the Circulation and Climate of the Ocean (ECCO) model, including the latest release V4r5 (at 1 degree resolution) and the actively developed LLC270 (at 1/3 degree resolution).

MOC↗
NASA NTRS1987

On the choice of orbits for an altimetric satellite to study ocean circulation and tides

The choice of an orbit for satellite altimetric studies of the ocean's circulation and tides requires an understanding of the orbital characteristics that influence the accuracy of the satellite's measurements of sea level and the temporal and spatial distribution of the measurements. The orbital characteristics that influence accurate calculations of the satellite's position as a function of time are examined, and the pattern of ground tracks laid down on the ocean's surface as a function of the satellite's altitude and inclination is studied. The results are used to examine the aliases in the measurements of surface geostrophic currents and tides. Finally, these considerations are used to specify possible orbits that may be useful for the upcoming Topex/Poseidon mission.

Parke, Michael E.↗
NASA NTRS1994

Preliminary assessment of the accuracy and precision of TOPEX/POSEIDON altimeter data with respect to the large-scale ocean circulation

TOPEX/POSEIDON sea surface height measurements are examined for quantitative consistency with known elements of the oceanic general circulation and its variability. Project-provided corrections were accepted but are at tested as part of the overall results. The ocean was treated as static over each 10-day repeat cycle and maps constructed of the absolute sea surface topography from simple averages in 2 deg x 2 deg bins. A hybrid geoid model formed from a combination of the recent Joint Gravity Model-2 and the project-provided Ohio State University geoid was used to estimate the absolute topography in each 10-day period. Results are examined in terms of the annual average, seasonal average, seasonal variations, and variations near the repeat period. Conclusion are as follows: the orbit error is now difficult to observe, having been reduced to a level at or below the level of other error sources; the geoid dominates the error budget of the estimates of the absolute topography; the estimated seasonal cycle is consistent with prior estimates; shorter-period variability is dominated on the largest scales by an oscillation near 50 days in spherical harmonics Y(sup m)(sub 1)(theta, lambda) with an amplitude near 10 cm, close to the simplest alias of the M(sub 2) tide. This spectral peak and others visible in the periodograms support the hypothesis that the largest remaining time-dependent errors lie in the tidal models. Though discrepancies attribute to the geoid are within the formal uncertainties of the good estimates, removal of them is urgent for circulation studies. Current gross accuracy of the TOPEX/POSEIDON mission is in the range of 5-10 cm, distributed overbroad band of frequencies and wavenumbers. In finite bands, accuracies approach the 1-cm level, and expected improvements arising from extended mission duration should reduce these numbers by nearly an order of magnitude.

Wunsch, Carl↗
NASA NTRS2023

The Hydrological Cycle and Ocean Circulation of the Maritime Continent in the Mid-Pliocene: Results From PlioMIP2

The Maritime Continent (MC) forms the western boundary of the tropical Pacific Ocean, and relatively small changes in this region can impact the climate locally and remotely. In the mid-Piacenzian warm period of the Pliocene (mPWP; 3.264 to 3.025 Ma) atmospheric CO2 concentrations were ∼ 400 ppm, and the subaerial Sunda and Sahul shelves made the land–sea distribution of the MC different to today. Topographic changes and elevated levels of CO2, combined with other forcings, are therefore expected to have driven a substantial climate signal in the MC region at this time. By using the results from the Pliocene Model Intercomparison Project Phase 2 (PlioMIP2), we study the mean climatic features of the MC in the mPWP and changes in Indonesian Throughflow (ITF) with respect to the preindustrial. Results show a warmer and wetter mPWP climate of the MC and lower sea surface salinity in the surrounding ocean compared with the preindustrial. Furthermore, we quantify the volume transfer through the ITF; although the ITF may be expected to be hindered by the subaerial shelves, 10 out of 15 models show an increased volume transport compared with the preindustrial. In order to avoid undue influence from closely related models that are present in the PlioMIP2 ensemble, we introduce a new metric, the multi-cluster mean (MCM), which is based on cluster analysis of the individual models. We study the effect that the choice of MCM versus the more traditional analysis of multi-model mean (MMM) and individual models has on the discrepancy between model results and data. We find that models, which reproduce modern MC climate well, are not always good at simulating the mPWP climate anomaly of the MC. By comparing with individual models, the MMM and MCM reproduce the preindustrial sea surface temperature (SST) of the reanalysis better than most individual models and produce less discrepancy with reconstructed sea surface temperature anomalies (SSTA) than most individual models in the MC. In addition, the clusters reveal spatial signals that are not captured by the MMM, so that the MCM provides us with a new way to explore the results from model ensembles that include similar models.

Hydrological cycle↗
DOE OSTI2022

Global energy spectrum of the general oceanic circulation

Abstract Advent of satellite altimetry brought into focus the pervasiveness of mesoscale eddies $${{{{{{{\bf{{{{{{{{\mathcal{O}}}}}}}}}}}}}}}}({100})$$ O ( 100 ) km in size, which are the ocean’s analogue of weather systems and are often regarded as the spectral peak of kinetic energy (KE). Yet, understanding of the ocean’s spatial scales has been derived mostly from Fourier analysis in small "representative” regions that cannot capture the vast dynamic range at planetary scales. Here, we use a coarse-graining method to analyze scales much larger than what had been possible before. Spectra spanning over three decades of length-scales reveal the Antarctic Circumpolar Current as the spectral peak of the global extra-tropical circulation, at ≈ 10 4 km, and a previously unobserved power-law scaling over scales larger than 10 3 km. A smaller spectral peak exists at ≈ 300 km associated with mesoscales, which, due to their wider spread in wavenumber space, account for more than 50% of resolved surface KE globally. Seasonal cycles of length-scales exhibit a characteristic lag-time of ≈ 40 days per octave of length-scales such that in both hemispheres, KE at 10 2 km peaks in spring while KE at 10 3 km peaks in late summer. These results provide a new window for understanding the multiscale oceanic circulation within Earth’s climate system, including the largest planetary scales.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2021

Characterizing the Roles of Biogeochemical Cycling and Ocean Circulation in Regulating Marine Copper Distributions

Copper (Cu) is a key micronutrient for marine phytoplankton. Its oceanic biogeochemical cycle has elicited considerable attention due to dissolved Cu exhibiting a unique linear profile with depth. Several processes have been proposed for explaining this behavior. Here, in this study, we characterize the relationships between the observed Cu, PO 4 3– , and Si on a global scale. We find that the depth profiles of Cu resemble those of Si more than of PO 4 3– in the global ocean. To understand their relationships, we couple the biogeochemical and internal circulation processes in a model, fitting optimal Cu:PO 4 3– uptake ratios and remineralization length-scales to replicate the marine Cu distributions. The modeling results suggest that Cu uptake needs in the Southern Ocean are substantially higher than those in other oceanic regions. In addition, our modeling results indicate a deep Cu remineralization in the global ocean. We offer an alternative mechanism that relies on biogeochemical cycling and internal circulation to produce the linear depth profiles of dissolved Cu. Our results suggest that diatoms are likely the major phytoplankton dominating oceanic Cu cycling.

54 ENVIRONMENTAL SCIENCES↗
NASA NTRS1973

Numerical simulation of the world ocean circulation

A multi-level model, based on the primitive equations, is developed for simulating the temperature and velocity fields produced in the world ocean by differential heating and surface wind stress. The model ocean has constant depth, free slip at the lower boundary, and neglects momentum advection; so that there is no energy exchange between the barotropic and baroclinic components of the motion, although the former influences the latter through temperature advection. The ocean model was designed to be coupled to the UCLA atmospheric general circulation model, for the study of the dynamics of climate and climate changes. But here, the model is tested by prescribing the observed seasonally varying surface wind stress and the incident solar radiation, the surface air temperature and humidity, cloudiness and the surface wind speed, which, together with the predicted ocean surface temperature, determine the surface flux of radiant energy, sensible heat and latent heat.

Takano, K.↗