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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 235 records · Page 13
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NASA NTRS1989

Verification of regional climates of GISS GCM. Part 2: Summer

Verification is made of the synoptic fields, sea-level pressure, precipitation rate, 200mb zonal wind and the surface resultant wind generated by two versions of the Goddard Institute for Space Studies (GISS) climate model. The models differ regarding the horizontal resolution of the computation grids and the specification of the sea-surface temperatures. Maps of the regional distributions of seasonal means of the model fields are shown alongside maps that show the observed distributions. Comparisons of the model results with observations are discussed and also summarized in tables according to geographic region.

Druyan, Leonard M.↗
NASA NTRS1989

Implementing the Simple Biosphere Model (SiB) in a general circulation model: Methodologies and results

The Simple Biosphere MOdel (SiB) of Sellers et al., (1986) was designed to simulate the interactions between the Earth's land surface and the atmosphere by treating the vegetation explicitly and relistically, thereby incorporating biophysical controls on the exchanges of radiation, momentum, sensible and latent heat between the two systems. The steps taken to implement SiB in a modified version of the National Meteorological Center's spectral GCM are described. The coupled model (SiB-GCM) was used with a conventional hydrological model (Ctl-GCM) to produce summer and winter simulations. The same GCM was used with a conventional hydrological model (Ctl-GCM) to produce comparable 'control' summer and winter variations. It was found that SiB-GCM produced a more realistic partitioning of energy at the land surface than Ctl-GCM. Generally, SiB-GCM produced more sensible heat flux and less latent heat flux over vegetated land than did Ctl-GCM and this resulted in the development of a much deeper daytime planetary boundary and reduced precipitation rates over the continents in SiB-GCM. In the summer simulation, the 200 mb jet stream and the wind speed at 850 mb were slightly weakened in the SiB-GCM relative to the Ctl-GCM results and equivalent analyses from observations.

Sato, N.↗
NASA NTRS1988

Diabatic initialization for a mesoscale model simulation experiment

A mesoscale model simulation of a 'surrogate' atmosphere designed for the evaluation of adiabatic initialization and moisture enhancement techniques is briefly described. The simulation provides mesoscale precipitation rates and associated diabatic heating fields which are known exactly and are internally consistent within the context of the model. The advantage of this approach is that a numerical model can easily serve as a source of mesoscale data in the usual absence of internally consistent mesoscale observed data sets.

Kalb, Michael W.↗
NASA NTRS1989

Effects of implementing the Simple Biosphere Model in a general circulation model

The Simple Biosphere Model (SiB) of Sellers et al., was designed to simulate the interactions between the earth's land surface and the atmosphere by treating the vegetation explicitly and realistically, thereby incorporating the biophysical controls on the exchanges of radiation, momentum, sensible and latent heat between the two systems. This paper describes the steps taken to implement SiB in a modified version of the National Meteorological Center's global spectral general circulation model (GCM) and explores the impact of the implementation on the simulated land surface fluxes and near-surface meteorological conditions. The coupled model (SiB-GCM) was used to produce summer and winter simulations. The same GCM was used with a conventional hydrological model (Ctl-GCM) to produce comparable 'control' summer and winter simulations for comparison. It was found that SiB-GCM produced a more realistic partitioning of energy at the land surface than Ctl-GCM. Generally, SiB-GCM, produced more sensible heat flux and less latent heat flux over vegetated land than did Ctl-GCM and this resulted in a much deeper daytime planetary boundary layer and reduced precipitation rates over the continents in SiB-GCM. In the summer simulation, the 200 mb jet stream was slightly weakened in the SiB-GCM relative to the Ctl-GCM results and analyses made from observations.

Sato, N.↗
NASA NTRS1990

Retrieval of precipitation profiles from airborne radar and passive radiometer measurements - Comparison with dual-frequency radar measurements

Precipitation-rate profiles derived from a single-frequency radar and a radiometer are compared with profiles derived from a dual-frequency radar, using data obtained during the 1985-1986 Communication Research Laboratory/NASA rain measuring experiment over the Atlantic Ocean from a dual-frequency X- and Ka-band radars and an X-band passive radiometer. Profiles were retrieved using a modification of the Hitschfeld-Bordan (1954) algorithm constrained by a measurement of the path integrated extinction derived from passive radiometry. It was found that the two techniques under comparison yielded average rainfall rates that agreed within about 25 percent. It is suggested that, while a single-frequency radar operating in conjunction with multifrequency passive radiometers might provide cost-effective spaceborne measurements of tropical rainfall distributions, a dual-frequency radar might be able to remove some ambiguities that were encountered in this study.

Weinman, J. A.↗
NASA NTRS1991

Evaluation of cloudiness parameterizations using a cumulus ensemble model

Diagnostic cloudiness parameterizations in large-scale models are evaluated by using a two-dimensional numerical cumulus ensemble model. The model covers a large horizontal domain (512 km) but resolves individual clouds. This study explores the dependence of diagnostic relations (between cloud amount and a large-scale variable) on cloud regime, horizontal averaging distance, and cloud type for tropical convective cloud regimes. Large-scale variables, including relative humidity, cumulus mass flux, large-scale vertical velocity and surface precipitation rate, are examined. It is shown that the total cloud amount can be better estimated as the sum of separate estimates of stratiform and convective cloud amounts using different large-scale variables than by an estimate of the total cloud amount using any single large-scale variable. The stratiform cloud amount can best be estimated by using relative humidity. The convective cloud amount can be diagnosed by using cumulus mass flux. Neither set of diagnostic relations depends significantly on the stimulated cloud regime or horizontal averaging distance, but other diagnostic relations do show some such dependence. These results are interpreted and their implications for cloudiness parameterization are discussed.

Xu, Kuan-Man↗
NASA NTRS1992

Global aspects of the Los Alamos general circulation model hydrologic cycle

The global hydrologic cycle in the Los Alamos general circulation model (GCM) is compared to available global observations. Global observations of the water vapor, water-vapor flux and water-vapor flux divergence are derived from the National Meteorological Center's final analysis for the period 1986-1989. The new precipitation data set of Legates and Willmott (1990) is used for the global precipitation observations. Global evaporation is derived as a residual of the precipitation and water-vapor flux divergence. There are a number of similarities as well as discrepancies between the GCM and observations. The large-scale nondivergent and divergent GCM circulations are remarkably similar to the observed circulations; the large-scale GCM precipitation and evaporation patterns are also qualitatively similar to observations. Discrepancies are mainly quantitative and small-scale in nature: the GCM atmosphere is relatively dry which results in a slightly greater evaporation and precipitation rate than is observed; the GCM South Pacific convergence zone is displaced too far to the northwest.

Roads, J. O.↗
NASA NTRS1993

Some climatological variables for TOGA-COARE domains - 1985-1990

Results are presented of the Tropical Oceans Global Atmosphere-Coupled Ocean Atmosphere Response Experiment (TOGA-COARE) conducted in the western Pacific, with particular attention given to the atmospheric component of the experiment. The climatological variables explored are the mean sea level pressure, precipitable water, sea surface-air temperature difference, zonal wind component at 200 mb and 10 m, vertical motion at 500 mb, and precipitation rates. The paper provides some of the large-scale flow patterns in which other circulation features reside. Results are presented for three of the TOGA-COARE domains bounded by the following: (1) the Upper Air Network, 30 deg N-30 deg S, 90 deg E-70 deg W; (2) the Large-Scale Array, 10 deg N-10 deg S, 140 deg E-180 deg; and (3) the Equatorial Synoptic Array, 5 deg N-5 deg S, 150 deg E-180 deg.

Vincent, Dayton G.↗
NASA NTRS1993

A climatological study of the TOGA-COARE region

The tropical western pacific 'warm pool' region, which plays a significant role in the initiation and/or enhancement of several atmospheric and oceanic phenomena on a variety of time and space scales, was seleted for the TOGA-COARE field program conducted in the northern winter season of 1992-1993. This paper provides some of the recent background climatology for the TOGA-COARE region. The variables illustrated and discussed represent a sample of those taken from an atlas being prepared (e.g., the mean sea level pressure for July 1985 and January 1986; three-month running means of precipitable water (W) and zonal wind at selected grid points; monthly mean averages of W and zonal wind for April 1986-1990, April 1987 anomaly, and January 1989 anomaly; and three-month running means of precipitation rate in mm/day for selected equatorial grid points and a grid point at 10 S, 150 E). Graphs and charts presented are constructed using data sets from the WCRP/TOGA archive II ECMWF global analyses.

Sliwinski, L. D.↗
NASA NTRS1994

The design and development of signal-processing algorithms for an airborne x-band Doppler weather radar

Improved measurements of precipitation will aid our understanding of the role of latent heating on global circulations. Spaceborne meteorological sensors such as the planned precipitation radar and microwave radiometers on the Tropical Rainfall Measurement Mission (TRMM) provide for the first time a comprehensive means of making these global measurements. Pre-TRMM activities include development of precipitation algorithms using existing satellite data, computer simulations, and measurements from limited aircraft campaigns. Since the TRMM radar will be the first spaceborne precipitation radar, there is limited experience with such measurements, and only recently have airborne radars become available that can attempt to address the issue of the limitations of a spaceborne radar. There are many questions regarding how much attenuation occurs in various cloud types and the effect of cloud vertical motions on the estimation of precipitation rates. The EDOP program being developed by NASA GSFC will provide data useful for testing both rain-retrieval algorithms and the importance of vertical motions on the rain measurements. The purpose of this report is to describe the design and development of real-time embedded parallel algorithms used by EDOP to extract reflectivity and Doppler products (velocity, spectrum width, and signal-to-noise ratio) as the first step in the aforementioned goals.

Nicholson, Shaun R.↗
NASA NTRS1994

The environmental influence on tropical cyclone precipitation

The intensity, spatial, and temporal changes in precipitation were examined in three North Atlantic hurricanes during 1989 (Dean, Gabrielle, and Hugo) using precipitation estimates made from Special Sensor Microwave/Imager (SSM/I) measurements. In addition, analyses from a barotropic hurricane forecast model and the European Centre for Medium-Range Weather Forecast model were used to examine the relationship between the evolution of the precipitation in these tropical cyclones and external forcing. The external forcing parameters examined were (1) mean climatological sea surface temperatures, (2) vertical wind shear, (3) environmental tropospheric water vapor flux, and (4) upper-tropospheric eddy relative angular momentum flux convergence. The analyses revealed that (1) the SSM/I precipitation estimates were able to delineate and monitor convective ring cycles similar to those observed with land-based and aircraft radar and in situ measurements; (2) tropical cyclone intensification was observed to occur when these convective rings propagated into the inner core of these systems (within 111 km of the center) and when the precipitation rates increased; (3) tropical cyclone weakening was observed to occur when these inner-core convective rings dissipated; (4) the inward propagation of the outer convective rings coincided with the dissipation of the inner convective rings when they came within 55 km of each other; (5) in regions with the combined warm sea surface temperatures (above 26 C) and low vertical wind shear (less than 5 m/s), convective rings outside the region of strong lower-tropospheric inertial stability could be initiated by strong surges of tropospheric moisture, while convective rings inside the region of strong lower-tropospheric inertial stability could be enhanced by upper-tropospheric eddy relative angular momentum flux convergence.

Rodgers, Edward B.↗
NASA NTRS1994

Clouds, hazes, and the stratospheric methane abundance in Neptune

Analysis of high-spatial-resolution (approximately 0.8 arcsec) methane band and continuum imagery of Neptune's relatively homogeneous Equatorial Region yields significant constraints on (1) the stratospheric gaseous methane mixing ratio (f(sub CH4, S)), (2) the column abundances and optical properties of stratospheric and tropospheric hydrocarbon hazes, and (3) the wavelength-dependent single-scattering albedo of the 3-bar opaque cloud. From the center-to-limb behavior of the 7270-A and 8900-A CH4 bands, the stratospheric methane mixing ratios is limited to f(sub CH4, S) less than 1.7 x 10(exp -3), with a nominal value of f(sub CH4, S) = 3.5 x 10(exp -4), one to two orders of magnitude less than pre-Voyager estimates, but in agreement with a number of recent ultraviolet and thermal infrared measurements, and largely in agreement with the tropopause mixing ratio implied by Voyager temperature measurements. Upper limits to the stratospheric haze mass column abundance and 6190-A and 8900-A haze opacities are 0.61 micrograms/sq cm and 0.075 and 0.042, respectively, with nominal values of 0.20 micrograms/sq cm and 0.025 and 0.014 for the 0.2 micrometers radius particles preferred by the recent Voyager PPS analysis of Pryor et al. (1992). The tropospheric CH4 haze opacities are comparable to that found in the stratosphere, i.e., upper limits of 0.104 and 0.065 at 6190 A and 8900 A, respectively, with nominal values of 0.085 and 0.058. This indicates a column abundance less than 11.0 micrograms/sq cm, corresponding to the methane gas content within a well-mixed 3% methane tropospheric layer only 0.1 cm thick near the 1.5-bar CH4 condensation level. Conservative scattering is ruled out for the opaque cloud near 3 bars marking the bottom of the visible atmosphere. Specifically, we find cloud single-scattering albedos of 0.915 +/- 0.006 at 6340 A, 0.775 +/- 0.012 at 7490 A, and 0.803 +/- 0.010 at 8260 A. Global models utilizing a complete global spectrum confirm the red-absorbing character of the 3-bar cloud. The global-mean model has approximately 7.7 times greater stratospheric aerosol content than the Equatorial Region. An analysis of stratospheric haze precipitation rates indicates a steady-state haze production rate of 0.185-1.5 x 10(exp -14) g/sq cm/s, in agreement with recent theoretical photochemical estimates. Finally, reanalysis of the Voyager PPS 7500-A phase angle data utilizing the f(sub CH4, S) value derived here confirms the Pryor et al. result of a tropospheric CH4 haze opacity of a few tenths in the 22-30 degs S latitude region, several times that of the Equatorial Region or of the globe. The factor-of-10 reduction in f(sub CH4, S) below that assumed by Pryor et al. implies decreased gas absorption and consequently a decrease in the forward-scattering component of tropospheric aerosols.

Baines, Kevin H.↗
NASA NTRS1994

Mathematical Model for the Mineralization of Bone

A mathematical model is presented for the transport and precipitation of mineral in refilling osteons. One goal of this model was to explain calcification 'halos,' in which the bone near the haversian canal is more highly mineralized than the more peripheral lamellae, which have been mineralizing longer. It was assumed that the precipitation rate of mineral is proportional to the difference between the local concentration of calcium ions and an equilibrium concentration and that the transport of ions is by either diffusion or some other concentration gradient-dependent process. Transport of ions was assumed to be slowed by the accumulation of mineral in the matrix along the transport path. The model also mimics bone apposition, slowing of apposition during refilling, and mineralization lag time. It was found that simple diffusion cannot account for the transport of calcium ions into mineralizing bone, because the diffusion coefficient is two orders of magnitude too low. If a more rapid concentration gradient-driven means of transport exists, the model demonstrates that osteonal geometry and variable rate of refilling work together to produce calcification halos, as well as the primary and secondary calcification effect reported in the literature.

Martin, Bruce↗
NASA NTRS1997

Seventh Annual V. M. Goldschmidt Conference

Topics considered include: Subduction of the Aseismic Cocos Ridge Displaced Magma Sources Beneath the Cordillera de Talamanca, Costa Rica; Topography of Transition Zone Discontinuities: A Measure of 'Olivine' Content and Evidence for Deep Cratonic Roots; Uranium Enrichment in Lithospheric Mantle: Case Studies from French Massif Central; Rare-Earth-Element Anomalies in the Decollement Zone of the nankai Accretionary Prism, Japan: Evidence of Fluid Flow?; Rare Earth Elements in Japanese Mudrocks: The Influence of Provenance; The Evolution of Seawater Strontium Isotopes in the Last Hundred Million Years: Reinterpretation and Consequences for Erosion and Climate Models; From Pat to Tats: The Lead Isotope Legacy in the Studies of the Continental Crust-Upper Mantle System; Geochronology of the Jack Hills Detrital Zircons by Precise Uranium-Lead Isotope-Dilution Analysis of Crystal Fragments; Iridium in the Oceans; The Helium-Heat-Lead Paradox; Control of Distribution Patterns of Heavy Metals in Ganga Plain Around Kanpur Region, India, by Fluvial Geomorphic Domains; Geochemical and Isotopic Features of Ferrar Magmatic Provience (Victoria Land, Antarctica); Rare Earth Elements in Marine Fine-Grained Sediments from the Northwestern Portuguese Shelf (Atlantic); Aspects of Arc Fluxes; General Kinetic Model for Dolomite Precipitation Rate with Application to the Secular History of Seawater Composition; High-Precision Uranium-series Chronology from Speleothems; Trace-Element Modeling of Aqueous Fluid-Peridotite Interaction in the Mantle Wedge of Subduction Zones; Rainfall Variations in Southeastern Australia over the Last 500,000 Years from Speleothem Deposition; The Role of Water in High-Pressure Fluids; The Kinetic Conditions of Metamorphic Minearogenesis: Evidence from Minerals and Assemblages.

Source record↗
NASA NTRS1994

Mathematical Model for the Mineralization of Bone

A mathematical model is presented for the transport and precipitation of mineral in refilling osteons. One goal of this model was to explain calcification 'halos,' in which the bone near the haversian canal is more highly mineralized than the more peripheral lamellae, which have been mineralizing longer. It was assumed that the precipitation rate of mineral is proportional to the difference between the local concentration of calcium ions and an equilibrium concentration and that the transport of ions is by either diffusion or some other concentration gradient-dependent process. Transport of ions was assumed to be slowed by the accumulation of mineral in the matrix along the transport path. ne model also mimics bone apposition, slowing of apposition during refilling, and mineralization lag time. It was found that simple diffusion cannot account for the transport of calcium ions into mineralizing bone, because the diffusion coefficient is two orders of magnitude too low. If a more rapid concentration gradient-driven means of transport exists, the model demonstrates that osteonal geometry and variable rate of refilling work together to produce calcification halos, as well as the primary and secondary calcification effect reported in the literature.

Martin, Bruce↗
NASA NTRS1997

Velocities of Pine Island and Thwaites glaciers, West Antarctica, from ERS-1 SAR images

Average velocities of Pine Island and Thwaites glaciers (West Antarctica) were measured for the time periods between 1992 and 1994 by tracking ice-surface patterns. Velocities of the central flow of the Pine Island glacier range from 1.5 km/yr above the grounding line (separating the grounded from the floating parts of a glacier) to 2.8 km/yr near the terminus; velocities of the central Thwaites glacier range from 2.2 km/yr above the grounding line to 3.4 km/yr at the limit of measurements on the tongue. Both glaciers show an increase in velocity of about 1 km/yr where they cross their grounding lines. The velocities derived from ERS-1 images are higher than those previously derived from Landsat images, perhaps reflecting acceleration of the glaciers. Both glaciers are exceptionally fast. The high velocities may be due to high precipitation rates over West Antarctica and the lack of a major buttressing ice shelf.

Lucchita, Baerbel K.↗
NASA NTRS1999

Photochemistry of Pluto's Atmosphere

This work include studies of two problems: (1) Modeling thermal balance, structure. and escape processes in Pluto's upper atmosphere. This study has been completed in full. A new method, of analytic solution for the equation of hydrodynamic flow from in atmosphere been developed. It was found that the ultraviolet absorption by methane which was previously ignored is even more important in Pluto's thermal balance than the extreme ultraviolet absorption by nitrogen. Two basic models of the lower atmosphere have been suggested, with a tropopause and a planetary surface at the bottom of the stellar occultation lightcurve, respectively, Vertical profiles, of temperature, density, gas velocity, and the CH4 mixing ratio have been calculated for these two models at low, mean, and high solar activity (six models). We prove that Pluto' " s atmosphere is restricted to 3060-4500 km, which makes possible a close flyby of future spacecraft. Implication for Pluto's evolution have also been discussed. and (2) Modeling of Pluto's photochemistry. Based on the results of (1), we have made some changes in the basic continuity equation and in the boundary conditions which reflect a unique can of hydrodynamic escape and therefore have not been used in modeling of other planetary atmospheres. We model photochemistry of 44 neutral and 23 ion species. This work required solution of a set of 67 second-order nonlinear ordinary differential equations. Two models have been developed. Each model consists of the vertical profiles for 67 species, their escape and precipitation rates. These models predict the chemical structure and basic chemical processes in the current atmosphere and possible implication of these processes for evolution. This study has also been completed in full.

Krasnopolsky, Vladimir A.↗
NASA NTRS1998

Comparison of Globally Complete Versions of GPCP and CMAP Monthly Precipitation Analyses

In this study two global observational precipitation products, namely the Global Precipitation Climatology Project's (GPCP) community data set and CPC's Merged Analysis of Precipitation (CMAP), are compared on global to regional scales in the context of the different satellite and gauge data inputs and merger techniques. The average annual global precipitation rates, calculated from data common in regions/times to both GPCP and CMAP, are similar for the two. However, CMAP is larger than GPCP in the tropics because: (1) CMAP values in the tropics are adjusted month-by month to atoll gauge data in the West Pacific, which are greater than any satellite observations used; and (2) CMAP is produced from a linear combination of data inputs, which tends to give higher values than the microwave emission estimates alone to which the inputs are adjusted in the GPCP merger over the ocean. The CMAP month-to-month adjustment to the atolls also appears to introduce temporal variations throughout the tropics which are not detected by satellite-only products. On the other hand, GPCP is larger than CMAP in the high-latitude oceans, where CMAP includes the scattering based microwave estimates which are consistently smaller than the emission estimates used in both techniques. Also, in the polar regions GPCP transitions from the emission microwave estimates to the larger TOVS-based estimates. Finally, in high-latitude land areas GPCP can be significantly larger than CMAP because GPCP attempts to correct the gauge estimates for errors due to wind loss effects.

Curtis, Scott↗