Search NASA⌕ Search

SEARCH · Search NASA

Results for “Stratospheric”

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.

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

At least 325 records · Page 18
All sourcesNASA NTRSDOE OSTI
NASA NTRS1995

Heterogeneous Chemistry Related to Stratospheric Aircraft

Emissions from stratospheric aircraft that may directly or indirectly affect ozone include NO(y), H2O, soot and sulfuric acid. To fully assess the impact of such emissions, it is necessary to have a full understanding of both the homogeneous and heterogeneous transformations that may occur in the stratosphere. Heterogeneous reactions on stratospheric particles play a key role in partitioning ozone-destroying species between their active and reservoir forms. In particular, heterogeneous reactions tend to activate odd chlorine while deactivating odd nitrogen. Accurate modeling of the net atmospheric effects of stratospheric aircraft requires a thorough understanding of the competing effects of this activation/deactivation. In addition, a full understanding of the potential aircraft impacts requires that the abundance, composition and formation mechanisms of the particles themselves be established. Over the last three years with support from the High Speed Research Program, we have performed laboratory experiments to determine the chemical composition, formation mechanism, and reactivity of stratospheric aerosols.

Tolbert, Margaret A.↗
NASA NTRS1995

Stratospheric Tracers of Atmospheric Transport (STRAT) Campaign: ER-2 Participation

The NASA Stratospheric Tracers of Atmospheric Transport (STRAT) mission was initiated to advance knowledge of the major transport mechanisms of the upper troposphere-lower stratosphere. This is the region of the atmosphere within which exchange processes take place that critically determine the response of the climate system and ozone distribution to changing conditions triggered by the release of chemicals at the surface. The mission series that extended from October 1995 to November 1997 was extremely successful. The scientific advances that emerged from that mission include analyses of: (1)troposphere-to-stratosphere transport in the lowermost stratosphere from measurements of H2O, CO2, N2O, and O3; (2) the effects of tropical cirrus clouds on the abundance of lower stratospheric ozone; and (3) the role of HO(x) in super- and subsonic aircraft exhaust plumes; and dehydration and denitrification in the arctic polar vortex during the 1995-96 winter.

Anderson, James G.↗
NASA NTRS1999

The Tropical Upper Troposphere and Lower Stratosphere in the GEOS-2 GCM

The structure of the tropical upper troposphere and lower stratosphere in the GEOS-2 General Circulation Model (GCM) is discussed. The emphasis of this study is on the reality of monthly-mean temperature and water vapor distributions in the model, compared to reasonable observational estimates. It is shown that although the zonal-mean temperature is in good agreement with observations, the GCM supports an excessive zonal asymmetry near the tropopause compared to the ECMWF Reanalyses. In reality there is a QBO-related variability in the zonally averaged lower stratospheric temperature which is not captured by the model. The observed upper tropospheric temperature and humidity fields show variations related to those in the sea surface temperature, which are not incorporated in the GCM; nevertheless, there is some interannual variability in the GCM, indicating a component arising from internal processes. The model is too moist in the middle troposphere (500 hPa) but too dry in the upper troposphere, suggesting that there is too little vertical transport or too much drying in the GCM. Transport into the stratosphere shows a pronounced annual cycle, with drier air entering the tropical stratosphere when the tropopause is coldest in northern winter; while the alternating dry and moist air masses can be traced ascending through the tropical lower stratosphere, the progression of the anomalies is too rapid.

Pawson, S.↗
NASA NTRS1998

Stratospheric Cooling and Arctic Ozone Recovery

We present sensitivity studies using the AER box model for an idealized parcel in the lower stratosphere at 70 deg N during winter/spring with different assumed stratospheric cooling and chlorine loadings. Our calculations show that stratospheric cooling could further deplete ozone via increased polar stratospheric cloud (PSC) formation and retard its expected recovery even with the projected chlorine loading decrease. We introduce the concept of chlorine-cooling equivalent and show that a 1 K Cooling could provide the same local ozone depletion as an increase of chlorine by 0.4-0.7 ppbv for the scenarios considered. Thus, sustained stratospheric cooling could further reduce Arctic ozone content and delay the anticipated ozone recovery in the Northern Hemisphere even with the realization of the Montreal Protocol and its Amendments.

Danilin, Michael Y.↗
NASA NTRS1999

Stratospheric Tracers of Atmospheric Transport (STRAT) Campaign: ER-2 Participation

The NASA Stratospheric Tracers of Atmospheric Transport (STRAT) mission was initiated to advance knowledge of the major transport mechanisms of the upper troposphere-lower stratosphere. This is the region of the atmosphere within which exchange processes take place that critically determine the response of the climate system and ozone distribution to changing conditions triggered by the release of chemicals at the surface. The mission series that extended from October 1995 to November 1997 was extremely successful. The scientific advances that emerged from that mission include analyses of: (1) troposphere-to-stratosphere transport in the lowermost stratosphere from measurements of H2O, CO2, N2O, and O3; (2) the effects of tropical cirrus clouds on the abundance of lower stratospheric ozone; (3) the role of HO(sub x) in super- and subsonic aircraft exhaust plumes; and (4) dehydration and denitrification in the arctic polar vortex during the 1995-96 winter. The abstracts from published papers are included.

Anderson, James G.↗
NASA NTRS1997

The Life Cycle of Stratospheric Aerosol Particles

This paper describes the life cycle of the background (nonvolcanic) stratospheric sulfate aerosol. The authors assume the particles are formed by homogeneous nucleation near the tropical tropopause and are carried aloft into the stratosphere. The particles remain in the Tropics for most of their life, and during this period of time a size distribution is developed by a combination of coagulation, growth by heteromolecular condensation, and mixing with air parcels containing preexisting sulfate particles. The aerosol eventually migrates to higher latitudes and descends across isentropic surfaces to the lower stratosphere. The aerosol is removed from the stratosphere primarily at mid- and high latitudes through various processes, mainly by isentropic transport across the tropopause from the stratosphere into the troposphere.

Hamill, Patrick↗
NASA NTRS1999

High-Altitude Aircraft and Balloon-Borne Observations of OH, HO2, ClO, BrO, NO2, ClONO2, ClOOCl, H2O, and O3 in Earth's Stratosphere

Using observations from balloon-borne instruments and aircraft-borne instruments the investigation arrived at the following developments.: (1) Determination of the dominant catalytic cycles that destroy ozone in the lower stratosphere; (2) The partial derivatives of the rate limiting steps are observables in the lower stratosphere; (3) Recognition that the "Low NOx" condition is the regime that holds the greatest potential for misjudgement of Ozone loss rates; (4) Mapping of the Bromine radical contribution to the ozone destruction rate in the lower stratosphere; (5) Observation of OH, HO2 and ClO in the plume of the Concorde SST in the stratosphere; (6) Determination of the diurnal behavior of OH in the lower stratosphere; (7) Observed OH and H02 in the Troposphere and the interrelationship between Ozone and OH, HO2, CO and NO; (8) Analysis of the Catalytic Production of Ozone and Reactions that Couple OH and H02 in the Troposphere; (9) The continuing development of the understanding of the Tropopause temperatures, water vapor mixing ratios, and vertical advection and the mixing in of mid-latitude air; (10) Performed Multiple Tracer Analyses as a diagnostic of water vapor intrusion into the "Middle World" (i.e., the lowermost stratsophere); (11) Flight testing of a new instrument for the In Situ detection of ClON02 from the ER-2; (12) Laser induced fluorescence detection of NO2. There is included an in depth discussion of each of these developments and observations.

Anderson, James G.↗
NASA NTRS1999

Stratospheric Tracers of Atmospheric Transport (STRAT) Campaign: ER-2 Participation

The NASA Stratospheric Tracers of Atmospheric Transport (STRAT) mission was initiated to advance knowledge of the major transport mechanisms of the upper troposphere-lower stratosphere. This is the region of the atmosphere within which exchange processes take place that critically determine the response of the climate system and ozone distribution to changing conditions triggered by the release of chemicals at the surface. The mission series that extended from October 1995 to November 1997 was extremely successful. The scientific advances that emerged from that mission include analyses of- troposphere-to-stratosphere transport in the lowermost stratosphere from measurements of H2O, CO2, N2O, and O3; the effects of tropical cirrus clouds on the abundance of lower stratospheric ozone; the role of HO, in super- and subsonic aircraft exhaust plumes; and dehydration and denitrification in the arctic polar vortex during the 1995-96 winter.

Anderson, James G.↗
NASA NTRS1999

Quantifying the Wave Driving of the Stratosphere

The zonal mean eddy heat flux is directly proportional to the wave activity that propagates from the troposphere into the stratosphere. This quantity is a simple eddy diagnostic which is easily calculated from conventional meteorological analyses. Because this "wave driving" of the stratosphere has a strong impact on the stratospheric temperature, it is necessary to compare the impact of the flux with respect to stratospheric radiative changes caused by greenhouse gas changes. Hence, we must understand the precision and accuracy of the heat flux derived from our global meteorological analyses. Herein, we quantify the stratospheric heat flux using five different meteorological analyses, and show that there are 30% differences between these analyses during the disturbed conditions of the northern hemisphere winter. Such large differences result from the planetary differences in the stationary temperature and meridional wind fields. In contrast, planetary transient waves show excellent agreement amongst these five analyses, and this transient heat flux appears to have a long term downward trend.

Newman, Paul A.↗
NASA NTRS1999

Seasonal Variability of Middle Latitude Ozone in the Lowermost Stratosphere Derived from Probability Distribution Functions

We present a study of the distribution of ozone in the lowermost stratosphere with the goal of understanding the relative contribution to the observations of air of either distinctly tropospheric or stratospheric origin. The air in the lowermost stratosphere is divided into two population groups based on Ertel's potential vorticity at 300 hPa. High [low] potential vorticity at 300 hPa suggests that the tropopause is low [high], and the identification of the two groups helps to account for dynamic variability. Conditional probability distribution functions are used to define the statistics of the mix from both observations and model simulations. Two data sources are chosen. First, several years of ozonesonde observations are used to exploit the high vertical resolution. Second, observations made by the Halogen Occultation Experiment [HALOE] on the Upper Atmosphere Research Satellite [UARS] are used to understand the impact on the results of the spatial limitations of the ozonesonde network. The conditional probability distribution functions are calculated at a series of potential temperature surfaces spanning the domain from the midlatitude tropopause to surfaces higher than the mean tropical tropopause [about 380K]. Despite the differences in spatial and temporal sampling, the probability distribution functions are similar for the two data sources. Comparisons with the model demonstrate that the model maintains a mix of air in the lowermost stratosphere similar to the observations. The model also simulates a realistic annual cycle. By using the model, possible mechanisms for the maintenance of mix of air in the lowermost stratosphere are revealed. The relevance of the results to the assessment of the environmental impact of aircraft effluence is discussed.

Cerniglia, M. C.↗
NASA NTRS1999

Temporal Behavior of Ammonia and Temperature in the Jovian Stratosphere following the SL9 Impacts

We will present new results in the study of temporal changes in ammonia (NH3) abundance, altitude distribution, and temperature in the stratosphere of Jupiter after the Comet Shoemaker-Levy 9 impact in 1994. Data obtained by Betz et al. (1994) using infrared heterodyne spectroscopy were analyzed using a newly developed beam integration radiative transfer code. The spectra are from six different impact regions and were acquired from hours to three weeks following the impact. The data consist of single NH3 stratospheric emission line profiles near 10 microns measured at a resolving power of approximately 10(exp 7). The true line profiles and the new radiative transfer program permitted the simultaneous retrieval of information on both the NH3 abundance and thermal structure as well as to set constraints on the altitude distribution of stratospheric ammonia. Retrieved column densities varied from approximately 10(exp 18) to 10(exp 16) over the three week period. Over the same time period the altitude of the emitting region varied from levels above the few mbar pressure region to below the 50 mbar pressure regions. Stratospheric temperatures hours after impact were approximately 220 K and about 8 days after impact returned to the quiescent levels (approximately 170-180 K). Results from this self-consistent set of measurements will be presented, compared to those from other measurements, and compared to theoretical retrievals from photochemical models for NH3 in the Jovian stratosphere.

Kostiuk, Ttheodor↗
NASA NTRS1999

Seasonal Variability of Middle Latitude Ozone in the Lowermost Stratosphere Derived from Probability Distribution Functions

We present a study of the distribution of ozone in the lowermost stratosphere with the goal of understanding the relative contribution to the observations of air of either distinctly tropospheric or stratospheric origin. The air in the lowermost stratosphere is divided into two population groups based on Ertel's potential vorticity at 300 hPa. High [low] potential vorticity at 300 hPa suggests that the tropopause is low [high], and the identification of the two groups helps to account for dynamic variability. Conditional probability distribution functions are used to define the statistics of the mix from both observations and model simulations. Two data sources are chosen. First, several years of ozonesonde observations are used to exploit the high vertical resolution. Second, observations made by the Halogen Occultation Experiment [HALOE) on the Upper Atmosphere Research Satellite [UARS] are used to understand the impact on the results of the spatial limitations of the ozonesonde network. The conditional probability distribution functions are calculated at a series of potential temperature surfaces spanning the domain from the midlatitude tropopause to surfaces higher than the mean tropical tropopause [approximately 380K]. Despite the differences in spatial and temporal sampling, the probability distribution functions are similar for the two data sources. Comparisons with the model demonstrate that the model maintains a mix of air in the lowermost stratosphere similar to the observations. The model also simulates a realistic annual cycle. By using the model, possible mechanisms for the maintenance of mix of air in the lowermost stratosphere are revealed. The relevance of the results to the assessment of the environmental impact of aircraft effluence is discussed.

Cerniglia, M. C.↗
NASA NTRS1998

Stratospheric Cooling and Arctic Ozone Recovery

We present sensitivity studies using the AER box model for an idealized parcel in the lower stratosphere at 70 deg N during winter/spring with different assumed stratospheric cooling and chlorine loadings. Our calculations show that stratospheric cooling could further deplete ozone via increased polar stratospheric cloud (PSC) formation and retard its expected recovery even with the projected chlorine loading decrease. We introduce the concept of chlorine-cooling equivalent and show that a 1 K cooling could provide the same local ozone depletion as an increase of chlorine by 0.4 - 0.7 ppbv for the scenarios considered. Thus, sustained stratospheric cooling could further reduce Arctic ozone content and delay the anticipated ozone recovery in the Northern Hemisphere even with the realization of the Montreal Protocol and its Amendments.

Danilin, Michael Y.↗
NASA NTRS2000

Performance of the GEOS-3/Terra Data Assimilation System in the Northern Stratospheric Winter 1999/2000

As part of NASA's support for the Terra satellite, which became operational in January 2000, the Data Assimilation Office introduced a new version of the GEOS data assimilation system (DAS) in November 1999. This system, GEOS-3/Terra, differs from its predecessor in several ways, notably through an increase in horizontal resolution (from 2-by-2.5 degrees to 1-by-1 degree), a slightly lower upper boundary (0.1 instead of 0.01hPa) with fewer levels (48 as opposed to 70), and substantial changes to the tropospheric physics package. This paper will address the performance of the GEOS-3/Terra DAS in the stratosphere. it focusses on the analyses (produced four times daily) and the five-day forecasts (produced twice daily). These were important for the meteorological support of the SAGE-3 Ozone Loss and Validation Experiment, based in Kiruna, Northern Sweden, in the winter of 1999/2000. It is shown that the analyses of basic meteorological fields (temperature, geopotential height, and horizontal wind) are in good agreement with those from other centers. The analyses captured the cold polar vortex which persisted through most of the winter. It is shown that forecasts (up to five days) tend to have a warm bias, which is important for the prediction of polar stratospheric clouds, which are triggered by temperatures of 195K (or lower). The importance of accurate upper tropospheric forecasts in predicting the stratospheric flow is highlighted in the context of the evolution of the shape of the stratospheric polar vortex. A prominent blocking high in the Atlantic region in January was an important factor determining the shape of the distorted lower stratospheric vortex; the predictive skill of these features was strongly coupled in the GEOS-3/Terra system.

Pawson, S.↗
NASA NTRS2000

Troposphere-Stratosphere Connections in Recent Northern Winters in NASA GEOS Assimilated Datasets

The northern winter stratosphere displays a wide range of interannual variability, much of which is believed to result from the response to the damping of upward-propagating waves. However, there is considerable (growing) evidence that the stratospheric state can also impact the tropospheric circulation. This issue will be examined using datasets generated in the Data Assimilation Office (DAO) at NASA's Goddard Space Flight Center. Just as the tropospheric circulation in each of these years was dominated by differing synoptic-scale structures, the stratospheric polar vortex also displayed different evolutions. The two extremes are the winter 1998/1999, when the stratosphere underwent a series of warming events (including two major warmings), and the winter 1999/2000, which was dominated by a persistent, cold polar vortex, often distorted by a dominant blocking pattern in the troposphere. This study will examine several operational and research-level versions of the DAO's systems. The 70-level-TRMM-system with a resolution of 2-by-2.5 degrees and the 48-level, 1-by-l-degree resolution ''Terra'' system were operational in 1998/1999 and 1999/2000, respectively. Research versions of the system used a 48-level, 2-by-2.5-degree configuration, which facilitates studies of the impact of vertical resolution. The study includes checks against independent datasets and error analyses, as well as the main issue of troposphere-stratosphere interactions.

Pawson, Steven↗
NASA NTRS2001

The NO(x)-HNO3 System in the Lower Stratosphere: Insights from In Situ Measurements and Implications of the J(HNO3)-[OH] Relationship

During the 1997 Photochemistry of Ozone Loss in the Arctic Region in Summer (POLARIS) mission, simultaneous in situ observations of NOx and HOx radicals, their precursors, and the radiation field were obtained in the lower stratosphere. We use these observations to evaluate the primary mechanisms that control NOx-HNO3 exchange and to understand their control over the partitioning between NO2 and HNO3 in regions of continuous sunlight. We calculate NOx production (PNOx) and loss (LNOx) in a manner directly constrained by the in situ measurements and current rate constant recommendations, using approaches for representing albedo, overhead O3 and [OH] that reduce model uncertainty. We find a consistent discrepancy of 18% between modeled rates of NOx production and loss (LNOx = 1.18P(sub NOx)), which is within the measurement uncertainty of +/- 27%. The partitioning between NOx production processes is [HNO3 + OH (41 +/- 2)%; HNO3 + hv (59 +/- 2)%] and between NOx loss processes is [NO2 + OH, 90% to >97%; BrONO2 + H2O, 10% to <3%]. The steady-state description of NOx-HNO3 exchange reveals the significant influence of the tight correlation between the photolysis rate of HNO3 and [OH] established by in situ measurements throughout the lower stratosphere. Parametrizing this relationship, we find: (1) the steady-state value of [NO2](sub 24h-avg)/[HNO3] in the continuously sunlit, lower stratosphere is a function only of temperature and number density; and (2) the partitioning of NOx production between HNO3 + OH and HNO3 + hv is nearly constant throughout most of the lower stratosphere. We describe a methodology (functions of latitude, day, temperature, and pressure) for accurately predicting the steady-state value of [NO2](sub 24h-avg)/[HNO3] and the partitioning of NOx production within these regions. The results establish a metric to compare observations of [NO2](sub 24h-avg)/[HNO3] within the continuously sunlit region and provide a simple diagnostic for evaluating the accuracy of models that attempt to describe the coupled NOx-HOx photochemistry in the lower stratosphere.

Perkins, K. K.↗
NASA NTRS1999

The Effect of Climate Change on Ozone Depletion through Changes in Stratospheric Water Vapour

Several studies have predicted substantial increases in Arctic ozone depletion due to the stratospheric cooling induced by increasing atmospheric CO2 concentrations. But climate change may additionally influence Arctic ozone depletion through changes in the water vapor cycle. Here we investigate this possibility by combining predictions of tropical tropopause temperatures from a general circulation model with results from a one-dimensional radiative convective model, recent progress in understanding the stratospheric water vapor budget, modelling of heterogeneous reaction rates and the results of a general circulation model on the radiative effect of increased water vapor. Whereas most of the stratosphere will cool as greenhouse-gas concentrations increase, the tropical tropopause may become warmer, resulting in an increase of the mean saturation mixing ratio of water vapor and hence an increased transport of water vapor from the troposphere to the stratosphere. Stratospheric water vapor concentration in the polar regions determines both the critical temperature below which heterogeneous reactions on cold aerosols become important (the mechanism driving enhanced ozone depletion) and the temperature of the Arctic vortex itself. Our results indicate that ozone loss in the later winter and spring Arctic vortex depends critically on water vapor variations which are forced by sea surface temperature changes in the tropics. This potentially important effect has not been taken into account in previous scenarios of Arctic ozone loss under climate change conditions.

Kirk-Davidoff, Daniel B.↗
NASA NTRS2001

Two-Dimensional Model Simulations of Interannual Variability in the Tropical Stratosphere

Meteorological data from the United Kingdom Meteorological Office (UKMO) and constituent data from the Upper Atmospheric Research Satellite (UARS) are used to construct yearly zonal mean dynamical fields for the 1990s for use in the GSFC 2-D chemistry and transport model. This allows for interannual dynamical variability to be included in the model constituent simulations. In this study, we focus on the tropical stratosphere. We find that the phase of quasi-biennial oscillation (QBO) signals in equatorial CH4, and profile and total column 03 data is resolved quite well using this empirically- based 2-D model transport framework. However. the QBO amplitudes in the model constituents are systematically underestimated relative to the observations at most levels. This deficiency is probably due in part to the limited vertical resolutions of the 2-D model and the UKMO and UARS input data sets. We find that using different heating rate calculations in the model affects the interannual and QBO amplitudes in the constituent fields, but has little impact on the phase. Sensitivity tests reveal that the QBO in transport dominates the ozone interannual variability in the lower stratosphere. with the effect of the temperature QBO being dominant in the tipper stratosphere via the strong temperature dependence of the ozone loss reaction rates. We also find that the QBO in odd nitrogen radicals, which is caused by the QBO modulated transport of NOy, plays a significant but not dominant role in determining the ozone QBO variability in the middle stratosphere. The model mean age of air is in good overall agreement with that determined from tropical lower,middle stratospheric OMS balloon observations of SF6 and CO2. The interannual variability of tile equatorial mean age in the model increases with altitude and maximizes near 40 km, with a range, of 4-5 years over the 1993-2000 time period.

Fleming, Eric L.↗