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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 541 records · Page 30
All sourcesNASA NTRSDOE OSTI
NASA NTRS2004

Research on the Natural Variability of Climate

The scheme for ocean vertical mixing presented in Canuto, Howard, Cheng & Dubovikov and Canuto, Howard, Hogan, Cheng, Dubovikov & Montenegro [GISS mixing scheme] was extended to include the latitudinal dependence reported by Gregg, Sanford & Winkel of the input to the interior ocean turbulence field of energy from internal waves. The resulting latitude dependence was implemented in our module of code for the GISS vertical mixing scheme and tested in the global NCAR-CSM ocean model with 3 degree X 3 degree resolution and 25 levels in the vertical. With the latitude dependence, the background diffusivity decreases from approx. 0.1 sq cm/sec at midlatitudes to approx. less than 0.01 sq cm/sec at the equator. A significant improvement was seen in the tropical ocean, with tropical thermoclines being sharpened in agreement with the requirements of observational studies and the needs of ENS0 modeling. At the same time global measures nf performance such as the meridional overturning and northward heat transport were not adversely affected. Results were presented at the 2004 Layered Ocean Modeling meeting and a paper has been prepared and submitted to Geophysical Research Letters.

Source record↗
NASA NTRS2023

GOLD Synoptic Observations of Quasi-6-Day Wave Modulations of Post-Sunset Equatorial Ionization Anomaly During the September 2019 Antarctic Sudden Stratospheric Warming

Using observations from the Global-scale Observations of the Limb and Disk (GOLD) mission, we investigate post-sunset ionospheric responses to the September 2019 Antarctic sudden stratospheric warming –first ever from a synoptic perspective. Observations reveal a prevalent quasi-6-day periodicity in the equatorial ionization anomaly region over South America and the Atlantic, coincident with enhanced quasi-6-day wave (Q6DW) activity in the mesosphere (Liu et al., 2021, https://doi.org/10.1029/2020JA028909). The atmosphere-ionosphere coupling via large-scale waves is rarely studied over the ocean due to the lack of observations. More importantly, further analyses suggest that multiple pathways are involved in transmitting the quasi-6-day periodicity from the middle atmosphere into the post-sunset F-region ionosphere, including modulation of F-region field aligned winds and pre-reversal enhancements by the tides and or Q6DW. A remarkable depletion in electron density, attributable to the overall change in thermosphere composition driven by the dissipative tides and or Q6DWs, is also seen during the period of enhanced Q6DW activity.

atmosphere-ionosphere coupling↗
NASA NTRS2011

The Role of African Easterly Wave on Dust Transport and the Interaction Between Saharan Dust Layer and Atlantic ITCZ During Boreal Summer

Saharan dust outbreaks not only transport large amount of dust to the northern Atlantic Ocean, but also alter African easterly jet and wave activities along the jet by changing north-south temperature gradient. Recent modeling and observational studies show that during periods of enhance outbreaks, rainfall on the northern part of ITCZ increases in conjunction with a northward shift of ITCZ toward the dust layer. In this paper, we study the radiative forcing of Saharan dust and its interactions with the Atlantic Inter-tropical Convergence Zone (ITCZ), through African easterly waves (AEW), African easterly jet (AEJ), using the Terra/Aqua observations as well as MERRA data. Using band pass filtered EOF analysis, we find that African easterly waves propagating westward along two principal tracks, centered at 15-25N and 5-10N respectively. The easterly waves in the northern track are slower, with propagation speed of 9 ms-1, and highly correlated with major dust outbreak over North Africa. On the other hand, easterly waves along the southern track are faster with propagating speed of 10 ms-1, and are closely tied to rainfall/cloud variations along the Atlantic ITCZ. Dust transport along the southern track leads rainfall/cloud anomalies in the same region by one or two days, suggesting the southern tracks of dust outbreak are regions of strong interaction between Saharan dust layer and Atlantic ITCZ. Possible linkage between two tracks of easterly waves, as well as the long-term change of easterly wave activities and dust outbreaks, are also discussed.

Kim, Kyu-Myong↗
NASA NTRS1974

A dual frequency radar for ocean roughness sampling

A microwave technique for determining the roughness (rms wave height) of a randomly varying air-water interface has been developed theoretically, verified with laboratory wavetank studies and is currently being implemented for ocean surface measurements in a series of applications flight experiments. These aircraft observations will be near the Chesapeake Light Tower and will include a range of altitudes and sea conditions. The measurement concept involves cross-correlating the envelope fluctuations on two received carriers that are monochromatic when transmitted in a normal direction to the interface and are observed in a backscatter direction after reflection by the large number of randomly distributed specular points on the surface. The measured correlation coefficient (normalized covariance) as a function of carrier frequency separation will depend on the surface roughness, specifically the probability density function of the specular point height. Details of the flight system are discussed, and preliminary flight results are presented.

Weissman, D. E.↗
NASA NTRS1996

Evidence of Boundary Reflection of Kelvin and First-Mode Rossby Waves from Topex/Poseidon Sea Level Data

The TOPEX/POSEIDON sea level data lead to new opportunities to investigate some theoretical mechanisms suggested to be involved in the El Nino-Southern Oscillation phenomenon in the tropical Pacific ocean. In particular, we are interested in studying the western boundary reflection, a process crucial for the delayed action oscillator theory, by using the TOPEX/POSEIDON data from November 1992 to May 1995. We first projected the sea level data onto Kelvin and first-mode Ross waves. Then we estimated the contribution of wind forcing to these waves by using a single baroclinic mode simple wave model forced by the ERS-1 wind data. Wave propagation was clearly observed with amplitudes well explained by the wind forcing in the ocean interior. Evidence of wave reflection was detected at both the western and eastern boundaries of the tropical Pacific ocean. At the eastern boundary, Kelvin waves were seen to reflect as first-mode Rossby waves during the entire period. The reflection efficiency (in terms of wave amplitude) of the South American coasts was estimated to be 80% of that of an infinite meridional wall. At the western boundary, reflection was observed in April-August 1993, in January-June 1994, and, later, in December 1994 to February 1995. Although the general roles of these reflection events in the variability observed in the equatorial Pacific ocean are not clear, the data suggest that the reflections in January-June 1994 have played a role in the onset of the warm conditions observed in late 1994 to early 1995. Indeed, during the January-June 1994 period, as strong downwelling first-mode Rossby waves reflected into downwelling Kelvin waves, easterly wind and cold sea surface temperature anomalies located near the date line weakened and eventually reversed in June-July 1994. The presence of the warm anomalies near the date line then favored convection and westerly wind anomalies that triggered strong downwelling Kelvin waves propagating throughout the basin simultaneously with the beginning of the 1994-1995 warm conditions.

Boulanger, Jean-Philippe↗
NASA NTRS1978

Orbit analysis for Seasat-A

Seasat-A is a NASA earth satellite for measuring global ocean dynamics from space. The instruments on the spacecraft will provide data on wave height and direction, surface wind speed and direction, ice fields, ocean surface topography and atmospheric water content. This paper is concerned with the orbit analysis for Seasat-A. The first topic is the selection of the orbit which best satisfies the measurement objectives of the various instruments. The maintenance of this orbit under drag and other perturbations is also discussed. The second topic is precision orbit determination analysis which is required to achieve ocean topography objectives of the mission.

Cutting, E.↗
NASA NTRS1975

Project GEOS-C

An oceanographic-geodetic satellite, designated Geodynamics Experimental Ocean Satellite-C (GEOS-C), an earth-orbiting spacecraft designed to measure precisely the topography of the ocean surface and the sea state (wave height, wave period, wave propagation direction) is described. Launch operations, spacecraft description, and mission objectives are included along with a brief flight history of the NASA satellite geodesy program. Principal investigations to be performed by the GEOS-C mission are discussed.

Source record↗
NASA NTRS1975

Determining the parameters of the prognostic operator for undamped fluctuations by the use of the D sub m(kappa; alpha 1,..., alpha sub m)

The prognostic operator is defined as the matrix or integral operation which, when applied to a set of known values of the vector for various earlier moments of time, predicts a value for the vector at a future moment by the amount ahead of time. If the vector represents a function that decays with time, then the predicted values of the function are given as series expansions in terms of the same functions but with unknown coefficients if some change in the process occurs at the moment of prediction. As examples of such changes are considered: (1) the circulation mechanisms of the atmosphere under the influence of solar activity; (2) brightness fields fluctuations; and (3) wave formations or currents in the ocean after a change in wind field.

Dmitriyev, A. A.↗
NASA NTRS1974

SEASAT-A - A user oriented systems design

The SEASAT-A spacecraft is tentatively scheduled for launch in 1978 into a nearly circular orbit with an altitude of approximately 800 km. The spacecraft is to demonstrate a capability for the global monitoring of wave height and spectra, surface winds, ocean temperature, and current patterns. Other objectives include the charting of ice fields and a mapping of the global geoid. The sensors to be carried by the spacecraft are discussed and a description is given of the satellite system and the subsystems.

Mccandless, S. W., Jr.↗
NASA NTRS1980

Selective decay hypothesis at high mechanical and magnetic Reynolds numbers

Implications of certain applications of turbulence theory to two-dimensional turbulence and magnetohydrodynamic flow are discussed. It is shown that the use of the Navier-Stokes equation (NSE) for measurements of turbulent fluctuations has been effective only for three-dimensional flows. For two-dimensional flows, used for the study of large-scale motions in the atmosphere or ocean, enstrophy is cascaded to high wave numbers and dissipated at a finite rate even at infinite Re. MHD flows are numerically calculated for the two-dimensional case and analytically for the three-dimensional case, for which discrepancies in the relative rates of energy and cross helicity decay lead to a recommendation that numerical calculations for the three-dimensional case be carried out to determine the precise decayed states.

Matthaeus, W. H.↗
NASA NTRS1984

Evaluation of SIR-B imagery for geologic and geomorphic mapping, hydrology, and oceanography in Australia

The objectives of a study to evaluate the potential of Shuttle Imaging Radar-B (SIR-B) imagery for various applications are outlined. Specific goals include: the development of techniques for registration multiple acquisition, varied illumination, and incidence-angle SIR-B imagery, and a model for estimation of the relative contributions to the backscattered radiation of topography, surface roughness, and dielectric and conductivity components; (2) the evaluation of SIR-B imagery for delineation of agricultural lands affected by secondary salinity in the southwest and southeast agricultural regions of Australia; (3) the development of techniques for application of SIR-B imagery for geologic, geomorphologic and soils mapping and mineral exploration; and (4) the evaluation of the use of SIR-B imagery in determining ocean currents, current shear patterns, internal waves and bottom features for specific locations off the Australian coast.

Honey, F. R.↗
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 NTRS1991

Convection wave studies over land and sea

Preliminary results of recent case studies conducted over land and sea are given. Two dimensional convection (roll vortex/cloudstreet) and three dimensional convection in the underlying boundary layer are dealt with. Vertical momentum flux profiles and time series of important parameters and vertical soundings taken in the experiment area are shown. The three cases described show that convection waves occur over land and over ocean, over three dimensional convection and over two dimensional convection.

Kuettner, Joachim↗
NASA NTRS1985

The WINDSAT concept for measuring the global wind field

The Wave Propagation Laboratory of the National Oceanic and Atmospheric Administration's (NOAA) Environmental Research Laboratories has investigated the feasibility of measuring the global wind field by using an infrared coherent laser radar under a joint program with the U.S. Air Force Space Division Defense Meteorological Satellite Program (DMSP). These studies considered both the analytical and hardware feasibility of a spaceborne global wind measuring coherent laser radar (WINDSAT). Objectives and requirements of the Air Force Defense Meteorological Satellite Program were used in the study. The vertical distributions of the horizontal wind field were required throughout the troposphere with 300 km square horizontal and 1 km vertical resolution with a measurements accuracy of 1 m/s. Complete global coverage was required. The lidar system performance should also be scalable to operational satellite conditions. The analytical studies were performed for both a 300 km altitude Space Shuttle orbit and an operational polar orbit of 800 km altitude (Huffaker, 1978; Huffaker et al., 1980). A hardware definition study was performed for a Space Shuttle demonstration test flight (Lockheed Missiles and Space Co., 1981). Studies have also been conducted to determine the feasibility of mounting a WINDSAT payload on an Advanced TIROS-N spacecraft (RCA Corporation, 1983).

Huffaker, R. Milton↗
NASA NTRS2003

Software for a GPS-Reflection Remote-Sensing System

A special-purpose software Global Positioning System (GPS) receiver designed for remote sensing with reflected GPS signals is described in Delay/Doppler-Mapping GPS-Reflection Remote-Sensing System (NPO-30385), which appears elsewhere in this issue of NASA Tech Briefs. The input accepted by this program comprises raw (open-loop) digitized GPS signals sampled at a rate of about 20 MHz. The program processes the data samples to perform the following functions: detection of signals; tracking of phases and delays; mapping of delay, Doppler, and delay/Doppler waveforms; dual-frequency processing; coherent integrations as short as 125 s; decoding of navigation messages; and precise time tagging of observable quantities. The software can perform these functions on all detectable satellite signals without dead time. Open-loop data collected over water, land, or ice and processed by this software can be further processed to extract geophysical information. Possible examples include mean sea height, wind speed and direction, and significant wave height (for observations over the ocean); bistatic-radar terrain images and measures of soil moisture and biomass (for observations over land); and estimates of ice age, thickness, and surface density (for observations over ice).

Lowe, Stephen↗
NASA NTRS2022

Infrared Spectral Responses of the Ocean Color Instrument (OCI) Pre-assembly and Integration

Spectral characterizations were made of the Ocean Color Instrument (OCI) short-wave infrared (SWIR) Detection Subassembly (SDS) responses (940–2260 nm) prior to their integration. Using modulated output light from a Fourier transform spectrometer, the in-band relative spectral responses of the nine different configurations of SDSs were found along with out-of-band (OOB) sensitivity. From these spectral responses, the center wavelengths (λ0), full widths at half of the maximum, full widths at 1% of the maximum, and OOB rejection ratios were determined. All spectral parameters are within requirements. There are 2–8 repeats of each configuration, and the 1 σ spread among repeats is largest for the 1250 nm and 1615 nm high-gain configurations and is greater than 1 nm. The engineering requirement is for these values to be within ±4 nm and ±10 nm, respectively, of 19 the nominal λ0. There is also a λ0 temperature dependence, which is expected. This temperature dependence is nearly a linear function of wavelength with a 9.5 × 10−3 nm K−1 relationship on average.

PACE↗
NASA NTRS2007

Intraseasonal Variability of the Equatorial Indian Ocean Observed from Sea Surface Height, Wind, and Temperature Data

The forcing of the equatorial Indian Ocean by the highly periodic monsoon wind cycle creates many interesting intraseasonal variabilities. The frequency spectrum of the wind stress observations from the European Remote Sensing Satellite scatterometers reveals peaks at the seasonal cycle and its higher harmonics at 180, 120, 90, and 75 days. The observations of sea surface height (SSH) from the Jason and Ocean Topography Experiment (TOPEX)/Poseidon radar altimeters are analyzed to study the ocean's response. The focus of the study is on the intraseasonal periods shorter than the annual period. The semiannual SSH variability is characterized by a basin mode involving Rossby waves and Kelvin waves traveling back and forth in the equatorial Indian Ocean between 10(deg)S and 10(deg)N. However, the interference of these waves with each other masks the appearance of individual Kelvin and Rossby waves, leading to a nodal point (amphidrome) of phase propagation on the equator at the center of the basin. The characteristics of the mode correspond to a resonance of the basin according to theoretical models. The theory also calls for similar modes at 90 and 60 days.

wind stress observations↗