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At least 1,171 records · Page 65
All sourcesNASA NTRSDOE OSTI
NASA NTRS1982

Altitude variations in stratospheric aerosols of a tropical region

To investigate the possibility that significant amounts of tropical tropospheric air may be convectively introduced into the stratosphere, aerosol samplings over Panama were made at various altitudes using a wire impactor collector. The percentage of particle sizes less than the mean mode decreases with height above the tropopause, suggesting depletion of small particles, possibly due to coagulation. Larger aerosols (greater than 0.3 micron in diam.) are more abundant farther above the tropopause, indicating growth, mainly by condensation. The total particle concentration decreases with increasing height above the tropopause, and also with increasing temperature. Aerosols containing smaller-size particles are thus found closer to the tropopause, and larger-size, more-evolved aerosols occur at higher altitudes. These data indicate that convective activity at the Intertropical Convergence Zone may be a source mechanism for stratospheric aerosols.

Goodman, J.↗
NASA NTRS1981

Satellite profile measurements of stratospheric ozone

A description is presented of preliminary results obtained in connection with the Stratospheric Aerosol and Gas Experiment (SAGE). SAGE, which uses a limb scanning solar radiometer, is an experiment aboard the Applications Explorer Mission 2 spacecraft which was launched on February 18, 1979. The instrument utilizes the technique of solar occultation to measure limb-path atmospheric extinction profiles which are inverted to yield vertical profiles of various atmospheric constituents in the latitude range from 79 deg South to 79 deg North. The ozone spectral channel is centered at 0.60 micrometers in the middle of the Chappuis absorption band. The general characteristics of the ozone profile measurements are shown in a graph. Each profile represents a day's average of approximately 15 measurements at the latitude band indicated. The SAGE ozone measurements are generating a highly detailed picture of the stratospheric ozone distribution.

Mccormick, M. P.↗
NASA NTRS1982

Vacillation, sudden warmings and potential enstrophy balance in the stratosphere

The balance of potential enstrophy and its relationship to vacillation cycles and the sudden warming is studied for a beta-channel model of the stratosphere. It is shown that the mean flow cannot be steady in the presence of large-amplitude quasi-geostrophic waves (approximately 1-0.25 geopotential kilometers /gpkm/) when any dissipation is present, and the maximum wave amplitude allowed is approximately 2 gpkm. If wave forcing (transience plus dissipation) is artificially maintained, the mean flow decelerates slowly at first then explosively as the potential vorticity gradient of the basic state is wiped out over the channel. This process is called wave saturation. The initial phase of the explosive deceleration resembles both the observed and modeled mean flow evolution during a sudden stratospheric warming. A simple vacillation model based upon these ideas shows remarkable similarity to the results of Holton and Mass (1976) and Davies (1981).

Schoeberl, M. R.↗
NASA NTRS1982

Precursor gases of aerosols in the Mount St. Helens eruption plumes at stratospheric altitudes

Nineteen stratospheric samples from the eruption plumes of Mount St. Helens were collected in five flight experiments. The plume samples were collected at various altitudes from 13.1 to 20.7 km by using the Ames cryogenic sampling system on board the NASA U-2 aircraft. The enriched, cryogenically collected samples were analyzed by chromatography. The concentrations of aerosols precursor gases (OCS, SO2, and CS2), CH3Cl, N2O, CF2Cl2, and CFCl3 were measured by gas chromatography. Large enhancement of the mixing ratio of SO2 and moderate enhancement of CS2 and OCS were found in the plume samples compared with similar measurement under pre-volcanic conditions. A fast decay rate of the SO2 mixing ratio in the plume was observed. Measurement of Cl(-), SO2(2-), and NO3(-) by ion chromatography was also carried out on water solutions prepared from the plume samples. The results obtained with this technique imply large mixing ratios of HCl, (NO + NO2 + HNO3), and SO2, in which these constituents are the respective sources of the anions. Measurement of the Rn222 concentration in the plume was made. Other stratospheric constituents in the plume samples, such as H2O, CO2, CH4, and CO, were also observed.

Inn, E. C. Y.↗
NASA NTRS1982

Time variations of aerosols in the stratosphere following Mount St. Helens eruptions

Samples of stratospheric aerosols collected with U-2 aircraft for several months following the first three major eruptions of Mount St. Helens were analyzed for ash and liquid acid content. Ash grain sizes and compositions vary depending on collection altitude, location within the drifting cloud, and days following their injection. s computers Size distributions of ash particles vary with altitude. Generally small particles are depleted more rapidly at low altitudes (12 km) than at higher altitudes (17-18 km). Although samples collected 1 day after the first eruption of May 18, 1980, were dry, flow marks on the aircraft indicated parts of the cloud contained heavy acid concentrations. Indeed, all other samples obtained within 1 to 4 days after later eruptions (May 25 and June 12, 1980) were covered with copious amounts of liquid acid. Proportions of liquid to ash varied considerably depending on sampling location and cloud age. Because the acid-coated ash globules were large, they rapidly fell from the stratosphere until, by late June 1980, only a residue of acid droplets remained. Size distributions and concentrations of these droplets varied considerably.

Farlow, N. H.↗
NASA NTRS1982

Ground-based and airborne measurements of the Mount St. Helens stratospheric effluents

Shortly after the 18 May eruption, a series of airborne lidar flights were made over the Eastern United States. During the same period, ground-based systems were activated throughout the world. The available worldwide lidar data is put together in a consistent set. These data show the dispersion of material at different altitudes during the early global circuits. The material in the lower stratosphere and upper troposphere was very patchy in horizontal extent with backscattering ratio values over the east coast of the United States greater than 100 at the ruby wavelength of 0.6943. Two wavelength ratios and depolarization values for the material in the lower stratosphere (12 to 18 km) appear to have returned to the pre-18 May values within a month after the eruption and this indicated a rapid conversion to spherical shapes and normal indices of refraction. The material above 20 km moved slowly westward while most of the ejecta moved eastward at various speeds and directions which varied considerably with altitude. The westward material was detected first by the Japanese lidar system and then subsequently by the European and American ground-based systems. It circuited the globe in about 60 days. An airborne lidar flight in early September across the continental United States showed the layers to have homogenized considerably one broad layer between about 14 and 21 km peaking at 18 to 19 km and another more intermittent thin layer between 21 and 22 km. The ruby peak backscattering ratio of the broad layer was between 1.3 and 1.5.

Mccormick, M. P.↗
NASA NTRS1981

Spectral line inversion for sounding of stratospheric minor constituents by infrared heterodyne technique from balloon altitudes

A combination of two different techniques for the inversion of infrared laser heterodyne measurements of tenuous gases in the stratosphere by solar occulation is presented which incorporates the advantages of each technique. An experimental approach and inversion technique are developed which optimize the retrieval of concentration profiles by incorporating the onion peel collection scheme into the spectral inversion technique. A description of an infrared heterodyne spectrometer and the mode of observations for solar occulation measurement is presented, and the results of inversions of some synthetic ClO spectral lines corresponding to solar occulation limb-scans of the stratosphere are examined. A comparison between the new techniques and one of the current techniques indicates that considerable improvement in the accuracy of the retrieved profiles can be achieved. It is found that noise affects the accuracy of both techniques but not in a straightforward manner since there is interaction between the noise level, noise propagation through inversion, and the number of scans leading to an optimum retrieval.

Abbas, M. M.↗
NASA NTRS1982

An inventory of particles from stratospheric collectors - Extraterrestrial and otherwise

Examination of 526 particles in the 2-50 micron size range obtained from stratospheric impaction collectors has shown that most of them fit into one of three groups on a simple plot of Mg/Si versus Al/Si energy dispersive X ray peak ratios. The particles within a given group exhibit strong correlations in composition and mineralogy to one another, and the groups appear to largely consist either of earth crustal, manmade, or extraterrestrial materials. The temporal variability and relatively flat size distribution of material in the earth crustal group, in particular, suggests an aircraft-related, as opposed to stratospheric, source for these particles.

Fraundorf, P.↗
NASA NTRS1983

Stationary waves in the winter stratosphere - Seasonal and interannual variability

The zonal mean wind and stationary waves 1 and 2 in the January 1973 - February 1977 northern winter stratosphere are determined, on the basis of monthly average conventional and satellite data, by diagnosing wave propagation with the aid of the Eliassen-Palm (1961) flux and the refractive index-squared. Both the seasonal trend and the interannual variability of the amplitude of wave 1 reflect variations in zonal mean wind and the corresponding refractive index. During each year studied, a midwinter minimum in wave 1 amplitude occurs at and above 1 mb as a consequence of a midwinter curvature maximum. In three of the four sudden warmings of wave 1 type which occurred during the study period, the month prior to the warming was characterized by abnormally weak winds near the climatological mean jet, a detached secondary jet at low and high altitude, and abnormally large wave 1 amplitude throughout the upper and middle stratosphere.

Smith, A. K.↗
NASA NTRS1983

The Delta band dissociation of nitric oxide - A potential mechanism for coupling thermospheric variations to the mesosphere and stratosphere

Depletion of solar radiation at discrete wavelengths by nitric oxide has a significant impact on the dissociation rate of this gas in the delta(0, 0) and delta(1, 0) bands. Inclusion of the opacity provided by a typical NO profile reduces the dissociation rate in the upper stratosphere to 50-75 pct of that predicted when the optical depth calculation omits this contribution. A substantial fraction of the NO column abundance as measured near the stratopause resides in the lower thermosphere where correlations of NO with solar and magnetic activity are well documented. Variations in the thermospheric NO abundance therefore modulate the radiation field at the precise wavelengths absorbed by this molecule in the mesosphere and upper stratosphere. Predicted changes in the dissociation rate arising from a varying thermospheric opacity exceed 8 pct throughout the mesosphere and reach 15 pct between 65 km and 95 km.

Frederick, J. E.↗
NASA NTRS1983

A study of stratospheric vacillations and sudden warmings on a beta-plane. I - Single wave-mean flow interaction

A beta-plane model of the stratosphere is used to investigate the planetary-wave amplitude vacillations first reported by Holton and Mass (1976). This model differs from theirs in allowing more horizontal modes. For low surface wave amplitudes, a new class of solutions is found which exhibits a stationary, partially reflecting critical line at steady state. The critical line equilibrates at lower altitudes as the wave forcing is increased. Vacillating solutions occur when the steady state critical line occurs near the lower boundary. The maximum wave amplitude and the maximum steady-state wave amplitude found in the model are in the ratio of 2:1, in good agreement with theoretical predictions. The maximum wave amplitude never exceeds 2200 gpm which is quite close to the saturation limit predicted by Schoeberl (1982). An analysis of the statistics of slowly and rapidly vacillating flows shows that both the wave and zonal mean variances are important in determining the time mean, zonal mean dynamics of the upper stratosphere.

Schoeberl, M. R.↗
NASA NTRS1983

Design and performance of the Stratospheric Aerosol and Gas Experiment II (SAGE II) instrument

Design and performance data are analyzed for the Stratospheric Aerosol and Gas Experiment II (SAGE II) instrument, which has been developed for the NASA Earth Radiation Budget Satellite (ERBS). SAGE II is designed to monitor globally, from 70 degrees S to 70 degrees N latitude, the vertical distribution of stratospheric aerosols, ozone, water vapor, and nitrogen dioxide by measuring the extinction of solar radiation through the earth's atmosphere during the ERBS observatory solar occultations. A flat scanning mirror reflects solar radiation into a Cassegrain type telescope, which forms a solar image on the entrance slit of a grating spectrometer. The instantaneous-field-of-view of the SAGE II is scanned along the vertical solar diameter by the elevation scan mirror. The optical system is contained within an azimuth gimbal which tracks the solar radiometric centroid during the data event, while the spectrometer isolates seven spectral wavelengths from 0.385-1.02 micrometers. The seven channels of the spectrometer use silicon photodiode dedectors operated in the photovoltaic mode. The detector outputs are multiplexed into a serial data stream for readout by the ERBS telemetry system, with each output being sampled 64 times per second and digitized to 12 bit resolution.

Zaun, N. H.↗
NASA NTRS1983

Asymmetries of the upper stratospheric ozone distribution between two hemispheres

In connection with the eccentricity of the earth's orbit, conditions of solar radiation are not strictly symmetrical for the two hemispheres. The intensity of solar irradiation is approximately 6.6 percent higher near perihelion than near aphelion. As the ozone densities in the upper stratosphere and mesosphere are mainly controlled by photochemical processes, the asymmetry of irradiation conditions for both hemispheres could result in corresponding asymmetries regarding the ozone content. The present investigation is concerned with this possibility. The investigation takes into account Nimbus-7 and Nimbus-4 satellite data. It is found that the hemispheric asymmetries of the ozone distribution in the summer mesosphere and upper stratosphere are fully ascribable to the hemispheric temperature differences due to the combined effects of the earth's orbital ellipticity and its tilted spin axis from the ecliptic plane. The wintertime hemispheric asymmetries imply the presence of additional effects.

Maeda, K.↗
NASA NTRS1983

The function and response of an improved stratospheric condensation nucleus counter

An improved condensation nucleus counter (CNC) for use in the stratosphere is described. The University of Minnesota CNC (UMCNC) has a sequential saturator and condenser and uses n-butyl alcohol as the working fluid. The use of a coaxial saturator flow, with aerosol in the center and filtered, alcohol-laden air around it, speeds the response of this instrument and improves its stability as pressure changes. The counting efficiency has been studied as a function of particle size and pressure. The UMCNC provides an accurate measure of submicron aerosol concentration as long as the number distribution is not dominated by sub-0.02 micron diameter aerosol. The response of the UMCNC is compared with that of other stratospheric condensation nucleus counters, and the results of a (near) comparison with a balloon-borne condensation nucleus counter are presented. The UMCNC has operated 14 times on a NASA U-2 aircraft at altitudes from 8 to 21.5 km.

Wilson, J. C.↗
NASA NTRS1983

Balloon-borne diode-laser absorption spectrometer for measurements of stratospheric trace species

An instrument has been designed for the measurement of stratospheric trace species which utilizes tunable infrared diode lasers as sources for sensitive in situ absorption spectroscopy in selected wavelength regions. This instrument, the Balloon-Borne Laser In Situ Sensor (BLISS), is a high-resolution absorption spectrometer designed to provide measurements of the concentrations of stratospheric species and their diurnal variations. The instrument employs second-harmonic detection of the absorption of tunable diode laser (TDL) radiation (3-30 microns) in a 1 km path length defined by a retroreflector lowered 0.5 km below the BLISS gondola. Retroreflector tracking under microprocessor control is obtained using a He-Ne laser and coaligned TV camera with CID imaging. Simultaneous measurements of molecular species in the 20-40 km altitude range will be performed using four TDLs, with the predicted minimum-detectable mixing ratio at 30 km being typically less than or equal to 0.1 ppbv.

Menzies, R. T.↗
NASA NTRS1983

Stratospheric aerosol mass and latitudinal distribution of the El Chichon eruption cloud for October 1982

The eruptions of El Chicon in Mexico during March and April, 1982, produced the largest enhancements in stratospheric aerosols, which were experienced in at least the last 20 years. An experimental survey flight was conducted in October-November 1982 to underfly El Chichon's eruption cloud and to map out its latitudinal distribution. A NASA aircraft was flown between 46 deg N latitude and 46 deg S latitude in a coordinated field campaign. The present investigation is concerned with the results of lidar stratospheric measurements taken over the entire mission. The employed airborne lidar system consists of a ruby laser, nominally emitting 1 joule/pulse at 0.5 pulse/sec during flight, and a 35.6-cm receiving Cassegrainian-configured telescope. The lidar data presented are described in two forms, taking into account the lidar backscattering ratio and the integrated aerosol backscattering function.

Mccormick, M. P.↗
NASA NTRS1984

Toward a complete inventory of stratospheric dust particles with implications and their classification

As the Earth travels about the Sun it continuously sweeps up material laying in its path. The material includes dust-sized fragments of the meteors, comets and asteroids that have passed by as well as much older particles from out between the stars. These grains first become caught in the mesosphere and then slowly pass down through the stratosphere and the troposphere, finally raining down upon the Earth's surface. In the stratosphere the cosmic dust particles encounter increasing amounts of contaminants from the Earth. At the highest reaches of Earth's atmosphere these contaminants consists mainly of dust from the most explosive volcanoes, rocket exhaust, and other manmade space debris. In the troposphere windborne particles and pollen become an increasingly larger fraction of the atmospheric dust load. An increased knowledge of the nature of cosmic particles is suggested.

Zolensky, M. E.↗
NASA NTRS1984

Advanced laser stratospheric monitoring systems analyses

This report describes the software support supplied by Systems and Applied Sciences Corporation for the study of Advanced Laser Stratospheric Monitoring Systems Analyses under contract No. NAS1-15806. This report discusses improvements to the Langley spectroscopic data base, development of LHS instrument control software and data analyses and validation software. The effect of diurnal variations on the retrieved concentrations of NO, NO2 and C L O from a space and balloon borne measurement platform are discussed along with the selection of optimum IF channels for sensing stratospheric species from space.

Larsen, J. C.↗