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At least 559 records · Page 31
All sourcesNASA NTRSDOE OSTI
NASA NTRS1997

The Role of Sea Ice in 2 x CO2 Climate Model Sensitivity: Hemispheric Dependencies - Part 2

How sensitive are doubled CO2 simulations to GCM control-run sea ice thickness and extent? This issue is examined in a series of 10 control-run simulations with different sea ice and corresponding doubled CO2 simulations. Results show that with increased control-run sea ice coverage in the Southern Hemisphere, temperature sensitivity with climate change is enhanced, while there is little effect on temperature sensitivity of (reasonable) variations in control-run sea ice thickness. In the Northern Hemisphere the situation is reversed: sea ice thickness is the key parameter, while (reasonable) variations in control-run sea ice coverage are of less importance. In both cases, the quantity of sea ice that can be removed in the warmer climate is the determining factor. Overall, the Southern Hemisphere sea ice coverage change had a larger impact on global temperature, because Northern Hemisphere sea ice was sufficiently thick to limit its response to doubled CO2, and sea ice changes generally occurred at higher latitudes, reducing the sea ice-albedo feedback. In both these experiments and earlier ones in which sea ice was not allowed to change, the model displayed a sensitivity of -0.02 C global warming per percent change in Southern Hemisphere sea ice coverage.

Rind, D.↗
NASA NTRS2000

BOREAS TE-5 Diurnal CO2 Canopy Profile Data

The BOREAS TE-5 team collected several data sets to investigate the vegetation-atmosphere CO2 and H2O exchange processes. These data were collected to provide detailed information within the canopy during times when TE-05 sampled canopy CO2 for carbon and oxygen isotope analysis. These measurements were made in both the NSA and SSA at the OJP, OBS, UBS, and OA sites from 25-May1994 to 08-Sep1994. CO2 profile data were not collected at SSA-OA during the first IFC. The data are available in tabular ASCII files. The data files are available on a CD-ROM (see document number 20010000884), or from the Oak Ridge National Laboratory (ORNL) Distributed Activity Archive Center (DAAC).

Hall, Forrest G.↗
NASA NTRS1998

Low-Power CO2 Compression Technology

Presently, the most feasible processes for extracting oxygen from the Martian atmosphere either require or are much more efficient if the atmospheric CO2 feed is provided at pressures well above the Martian ambient. Electrical power for performing the desired compression is likely to be an extremely limited resource on the Mars surface. Even if "cheap" nuclear power is available at a central site/launch facility where rocket propellent and oxidant are manufactured, life support applications needing oxygen production capabilities, such as rovers, portable life support, and remote or independent exploration stations, will benefit from extremely low-power atmospheric compression technology, such as the one discussed here. Our experiments show the potential of one very low-power approach to performing CO2 compression that uses the Mars diurnal temperature cycle to drive a heat engine. The 1 kg compressor has been tested over an extended period in a Mars environmental simulation chamber that mimics the composition, pressure, and temperature cycles that can occur on the Martian surface. The simple design, which has very few moving parts and can easily be scaled to larger or smaller sizes, produces a CO2 stream at a rate of 100 g/ day at a quality and pressure suitable for a variety of oxygen production processes.

Finn, John E.↗
NASA NTRS2002

An Assessment of the Ability of Potential Satellite Instruments to Resolve Spatial and Temporal Variability of Atmospheric CO2

Sufficiently precise satellite observations with adequate spatial and temporal resolution would substantially increase our knowledge of the atmospheric CO2 distribution and would undoubtedly lead to reduced uncertainty in estimates of the global carbon budget. An overview of possible strategies for measuring CO2 from space will be presented, including IR and nearby measurements, active sensors and broad band and narrow band passive sensors. The ability of potential satellite instruments with a variety of orbits, horizontal resolution and vertical weighting functions to capture the variation in atmospheric CO2 mixing ratios will be illustrated using a combination of surface data, aircraft data and model results.

Andrews, A.↗
NASA NTRS2004

[CO2 Budget and Atmospheric Rectification (COBRA) Over North America]

The purpose of the CO2 Budget and Rectification Airborne (COBRA) study was to assess terrestrial sources and sinks of carbon dioxide using an air-borne study. The study was designed to address the measurement gap between plot-scale direct flux measurements and background hemispheric-scale constraints and to refine techniques for measuring terrestrial fluxes at regional to continental scales. The initial funded effort (reported on here) was to involve two air-borne campaigns over North America, one in summer and one in winter. Measurements for COBRA (given the acronym C02BAR in the initial proposal) were conducted from the University of North Dakota Citation 11, a twin-engine jet aircraft capable of profiling from the surface to 12 km and cruising for up to 4 hours and 175m/s. Onboard instrumentation measured concentrations of CO2, CO, and H2O, and meteorological parameters at high rates. In addition, two separate flask sampling systems collected discrete samples for laboratory analysis of CO2,CO, CH4, N2O, SF6, H2, 13CO2, C18O16O,O2/N2, and Ar/N2. The project involved a collaboration between a number of institutions, including (but not limited to) Harvard, NOAA-CMDL, the University of North Dakota, and Scripps.

Source record↗
NASA NTRS2003

Reconciling the MOLA, TES, and Neutron Observations of the North Polar CO2 Mass Budget on Mars

There are now three independent observations of the CO2 polar cap mass budget of Mars' north polar cap. The first is based elevation changes detected by the Mars Orbiter Laser Altimeter (MOLA) on the Mars Global Surveyor (MGS). The second is based on MGS Thermal Emission Spectrometer (TES) broadband observations of the solar and infrared radiation fields at the top of the atmosphere. The third is based on neutron counts measured by the neutron spectrometer (NS) on Odyssey. The TES data are based on an energy balance. The net radiative loss (gain) in a column is balanced by latent heating due condensation (sublimation) of CO2. In calculating the mass budget, the other main energy sources, atmospheric heat transport and subsurface conduction, were neglected. At the pole, atmospheric heat transport is indeed a small term. However, subsurface heat conduction can be significant because at the North Pole water ice, which has a high thermal conductivity compared to bare soil, is a dominant component of the subsurface. Thus, heat conducted down into the ice during summer will slowly bleed back out during fall and winter reducing the amount of CO2 that condenses on the pole. We have taken a first cut at quantifying this effect by fitting a curve to Paige's estimates of the conducted energy flux in his analysis of Viking IRTM data.

Haberle, R. M.↗
NASA NTRS2001

Long-distance signaling within Coleus x hybridus leaves; mediated by changes in intra-leaf CO2?

Rapid long-distance signaling in plants can occur via several mechanisms, including symplastic electric coupling and pressure waves. We show here in variegated Coleus leaves a rapid propagation of electrical signals that appears to be caused by changes in intra-leaf CO2 concentrations. Green leaf cells, when illuminated, undergo a rapid depolarization of their membrane potential (Vm) and an increase in their apoplastic pH (pHa) by a process that requires photosynthesis. This is followed by a slower hyperpolarization of Vm and apoplastic acidification, which do not require photosynthesis. White (chlorophyll-lacking) leaf cells, when in isolated white leaf segments, show only the slow response, but when in mixed (i.e. green and white) segments, the rapid Vm depolarization and increase in pHa propagate over more than 10 mm from the green to the white cells. Similarly, these responses propagate 12-20 mm from illuminated to unilluminated green cells. The fact that the propagation of these responses is eliminated when the leaf air spaces are infiltrated with solution indicates that the signal moves in the apoplast rather than the symplast. A depolarization of the mesophyll cells is induced in the dark by a decrease in apoplastic CO2 but not by an increase in pHa. These results support the hypothesis that the propagating signal for the depolarization of the white mesophyll cells is a photosynthetically induced decrease in the CO2 level of the air spaces throughout the leaf.

NASA Discipline Plant Biology↗
NASA NTRS1988

Uniformity of environmental conditions and plant growth in a hydroponic culture system for use in a growth room with aerial CO2 control

A portable system of hydroponic culture was developed that maintained temperature, pH, and nutrient concentrations of circulating nutrient solutions. The hydroponic system is used within a controlled-environment room (CER) for control of aerial environment. The CER was equipped with an auto-calibrating system for atmospheric CO2 control. The control systems for the hydroponic chambers were able to maintain acidity within +/- 0.2 pH units and the temperature with +/- 0.5 degree C. Mixing time for the 200-liter volume of solution within a hydroponic chamber was less than 12 min. The CO2 control system was able to maintain aerial concentrations within +/- 10 ppm CO2 during the light period. The only gradient found to occur within the hydroponic chambers or CER was a slight gradient in aerial temperature along the length of hydroponic chambers. Growth of soybeans [Glycine max (L.) Merr.] was characterized during a 3-week period of vegetative development by leaf number and area, plant dry weight, total N content of plants, and N depletion from the nutrient solution. The growth characteristics among populations for three hydroponic chambers within the CER were not significantly different, and the percent standard errors of means of the measurements within populations from each chamber were nearly all less than 10%. Thus, the uniformity of plant growth reflected the uniformity of environmental conditions.

NASA Discipline Life Support Systems↗
NASA NTRS2005

Prospects for Precision Measurement of CO2 Column from Space

In order to address the problem of sources and sinks of CO2 measurements are needed on a global scale. Clearly a satellite is a promising approach to meeting this requirement. Unfortunately, most methods for making a CO2 measurement from space involve the whole column. Since sources and sinks at the surface represent a small perturbation to the total column one is faced with the need to measure the column with a precision better than 1%. No species has ever been measured from space at this level. We have developed over the last 3 years a small instrument based upon a Fabry-Perot interferometer that is very sensitive to atmospheric CO2 and has a high signal to noise ratio. We have tested this instrument in a ground based configuration and from aircraft platforms simulating operation from a satellite. We will present results from these tests and discuss ways that this promising new instrument could be used to improve our understanding of the global carbon budget.

Heaps, William S.↗
NASA NTRS2005

III-V Compound Detectors for CO2 DIAL Measurements

Profiling of atmospheric carbon dioxide (CO2) is important for understanding the natural carbon cycle on Earth and its influence on global warming and climate change. Differential absorption lidar is a powerful remote sensing technique used for profiling and monitoring atmospheric constituents. Recently there has been an interest to apply this technique, at the 2 m wavelength, for investigating atmospheric CO2. This drives the need for high quality detectors at this wavelength. Although 2 m detectors are commercially available, the quest for a better detector is still on. The detector performance, regarding quantum efficiency, gain and associated noise, affects the DIAL signal-to-noise ratio and background signal, thereby influencing the instrument sensitivity and dynamic range. Detectors based on the III-V based compound materials shows a strong potential for such application. In this paper the detector requirements for a long range CO2 DIAL profiles will be discussed. These requirements were compared to newly developed III-V compound infrared detectors. The performance of ternary InGaSb pn junction devices will be presented using different substrates, as well as quaternary InGaAsSb npn structure. The performance study was based on experimental characterization of the devices dark current, spectral response, gain and noise. The final results are compared to the current state-of-the-art InGaAs technology. Npn phototransistor structure showed the best performance, regarding the internal gain and therefore the device signal-to-noise ratio. 2-micrometers detectivity as high as 3.9 x 10(exp 11) cmHz(sup 1/2)/W was obtained at a temperature of -20 C and 4 V bias voltage. This corresponds to a responsivity of 2650 A/W with about 60% quantum efficiency.

Refaat, Tamer F.↗
NASA NTRS2006

Rapid Cycling CO2 and H2O Removal System for EMU

NASA's planned future missions set stringent demands on the design of the Portable Life Support Systems (PLSS), requiring dramatic reductions in weight, decreased reliance on supplies and greater flexibility on the types of missions. Use of regenerable systems that reduce weight and volume of the EMU is of critical importance to NASA, both for low orbit operations and for long duration manned missions. The CO2 and humidity control unit in the existing PLSS design is relatively large, since it has to remove 8 hours worth of CO2. If the sorbent regeneration can be carried out during the extravehicular activity (EVA) with a relatively high regeneration frequency, the size of the sorbent canister and weight can be significantly reduced. TDA Research, Inc. (TDA) is developing a compact, regenerable sorbent-based system to control CO2 and humidity in the space suit ventilation loop. The sorbent can be regenerated using space vacuum during the EVA, eliminating all duration-limiting elements in the life support system. This paper summarizes the results of the sorbent development and testing, and evaluation efforts. The results of a preliminary system analysis are also included, showing the size and volume reductions provided by the new system.

Alptekin, Gokhan↗
NASA NTRS2007

Development of a Rapid Cycling CO2 and H2O Removal Sorbent

The National Aeronautics and Space Administration (NASA) planned future missions set stringent demands on the design of the Portable Life Support System (PLSS), requiring dramatic reductions in weight, decreased reliance on supplies and greater flexibility on the types of missions. Use of regenerable systems that reduce weight and volume of the Extravehicular Mobility Unit (EMU) is of critical importance to NASA, both for low orbit operations and for long duration manned missions. The carbon dioxide and humidity control unit in the existing PLSS design is relatively large, since it has to remove and store eight hours worth of carbon dioxide (CO2). If the sorbent regeneration can be carried out during the Extravehicular Activity (EVA) with a relatively high regeneration frequency, the size of the sorbent canister and weight can be significantly reduced. TDA Research, Inc. is developing compact, regenerable sorbent materials to control CO2 and humidity in the space suit ventilation loop. The sorbent can be regenerated using space vacuum during the EVA, eliminating all CO2 and humidity duration-limiting elements in the life support system. The material also has applications in other areas of space exploration including long duration exploration missions requiring regenerable technologies and possibly the Crew Exploration Vehicle (CEV) spacecraft. This paper summarizes the results of the sorbent development, testing, and evaluation efforts to date.

Alptekin, Gokhan↗
NASA NTRS2007

Radiative and Physiological Effects of Increased CO2. How does this interaction affect Climate in the Mediterranean Region?

the radiative and physiological effects of doubled atmospheric carbon dioxide concentration (CO2) on climate are described using climate simulations. When CO2 was increased for vegetation only assuming no radiative effect, the response was a decrease in stomatal conductance followed by a temperature increase. This temperature increase was stronger when the vegetation physiological down-regulation was allowed in the model. The radiative forcing alone did not affect the global mean photosynthesis, however, some stimulation was observed in cold places. The interactions between the physiological and the radiative effects of doubled CO2 are not linearly additive and when acting together they tend to reduce the warming in the Mediterranean region.

Bounoua, Lahouari↗
NASA NTRS2007

Coupled Stochastic Time-Inverted Lagrangian Transport/Weather Forecast and Research/Vegetation Photosynthesis and Respiration Model: Simulations of Tower-Based and Airborne CO2 Measurements - Part II

This paper evaluates simulations of atmospheric CO2 measured in 2004 at continental surface and airborne receptors, intended to test the capability to use data with high temporal and spatial resolution for analyses of carbon sources and sinks at regional and continental scales. The simulations were performed using the Stochastic Time-Inverted Lagrangian Transport (STILT) model driven by the Weather Forecast and Research (WRF) model, and linked to surface fluxes from the satellite-driven Vegetation Photosynthesis and Respiration Model (VPRM). The simulations provide detailed representations of hourly CO2 tower data and reproduce the shapes of airborne vertical profiles with high fidelity. WRF meteorology gives superior model performance compared with standard meteorological products, and the impact of including WRF convective mass fluxes in the STILT trajectory calculations is significant in individual cases. Important biases in the simulation are associated with the nighttime CO2 build-up and subsequent morning transition to convective conditions, and with errors in the advected lateral boundary condition. Comparison of STILT simulations driven by the WRF model against those driven by the Brazilian variant of the Regional Atmospheric Modeling System (BRAMS) shows that model-to-model differences are smaller than between an individual transport model and observations, pointing to systematic errors in the simulated transport. Future developments in the WRF model s data assimilation capabilities, basic research into the fundamental aspects of trajectory calculations, and intercomparison studies involving other transport models, are possible venues for reducing these errors. Overall, the STILT/WRF/VPRM offers a powerful tool for continental and regional scale carbon flux estimates.

Eluszkiewicz, Janusz↗
NASA NTRS2006

A Ground-Based 2-Micron DIAL System to Profile Tropospheric CO2 and Aerosol Distributions for Atmospheric Studies

System will operate at a temperature insensitive CO2 line (2050.967 nm) with side-line tuning and off-set locking. Demonstrated an order of magnitude improvement in laser line locking needed for high precision measurements, side-line operation, and simultaneously double pulsing and line locking. Detector testing of phototransistor has demonstrated sensitivity to aerosol features over long distances in the atmosphere and resolve features approx. 100m. Optical systems that collect light onto small area detectors work well. Receiver optical designs are being optimized and data acquisition systems developed. CO2 line parameter characterization in progress In situ sensor calibration in progress for validation of DIAL CO2 system.

Ismail, Syed↗
NASA NTRS2008

An Instrument to Enable Identification of Anthropogenic CO2 Emissions Using Concurrent CO Measurements

We have developed an instrument concept that will enable the measurement of CO from the top of the atmosphere to the Earth's surface with very high sensitivity and at the high spatial and temporal resolutions required by the NRC Decadal Survey mission Active Sensing of Carbon Dioxide (CO2) over Nights, Days and Seasons (ASCENDS). We are developing an innovative CO sensor that will enable the ASCENDS mission to differentiate between anthropogenic and natural sources and sinks of global carbon. The NRC Decadal Survey places particular emphasis on retrieving CO information for the planetary boundary layer. Measurement made using both the 2.3 micron and 4.7 micron channels are needed to achieve the sensitivity required in the lower atmosphere where the degree of CO - CO2 correlation is indicative of anthropogenic sources of CO2. Measurements made using only the 4.7 micron channel cannot provide sufficient sensitivity to CO in the very lowest layers of the atmosphere. The fundamental method we use is Gas Filter Correlation Radiometry (GFCR), a highly successful technique used in other airborne and space-based missions for detecting trace species in the Earth's atmosphere. Our version of GFCR overcomes many of the limitations encountered by prior and existing instruments, allowing us to measure weak signals from small targets very quickly and with extremely high specificity by employing a new dual beam radiometer concept using a focal plane array. Our design will provide a means to make the desired CO measurements for the ASCENDS mission. A simple change in gas filter cell contents would allow the same hardware to measure CH4 with high precision under the nominal ASCENDS mission spatial and temporal constraints. All critical components in the sensor design are mature, many subsystems tested, and the system has been extensively modeled, bringing it to a present Technology Readiness Level (TRL) of 3 (though some individual components are at TRLs 6-9). We are presently developing critical components for the new spectrometer and advancing our understanding of the measurement requirements for both CO and CH4. This new GFCR technique/sensor will enable measurements of trace gases with high sensitivity while maintaining the inherent robustness and simplicity of the more traditional radiometer hardware. Initial estimates of cost/risk of a spacebased 2-channel GFCR indicate that our design is extremely cost effective and will fit within existing ASCENDS mission budget constraints as determined by the NRC Decadal Survey and a NASA-sponsored mission study.

Cook, William B.↗
NASA NTRS2008

CO2 Sensors Based on Nanocrystalline SnO2 Doped with CuO

Nanocrystalline tin oxide (SnO2) doped with copper oxide (CuO) has been found to be useful as an electrical-resistance sensory material for measuring the concentration of carbon dioxide in air. SnO2 is an n-type semiconductor that has been widely used as a sensing material for detecting such reducing gases as carbon monoxide, some of the nitrogen oxides, and hydrocarbons. Without doping, SnO2 usually does not respond to carbon dioxide and other stable gases. The discovery that the electrical resistance of CuO-doped SnO2 varies significantly with the concentration of CO2 creates opportunities for the development of relatively inexpensive CO2 sensors for detecting fires and monitoring atmospheric conditions. This discovery could also lead to research that could alter fundamental knowledge of SnO2 as a sensing material, perhaps leading to the development of SnO2-based sensing materials for measuring concentrations of oxidizing gases. Prototype CO2 sensors based on CuO-doped SnO2 have been fabricated by means of semiconductor-microfabrication and sol-gel nanomaterial-synthesis batch processes that are amendable to inexpensive implementation in mass production.

Xu, Jennifer C.↗
NASA NTRS2008

Effects of Doubled CO2 on Tropical Sea-Surface Temperature (SSTs) for Onset of Deep Convection and Maximum SST-GCM Simulations Based Inferences

A primary concern of CO2-induced warming is the associated rise of tropical (10S-10N) seasurface temperatures (SSTs). GISS Model-E was used to produce two sets of simulations-one with the present-day and one with doubled CO2 in the atmosphere. The intrinsic usefulness of model guidance in the tropics was confirmed when the model simulated realistic convective coupling between SSTs and atmospheric soundings and that the simulated-data correlations between SSTs and 300 hPa moiststatic energies were found to be similar to the observed. Model predicted SST limits: (i) one for the onset of deep convection and (ii) one for maximum SST, increased in the doubled C02 case. Changes in cloud heights, cloud frequencies, and cloud mass-fractions showed that convective-cloud changes increased the SSTs, while warmer mixed-layer of the doubled CO2 contained approximately 10% more water vapor; clearly that would be conducive to more intense storms and hurricanes.

Sud, Y. C.↗