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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 901 records · Page 50
All sourcesNASA NTRSDOE OSTI
NASA NTRS1981

Analysis of GOES imagery and digitized data for the SEV-UPS period, August 1979

In support of the Southeastern Virginia Urban Plume Study (SEV-UPS), GOES satellite imagery was analyzed for the month of August 1979. The analyzed GOES images provide an additional source of meteorological input useful in the evaluation of air quality data collected during the month long period of the SEV-UPS experiment. In addition to the imagery analysis, GOES digitized data were analyzed for the period of August 6 to 11, during which a regional haze pattern was detectable in the imagery. The results of the study indicate that the observed haze patterns correspond closely with areas shown in surface based measurements to have reduced visibilities and elevated pollution levels. Moreover, the results of the analysis of digitized data indicate that digital reflectance counts can be directly related to haze intensity both over land and ocean. The model results agree closely with the observed GOES digital reflectance counts, providing further indication that satellite remote sensing can be a useful tool for monitoring regional elevated pollution episodes.

Bowley, C. J.↗
NASA NTRS1981

Analysis of the surface heat balance over the world ocean

The net surface heat fluxes over the global ocean for all calendar months were evaluated. To obtain a formula in the form Qs = Q2(T*A - Ts), where Qs is the net surface heat flux, Ts is the sea surface temperature, T*A is the apparent atmospheric equilibrium temperature, and Q2 is the proportionality constant. Here T*A and Q2, derived from the original heat flux formulas, are functions of the surface meteorological parameters (e.g., surface wind speed, air temperature, dew point, etc.) and the surface radiation parameters. This formulation of the net surface heat flux together with climatological atmospheric parameters provides a realistic and computationally efficient upper boundary condition for oceanic climate modeling.

Esbenson, S. K.↗
NASA NTRS1983

A novel algorithm for sea surface height estimation using complex SAR data

A method of extracting sea height information from Synthetic Aperture Radar (SAR) complex data was studied. A fundamental SAR ocean imaging model for gravity waves showed that information about the long wave is present in the SAR complex data, especially its phase. Phase demodulation algorithm followed by linear regression and filtering was employed. Only the latter two steps incorporated a priori information that might be available. A relatively simplified simulation indicated that the finite bandwidth of the SAR system imposed the apparently most serious limitation. A preliminary application to SEASAT-SAR complex imagery was encouraging. Information about the long wave, if incorporated into a more sophisticated phase demodulation structure, i.e., at an earlier point in the algorithm, could conceivably mitigate this bandwidth limitation.

Harger, R. O.↗
NASA NTRS1984

Sea Ice

Scientific objectives and observational requirements relative to sea ice studies in the 1990's are discussed. The development of coupled ice-ocean-atmosphere models that provide information comparable to real data sets through interactive processes is discussed. A series of particular problems that would provide the basis for such a verification data set and which is amenable to satellite systems available or realizable over the next 20 years is presented.

Ackley, S. F.↗
NASA NTRS1986

A comparison of SIR-B directional ocean wave spectra with aircraft scanning radar spectra

Directional ocean wave spectra derived from Shuttle Imaging Radar-B (SIR-B) L-band imagery collected off the coast of Southern Chile on 11 and 12 October 1984 were compared with independent spectral estimates from two airborne scanning radars. In sea states with significant wave heights ranging from 3 to 5 meters, the SIR-B-derived sspectra at 18 deg and 25 deg off nadir yielded reasonable estimates of wavelengths, directions, and spectral shapes for all wave systems encountered, including a purely azimuth-traveling system. A SIR-B image intensity variance spectrum containing predominantly range-traveling waves closely resembles an independent aircraft estimate of the slope variance spectrum. The prediction of a U.S. Navy global spectral ocean wave model on 11 October 1984 exhibited no significant bias in dominant wave number but contained a directional bias of about 30 deg with respect to the mean of the aircraft and spacecraft estimates.

Beal, R. C.↗
NASA NTRS1986

SAR imaging of bottom topography in the ocean: Results from an improved model

A two-space dimensional model, which is applicable to arbitrary bottom topography and wind, is applied to Seasat Revs. 762, 957, 1430, and 1473. The model includes the additional modulational effects of a long-wave field on the short Bragg waves, both in the presence of a variable current field and results compared to data. Modulations associated with other radar frequencies are also calculated under Rev. 762 conditions. It is shown that when the long-wave field effects are included, signature strength does not decrease with increasing radar frequency. The percentage enhancement due to long waves ranges from 7% for L band to 850% for K band.

Yuen, H. C.↗
NASA NTRS1986

Partial spline models for the inclusion of tropopause and frontal boundary information in otherwise smooth two- and three-dimensional objective analysis

A new method, based on partial spline models, is developed for including specified discontinuities in otherwise smooth two- and three-dimensional objective analyses. The method is appropriate for including tropopause height information in two- and three-dimensinal temperature analyses, using the O'Sullivan-Wahba physical variational method for analysis of satellite radiance data, and may in principle be used in a combined variational analysis of observed, forecast, and climate information. A numerical method for its implementation is described and a prototype two-dimensional analysis based on simulated radiosonde and tropopause height data is shown. The method may also be appropriate for other geophysical problems, such as modeling the ocean thermocline, fronts, discontinuities, etc.

Shiau, Jyh-Jen↗
NASA NTRS1986

Analysis/forecast experiments with a flow-dependent correlation function using FGGE data

The use of a flow-dependent correlation function to improve the accuracy of an optimum interpolation (OI) scheme is examined. The development of the correlation function for the OI analysis scheme used for numerical weather prediction is described. The scheme uses a multivariate surface analysis over the oceans to model the pressure-wind error cross-correlation and it has the ability to use an error correlation function that is flow- and geographically-dependent. A series of four-day data assimilation experiments, conducted from January 5-9, 1979, were used to investigate the effect of the different features of the OI scheme (error correlation) on forecast skill for the barotropic lows and highs. The skill of the OI was compared with that of a successive correlation method (SCM) of analysis. It is observed that the largest difference in the correlation statistics occurred in barotropic and baroclinic lows and highs. The comparison reveals that the OI forecasts were more accurate than the SCM forecasts.

Baker, W. E.↗
NASA NTRS1989

Radial deformation of the earth by oceanic tidal loading

A high-degree spherical harmonic series is used to compute the radial deformation of the Earth by oceanic tidal loading. By exploiting fast numerical transforms, this approach is found to be much more efficient, but no less accurate, than the traditional Green's function approach. The method is used to derive an atlas of load tide maps for 10 constitutents of the NSWC ocean tide model.

Ray, R. D.↗
NASA NTRS1989

Inferring surface solar absorption from broadband satellite measurements

An atmospheric solar radiation model and surface albedo models that include wavelength dependence and surface anisotropy are combined to study the possibility of inferring the surface solar absorption from satellite measurements. The model includes ocean, desert, pasture land, savannah, and bog surface categories. Problems associated with converting narrowband measurements to broadband quantities are discussed, suggesting that it would be easier to infer surface solar absorption from broadband measurements directly. The practice of adopting a linear relationship between planetary and surface albedo to estimate surface albedos from satellite measurements is examined, showing that the linear conversion between broadband planetary and surface albedos is strongly dependent on vegetation type. It is suggested that there is a linear slope-offset relationship between surface and surface-atmosphere solar absorption.

Cess, Robert D.↗
NASA NTRS1991

The role of the sea-surface temperature distribution on numerically simulated cyclogenesis during ERICA

The goal was to quantify the extent to which a sea surface temperature (SST) front can influence cyclogenesis. The approach was to use the Drexel Limited-Area Mesoscale Prediction System (LAMPS) dynamical model to simulate cyclogenesis over various SST fields. Research during the past year focused on the development and testing of a four dimensional data assimilation (FDDA) technique within LAMPS. The technique is a continuous dynamical assimilation where forcing terms are added to the governing model equations to gradually nudge the model solution toward a gridded analysis. Here, the nudging is used as a dynamic initialization tool during a 12 hour preforecast to generate model balanced initial conditions for a subsequent 24 hour numerical prediction. Tests were performed to determine which variables to nudge and how to specify the four dimensional weighting function used to scale the nudging terms. To date, optimal results were obtained by nudging the u and v components of the wind along with the potential temperature. The weighting function ranged from 0 to 1 and varies in time as a quadratic polynomial. It was initialized at 0, reached its maximum at 9 hours into the preforecast, and fell back at 0 to 12 hours. The nudging terms are included in the model equations for all grid points except those within the model predicted oceanic boundary layer. This design attempts to confine changes imposed by the specified SST field to the oceanic boundary layer during the preforecast period.

Lapenta, William M.↗
NASA NTRS1992

Glacial and marine chronology of Mars

A summary is given of the glacial and marine chronology of Mars. Hydrological models of oceans and ice sheets, the cratering record, hydrological cycling, and episodic glaciation are discussed. Evidence for a Noachian ocean is evaluated.

Strom, Robert G.↗
NASA NTRS1991

Ocean circulation using altimetry

Our group has been very actively involved in promoting satellite altimetry as a unique tool for observing ocean circulation and its variability. TOPEX/POSEIDON is particularly interesting as it is optimized for this purpose. It will probably be the first instrument really capable of observing the seasonal and interannual variability of subtropical and polar gyres and the first to eventually document the corresponding variability of their heat flux transport. The studies of these phenomena require data of the best quality, unbiased extraction of the signal, mixing of these satellite data with in situ measurements, and assimilation of the whole set into a dynamic description of ocean circulation. Our group intends to develop responses to all these requirements. We will concentrate mostly on the circulation of the South Atlantic and Indian Oceans: This will be done in close connection with other groups involved in the study of circulation of the tropical Atlantic Ocean, in the altimetry measurements (in particular, those of the tidal issue), and in the techniques of data assimilation in ocean circulation models.

Minster, Jean-Francois↗
NASA NTRS1991

Ocean dynamics in the Nordic Seas using satellite altimetry

The main objective of this TOPEX/POSEIDON project is to integrate the accurately measured sea surface topography, as resolved by both TOPEX/POSEIDON radar altimeters, into the above-mentioned quantitative studies of the short- and long-term variations in the mesoscale ocean dynamics of the Nordic Seas south of 66 deg N. This implies: (1) comparison and validation of the capability to resolve the general basin-scale circulation and the mesoscale variability by, respectively, radar altimeters and numerical ocean circulation models; (2) calibration and validation of the altimeter-derived sea surface topography against in situ measurements from research vessels and moorings, particularly under extreme wind and wave conditions; and (3) improved monitoring and understanding of the flux variations between the North Atlantic and the Nordic Seas, both on the short and seasonal time scales.

Pettersson, Lasse H.↗
NASA NTRS1993

Lunar mare volcanism: Mixing of distinct, mantle source regions with KREEP-like component

Mare basalts comprise less than 1% of the lunar crust, but they constitute our primary source of information on the moon's upper mantle. Compositional variations between mare basalt suites reflect variations in the mineralogical and geochemical composition of the lunar mantle which formed during early lunar differentiation (4.5-4.4 AE). Three broad suites of mare basalt are recognized: very low-Ti (VLT) basalts with TiO2 less than 1 wt%, low-Ti basalts with TiO2 = 2-4 wt%, and high-Ti basalts with TiO2 = 10-14 wt%. Important subgroups include the Apollo 12 ilmenite basalts (TiO2 = 5-6 wt%), aluminous low-Ti mare basalts (TiO2 = 2-4 wt%, Al2O3 = 10-14 wt%), and the newly discovered Very High potassium (VHK) aluminous low-Ti basalts, with K2O = 0.4-1.5 wt%. The mare basalt source region has geochemical characteristics complementary to the highlands crust and is generally thought to consist of mafic cumulates from the magma ocean which formed the felsic crust by feldspar flotation. The progressive enrichment of mare basalts in Fe/Mg, alkalis, and incompatible trace elements in the sequence VLT basalt yields low-Ti basalt yields high-Ti basalt is explained by the remelting of mafic cumulates formed at progressively shallower depths in the evolving magma ocean. This model is also consistent with the observed decrease in compatible element concentrations and the progressive increase in negative Eu anomalies.

Shervais, John W.↗
NASA NTRS1994

Investigation of passive atmospheric sounding using millimeter and submillimeter wavelength channels

Progress by the Georgia Institute of Technology's Laboratory for Radio-science and Remote Sensing in developing techniques for passive microwave retrieval of water vapor profiles and cloud and precipitation parameters using millimeter and submillimeter wavelength channels is reviewed. Channels of particular interest are in the tropospheric transmission windows at 90, 166, 220, 340, and 410 GHz and centered around the water vapor lines at 183 and 325 GHz. Collectively, these channels have potential application in high-resolution precipitation mapping (e.g., from geosynchronous orbit), remote sensing of cloud and precipitation parameters, including cirrus ice mass, and improved retrieval of water vapor profiles. During the period from January 1, 1994 through June 30, 1994 research activities focussed on calibrating and interpreting data from the Millimeter-Wave Imaging Radiometer (MIR). The MIR was deployed on the NASA ER-2 during the Convective Atmospheric Moisture Experiment (CAMEX, September-October 1993) to obtain the first submillimeter-wave tropospheric imagery of convective precipitations. A 325-GHz radiometer consisted of a submillimeter-wave DSB receiver with three IF channels at +/- 1, 3, and 8.5 GHz, and approximately 14 dB DSB noise figure was successfully operated during these experiments. Activities supported under this grant include a study of the impact of local oscillator reflections from the MIR calibration loads, the development of optimal gain and offset filters for radiometric calibration, and the modeling and interpretation of the MIR 325-GHz data over both clear and cloudy atmospheres. In addition, polarimetric radiometer measurements and modeling for ocean surface and atmospheric cloud-ice studies_were supported.

Gasiewski, Albin J.↗