SEARCH · Search NASA

Results for “Cryosphere”

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.

SourceResearch connectionFrom yearThrough year

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 145 records · Page 8

All sources NASA NTRS DOE OSTI

NASA NTRS1992

Atmosphere, ocean, and land: Critical gaps in Earth system models

We briefly review current knowledge and pinpoint some of the major areas of uncertainty for the following fundamental processes: (1) convection, condensation nuclei, and cloud formation; (2) oceanic circulation and its coupling to the atmosphere and cryosphere; (3) land surface hydrology and hydrology-vegetation coupling; (4) biogeochemistry of greenhouse gases; and (5) upper atmospheric chemistry and circulation.

Prinn, Ronald G.↗

NASA NTRS1992

Comprehensive system models: Strategies for evaluation

The task of evaluating comprehensive earth system models is vast involving validations of every model component at every scale of organization, as well as tests of all the individual linkages. Even the most detailed evaluation of each of the component processes and the individual links among them should not, however, engender confidence in the performance of the whole. The integrated earth system is so rich with complex feedback loops, often involving components of the atmosphere, oceans, biosphere, and cryosphere, that it is certain to exhibit emergent properties very difficult to predict from the perspective of a narrow focus on any individual component of the system. Therefore, a substantial share of the task of evaluating comprehensive earth system models must reside at the level of whole system evaluations. Since complete, integrated atmosphere/ ocean/ biosphere/ hydrology models are not yet operational, questions of evaluation must be addressed at the level of the kinds of earth system processes that the models should be competent to simulate, rather than at the level of specific performance criteria. Here, we have tried to identify examples of earth system processes that are difficult to simulate with existing models and that involve a rich enough suite of feedbacks that they are unlikely to be satisfactorily described by highly simplified or toy models. Our purpose is not to specify a checklist of evaluation criteria but to introduce characteristics of the earth system that may present useful opportunities for model testing and, of course, improvement.

Field, Christopher↗

NASA NTRS1994

Archean geochemistry of formaldehyde and cyanide and the oligomerization of cyanohydrin

The sources and speciation of reduced carbon and nitrogen inferred for the early Archean are reviewed in terms of current observations and models, and known chemical reactions. Within this framework hydrogen cyanide and cyanide ion in significant concentration would have been eliminated by reaction with excess formaldehyde to form cyanohydrin (glycolonitrile), and with ferrous ion to formferrocyanide. Natural reactions of these molecules would under such conditions deserve special consideration in modeling of primordial organochemical processes. As a step in this direction, transformation reactions have been investigated involving glycolonitrile in the presence of water. We find that glycolonitrile, formed from formaldehyde and hydrogen cyanide or cyanide ion, spontaneously cyclodimerizes to 4-amino-2-hydroxymethyloxazole. The crystalline dimer is the major product at low temperatue (approximately 0 C); the yield diminishes with increasing temperature at the expense of polymerization and hydrolysis products. Hydrolysis of glycolamide and of oxazole yields a number of simpler organic molecules, including ammonia and glycolamide. The spontaneous polymerization of glycolonitrile and its dimer gives rise to soluble, cationic oligomers of as yet unknown structure, and, unless arrested, to a viscous liquid, insoluble in water. A loss of cyanide by reaction with formaldehyde, inferred for the early terrestrial hydrosphere and cryosphere would present a dilemma for hypotheses invoking cyanide and related compounds as concentrated reactants capable of forming biomolecular precursor species. Attempts to escape from its horns may take advantage of the efficient concentration and separation of cyanide as solid ferriferrocyanide, and most directly of reactions of glycolonitrile and its derivatives.

Arrhenius, T.↗

NASA NTRS1995

Nonlinear dynamics of global atmospheric and earth system processes

During the grant period, the authors continued ongoing studies aimed at enhancing their understanding of the operation of the atmosphere as a complex nonlinear system interacting with the hydrosphere, biosphere, and cryosphere in response to external radiative forcing. Five papers were completed with support from the grant, representing contributions in three main areas of study: (1) theoretical studies of the interactive atmospheric response to changed biospheric boundary conditions measurable from satellites; (2) statistical-observational studies of global-scale temperature variability on interannual to century time scales; and (3) dynamics of long-term earth system changes associated with ice sheet surges.

Zhang, Taiping↗

NASA NTRS1998

The Study of Effects of Time Variations in the Earth's Gravity Field on Geodetic Satellites

The temporal variations in the Earth's gravity field are the consequences of complex interactions between atmosphere, ocean, solid Earth, hydrosphere and cryosphere. The signal ranges from several hours to 18.6 years to geological time scale. The direct and indirect consequences of these variations are manifested in such phenomena as changes in the global sea level and in the global climate pattern. These signals produce observable geodetic satellites. The primary objectives of the proposed effects on near-Earth orbiting investigation include (1) the improved determination of the time-varying gravity field parameters (scale from a few hour to 18.6 year and secular) using long-term satellite laser rs ranging (SLR) observations to multiple geodetic satellites, and (2) the enhanced understanding of these variations with their associated meteorological and geophysical consequences.

Shum, C. K.↗

NASA NTRS1997

MODIS Snow and Ice Products from the NSIDC DAAC

The National Snow and Ice Data Center (NSIDC) Distributed Active Archive Center (DAAC) provides data and information on snow and ice processes, especially pertaining to interactions among snow, ice, atmosphere and ocean, in support of research on global change detection and model validation, and provides general data and information services to cryospheric and polar processes research community. The NSIDC DAAC is an integral part of the multi-agency-funded support for snow and ice data management services at NSIDC. The Moderate Resolution Imaging Spectroradiometer (MODIS) will be flown on the first Earth Observation System (EOS) platform (AM-1) in 1998. The MODIS Instrument Science Team is developing geophysical products from data collected by the MODIS instrument, including snow and ice products which will be archived and distributed by NSIDC DAAC. The MODIS snow and ice mapping algorithms will generate global snow, lake ice, and sea ice cover products on a daily basis. These products will augment the existing record of satellite-derived snow cover and sea ice products that began about 30 years ago. The characteristics of these products, their utility, and comparisons to other data set are discussed. Current developments and issues are summarized.

Scharfen, Greg R.↗

NASA NTRS2000

The State, Potential Distribution, and Biological Implications of Methane in the Martian Crust

The search for life on Mars has recently focused on its potential survival in deep (>2 km) subpermafrost aquifers where anaerobic bacteria, similar to those found in deep subsurface ecosystems on Earth, may have survived in an environment that has remained stable for billions of years. An anticipated by-product of this biological activity is methane. The detection of large deposits of methane gas and hydrate in the Martian cryosphere, or as emissions from deep fracture zones, would provide persuasive evidence of indigenous life and confirm the presence of a valuable in situ resource for use by future human explorers.

Max, Michael D.↗

NASA NTRS2000

NASA's Earth Observation Program: Past, Present and Future

The Earth Observing System (EOS) is a space-based observing system comprised of a series of satellite sensors by which scientists can monitor the Earth, a Data and Information System (EOSDIS) enabling researchers worldwide to access the satellite data, and an interdisciplinary science research program to interpret the satellite data. In this electronic theater presentation I will illustrate how scientists can learn about the Earth's atmosphere, land, oceans, and cryosphere from the vantage point of space-based global observations. This presentation will emphasize, but will not be limited to, Earth observations from space that highlight the ecosystem and environment of southern Africa, including: (i) dynamic geosynchronous satellite observations of southern Africa and nearby Indian Ocean, (ii) vegetation dynamics (normalized difference vegetation index and leaf area index), (iii) sea surface temperature, ocean topography, and surface winds over the Benguela and Agulhas Currents, (iv) Landsat 7 imagery of Cape Town, Etosha Pan, and other regions of southern Africa (v) fire distribution and dynamics in the Miombo woodland of Zambia, Angola, and Malawi, (vi) aerosol and cloud properties in southern Africa, and (vii) ice sheet distribution in and around Antarctica. We will illustrate these and other topics with a dynamic theater-style presentation, along with animations of satellite launch deployments and orbital mapping to highlight aspects of Earth observations from space.

King, Michael D.↗

NASA NTRS2000

MALDI for Europa Planetary Science and Exobiology

TOF MS for Europa landed science can identify small molecules of the cryosphere and complex biomolecules upwelling from a subsurface water ocean. A matrix-assisted laser-desorption ionization (MALDI) testbed for cryo-ice mixtures is being developed.

Wdowiak, T. J.↗

NASA NTRS1999

Exploration of Uncertainty in Glacier Modelling

There are procedures and methods for verification of coding algebra and for validations of models and calculations that are in use in the aerospace computational fluid dynamics (CFD) community. These methods would be efficacious if used by the glacier dynamics modelling community. This paper is a presentation of some of those methods, and how they might be applied to uncertainty management supporting code verification and model validation for glacier dynamics. The similarities and differences between their use in CFD analysis and the proposed application of these methods to glacier modelling are discussed. After establishing sources of uncertainty and methods for code verification, the paper looks at a representative sampling of verification and validation efforts that are underway in the glacier modelling community, and establishes a context for these within overall solution quality assessment. Finally, an information architecture and interactive interface is introduced and advocated. This Integrated Cryospheric Exploration (ICE) Environment is proposed for exploring and managing sources of uncertainty in glacier modelling codes and methods, and for supporting scientific numerical exploration and verification. The details and functionality of this Environment are described based on modifications of a system already developed for CFD modelling and analysis.

Thompson, David E.↗

NASA NTRS2000

The Global Precipitation Mission: Understanding Rainfall Across the Scale Spectrum

The outstanding success of the Tropical Rainfall Measuring Mission (TRMM) stemmed from a near flawless launch and deployment, a high successful measurement campaign, achievement of all original scientific objectives before the mission life had ended, and the accomplishment a number of unanticipated but important additional scientific advances This success and the realization that satellite rainfall datasets are now foremost tool in the understanding of decadal climate variability has helped motivate a comprehensive global rainfall measuring mission called "The Global Precipitation Mission" (GPM). The intent of this mission is to address looming scientific questions arising in the contex global climate-water cycle interactions, hydrometeorology, weather prediction, the global carbon budget, and atmosphere-biosphere-cryosphere chemistry. This paper addresses the status and prospects that mission currently planned for launch in the early 2007 time frame.

Smith, Eric A.↗

NASA NTRS2000

A Plan for Measuring Climatic Scale Global Precipitation Variability: The Global Precipitation Mission

The outstanding success of the Tropical Rainfall Measuring Mission (TRMM) stemmed from a near flawless launch and deployment, a highly successful measurement campaign, achievement of all original scientific objectives before the mission life had ended, and the accomplishment of a number of unanticipated but important additional scientific advances. This success and the realization that satellite rainfall datasets are now a foremost tool in the understanding of decadal climate variability has helped motivate a comprehensive global rainfall measuring mission, called 'The Global Precipitation Mission' (GPM). The intent of this mission is to address looming scientific questions arising in the context of global climate-water cycle interactions, hydrometeorology, weather prediction, the global carbon budget, and atmosphere-biosphere-cryosphere chemistry. This paper addresses the status of that mission currently planed for launch in the early 2007 time frame. The GPM design involves a nine-member satellite constellation, one of which will be an advanced TRMM-like 'core' satellite carrying a dual-frequency Ku-Ka band radar (df-PR) and a TMI-like radiometer. The other eight members of the constellation can be considered drones to the core satellite, each carrying some type of passive microwave radiometer measuring across the 10.7-85 GHz frequency range, likely based on both real and synthetic aperture antenna technology and to include a combination of new lightweight dedicated GPM drones and both co-existing operational and experimental satellites carrying passive microwave radiometers (i.e., SSM/l, AMSR, etc.). The constellation is designed to provide a minimum of three-hour sampling at any spot on the globe using sun-synchronous orbit architecture, with the core satellite providing relevant measurements on internal cloud precipitation microphysical processes. The core satellite also enables 'training' and 'calibration' of the drone retrieval process. Additional information is contained in the original extended abstract.

Smith, Eric A.↗

NASA NTRS2001

Observation of Sea Ice Surface Thermal States Under Cloud Cover

Clouds interfere with the distribution of short-wave and long-wave radiations over sea ice, and thereby strongly affect the surface energy balance in polar regions. To evaluate the overall effects of clouds on climatic feedback processes in the atmosphere-ice-ocean system, the challenge is to observe sea ice surface thermal states under both clear sky and cloudy conditions. From laboratory experiments, we show that C-band radar (transparent to clouds) backscatter is very sensitive to the surface temperature of first-year sea ice. The effect of sea ice surface temperature on the magnitude of backscatter change depends on the thermal regimes of sea ice thermodynamic states. For the temperature range above the mirabilite (Na2SO4.10H20) crystallization point (-8.2 C), C-band data show sea ice backscatter changes by 8-10 dB for incident angles from 20 to 35 deg at both horizontal and vertical polarizations. For temperatures below the mirabilite point but above the crystallization point of MgCl2.8H2O (-18.0 C), relatively strong backwater changes between 4-6 dB are observed. These backscatter changes correspond to approximately 8 C change in temperature for both cases. The backscattering mechanism is related to the temperature which determines the thermodynamic distribution of brine volume in the sea ice surface layer. The backscatter is positively correlated to temperature and the process is reversible with thermodynamic variations such as diurnal insolation effects. From two different dates in May 1993 with clear and overcast conditions determined by the Advanced Very High Resolution Radiometer (AVHRR), concurrent Earth Resources Satellite 1 (ERS-1) C-band ice observed with increases in backscatter over first-year sea ice, and verified by increases in in-situ sea ice surface temperatures measured at the Collaborative-Interdisciplinary Cryosphere Experiment (C-ICE) site.

Nghiem, S. V.↗

NASA NTRS2000

NASA's Future Active Remote Sensing Missing for Earth Science

Since the beginning of space remote sensing of the earth, there has been a natural progression widening the range of electromagnetic radiation used to sense the earth, and slowly, steadily increasing the spatial, spectral, and radiometric resolution of the measurements. There has also been a somewhat slower trend toward active measurements across the electromagnetic spectrum, motivated in part by increased resolution, but also by the ability to make new measurements. Active microwave instruments have been used to measure ocean topography, to study the land surface. and to study rainfall from space. Future NASA active microwave missions may add detail to the topographical studies, sense soil moisture, and better characterize the cryosphere. Only recently have active optical instruments been flown in space by NASA; however, there are currently several missions in development which will sense the earth with lasers and many more conceptual active optical missions which address the priorities of NASA's earth science program. Missions are under development to investigate the structure of the terrestrial vegetation canopy, to characterize the earth's ice caps, and to study clouds and aerosols. Future NASA missions may measure tropospheric vector winds and make vastly improved measurements of the chemical components of the earth's atmosphere.

Hartley, Jonathan B.↗

NASA NTRS2000

Towards GPS Surface Reflection Remote Sensing of Sea Ice Conditions

This paper describes the research to extend the application of Global Positioning System (GPS) signal reflections, received by airborne instruments, to cryospheric remote sensing. The characteristics of the GPS signals and equipment afford the possibility of new measurements not possible with existing radar and passive microwave systems. In particular, the GPS receiving systems are small and light-weight, and as such are particularly well suited to be deployed on small aircraft or satellite platforms with minimal impact. Our preliminary models and experimental results indicate that reflected GPS signals have potential to provide information on the presence and condition of sea and fresh-water ice as well as the freeze/thaw state of frozen ground. In this paper we show results from aircraft experiments over the ice pack near Barrow, Alaska suggesting correlation between forward scattered GPS returns and RADARSAT backscattered signals.

Komjathy, A.↗

NASA NTRS2000

Ice-age Ice-sheet Rheology: Constraints from the Last Glacial Maximum Form of the Laurentide Ice Sheet

State-ot-the-art thermomechanical models of the modern Greenland ice and the ancient Laurenticle ice sheet that covered Canada at the Last Glacial Maximum (LGM) are not able to explain simultaneously the observed forms of these cryospheric structures when the same, anisotropy-enhanced, version of the conventional Glen flow law is employed to describe their rheology. The LGM Laurenticle ice sheet. predicted to develop in response to orbital climate forcing, is such that the ratio of its thickness to its horizontal extent is extremely large compared to the aspect ratio inferred on the basis of surface-geomorphological and solid-earth-geophysical constraints. We show that if the Glen flow law representation of the rheology is replaced with a new rheology based upon very high quality laboratory measurements of the stress-strain-rate relation, then the aspect ratios of both the modern Greenland ice sheet and the Laurenticle ice sheet, that existed at the LGM, are simultaneously explained with little or no retuning of the flow law.

Peltier, W. Richard↗

NASA NTRS2000

Sea Ice Remote Sensing Using Surface Reflected GPS Signals

This paper describes a new research effort to extend the application of Global Positioning System (GPS) signal reflections, received by airborne instruments, to cryospheric remote sensing. Our experimental results indicate that reflected GPS signals have potential to provide information on the presence and condition of sea and freshwater ice as well as the freeze/thaw state of frozen ground. In this paper we show results from aircraft experiments over the ice pack near Barrow, Alaska indicating correlation between forward-scattered GPS returns and RADARSAT backscattered measurements.

Komjathy, Attila↗

NASA NTRS2001

Microwave Remote Sensing and the Cold Land Processes Field Experiment

The Cold Land Processes Field Experiment (CLPX) has been designed to advance our understanding of the terrestrial cryosphere. Developing a more complete understanding of fluxes, storage, and transformations of water and energy in cold land areas is a critical focus of the NASA Earth Science Enterprise Research Strategy, the NASA Global Water and Energy Cycle (GWEC) Initiative, the Global Energy and Water Cycle Experiment (GEWEX), and the GEWEX Americas Prediction Project (GAPP). The movement of water and energy through cold regions in turn plays a large role in ecological activity and biogeochemical cycles. Quantitative understanding of cold land processes over large areas will require synergistic advancements in 1) understanding how cold land processes, most comprehensively understood at local or hillslope scales, extend to larger scales, 2) improved representation of cold land processes in coupled and uncoupled land-surface models, and 3) a breakthrough in large-scale observation of hydrologic properties, including snow characteristics, soil moisture, the extent of frozen soils, and the transition between frozen and thawed soil conditions. The CLPX Plan has been developed through the efforts of over 60 interested scientists that have participated in the NASA Cold Land Processes Working Group (CLPWG). This group is charged with the task of assessing, planning and implementing the required background science, technology, and application infrastructure to support successful land surface hydrology remote sensing space missions. A major product of the experiment will be a comprehensive, legacy data set that will energize many aspects of cold land processes research. The CLPX will focus on developing the quantitative understanding, models, and measurements necessary to extend our local-scale understanding of water fluxes, storage, and transformations to regional and global scales. The experiment will particularly emphasize developing a strong synergism between process-oriented understanding, land surface models and microwave remote sensing. The experimental design is a multi-sensor, multi-scale (1-ha to 160,000 km ^ {2}) approach to providing the comprehensive data set necessary to address several experiment objectives. A description focusing on the microwave remote sensing components (ground, airborne, and spaceborne) of the experiment will be presented.

Kim, Edward J.↗