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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 37 records · Page 2
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NASA NTRS1984

Ensemble formulation of surface fluxes and improvement in evapotranspiration and cloud parameterizations in a GCM

The influence of some modifications to the parameters of the current general circulation model (GCM) is investigated. The aim of the modifications was to eliminate strong occasional bursts of oscillations in planetary boundary layer (PBL) fluxes. Smoothly varying bulk aerodynamic friction and heat transport coefficients were found by ensemble averaging of the PBL fluxes in the current GCM. A comparison was performed of the simulations of the modified model and the unmodified model. The comparison showed that the surface fluxes and cloudiness in the modified model simulations were much more accurate. The planetary albedo in the model was also realistic. Weaknesses persisted in the models positioning of the Inter-tropical convergence zone (ICTZ) and in the temperature estimates for polar regions. A second simulation of the model following reparametrization of the cloud data showed improved results and these are described in detail.

Sud, Y. C.↗
NASA NTRS1988

Venus mesosphere and thermosphere. III - Three-dimensional general circulation with coupled dynamics and composition

The three-dimensional structure and circulation of Venus' upper mesosphere and thermosphere is examined by means of a modification of NCAR's earth thermosphere general circulation model, using the parameterizations from an earlier two-dimensional Venus model that included eddy diffusion and wave drag. Many of the observed Venus thermosphere features are found to be reproduced by the model, which thereby serves as a benchmark on which to incorporate additional minor constituents and test new self-consistent parameterizations for wave drag and superrotation.

Bougher, S. W.↗
NASA NTRS1990

Modification of the background flow by roll vortices

Use of observed wind profiles, such as those obtained from ascent or descent aircraft soundings, for the identification of the expected roll modes is hindered by the fact that these modes are able to modify the wind profiles. When such modified wind profiles are utilized to estimate the critical values of the dynamic and thermodynamic forcing rates, large errors in the preferred orientation angles and aspect ratios of the rolls may result. Nonlinear analysis of a 14 coefficient spectral model of roll circulations shows that the primary modification of the background wind is the addition of a linear component. When the linear profile having the correct amount of shear is subtracted from the observed cross-roll winds, then the pre-roll wind profile can be estimated. A preliminary test of this hypothesis is given for a case in which cloud streets were observed during FIRE.

Shirer, Hampton N.↗
NASA NTRS1979

Description and preliminary results of the 9-level UCLA general circulation model

The 9-level general circulation model, with the upper boundary of 50 mb, is a modification of the earlier 6- and 12-level versions used at UCLA. Two major design changes have been made in an effort to improve the model: (1) a potential enstrophy conserving scheme in the equation of motion has replaced the previous scheme which only conserved enstrophy for nondivergent flow, and (2) the treatment of the planetary boundary layer has been modified by making the predicted planetary boundary layer top a coordinate surface. Experiments with idealized steep mountains have been made to test each of the major modifications, and the model is now ready for general circulation simulation experiments.

Suarez, M. J.↗
NASA NTRS1982

The evolution of the mesoscale environment of severe local storms Preliminary modeling results

A mesoscale model is employed for predicting two severe weather events observed during thy 1979 SESAME field programs. Particular attention is given to the development and decay of a low-level jet, to the formation of a mesoscale convective complex (MCC) and its modification of lower- and upper-level circulation, to the formation of mesoscale regions of heavy precipitation, the intensification of surface warm and cold fronts, the formation of drylines, dynamic coupling of upper- and low-level jets, the formation of a mountain wave, and the formation and maintenance of capping inversions. A summary of the physics and parameters of a tornado outbreak and a heavy precipitation event are given for a simple bulk-PBL formulation with no heating. A ten-layer model was demonstrated to be sufficient for generating and maintaining distinct vertical gradients of temperature, moisture, and wind across low-level inversions.

Anthes, R. A.↗
NASA NTRS1984

CO2 induced climatic change and spectral variations in the outgoing terrestrial infrared radiation

The published temperature changes produced in general circulation model simulations of CO2 induced climate modification are used to compute the top of the atmosphere, clear sky outgoing infrared radiance changes expected for doubled CO2. A significant wavenumber shift is produced, with less radiance emerging in the 500-800 per cm (20.0-12.5 micron) CO2 band and with more emerging in the 800-1200 per cm (12.5-8.3 micron) window. The effect varies greatly with latitude. The radiance shift in the 2300 per cm (4.3 micron) region is of the order of 10-30 percent for doubled CO2. It is suggested that the 2300 per cm region be carefully monitored as an aid in detecting the climatic effects of increasing CO2. The change in the wavenumber-integrated radiant exitance is at most a few percent.

Charlock, T. P.↗
NASA NTRS2011

Impacts of Aerosol Direct Effects on the South Asian Climate: Assessment of Radiative Feedback Processes Using Model Simulations and Satellite/Surface Measurements

Current assessment of aerosol radiative effect is hindered by our incomplete knowledge of aerosol optical properties, especially absorption, and our current inability to quantify physical and microphysical processes. In this research, we investigate direct aerosol radiative effect over heavy aerosol loading areas (e.g., Indo-Gangetic Plains, South/East Asia) and its feedbacks on the South Asian climate during the pre-monsoon season (March-June) using the Purdue Regional Climate Model (PRCM) with prescribed aerosol data derived by the NASA Goddard Earth Observing System Model (GEOS-5). Our modeling domain covers South and East Asia (60-140E and 0-50N) with spatial resolutions of 45 km in horizontal and 28 layers in vertical. The model is integrated from 15 February to 30 June 2008 continuously without nudging (i.e., only forced by initial/boundary conditions). Two numerical experiments are conducted with and without the aerosol-radiation effects. Both simulations are successful in reproducing the synoptic patterns on seasonal-to-interannual time scales and capturing a pre-monsoon feature of the northward rainfall propagation over Indian region in early June which shown in Tropical Rainfall Measuring Mission (TRMM) observation. Preliminary result suggests aerosol-radiation interactions mainly alter surface-atmosphere energetics and further result in an adjustment of the vertical temperature distribution in lower atmosphere (below 700 hPa). The modifications of temperature and associated rainfall and circulation feedbacks on the regional climate will be discussed in the presentation.

Wang, Sheng-Hsiang↗
NASA NTRS2016

Estimation of the Ocean Skin Temperature using the NASA GEOS Atmospheric Data Assimilation System

This report documents the status of the development of a sea surface temperature (SST) analysis for the Goddard Earth Observing System (GEOS) Version-5 atmospheric data assimilation system (ADAS). Its implementation is part of the steps being taken toward the development of an integrated earth system analysis. Currently, GEOS-ADAS SST is a bulk ocean temperature (from ocean boundary conditions), and is almost identical to the skin sea surface temperature. Here we describe changes to the atmosphere-ocean interface layer of the GEOS-atmospheric general circulation model (AGCM) to include near surface diurnal warming and cool-skin effects. We also added SST relevant Advanced Very High Resolution Radiometer (AVHRR) observations to the GEOS-ADAS observing system. We provide a detailed description of our analysis of these observations, along with the modifications to the interface between the GEOS atmospheric general circulation model, gridpoint statistical interpolation-based atmospheric analysis and the community radiative transfer model. Our experiments (with and without these changes) show improved assimilation of satellite radiance observations. We obtained a closer fit to withheld, in-situ buoys measuring near-surface SST. Evaluation of forecast skill scores corroborate improvements seen in the observation fits. Along with a discussion of our results, we also include directions for future work.

AGCM↗
NASA NTRS2005

Impacts and environmental catastrophes: A study of the effects of impact events on the climate system

The goal of this work is to investigate the perturbation of the climate system due to large impact events. Impacts are among the most important mechanisms for the evolution, distribution, and destruction of life in the universe. However, the possible climatic effects of an impact were not seriously considered until 1980, when Louis and Walter Alvarez suggested that the profound end-Cretaceous extinction might have been caused by the impact of an asteroid or comet about 10 km in diameter. Since then, the climatic change associated with the end-Cretaceous impact has become one of the most interesting and still unresolved questions in linking the well-known Chicxulub impact event and the end- Cretaceous mass extinction. While the end-Cretaceous impact offers the best-documented case of an impact affecting the Earth's climate and biota, even smaller (and more frequent in time) impacts could introduce significant perturbations of the climate comparable, if not larger, to the largest known volcanic perturbations. We propose to study the mechanical and thermal state of the atmosphere following an impact event. This will be done by using both one-dimensional and three-dimensional climate models. When necessary, modifications of the state-of-the-art general circulation models will b e carried out. We want to use the end-Cretaceous impact event as a case study. This allows us to take advantage of the extensive modeling of this impact event that has already been carried out through a previous Exobiology grant. Furthermore, a large experimental dataset, that can be used to constrain and test our models, is associated with the end-Cretaceous mass extinction (one of the largest of the Phanerozoic) and impact event.

Pierazzo, E.↗
NASA NTRS1983

Large-scale motions of the tropics in observations and theory

Charney (1963) characterized the tropical atmosphere in terms of a superposition of large regions of nearly nondivergent circulations containing local subdomains, or 'fissures', of active convection and latent heating. Tropical wave evolution is then appropriately treated in terms of quasi-rotational waves, to the extent that the divergent contribution is small. An attempt is presently made to interpret recent tropical analyses in the aforementioned terms, suggesting extensions of the simplest quasi-rotational model capable of reconciling observations and theory. First GARP Global Experiment (FGGE) observations suggest that strongly divergent local tropical circulations are forced by latent heating and produce important direct modifications of the total wind field; after describing the extent to which the resulting field consists of divergent and rotational components in different analyses of the FGGE data, independent supporting documentation of the results in terms of heating estimates and rainfall observations are given.

Paegle, J.↗
NASA NTRS2015

Maintaining Atmospheric Mass and Water Balance Within Reanalysis

This report describes the modifications implemented into the Goddard Earth Observing System Version-5 (GEOS-5) Atmospheric Data Assimilation System (ADAS) to maintain global conservation of dry atmospheric mass as well as to preserve the model balance of globally integrated precipitation and surface evaporation during reanalysis. Section 1 begins with a review of these global quantities from four current reanalysis efforts. Section 2 introduces the modifications necessary to preserve these constraints within the atmospheric general circulation model (AGCM), the Gridpoint Statistical Interpolation (GSI) analysis procedure, and the Incremental Analysis Update (IAU) algorithm. Section 3 presents experiments quantifying the impact of the new procedure. Section 4 shows preliminary results from its use within the GMAO MERRA-2 Reanalysis project. Section 5 concludes with a summary.

IAU↗
NASA NTRS1981

Transistor package for high pressure applications

TO63 transistor package can operate in hydraulic oil ar pressures of 200 psi or greater without leakage failure if it is reinforced by alumina disk brazed to cap and terminals. This inexpensive modification has been used successfully on power transistors in hydraulic circulating-pump assemblies for Space Shuttle orbiter and should be effective in other pressurized environments, such as in oil exploration equipment.

Zantos, P. J.↗
NASA NTRS2009

African Easterly Jet: Structure and Maintenance

This article investigates the African Easterly Jet (AEJ), its structure and the forcings contributing to its maintenance, critically revisiting previous work which attributed the maintenance of the jet to soil moisture gradients over tropical Africa. A state-of-the-art global model in a high-end computer framework is used to produce a 3-member 73-year ensemble run forced by observed SST to represent the Control run. The AEJ as produced by the Control is compared with the representation of the AEJ in the European Center for Medium Range Forecast Reanalyses (ERA-40) and other observational data sets and found very realistic. Five Experiments are then performed, each represented by sets of 3-member 22 year long (1980-2001) ensemble runs. The goal of the Experiments is to investigate the role of meridional soil moisture gradients, different land surface properties and orography. Unlike previous studies, which have suppressed soil moisture gradients within a highly idealized framework (i.e., the so-called bucket model), terrestrial evaporation control is here achieved with a highly sophisticated landsurface treatment and with an extensively tested and complex methodology. The results show that the AEJ is suppressed by a combination of absence of meridional evaporation gradients over Africa and constant vegetation, even if the individual forcings taken separately do not lead to the AEJ disappearance, but only its modification. Moreover, the suppression of orography also leads to a different circulation in which there is no AEJ. This work suggests that it is not just soil moisture gradients, but a unique combination of geographical features present only in northern tropical Africa, which causes and maintains the jet.

Wu, Man-Li C.↗
NASA NTRS1978

Potential acoustic benefits of circulation control rotors

The fundamental aeroacoustic mechanisms responsible for noise generation on a rotating blade are theoretically examined. Their contribution to the overall rotor sound pressure level is predicted. Results from a theory for airfoil trailing edge noise are presented. Modifications and extensions to other source theories are described where it is necessary to account for unique aspects of circulation control (CC) aerodynamics. The circulation control rotor (CCR), as embodied on an X-wing vertical takeoff and landing (VTOL) aircraft, is used as an example for computational purposes, although many of the theoretical results presented are generally applicable to other CC applications (such as low speed rotors, propellers, compressors, and fixed wing aircraft). Using the analytical models, it is shown that the utilization CC aerodynamics theoretically makes possible unprecedented advances in rotor noise reduction. For the X-wing VTOL these reductions appear to be feasible without incurring significant attendant performance and weight penalties.

Williams, R. M.↗
NASA NTRS1992

A numerical investigation of East Coast cyclogenesis during the cold-air damming event of 27-28 February 1982. II - Importance of physical mechanisms

This study presents a series of numerical experiments designed to examine the role of several physical processes on the evolution of and interaction between atmospheric phenomena having different scales, each of which contributed to the development of the storm of February 27-28, 1982 along a Carolina coastal front. The physical processes include: the role of diabatic heating associated with convective and grid-scale precipitation, the role of a thermally direct transverse circulation about the entrance region of a strong polar jet streak, and modification of the marine planetary boundary layer by fluxes of heat and moisture over the Gulf Stream. The diabatic heating associated with precipitation is found to have the most significant impact on storm development. Without latent heating, cyclogenesis does not occur along the Carolina coastal front despite the presence of strong low-level baroclinicity and cyclonic vorticity. A less dramatic but still important relationship is found between storm formation and the other two physical mechanisms.

Lapenta, William M.↗
NASA NTRS2006

Wissler Simulations of a Liquid Cooled and Ventilation Garment (LCVG) for Extravehicular Activity (EVA)

In order to provide effective cooling for astronauts during extravehicular activities (EVAs), a liquid cooling and ventilation garment (LCVG) is used to remove heat by a series off tubes through which cooling water is circulated. To better predict the effectiveness of the LCG and determine possible modifications to improve performance, computer simulations dealing with the interaction of the cooling garment with the human body have been run using the Wissler Human Model. Simulations have been conducted to predict the heat removal rate for various liquid cooled garment configurations. The current LCVG uses 48 cooling tubes woven into a fabric with cooling water flowing through the tubes. The purpose of the current project is to decrease the overall weight of the LCVG system. In order to achieve this weight reduction, advances in the garment heat removal rates need to be obtained. Currently, increasing the fabric s thermal conductivity along with also examining an increase in the cooling tube conductivity to more efficiently remove the excess heat generated during EVA is being simulated. Initial trials varied cooling water temperature, water flow rate, garment conductivity, tube conductivity, and total number of cooling tubes in the LCVG. Results indicate that the total number of cooling tubes could be reduced to 22 and still achieve the desired heat removal rate of 361 W. Further improvements are being made to the garment network used in the model to account for temperature gradients associated with the spacing of the cooling tubes over the surface of the garment

Kesterson, Matthew↗
NASA NTRS2004

Lunar and Planetary Science XXXV: Mars: Wind, Dust Sand, and Debris

The session "Mars: Wind, Dust Sand, and Debris" included: Mars Exploration Rovers: Laboratory Simulations of Aeolian Interactions; Thermal and Spectral Analysis of an Intracrater Dune Field in Amazonis Planitia; How High is that Dune? A Comparison of Methods Used to Constrain the Morphometry of Aeolian Bedforms on Mars; Dust Devils on Mars: Scaling of Dust Flux Based on Laboratory Simulations; A Close Encounter with a Terrestrial Dust Devil; Interpretation of Wind Direction from Eolian Features: Herschel Crater, Mars Erosion Rates at the Viking 2 Landing Site; Mars Dust: Characterization of Particle Size and Electrostatic Charge Distributions; Simple Non-fluvial Models of Planetary Surface Modification, with Application to Mars; Comparison of Geomorphically Determined Winds with a General Circulation Model: Herschel Crater, Mars; Analysis of Martian Debris Aprons in Eastern Hellas Using THEMIS; Origin of Martian Northern Hemisphere Mid-Latitude Lobate Debris Aprons; Debris Aprons in the Tempe/Mareotis Region of Mars;and Constraining Flow Dynamics of Mass Movements on Earth and Mars.

Source record↗
NASA NTRS2001

Wind-Related Modification of Some Small Impact Craters on Mars

Inferred wind-related modifications of impact craters are observed in the vicinity of the Mare Pathfinder (MPF) site and in other regions of Mars. Mars Orbiter Camera (MOC) images show three types of inferred wind-modified morphologies for craters 0.3-1 km in diameter Such modifications could be related to seasonal variations of the strongest winds and a possible paleowind regime. Geomorphic mapping of Big Crater at the MPF shows evidence of former aeolian modification of the crater rim and interiors similar to smaller craters in the area. The morphologic patterns are in good agreement with the results from the Mars Regional Atmospheric Modeling Simulation (MRAMS) of topographically forced wind circulation and atmosphere surface interactions generated by flow over small craters. Simulations show that the maximum surface stress is on the downwind crater rim, consistent with inferred wind modification of the crater rim seen in MOC images. The trend of the Inferred paleowind regime at the MPF site cannot be explained by a change In the global atmospheric circulation resulting ~ from changes in Mars obliquity. We suggest that this wind regime could be associated with a regional meteorological pattern that is not modeled by global scale circulation, An alternative explanation is that Mars spin axis was in a different geographic position than it is at present.

Kuzmin, Ruslan O.↗