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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 451 records · Page 25
All sourcesNASA NTRSDOE OSTI
NASA NTRS1978

An evaluation of in situ ozone sensor performance during a cold frontal passage

The capabilities of the electrochemical concentration cell ozonesonde for measuring the vertical profile of atmospheric ozone were studied during a three day experiment at Wallops Island, Virginia, and Norfolk, Virginia. Using ancillary measurements at the surface and the spectrophotometer, it was concluded that the ozonesonde measures the total ozone overburden to within 10% of the real value. By releasing the balloon-borne instruments at a rate of four per day at each of the two sites, an indication was obtained of the temporal and spatial scales of atmospheric ozone variability. No significant effects of a weak cold front passage or of the loss of insolation at night were seen. An isolated incident of anomalously high ozone concentration at the peak of the profile was attributed to sporadic instrument performance effects. The data base currently available is not adequate for determining an exact cause of the anomaly.

Parsons, C. L.↗
NASA NTRS1977

Vertical and horizontal fluxes of ozone at the tropopause from the first year of GASP data

Ozone measurements taken from commercial airlines (GASP data) are used to estimate the vertical and horizontal fluxes of ozone near the tropopause. The annual average flux of O3 into the troposphere at 30 to 50 deg N is nearly the same as indirect estimates based on surface O3 data, thus supporting the hypothesis that the amount of ozone in the troposphere is essentially controlled by injection from the stratosphere. The present GASP estimates of the total flux of O3 into the troposphere verify the model results of Cunnold et al. (1975), although the distribution of flux between mean motions and diffusion is different and suggests that models with coarse horizontal resolution must continue to parameterize much vertical transport by diffusion coefficients. A significant variation in the east-west spatial autocorrelation function of O3 near the tropopause is found to be about 1900 km. Monthly estimates of the horizontal transient eddy flux of ozone are generally smaller than seasonal or yearly results based on ozonesonde data. This is perhaps because the present estimates are made over monthly periods to reduce the influence of correlation between the annual variations in ozone and meridional wind. The available data support the hypothesis that transient eddy fluxes of O3 have large longitudinal variations.

Nastrom, G. D.↗
NASA NTRS1978

Effect of aerosols on the estimation of total ozone in an atmospheric column from the measurements of its ultraviolet radiance

The problem of estimating the total ozone amount of an atmospheric column in the presence of stratospheric and tropospheric aerosols is studied by means of simulated spectral measurements for the five-wavelength Nimbus 4 BUV configuration and the six-wavelength Nimbus G TOMS configuration, and by analyzing such measurements with appropriate total ozone estimation procedures. The simulated spectral measurements were generated for forty different atmospheric models arrived at by varying the total ozone content and various aerosol parameters. A total of ten different values of the solar zenith angle and eight different values of the Lambert reflectivity of the underlying surface were used. It was found that the values of total ozone in an atmospheric column estimated by the five-wavelength procedure can be in error by about + or -2% as a result of particulate contamination encountered in the terrestrial atmosphere under average conditions. Errors due to tropospheric particulate contamination can be reduced significantly by taking appropriate advantage of the additional spectral measurement offered by the Nimbus G TOMS instrument.

Dave, J. V.↗
NASA NTRS2017

Quantifying TOLNet Ozone Lidar Accuracy During the 2014 DISCOVER-AQ and FRAPPE Campaigns

The Tropospheric Ozone Lidar Network (TOLNet) is a unique network of lidar systems that measure high-resolution atmospheric profiles of ozone. The accurate characterization of these lidars is necessary to determine the uniformity of the network calibration. From July to August 2014, three lidars, the TROPospheric OZone (TROPOZ) lidar, the Tunable Optical Profiler for Aerosol and oZone (TOPAZ) lidar, and the Langley Mobile Ozone Lidar (LMOL), of TOLNet participated in the Deriving Information on Surface conditions from Column and Vertically Resolved Observations Relevant to Air Quality (DISCOVER-AQ) mission and the Front Range Air Pollution and Photochemistry Experiment (FRAPPA) to measure ozone variations from the boundary layer to the top of the troposphere. This study presents the analysis of the intercomparison between the TROPOZ, TOPAZ, and LMOL lidars, along with comparisons between the lidars and other in situ ozone instruments including ozonesondes and a P-3B airborne chemiluminescence sensor. The TOLNet lidars measured vertical ozone structures with an accuracy generally better than +/-15 % within the troposphere. Larger differences occur at some individual altitudes in both the near-field and far-field range of the lidar systems, largely as expected. In terms of column average, the TOLNet lidars measured ozone with an accuracy better than +/-5 % for both the intercomparison between the lidars and between the lidars and other instruments. These results indicate that these three TOLNet lidars are suitable for use in air quality, satellite validation, and ozone modeling efforts.

TOLNet↗
NASA NTRS2007

Chemical Data Assimilation Estimates of Continental US Ozone and Nitrogen Budgets during INTEX-A

Global ozone analyses, based on assimilation of stratospheric profile and ozone column measurements, and NOy predictions from the Real-time Air Quality Modeling System (RAQMS) are used to estimate the ozone and NOy budget over the Continental US during the July-August 2004 Intercontinental Chemical Transport Experiment-North America (INTEX-A). Comparison with aircraft, satellite, surface, and ozonesonde measurements collected during the INTEX-A show that RAQMS captures the main features of the global and Continental US distribution of tropospheric ozone, carbon monoxide, and NOy with reasonable fidelity. Assimilation of stratospheric profile and column ozone measurements is shown to have a positive impact on the RAQMS upper tropospheric/lower stratosphere ozone analyses, particularly during the period when SAGE III limb scattering measurements were available. Eulerian ozone and NOy budgets during INTEX-A show that the majority of the Continental US export occurs in the upper troposphere/lower stratosphere poleward of the tropopause break, a consequence of convergence of tropospheric and stratospheric air in this region. Continental US photochemically produced ozone was found to be a minor component of the total ozone export, which was dominated by stratospheric ozone during INTEX-A. The unusually low photochemical ozone export is attributed to anomalously cold surface temperatures during the latter half of the INTEX-A mission, which resulted in net ozone loss during the first 2 weeks of August. Eulerian NOy budgets are shown to be very consistent with previously published estimates. The NOy export efficiency was estimated to be 24 percent, with NOx+PAN accounting for 54 percent of the total NOy export during INTEX-A.

Pierce, Robert B.↗
NASA NTRS2015

File Specification for the MERRA Aerosol Reanalysis (MERRAero): MODIS AOD Assimilation based on a MERRA Replay

This document describes the gridded output files produced by the Goddard Earth Observing System version 5 (GEOS-5) Goddard Aerosol Assimilation System (GAAS) from July 2002 through December 2014. The MERRA Aerosol Reanalysis (MERRAero) is produced with the hydrostatic version of the GEOS-5 Atmospheric Global Climate Model (AGCM). In addition to standard meteorological parameters (wind, temperature, moisture, surface pressure), this simulation includes 15 aerosol tracers (dust, sea-salt, sulfate, black and organic carbon), ozone, carbon monoxide and carbon dioxide. This model simulation is driven by prescribed sea-surface temperature and sea-ice, daily volcanic and biomass burning emissions, as well as high-resolution inventories of anthropogenic emission sources. Meteorology is replayed from the MERRA Reanalysis.

GAAS↗
DOE OSTI2025

A compartmentalized model of multiphase chemical kinetics

There are significant challenges in predicting multiphase chemical kinetics due to the complex coupling of reaction and mass transport across a phase boundary (i.e., interface). Here, we describe a framework for predicting multiphase kinetics that embeds the elementary kinetic steps of reaction, solvation, and diffusion into a coarse grain spatial description of two phases. The model is constructed to bridge the short-timescale interfacial dynamics observed in molecular simulations with the longer timescales observed in kinetic experiments. A simple set of governing differential equations is derived, which, when solved numerically or analytically, yield accurate predictions of multiphase kinetics in microdroplets. Although the equations are formulated for gas-liquid reactions, the underlying conceptual framework is general and can be applied to transformations in other two-phase systems (solid-liquid, liquid-liquid, etc.).

Chemical kinetics and dynamics↗
NASA NTRS1972

Stratospheric ozone

The photochemical and transport processes in the earth stratosphere are discussed. The effects of certain trace constituents such as water vapor and oxides of nitrogen on the stratospheric ozone distribution are analyzed. The changes in the surface ultraviolet radiation levels which result from changes in the chemical composition in the stratosphere are examined. The influences of absorption and scattering of ultraviolet radiation on the thermal structure of the stratosphere are explained.

Stewart, R. W.↗
NASA NTRS1988

The origin and evolution of atmospheric oxygen

This paper discusses the chemical processes involved in the evolution of the earth's atmospheric oxygen and ozone, as well as the sources, sinks, and transfer rates of oxygen in the present atmosphere. Special attention is given the evolution of atmospheric O3 as a function of the buildup of O2, with the results of calculations presented as the vertical profiles of O3, in terms of the present atmospheric level (PAL) oxygen values. Calculations show that the total O3 column density that is approximately half of the present level was reached when atmospheric oxygen level reached 0.1 PAL. At this level of ozone, the biological shielding of the earth's surface from the UV radiation is believed to have been achieved.

Levine, Joel S.↗
NASA NTRS1993

Inference of cirrus cloud properties using satellite-observed visible and infrared radiances. I - Parameterization of radiance fields

The impact of using phase functions for spherical droplets and hexagonal ice crystals to analyze radiances from cirrus is examined. Adding-doubling radiative transfer calculations are employed to compute radiances for different cloud thicknesses and heights over various backgrounds. These radiances are used to develop parameterizations of top-of-the-atmosphere visible reflectance and IR emittance using tables of reflectances as a function of cloud optical depth, viewing and illumination angles, and microphysics. This parameterization, which includes Rayleigh scattering, ozone absorption, variable cloud height, and an anisotropic surface reflectance, reproduces the computed top-of-the-atmosphere reflectances with an accruacy of +/- 6 percent for four microphysical models: 10-micron water droplet, small symmetric crystal, cirrostratus, and cirrus uncinus. The accuracy is twice that of previous models.

Minnis, Patrick↗
NASA NTRS1994

Ground-based microwave observations of ozone in the upper stratosphere and mesosphere

A 9-month-long series of mesurements of ozone in the upper stratosphere and mesosphere is reported. The measurements are presented as monthly averages of profiles in blocks of roughly 20 min local time and as night-to-day ratios. An error analysis predicts accuracies of 5-26% for the monthly profiles and 2.5-9% for the ratios. The data are compared to historical data from Solar Mesosphere Explorer (SME) and limb infrared monitor of the stratosphere (LIMS), and it is shown how to remove the effect of different vertical resolution from the comparisons. The microwave data typically agree to better than 10% with SMF and nighttime LIMS ozone at all altitudes below the 0.1-mbar surface. Comparison of the microwave night-to-day ratio with the corresponding ratio from LIMS suggests that nonlocal thermodynamic equilibrium effects in the LIMS daytime data exceed 10% at all pressures less than or equal to 1 mbar.

Connor, Brian J.↗
NASA NTRS1995

A Model Simulation of Pinatubo Volcanic Aerosols in the Stratosphere

A one-dimensional, time-dependent model is used to study the chemical, microphysical, and radiative properties of volcanic aerosols produced by the Mount Pinatubo eruption on June 15, 1991. Our model treats gas-phase sulfur photochemistry, gas-to-particle conversion of sulfur, and the microphysics of sulfate aerosols and ash particles under stratospheric conditions. The dilution and diffusion of the volcanic eruption clouds are also accounted for in these conditions. Heteromolecular homogeneous and heterogeneous binary H2SO4/H2O nucleation, acid and water condensational growth, coagulation, and gravitational sedimentation are treated in detail in the model. Simulations suggested that after several weeks, the volcanic cloud was composed mainly of sulfuric acid/water droplets produced in situ from the SO2 emissions. The large amounts of SO2 (around 20 Mt) injected into the stratosphere by the Pinatubo eruption initiated homogeneous nucleation which generated a high concentration of small H2SO4/H2O droplets. These newly formed particles grew rapidly by condensation and coagulation in the first few months and then reach their stabilized sizes with effective radii in a range between 0.3 and 0.5 micron approximately one-half year after the eruption. The predicted volcanic cloud parameters reasonably agree with measurements in term of the vertical distribution and lifetime of the volcanic aerosols, their basic microphysical structures (e.g., size distribution, concentration, mass ratio, and surface area) and radiative properties. The persistent volcanic aerosols can produce significant anomalies in the radiation field, which have important climatic consequences. The large enhancement in aerosol surface area can result in measurable global stratospheric ozone depletion.

Zhao , Jing-xia↗
NASA NTRS1999

Advanced Geosynchronous Imager

For improved understanding of chaotic processes and the diurnal cycle, an advanced GOES imager must also have the multi-spectral spectral bands used by low earth orbit (LEO) imagers, with on-orbit calibration for all bands. A synergy between GEO and LEO radiometry would enable earth system scientists to fuse the remote sensing data from all the spaceborne platforms. These additional radiometric capabilities are designed to observe important physical processes that vary rapidly and unpredicably: smoke, fires, precipitation, ozone, volcanic ash, cloud phase and height, and surface temperature. We believe the technology now exists to develop an imaging system that can meet future weather reporting and earth system science needs. To meet this need, we propose a design for a comprehensive geosynchronous atmospheric imager. This imager is envisioned to fly on a GOES-N class spacecraft, within the volume, weight and power constraints of a platform similar to GOES-N while delivering 100 times more data and radiometric quality than the GOES-N imager. The higher data rate probably requires its own ground station, which could serve as a systems prototype for NOAA's next generation of operational satellites. For operational compatibility, our proposed advanced GOES imaging system contains the GOES-R requirements as a subset, and the GOES-N imager capabilities (and the sounder's imaging channels) as a further subset.

Chesters, Dennis↗
NASA NTRS1994

Heterogeneous Chemistry Important in the Polar Stratosphere

Aircraft emissions have been thought to enhance the formation of polar stratospheric clouds in the Arctic winter, and therefore heterogeneous reactions on the surfaces of these clouds may accelerate the polar ozone depletion.

polar stratosphere heterogeneous chemistry ozone d↗
NASA NTRS2014

The Impact of Different Absolute Solar Irradiance Values on Current Climate Model Simulations

Simulations of the preindustrial and doubled CO2 climates are made with the GISS Global Climate Middle Atmosphere Model 3 using two different estimates of the absolute solar irradiance value: a higher value measured by solar radiometers in the 1990s and a lower value measured recently by the Solar Radiation and Climate Experiment. Each of the model simulations is adjusted to achieve global energy balance; without this adjustment the difference in irradiance produces a global temperature change of 0.48C, comparable to the cooling estimated for the Maunder Minimum. The results indicate that by altering cloud cover the model properly compensates for the different absolute solar irradiance values on a global level when simulating both preindustrial and doubled CO2 climates. On a regional level, the preindustrial climate simulations and the patterns of change with doubled CO2 concentrations are again remarkably similar, but there are some differences. Using a higher absolute solar irradiance value and the requisite cloud cover affects the model's depictions of high-latitude surface air temperature, sea level pressure, and stratospheric ozone, as well as tropical precipitation. In the climate change experiments it leads to an underestimation of North Atlantic warming, reduced precipitation in the tropical western Pacific, and smaller total ozone growth at high northern latitudes. Although significant, these differences are typically modest compared with the magnitude of the regional changes expected for doubled greenhouse gas concentrations. Nevertheless, the model simulations demonstrate that achieving the highest possible fidelity when simulating regional climate change requires that climate models use as input the most accurate (lower) solar irradiance value.

climate change↗
NASA NTRS2016

CubeSat Constellation Cloud Winds(C3Winds) A New Wind Observing System to Study Mesoscale Cloud Dynamics and Processes

The CubeSat Constellation Cloud Winds (C3Winds) is a NASA Earth Venture Instrument (EV-I) concept with the primary objective to better understand mesoscale dynamics and their structures in severe weather systems. With potential catastrophic damage and loss of life, strong extratropical and tropical cyclones (ETCs and TCs) have profound three-dimensional impacts on the atmospheric dynamic and thermodynamic structures, producing complex cloud precipitation patterns, strong low-level winds, extensive tropopause folds, and intense stratosphere-troposphere exchange. Employing a compact, stereo IR-visible imaging technique from two formation-flying CubeSats, C3Winds seeks to measure and map high-resolution (2 km) cloud motion vectors (CMVs) and cloud geometric height (CGH) accurately by tracking cloud features within 5-15 min. Complementary to lidar wind observations from space, the high-resolution wind fields from C3Winds will allow detailed investigations on strong low-level wind formation in an occluded ETC development, structural variations of TC inner-core rotation, and impacts of tropopause folding events on tropospheric ozone and air quality. Together with scatterometer ocean surface winds, C3Winds will provide a more comprehensive depiction of atmosphere-boundary-layer dynamics and interactive processes. Built upon mature imaging technologies and long history of stereoscopic remote sensing, C3Winds provides an innovative, cost-effective solution to global wind observations with potential of increased diurnal sampling via CubeSat constellation.

mesoscale dynamics↗
NASA NTRS2021

Additional Characterization of Dome-C to Improve its Use as an Invariant Visible Calibration Target

Dome-C is a recommended CEOS invariant target that has been utilized by the calibration community for several decades for monitoring onboard sensor calibration systems as well radiometric inter-comparisons. Dome-C is a high-altitude Earth target located on the East Antarctic interior plateau, which has a permanent bright, flat, and homogeneous snow-covered surface with little aerosol, cloud cover, snowfall, and water vapor burden. This paper describes angular directional models for characterizing the Dome-C top-of-atmosphere (TOA)radiances as a function of cosine solar zenith angle for pre-solstice and post-solstice conditions. The 0.86-μm channel Dome-C reflectance decreases over the summer due to snow metamorphosisis not observed by the visible channels. Coinciding Terra and AquaMODIS Dome-C reflectance showed occasional inter-annual anomalies when compared against the deep convective cloud and Libya-4 invariant targets observations. Further characterization of the Dome-C reflectances with the Dome-C surface broadband albedo, Antarctic Oscillation(AAO) index, and ozone concentration values were evaluated. A strong correlation with ozone was found for the 0.55-μm and 0.65-μm MODIS channels. The monthly Dome-C reflectances were linearly regressed with ozone to derive the ozone correction coefficients. The uncertainty in the Aqua-and Terra-MODIS Dome-C trends was reduced by half after applying ozone corrections to both the 0.55-μm and 0.65-μm channelTOA observations.

David R Doelling↗