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Yue, G. K.

Publications and source records attributed to Yue, G. K..

At least 37 records · Page 2
All sourcesNASA NTRSDOE OSTI
NASA NTRS1987

Validation of SAM 2 and SAGE satellite

Presented are the results of a validation study of data obtained by the Stratospheric Aerosol and Gas Experiment I (SAGE I) and Stratospheric Aerosol Measurement II (SAM II) satellite experiments. The study includes the entire SAGE I data set (February 1979 - November 1981) and the first four and one-half years of SAM II data (October 1978 - February 1983). These data sets have been validated by their use in the analysis of dynamical, physical and chemical processes in the stratosphere. They have been compared with other existing data sets and the SAGE I and SAM II data sets intercompared where possible. The study has shown the data to be of great value in the study of the climatological behavior of stratospheric aerosols and ozone. Several scientific publications and user-oriented data summaries have appeared as a result of the work carried out under this contract.

Kent, G. S.↗
NASA NTRS1984

Latitudinal and altitudinal variation of size distribution of stratospheric aerosols inferred from SAGE aerosol extinction coefficient measurements at two wavelengths

A method of retrieving aerosol size distribution from the measured extinction of solar radiation at wavelengths of 0.45 microns and 1.0 microns has recently been proposed. This method is utilized to obtain latitudinal and altitudinal variations of size distributions of stratospheric aerosols from the Stratospheric Aerosol and Gas Experiment data for March 1979. Small particles are found in the lower stratosphere of the tropical region, and large particles are found at higher altitudes and latitudes in both hemispheres. Results of this study are consistent with the suggestion that the upper troposphere in tropical regions is a source of condensation nuclei in the stratosphere, and they become mature as they move to higher altitudes and latitude.

Yue, G. K.↗
NASA NTRS1984

A comparative study of aerosol extinction measurements made by the SAM II and SAGE satellite experiments

SAM II and SAGE are two satellite experiments designed to measure stratospheric aerosol extinction using the technique of solar occultation or limb extinction. Although each sensor is mounted aboard a different satellite, there are occasions when their measurement locations are nearly coincident, thereby providing opportunities for a measurement comparison. In this paper, the aerosol extinction profiles and daily contour plots for some of these events in 1979 are reported. The comparisons shown in this paper demonstrate that SAM II and SAGE are producing similar aerosol extinction profiles within their measurement errors and that since SAM II has been previously validated, these results show the validity of the SAGE aerosol measurements.

Yue, G. K.↗
NASA NTRS1983

Retrieval of stratospheric aerosol size distribution from atmospheric extinction of solar radiation at two wavelengths

A parametric study is presented of the effects of the size distribution and composition of stratospheric aerosols on the value R, the ratio of the extinction of solar radiation at wavelength 0.45 micron to the extinction at wavelength 1.0 micron. The aerosol size distributions under study comprise nine analytical expressions, including most of the stratospheric aerosol models used by investigators. The aerosol compositions considered are the supercooled sulfuric-acid droplets, with different weight percentages of H2SO4 in the aerosol. It is found that whereas R is not very sensitive to either the composition or the radii limits of the stratospheric aerosols under consideration, it is quite sensitive to the value of the variable parameter governing the mode radius of the size distribution of aerosol particles. The results of the parametric study underlie the method proposed here of retrieving the size distribution of aerosol particles in the stratosphere from the experimental results of the extinction of solar radiation at two wavelengths.

Yue, G. K.↗
NASA NTRS1983

Modelling atmospheric aerosol backscatter at CO2 laser wavelengths. I - Aerosol properties, modeling techniques, and associated problems. II - Modeled values in the atmosphere. III - Effects of changes in wavelength and ambient conditions

The various methods of calculating the atmospheric aerosol backscattering function, beta(CO2), both from measured aerosol characteristics and from optical measurements made at other wavelengths, are discussed in detail, with limits placed on their accuracy. The most significant factor in determining beta(CO2) is found to be the aerosol size distribution and concentration; this should be known accurately for particle radii up to at least 1 micron for stratospheric particles and 5 microns for tropospheric particles. Results are then presented from the modeling of the aerosol backscattering function at a wavelength of 10.6 microns in the lowest 20 km of the atmosphere. It is found that beta(CO2) varies from 10 to the -6th per m per sr in the planetary boundary layer to less than 10 to the -11th per m per sr in the stratosphere. It is next shown that, with the exception of (NH4)2SO4-containing aerosols, whose size distributions have relatively large numbers of small particles, the variation of backscattering with CO2 wavelength is less than a factor of approximately 3. For such (NH4)2SO4 aerosol distributions, however, the variation of backscatter function with CO2 wavelengths between 9.1 and 11.1 microns may reach one order of magnitude.

Kent, G.S.↗
NASA NTRS1982

Atmospheric Backscatter Model Development for CO Sub 2 Wavelengths

The results of investigations into the problems of modeling atmospheric backscatter from aerosols, in the lowest 20 km of the atmosphere, at CO2 wavelengths are presented, along with a summary of the relevant aerosol characteristics and their variability, and a discussion of the measurement techniques and errors involved. The different methods of calculating the aerosol backscattering function, both from measured aerosol characteristics and from optical measurements made at other wavelengths, are discussed in detail, and limits are placed on the accuracy of these methods. The effects of changing atmospheric humidity and temperature on the backscatter are analyzed and related to the actual atmosphere. Finally, the results of modeling CO2 backscatter in the atmosphere are presented and the variation with height and geographic location discussed, and limits placed on the magnitude of the backscattering function. Conclusions regarding modeling techniques and modeled atmospheric backscatter values are presented in tabular form.

Deepak, A.↗
NASA NTRS1982

Stratospheric aerosol effects from Soufriere Volcano as measured by the SAGE satellite system

During its April 1979 eruption series, Soufriere Volcano produced two major stratospheric plumes that the SAGE (Stratospheric Aerosol and Gas Experiment) satellite system tracked to West Africa and the North Atlantic Ocean. The total mass of these plumes, whose movement and dispersion are in agreement with those deduced from meteorological data and dispersion theory, was less than 0.5 percent of the global stratospheric aerosol burden; no significant temperature or climate perturbation is therefore expected.

Mccormick, M. P.↗
NASA NTRS1982

Calculation of composition distribution of ultrafine ion-H2O-H2SO4 clusters using a modified binary ion nucleation theory

Thomson's ion nucleation theory was modified to include the effects of curvature dependence of the microscopic surface tension of field dependent, nonlinear, dielectric properties of the liquid; and of sulfuric acid hydrate formation in binary mixtures of water and sulfuric acid vapors. The modified theory leads to a broadening of the ion cluster spectrum, and shifts it towards larger numbers of H2O and H2SO4 molecules. Whether there is more shifting towards larger numbers of H2O or H2SO4 molecules depends on the relative humidity and relative acidity of the mixture. Usually, a broadening of the spectrum is accompanied by a lowering of the mean cluster intensity. For fixed values of relative humidity and relative acidity, a similar broadening pattern is observed when the temperature is lowered. These features of the modified theory illustrate that a trace of sulfuric acid can facilitate the formation of ultrafine, stable, prenucleation ion clusters as well as the growth of the prenucleation ion clusters towards the critical saddle point conditions, even with low values of relative humidity and relative acidity.

Singh, J. J.↗
NASA NTRS1982

Temperature dependence of the formation of sulfate aerosols in the stratosphere

Classical nucleation theory is used in calculations of the temperature dependence of the characteristics and nucleation rates of sulfate aerosols in the binary H2SO4-H2O vapor mixture, in order to assess the influence of temperature on the formation of sulfate aerosols in the stratosphere, and to explore the possibility of new particle formation through homogeneous nucleation processes at regions where temperature is as low as -75 C, rather than the often-assumed -50 or -55 C. Calculation results indicate that the number of particles formed at a lower temperature is larger by several orders of magnitude than at higher temperatures, when water and sulfuric acid vapor concentrations are kept constant, and that large quantities of ultrafine particles which cannot be detected by conventional methods may exist at low-temperature stratospheric regions.

Yue, G. K.↗
NASA NTRS1982

Ion-induced nucleation in a binary mixture

Recent ion-induced nucleation studies in a binary mixture of H2O and H2SO4 vapors indicate that conventional classical nucleation theories cannot account for the experimentally observed ion-H2O-H2SO4 microcluster spectra. An empirical-analytical, semi-molecular theory of nucleation of a binary mixture of vapors on ions has been developed. This theory includes molecular approach to ion-induced changes in dielectric properties in the immediate neighborhood of an ion core as well as the size dependence of the surface tension of the microcluster. In addition to gaseous sulfuric acid and water molecules, the effect of ion-hydrates and sulfuric acid hydrates has also been considered. This theory is further simplified by using an empirical correction factor for the electrostatic term. This correction factor has been obtained by comparing the simplified model with the molecular dynamics calculations for selected ion hydrate formation. These two theoretical models are then compared with the classical theory for a variety of experimental conditions.

Smith, A. C.↗
NASA NTRS1982

Experimental studies of the ion-induced binary nucleation

The aerosol nucleation phenomenon is studied in a binary mixture of H2O and H2SO4 vapors in a carrier stream of N2 gas in the presence of ions produced by a low energy beta source. Cluster spectra of the form (H2SO4)n.(H2O)m.H(+) are identified from the measurements of the cluster masses using a quadrupole mass spectrometer. Results show that the number of H2SO4 molecules in the clusters ranged from 0 to 6 whereas the number of H2O molecules ranged from 1 to 20 depending on the concentration of H2SO4 and H2O vapors in the reaction chamber. Among other conclusions, it is noted that a large number of clusters of the type investigated are formed in the presence of an ionization source even when the partial pressures of H2SO4 and H2O are very low. The cluster composition is found to be strongly dependent on the r.h. and r.a. values in the reaction cell. The cluster spectrum (n, m, l) contains a large number of low n- and low m-value clusters when the reaction cell pressure is high.

Singh, J. J.↗
NASA NTRS1981

SAGE measurements of the stratospheric aerosol dispersion and loading from the Soufriere Volcano

Explosions of the Soufriere volcano on the Caribbean Island of St. Vincent reduced two major stratospheric plumes which the stratospheric aerosol and gas experiment (SAGE) satellite tracked to West Africa and the North Atlantic Ocean. The total mass of the stratospheric ejecta measured is less than 0.5% of the global stratospheric aerosol burden. No significant temperature or climate perturbation is expected. It is found that the movement and dispersion of the plumes agree with those deduced from high altitude meteorological data and dispersion theory. The stratospheric aerosol dispersion and loading from the Soufrier volcano was measured.

Mccormick, M. P.↗
NASA NTRS1981

Modeling of growth and evaporation effects on the extinction of 1.0-micron solar radiation traversing stratospheric sulfuric acid aerosols

The effects of growth and evaporation of stratospheric sulfuric acid aerosols on the extinction of solar radiation traversing such an aerosol medium are reported for the case of 1.0-micron solar radiation. Modeling results show that aerosol extinction is not very sensitive to the change of ambient water vapor concentration, but is sensitive to ambient temperature changes, especially at low ambient temperatures and high ambient water vapor concentration. A clarification is given of the effects of initial aerosol size distribution and composition on the change of aerosol extinction due to growth and evaporation processes. It is shown that experiments designed to observe solar radiation extinction of aerosols may also be applied to the determination of observed changes in aerosol optical properties, environmental parameters, or the physical and optical characteristics of sulfate aerosols.

Yue, G. K.↗
NASA NTRS1981

The formation and growth of sulfate aerosols in the stratosphere

The critical compositions, critical radii, and nucleation rates of sulfuric acid droplets formed through homogeneous heteromolecular nucleation process in the stratosphere under a variety of ambient conditions are calculated. Results are plotted as a function of H2SO4 concentration and H2O concentration so that characteristics of sulfate aerosols can be quickly estimated whenever environmental conditions are known. The effect of the uncertainty in the saturated vapor pressure of H2SO4 on the estimated properties of sulfate aerosols is elucidated. Plottings are presented that illustrate the relative importance of new particle formation by homogeneous nucleation vs growth by heteromolecular condensation on pre-existing nuclei in the stratosphere. The effects of ambient conditions, such as the concentrations of H2SO4 and H2O, the average stratospheric particle radius, and the number concentration of pre-existing nuclei on the relative importance of these two competing processes are discussed.

Yue, G. K.↗
NASA NTRS1981

Modeling the formation of ion clusters by applying classical nucleation theory

Experiments have been conducted to study the clustering of atmospheric trace gases around ion cores (Castleman and Tang, 1972; Searcy and Fenn, 1974; Castleman, 1978). The classical liquid-drop model is used to investigate this ion-induced formation mechanism. Results obtained from models of the distribution of Pb(+)-(H2O)n and H(+)-(H2O)n type clusters under various conditions are compared with experimental results. The distribution of water-ion clusters in the atmosphere as a function of altitude is calculated. In situ measurements of the water-ion cluster distributions in the upper atmosphere are then compared with present predictions. It is concluded that the classical nucleation theory can be used to predict rough estimates for ion cluster sizes under many conditions.

Yue, G. K.↗
NASA NTRS1981

A model study of the diurnal variation of mesospheric O3

Diurnal variation of ozone between 50 to 80 km is studied for both oxygen-only and O-N-H-C atmospheres. The temporal variation of ozone density along the ray path as well as that due to the change in the local zenith angle are included in the model computations. The difference between cases with and without the temporal variation of ozone density, is examined. It is found that the inclusion of this variation reduces the ozone concentration at all altitudes. In addition, the greatest effect on the ozone concentration is during sunrise and sunset.

Wang, P. H.↗
NASA NTRS1980

Modeling of growth, evaporation and sedimentation effects on transmission of visible and IR laser beams in artificial fogs

The dense polydisperse aerosol particles in a quiet chamber may spontaneously go through different microphysical processes including gravitational sedimentation, thermal coagulation, and growth or evaporation. In an earlier paper, we presented the results of a parametric study of the combined and separate effects of thermal coagulation and sedimentation on the time dependence of extinction of four visible and IR laser beams traversing an aerosol medium. As a continuation of this series of studies, the separate and combined effects of growth or evaporation and gravitational sedimentation on the time dependence of extinction of the same four visible and IR laser beams traversing in artificial fogs will be reported in this paper. The method of numerically modeling the change of water droplet size distribution with time due to growth/evaporation and the cutoff of larger aerosols due to gravitational sedimentation is described in detail. Factors governing the relative importance of these two processes are discussed. Results of this study show that the relative humidity or ambient temperature is a crucial parameter in determining the optical depth of the water droplet and aerosol media undergoing microphysical processes.

Yue, G. K.↗