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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 NTRS1978

Detailed 1 x 1 deg gravimetric Indian Ocean geoid and comparison with GEOS-3 radar altimeter geoid profiles

A new set of 1 x 1 deg mean free-air anomalies in the Indian Ocean is determined on the basis of previously published free-air anomaly maps (Talwani and Kahle, 1975) and the most recent Lamont surface ship gravity measurements. The data are then used to compute a (total) 1 x 1 deg gravimetric Indian Ocean geoid. The computation is carried out by combining the Goddard Space Flight Center (GSFC) GEM-6 geoid and a difference geoid that corresponds to the differences between the set of 1 x 1 deg surface gravity values and the GEM-6 gravity anomalies. The difference geoid is highest over the Madagascar Ridge (+20 m) and lowest over the Timor Trough (-30 m). The total geoid is compared with GEOS-3 radar altimeter-derived geoid profiles, and geophysical implications are discussed.

Kahle, H.-G.↗
NASA NTRS1979

Estimation of mean sea surfaces in the north Atlantic, the Pacific and the Indian Ocean using GEOS-3 altimeter data

The mean surfaces of several regions of the world's oceans were estimated using GEOS-3 altimeter data. The northwest Atlantic, the northeast Pacific off the coast of California, the Indian Ocean, the southwest Pacific, and the Phillipine Sea are included. These surfaces have been oriented with respect to a common earth center-of-mass system by constraining the separate solutions to conform to precisely determined laser reference control orbits. The same reference orbits were used for all regions assuring continuity of the separate solutions. Radial accuracies of the control orbits were in the order of one meter. The altimeter measured sea surface height crossover differences were minimized by the adjustment of tilt and bias parameters for each pass with the exception of laser reference control passes. The tilt and bias adjustments removed long wavelength errors which were primarily due to orbit error. Ocean tides were evaluated. The resolution of the estimated sea surfaces varied from 0.25 degrees off the east coast of the United States to about 2 degrees in part of the Indian Ocean near Australia. The rms crossover discrepancy after adjustment varied from 30 cm to 70 cm depending upon geographic location. Comparisons of the altimeter derived mean sea surface in the North Atlantic with the 5 feet x 5 feet GEM-8 detailed gravimetric geoid indicated a relative consistency of better than a meter.

Marsh, J. G.↗
NASA NTRS1995

Mean Sea Level Derived from Altimetry and Wind-Driven Numerical Models in the Indian Ocean

Wind-driven model skill in simulating sea level variations in the Indian Ocean depends on our knowledge of the mean ocean dynamic topography. This is demonstrated by running the nonlinear or linear version of a shallow-water model driven by observed winds over Geosat and TOPEX periods. Geosat variations are assimilated in the nonlinear shallow-water model with the objective of obtaining topography data.

numerical models Indian ocean mean sea level remot↗
NASA NTRS2009

Detection of Rossby Waves in Multi-Parameters in Multi-Mission Satellite Observations and HYCOM Simulations in the Indian Ocean

Rossby waves are difficult to detect with in situ methods. However, as we show in this paper, they can be clearly identified in multi-parameters in multi-mission satellite observations of sea surface height (SSH), sea surface temperature (SST) and ocean color observations of chlorophyll-a (chl-a), as well as 1/12-deg global HYbrid Coordinate Ocean Model (HYCOM) simulations of SSH, SST and sea surface salinity (SSS) in the Indian Ocean. While the surface structure of Rossby waves can be elucidated from comparisons of the signal in different sea surface parameters, models are needed to gain direct information about how these waves affect the ocean at depth. The first three baroclinic modes of the Rossby waves are inferred from the Fast Fourier Transform (FFT), and two-dimensional Radon Transform (2D RT). At many latitudes the first and second baroclinic mode Rossby wave phase speeds from satellite observations and model parameters are identified.

SSH (SEA SURFACE HEIGHT)↗
NASA NTRS1983

MAGSAT investigation of crustal magnetic anomalies in the eastern Indian Ocean

Crustal magnetic anomalies in a region of the eastern Indian Ocean were studied using data from NASA's MAGSAT mission. The investigation region (0 deg to 50 deg South, 75 to 125 deg East) contains several important tectonic features, including the Broken Ridge, Java Trench, Ninetyeast Ridge, and Southeast Indian Ridge. A large positive magnetic anomaly is associated with the Broken Ridge and smaller positive anomalies correlate with the Ninetyeast Ridge and western Australia. Individual profiles of scalar data (computed from vector components) were considered to determine the overall data quality and resolution capability. A set of MAGSAT ""Quiet-Time'' data was used to compute an equivalent source crustal magnetic anomaly map of the study region. Maps of crustal magnetization and magnetic susceptibility were computed from the equivalent source dipoles. Gravity data were used to help interpretation, and a map of the ratio of magnetization to density contrasts was computed using Poisson's relation. The results are consistent with the hypothesis of induced magnetization of a crustal layer having varying thickness and composition.

Sailor, R. V.↗
NASA NTRS1981

The effect of zonal gradients of sea surface temperature on the Indian Ocean winter monsoon

Several global climate simulations by the 7-layer, 8 x 10 GISS climate model were designed to test the contributions of various surface boundary conditions to the global climate. The model was run with the sun fixed at a perpetual January. In a comparison of run #5, in which realistic January surface boundary conditions were used, with run #4, which was the same except that a zonally symmetric climatological January sea surface temperature (SST) field was used, one of the results was that run #5 provided a better simulation of the Indian Ocean monsoon. A further comparison of the wind fields over the Indian Ocean that were generated by these two model runs is presented.

Cohen, C.↗
NASA NTRS1995

Dynamic interpretation of space shuttle photographs: Deepwater internal waves in the western equatorial Indian Ocean

Visible images of deep-ocean internal waves in the western equatorial Indian Ocean taken by the space shuttle Atlantis during mission STS 44 in 1991 are interpreted and analyzed. The internal waves occurred in the form of a multisoliton packet in which there are about a dozen solitons. The average wavelength of the solitons is 1.8 +/- 0.5 km, ranging from 1.1 to 2.6 km. The crest lines are mostly straight and reach as long as 100 km. The distance between two adjacent packets is about 66 km. Using the deepwater soliton theory, we derived that the mean amplitude of the solitons is 25 m, the nonlinear phase speed is 1.7 m/s, and the average period is 18 min. The internal semidiurnal tides are the principal generating mechanism. The oblique collision of two multisoliton packets shown on photograph STS 44-93-103 is examined. The results show that the deep-ocean internal waves obey the general properties of soliton collision. The leading solitons and a few followers exhibit some properties of inelastic collision characterized by a phase shift, and the rest of the solitons exhibits properties of elastic collision under resonance conditions.

Zheng, Quanan↗
NASA NTRS1993

Iridium in sediments containing large abundances of Australasian microtektites from DSDP hole 758B in the Eastern Indian Ocean and from DSDP hole 769A in the Sulu Sea

Excess Ir found in sediments at the Cretaceous/Tertiary (K/T) boundary and in other (e.g., Pliocene) sediments from deep sea drilling cores is widely interpreted as evidence of major impact events. The Australasian tektites originated in an impact event approximately 0.77 Ma ago; microtektites have been found in deep-sea sediment cores from throughout the Indian Ocean, the Philippine Sea, and western Pacific Ocean, but Ir has not been previously reported in these horizons. The deep-sea record of tektites is of particular interest, because in contrast to most continental occurrences, the stratigraphy preserves the original depositional position. Recently several cores having exceptionally high contents of Australasian microtektites have been investigated, Glass and Wu found shocked quartz associated with the microtektites. We used neutron activation to determine concentrations of Ir and other elements in two cores bearing microtektites, one from Deep Sea Drilling Project (DSDP) hole 758B in the Eastern Indian Ocean and one from DSDP hole 769A in the Sulu Sea (near Mindanao, Philippines). The sedimentation age for the microtektite layers in core 758B lies between 0.73 - 0.78 Ma and agrees well with the mean laser-fusion Ar-40/Ar-39 age of Australasian tektites of 0.77 +/- 0.02 Ma by Izett et al. We are able to resolve a small positive Ir enhancement in 758B. Core 769A shows too much scatter to allow resolution of an Ir peak.

Schmidt, Gerhard↗
NASA NTRS2005

Height Distribution Between Cloud and Aerosol Layers from the GLAS Spaceborne Lidar in the Indian Ocean Region

The Geoscience Laser Altimeter System (GLAS), a nadir pointing lidar on the Ice Cloud and land Elevation Satellite (ICESat) launched in 2003, now provides important new global measurements of the relationship between the height distribution of cloud and aerosol layers. GLAS data have the capability to detect, locate, and distinguish between cloud and aerosol layers in the atmosphere up to 40 km altitude. The data product algorithm tests the product of the maximum attenuated backscatter coefficient b'(r) and the vertical gradient of b'(r) within a layer against a predetermined threshold. An initial case result for the critical Indian Ocean region is presented. From the results the relative height distribution between collocated aerosol and cloud shows extensive regions where cloud formation is well within dense aerosol scattering layers at the surface. Citation: Hart, W. D., J. D. Spinhime, S. P. Palm, and D. L. Hlavka (2005), Height distribution between cloud and aerosol layers from the GLAS spaceborne lidar in the Indian Ocean region,

Hart, William D.↗
DOE OSTI2022

Rain-Induced Stratification of the Equatorial Indian Ocean and Its Potential Feedback to the Atmosphere

Surface freshening through precipitation can act to stably stratify the upper ocean, forming a rain layer (RL). RLs inhibit subsurface vertical mixing, isolating deeper ocean layers from the atmosphere. This process has been studied using observations and idealized simulations. The present ocean modeling study builds upon this body of work by incorporating spatially resolved and realistic atmospheric forcing. Fine-scale observations of the upper ocean collected during the Dynamics of the Madden-Julian Oscillation field campaign are used to verify the General Ocean Turbulence Model (GOTM). Spatiotemporal characteristics of equatorial Indian Ocean RLs are then investigated by forcing a 2D array of GOTM columns with realistic and well-resolved output from an existing regional atmospheric simulation. RL influence on the ocean-atmosphere system is evaluated through analysis of RL-induced modification to surface fluxes and sea surface temperature (SST). This analysis demonstrates that RLs cool the ocean surface on time scales longer than the associated precipitation event. A second simulation with identical atmospheric forcing to that in the first, but with rainfall set to zero, is performed to investigate the role of rain temperature and salinity stratification in maintaining cold SST anomalies within RLs. Approximately one third, or 0.1°C, of the SST reduction within RLs can be attributed to rain effects, while the remainder is attributed to changes in atmospheric temperature and humidity. The prolonged RL-induced SST anomalies enhance SST gradients that have been shown to favor the initiation of atmospheric convection. These findings encourage continued research of RL feedbacks to the atmosphere.

54 ENVIRONMENTAL SCIENCES↗
NASA NTRS1981

Analyses of MAGSAT tracks crossing the study region in the Indian Ocean

Progress in software development and in preliminary analysis of MAGSAT tracks crossing the Indian Ocean is reported. Tracks crossing the Java Trench, Broken Ridge, the Southeast Indian Ridge, and the Ninetyeast Ridge show that magnetic anomalies correlate with some of these features. Preliminary study of anomaly profiles indicates that tracks of anomaly data (the observations minus a core field model) have a power spectrum decreasing as the inverse square of the spatial frequency. An apparent noise floor of about one to two gammas rms is reached at wavelengths of about 360 km, corresponding to approximately 10 samples of the decimated Investigator tape data at a sampling rate of approximately 4.9 sec/sample.

Sailor, R. V.↗
NASA NTRS1982

Spatial resolution and repeatability of Magsat crustal anomaly data over the Indian Ocean

Preliminary results from analysis of individual Magsat tracks in the eastern Indian Ocean demonstrate the resolution capability and repeatability of these data. Spectrum analysis indicates that 250 km is the absolute lower limit for resolving crustal magnetic anomalies in Magsat along-track data. Spectral coherence analysis of closely-spaced tracks shows that magnetic anomaly features with wavelengths greater than 700 km are highly repeatable from track to track.

Sailor, R. V.↗
NASA NTRS1993

Constraints on lithospheric thermal structure for the Indian Ocean from depth and heat flow data

Models for the thermal evolution of oceanic lithosphere are primarily constrained by variations in seafloor depth and heat flow with age. These models have been largely based on data from the Pacific and Atlantic Ocean basins. We construct seafloor age relations for the Indian Ocean which we combine with bathymetric, sediment isopach and heat flow data to derive curves for depth and heat flow versus age. Comparison of these curves with predictions from three thermal models shows that they are better fit by the shallower depths and higher heat flow for the GDH1 model, which is characterized by a thinner and hotter lithosphere than previous models.

Shoberg, Tom↗
DOE OSTI2020

Improved Predictability of the Indian Ocean Dipole Using a Stochastic Dynamical Model Compared to the North American Multimodel Ensemble Forecast

This study assesses the predictive skill of eight North American Multimodel Ensemble (NMME) models in predicting the Indian Ocean dipole (IOD). We find that the forecasted ensemble-mean IOD–El Niño–Southern Oscillation (ENSO) relationship deteriorates away from the observed relationship with increasing lead time, which might be one reason that limits the IOD predictive skill in coupled models. We are able to improve the IOD predictive skill using a recently developed stochastic dynamical model (SDM) forced by forecasted ENSO conditions. The results are consistent with the previous result that operational IOD predictability beyond persistence at lead times beyond one season is mostly controlled by ENSO predictability and the signal-to-noise ratio of the Indo-Pacific climate system. The multimodel ensemble (MME) investigated here is found to be of superior skill compared to each individual model at most lead times. Importantly, the skill of the SDM IOD predictions forced with forecasted ENSO conditions were either similar or better than those of the MME IOD forecasts. Moreover, the SDM forced with observed ENSO conditions exhibits significantly higher IOD prediction skill than the MME at longer lead times, suggesting the large potential skill increase that could be achieved by improving operational ENSO forecasts. We find that both cold and warm biases of the predicted Niño-3.4 index may cause false alarms of negative and positive IOD events, respectively, in NMME models. Many false alarms for IOD forecasts at lead times longer than one season in the original forecasts disappear or are significantly reduced in the SDM forced by forecasted ENSO conditions.

54 ENVIRONMENTAL SCIENCES↗