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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 55 records · Page 3
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NASA NTRS2015

Stratospheric Aerosol and Gas Experiment III on the International Space Station (SAGE III/ISS)

The Stratospheric Aerosol and Gas Experiment III on the International Space Station (SAGE III/ISS) mission will extend the SAGE data record from the ideal vantage point of the International Space Station (ISS). The ISS orbital inclination is ideal for SAGE measurements providing coverage between 70 deg north and 70 deg south latitude. The SAGE data record includes an extensively validated data set including aerosol optical depth data dating to the Stratospheric Aerosol Measurement (SAM) experiments in 1975 and 1978 and stratospheric ozone profile data dating to the Stratospheric Aerosol and Gas Experiment (SAGE) in 1979. These and subsequent data records, notably from the SAGE II experiment launched on the Earth Radiation Budget Satellite in 1984 and the SAGE III experiment launched on the Russian Meteor-3M satellite in 2001, have supported a robust, long-term assessment of key atmospheric constituents. These scientific measurements provide the basis for the analysis of five of the nine critical constituents (aerosols, ozone (O3), nitrogen dioxide (NO2), water vapor (H2O), and air density using O2) identified in the U.S. National Plan for Stratospheric Monitoring. SAGE III on ISS was originally scheduled to fly on the ISS in the same timeframe as the Meteor-3M mission, but was postponed due to delays in ISS construction. The project was re-established in 2009.

Gasbarre, Joseph↗
NASA NTRS2023

The Calipso Version 4.5 Stratospheric Aerosol Subtyping Algorithm

The accurate classification of aerosol types injected into the stratosphere is important to properly characterize their chemical and radiative impacts within the Earth climate system. The updated stratospheric aerosol subtyping algorithm used in the version 4.5 (V4.5) release of the Cloud Aerosol Lidar with Orthogonal Polarization (CALIOP) level 2 data products now delivers more comprehensive and accurate classifications than its predecessor. The original algorithm identified four aerosol subtypes for layers detected above the tropopause: volcanic ash, smoke, sulfate/other, and polar stratospheric aerosol (PSA). In the revised algorithm, sulfates are separately identified as a distinct, homogeneous subtype, and the diffuse, weakly scattering layers previously assigned to the sulfate/other class are recategorized as a fifth “unclassified” subtype. By making two structural changes to the algorithm and revising two thresholds, the V4.5 algorithm improves the ability to discriminate between volcanic ash and smoke from pyrocumulonimbus injections, improves the fidelity of the sulfate subtype, and more accurately reflects the uncertainties inherent in the classification process. The 532 nm lidar ratio for volcanic ash was also revised to a value more consistent with the current state of knowledge. This paper briefly reviews the previous version of the algorithm (V4.1 and V4.2) then fully details the rationale and impact of the V4.5 changes on subtype classification frequency for specific events where the dominant aerosol type is known based on the literature. Classification accuracy is best for volcanic ash due to its characteristically high depolarization ratio. Smoke layers in the stratosphere are also classified with reasonable accuracy, though during the daytime a substantial fraction are misclassified as ash. It is also possible for mixtures of ash and sulfate to be misclassified as smoke. The V4.5 sulfate subtype accuracy is less than that for ash or smoke, with sulfates being misclassified as smoke about one-third of the time. However, because exceptionally tenuous layers are now assigned to the unclassified subtype and the revised algorithm levies more stringent criteria for identifying an aerosol as sulfate, it is more likely that layers labeled as this subtype are in fact sulfate compared to those assigned the sulfate/other classification in the previous data release.

Jason L Tackett↗
DOE OSTI2021

High-Latitude Stratospheric Aerosol Geoengineering Can Be More Effective if Injection Is Limited to Spring

Stratospheric aerosol geoengineering focused on the Arctic could substantially reduce local and worldwide impacts of anthropogenic global warming. Because the Arctic receives little sunlight during the winter, stratospheric aerosols present in the winter at high latitudes have little impact on the climate, whereas stratospheric aerosols present during the summer achieve larger changes in radiative forcing. Injecting SO 2 in the spring leads to peak aerosol optical depth (AOD) in the summer. We demonstrate that spring injection produces approximately twice as much summer AOD as year-round injection and restores approximately twice as much September sea ice, resulting in less increase in stratospheric sulfur burden, stratospheric heating, and stratospheric ozone depletion per unit of sea ice restored. Furthermore, we also find that differences in AOD between different seasonal injection strategies are small compared to the difference between annual and spring injection.

58 GEOSCIENCES↗
NASA NTRS2012

Toward a Combined SAGE II-HALOE Aerosol Climatology: An Evaluation of HALOE Version 19 Stratospheric Aerosol Extinction Coefficient Observations

Herein, the Halogen Occultation Experiment (HALOE) aerosol extinction coefficient data is evaluated in the low aerosol loading period after 1996 as the first necessary step in a process that will eventually allow the production of a combined HALOE/SAGE II (Stratospheric Aerosol and Gas Experiment) aerosol climatology of derived aerosol products including surface area density. Based on these analyses, it is demonstrated that HALOE's 3.46 microns is of good quality above 19 km and suitable for scientific applications above that altitude. However, it is increasingly suspect at lower altitudes and should not be used below 17 km under any circumstances after 1996. The 3.40 microns is biased by about 10% throughout the lower stratosphere due to the failure to clear NO2 but otherwise appears to be a high quality product down to 15 km. The 2.45 and 5.26 micron aerosol extinction coefficient measurements are clearly biased and should not be used for scientific applications after the most intense parts of the Pinatubo period. Many of the issues in the aerosol data appear to be related to either the failure to clear some interfering gas species or doing so poorly. For instance, it is clear that the 3.40micronaerosol extinction coefficient measurements can be improved through the inclusion of an NO2 correction and could, in fact, end up as the highest quality overall HALOE aerosol extinction coefficient measurement. It also appears that the 2.45 and 5.26 micron channels may be improved by updating the Upper Atmosphere Pilot Database which is used as a resource for the removal of gas species otherwise not available from direct HALOE measurements. Finally, a simple model to demonstrate the promise of mixed visible/infrared aerosol extinction coefficient ensembles for the retrieval of bulk aerosol properties demonstrates that a combined HALOE/SAGE II aerosol climatology is feasible and may represent a substantial improvement over independently derived data sets.

Thomason, L. W.↗
NASA NTRS1985

SAM II measurements of the polar stratospheric aerosol. Volume 6: April to October 1981

The Stratospheric Aerosol Measurement (SAM) II sensor is aboard the Earth-orbiting Nimbus 7 spacecraft providing extinction measurements of the Antarctic and Arctic stratospheric aerosols with a vertical resolution of 1 km. Representative examples and weekly averages of these aerosol data and corresponding temperature profiles (Apr. 1981 to Oct. 1981) are presented. Contours of aerosol extinction as a function of altitude and longitude or time are plotted and weekly aerosol optical depths are calculated. Stratospheric optical depths are 0.002 to 0.003 for the Antarctic region and 0.006 to 0.007 at the beginning to 0.003 to 0.004 at the end of the time period for the Arctic region. Polar stratospheric clouds at altitudes between the tropopause and 20 km were observed during the Antarctic winter. A ready-to-use format containing a representative sample of the sixth 6 months of data to be used in atmospheric and climatic studies is reported.

Mccormick, M. P.↗
NASA NTRS1993

Stratospheric Aerosol and Gas Experiment (SAGE 3)

The proposed SAGE III instrument would be the principal source of data for global changes of stratospheric aerosols, stratospheric water vapor, and ozone profiles, and a contributing source of data for upper tropospheric water vapor, aerosols, and clouds. The ability to obtain such data has been demonstrated by the predecessor instrument, SAGE II, but SAGE III will be substantially more capable, as discussed below. The capabilities for monitoring the profiles of atmospheric constituents have been verified in detail, including ground-based validations, for aerosol, ozone, and water vapor. Indeed, because of its self-calibrating characteristics, SAGE II was an essential component of the international ozone trend assessments, and SAGE II is now proving to be invaluable in tracking the aerosols from Mt. Pinatubo. Although SAGE profiles generally terminate at the height of the first tropospheric cloud layer, it has been found that the measurements extend down to 3 km altitude more than 40 percent of the time at most latitudes. Thus, useful information can also be obtained on upper tropospheric aerosols, water vapor, and ozone.

Mccormick, M. P.↗
NASA NTRS2007

CALIPSO Observations of Stratospheric Aerosols: A Preliminary Assessment

We have examined the 532-nm aerosol backscatter coefficient measurements by the Cloud- Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) for their use in the observation of stratospheric aerosol. CALIPSO makes observations that span from 82 S to 82 N each day and, for each profile, backscatter coefficient values reported up to approx. 40 km. The possibility of using CALIPSO for stratospheric aerosol observations is demonstrated by the clear observation of the 20 May 2006 eruption of Montserrat in the earliest CALIPSO data in early June as well as by observations showing the 7 October 2006 eruption of Tavurvur (Rabaul). However, the very low aerosol loading within the stratosphere makes routine observations of the stratospheric aerosol far more difficult than relatively dense volcanic plumes. Nonetheless, we found that averaging a complete days worth of nighttime only data into 5-deg latitude by 1-km vertical bins reveals a stratospheric aerosol data centered near an altitude of 20 km, the clean wintertime polar vortices, and a small maximum in the lower tropical stratosphere. However, the derived values are clearly too small and often negative in much of the stratosphere. The data can be significantly improved by increasing the measured backscatter (molecular and aerosol) by approximately 5% suggesting that the current method of calibrating to a pure molecular atmosphere at 30 km is most likely the source of the low values.

Thomason, Larry W.↗
NASA NTRS1988

The relationship of satellite-inferred stratospheric aerosol extinction to the position of the 50-mb north polar jet stream

The relationship between stratospheric aerosols and the location of the north polar night stratospheric jet stream was investigated for selected periods of four successive winters (1979-1982), using measurements from SAM II (Stratospheric Aerosol Measurement II) and SAGE I (Stratospheric Aerosol and Gas Experiment I) satellite-borne sun photometers and corresponding meteorological observations. Each period investigated included a polar stratospheric warming during which major dynamic meteorological changes are known to have perturbed the structure of the polar vortex. The analysis of variations in aerosol extinction mixing ratio patterns among winters and during major stratospheric warming events within separate winters showed a well-defined positive gradient in extinction mixing ratio and temperature across the jet stream from the cyclonic side to the anticyclonic side at altitudes between 20 and 30 km during each winter period. Estimates of extinction mixing ratio profiles measured near the center of the polar vortex suggest that a gradual subsidence took place within the polar vortex during at least three of the four winter periods.

Livingston, John M.↗
NASA NTRS1972

The stratospheric aerosol background.

The current state of observations of the stratosphere aerosol layer is reviewed. Monitoring programs used are briefly reviewed, and the long-term trend of aerosols in the mid-latitude stratosphere is shown. The effects of volcanism on stratospheric aerosol profiles are discussed.

Rosen, J. M.↗
NASA NTRS2019

Differences in the Vertical and Microphysical Evolution of Volcanic and Pyrocumulonimbus Stratospheric Aerosol Plumes as Observed by CALIOP and CATS Satellite Lidar

For some time, volcanic eruptions have been thought to be the only significant direct injectors of aerosols in the stratosphere. However, recent fire seasons have featured fire events resulting in large volcanic-sized pyrocumulonimbus plumes of smoke aerosols reaching many kilometers into the lower stratosphere. To understand and model the effects of these pyrocumulonimbus events on stratospheric composition and climate, a natural analogy lies with better studied volcanic events; however, differences in plume composition may limit this comparison. Using satellite lidar from both CATS and CALIOP, we show that the stratospheric aerosol plumes from the record-setting Pacific Northwest pyrocumulonimbus event of 2017 and the Calbuco volcanic eruption of 2015 evolve differently both vertically and microphysically. Specifically, depolarization ratios indicate that this pyrocumulonimbus event’s aerosol particles became more irregularly shaped over time in contrast to volcanic aerosols which become more spherical over time. Accounting for these changes in aerosol properties may be significant in assessing the effects of pyrocumulonimbus events on the Earth’s radiative balance and aid in refining stratospheric aerosol typing algorithms to differentiate volcanic from pyrocumulonimbus plumes.

Christian, Kenneth↗
NASA NTRS1985

UV lidar measurements of the stratospheric aerosol layer and comparison with other optical data

After the violent volcanic eruptions of El Chichon in Mexico (17.33 deg. N, 93.20 deg. W) in late March and early April 1982, enhanced stratospheric aerosols have been monitored by ruby (lasing wavelength lambda=694.3 nm) or Nd:YAG lidars (lambda=1064 or 532 nm). By these lidars, visible or near-infrared optical informations of stratospheric aerosols and their space-time variations can be obtained. It is usually difficult to measure the background level of stratospheric aerosols by an ultraviolet (UV) lidar, since Rayleigh scattering prevails over Mie scattering in the stratosphere. However, after the large volcanic eruptions, UV lidar measurements of stratospheric aerosols are possible. In order to obtain UV optical properties of stratospheric aerosols, measurements have been made at Fukuoka (33.65 deg. N, 130.35 deg. E) by a p-terphenyl dye laser at a wavelength of 340.5 nm. Observational results during October 1982, through May 1983, are shown and are compared with the results obtained by a ruby lidar at Tsukuba (36.05 deg. N, 140.13 deg. E).

Uchino, O.↗
NASA NTRS2018

Constraining Upper Troposphere/Lower Stratosphere Aerosol Physical Processes with High-Altitude Aircraft Measurements

Interest in a more complete understanding of the sources, composition and microphysics of stratospheric aerosol particles has intensified during recent years for several reasons: (1) small volcanic eruptions have been recognized as a driver of short-term changes in climate forcing; (2) emissions of sulfur dioxide (SO2) and other aerosol precursors have shifted to south Asia and other low latitude regions with intense vertical transport; (3) organic material has been recognized as a key contributor to lower stratospheric aerosol mass; and (4) interest in possible solar radiation management (geoengineering) through significant enhancements in stratospheric aerosols has intensified. To address stratospheric aerosol science issues, we are proposing a NASA Earth Ventures mission to NASA to provide extensive high-altitude aircraft measurements of critical gas-phase and aerosol properties at multiple locations across the planet. In this presentation, we will discuss the objectives of the proposed campaign, the measurements provided, the sampling strategy, and the modeling and analysis approaches that would be used to address specific science questions.

Jensen, Eric↗
NASA NTRS1983

SAM 2 measurements of the polar stratospheric aerosol. Volume 4: April 1980 to October 1980

The Stratospheric Aerosol Measurement (SAM) 2 sensor is aboard the Nimbus 7 spacecraft providing extinction measurements of the Antarctic and Arctic stratospheric aerosols with a vertical resolution of 1 km. Representative examples and weekly averages of these aerosol data and corresponding temperature profiles are presented. Contours of aerosols extinction as a function of altitude and longitude or time are plotted and weekly aerosol optical depths are calculated. Stratospheric optical depths are 0.002 to 0.003 for the Antarctic and 0.002 to 0.003 at the beginning to 0.005 to 0.006 at the end of the time period for the Arctic. Polar stratospheric clouds at altitudes between the tropopause and 20 km were observed during the Antarctic winter. A ready-to-use format containing a representative sample of the fourth 6 months of data to be used in atmospheric and climatic studies is reported.

Mccormick, M. P.↗
NASA NTRS1981

Measurements of the absorption coefficient of stratospheric aerosols

The absorption coefficients of stratospheric aerosols are measured using a variation on the integrating plate method. The technique is based on the decrease in the transparency of a substrate when an absorbing aerosol is deposited on it. A Lambert scatterer is placed behind the substrate to integrate forward scattered light and minimize the effect of scattering on the measurement. The low pressure in the stratosphere is used for the direct impaction of particles onto a narrow strip of opal glass. The eight samples collected had a median value of 4 x 10 to the -9th m with an uncertainty of + or - 5 x 10 to the -9th m. If this absorption is due to graphitic carbon, then its concentration is estimated at about 0.4 ng/cu m, or about 0.25% of the total aerosol mass concentration. Estimates of the aerosol scattering coefficients based on satellite extinction inversions result in an aerosol single-scattering albedo in the range of 0.96-1.0.

Ogren, J. A.↗
NASA NTRS1977

Microphysical processes affecting stratospheric aerosol particles

Physical processes which affect stratospheric aerosol particles include nucleation, condensation, evaporation, coagulation and sedimentation. Quantitative studies of these mechanisms to determine if they can account for some of the observed properties of the aerosol are carried out. It is shown that the altitude range in which nucleation of sulfuric acid-water solution droplets can take place corresponds to that region of the stratosphere where the aerosol is generally found. Since heterogeneous nucleation is the dominant nucleation mechanism, the stratospheric solution droplets are mainly formed on particles which have been mixed up from the troposphere or injected into the stratosphere by volcanoes or meteorites. Particle growth by heteromolecular condensation can account for the observed increase in mixing ratio of large particles in the stratosphere. Coagulation is important in reducing the number of particles smaller than 0.05 micron radius. Growth by condensation, applied to the mixed nature of the particles, shows that available information is consistent with ammonium sulfate being formed by liquid phase chemical reactions in the aerosol particles. The upper altitude limit of the aerosol layer is probably due to the evaporation of sulfuric acid aerosol particles, while the lower limit is due to mixing across the tropopause.

Hamill, P.↗
NASA NTRS1985

Laser radar observation of the polar stratospheric aerosol layer

The polar stratosphere has been speculated to be an active sink region of various stratospheric materials; ozone, water vapor, NOX, aerosol particles and so on, but this process is not theoretically and/or observationally made clear. The observation of the polar stratospheric aerosol layer using laser radar certainly contributes to the study of the global transport of these stratospheric minor constituents. In addition to this, from the viewpoint of aerosol science, there may be many interesting phenomena which cannot be found in the stratosphere at mid and low latitudes; the effect of precipitation of high energy molecules and atoms, of very cold winter stratosphere, of very cold mesopause in summer. Laser radar observation is one of the main activities of the Antarctic Middle Atmosphere (AMA) project at Syowa Station (69.00 deg S, 39.35 deg E), Antarctica since May 1983. Laser radar measurement at Syowa Station is discussed in detail.

Iwasaka, Y.↗
NASA NTRS2011

Major Influence of Tropical Volcanic Eruptions on the Stratospheric Aerosol Layer During the Last Decade

The variability of stratospheric aerosol loading between 1985 and 2010 is explored with measurements from SAGE II, CALIPSO, GOMOS/ENVISAT, and OSIRIS/Odin space-based instruments. We find that, following the 1991 eruption of Mount Pinatubo, stratospheric aerosol levels increased by as much as two orders of magnitude and only reached background levels between 1998 and 2002. From 2002 onwards, a systematic increase has been reported by a number of investigators. Recently, the trend, based on ground-based lidar measurements, has been tentatively attributed to an increase of SO2 entering the stratosphere associated with coal burning in Southeast Asia. However, we demonstrate with these satellite measurements that the observed trend is mainly driven by a series of moderate but increasingly intense volcanic eruptions primarily at tropical latitudes. These events injected sulfur directly to altitudes between 18 and 20 km. The resulting aerosol particles are slowly lofted into the middle stratosphere by the Brewer-Dobson circulation and are eventually transported to higher latitudes.

Vernier, Jean-Paul↗
NASA NTRS1995

Evidence of seasonally dependent stratosphere-troposphere exchange and purging of lower stratospheric aerosol from a multiyear lidar data set

Tropospheric and lower stratospheric aerosol backscatter data obtained from a calibrated backscatter lidar at Pasadena, California (34 deg N latitude) over the 1984-1993 period clearly indicate tightly coupled aerosol optical properties in the upper troposphere and lower stratosphere in the winter and early spring, due to the active midlatitude stratospheric-tropospheric (ST) exchange processes occurring at this time of year. Lidar data indicate that during pre-Pinaturbo background conditions, the subsequent purging of the aerosol in the upper troposphere caused a significant reduction in the aerosol content throughout the 8 - 18 km altitude region in the early spring period. The post-Pinatubo evidence of intense exchange in the winter and early spring is a significant increase in the upper tropospheric aerosol content, such that the backscatter levels reach values nearly equivalent to the enhanced backscatter levels existing in the lower stratosphere. The calculated stratospheric mass extrusion rate is consistent with a 45-day lifetime of lower stratospheric aerosol during this part of the year, which implies that midlatitude ST exchange is a significant sink for stratospheric aerosol.

Menzies, Robert T.↗