Showing papers on "Haze published in 1990"

Ice haze, snow, and the Mars water cycle

Abstract: Light curves and extinction profiles derived from Martian limb observations are used to constrain the atmospheric temperature structure in regions of the atmosphere with thin haze and to analyze the haze particle properties and atmospheric eddy mixing. Temperature between 170 and 190 K are obtained for three cases at levels in the atmosphere ranging from 20 to 50 km. Eddy diffusion coefficients around 100,000 sq cm/s, typical of a nonconvecting atmosphere, are derived in the haze regions at times when the atmosphere is relatively clear of dust. This parameter apparently changes by more than three orders of magnitude with season and local conditions. The derived particle size parameter varies systematically by more than an order of magnitude with condensation level, in such a way that the characteristic fall time is always about one Martian day. Ice hazes provide a mechanism for scavenging water vapor in the thin Mars atmosphere and may play a key role in the seasonal cycle of water on Mars.

Scatterers in Triton's Atmosphere: Implications for the Seasonal Volatile Cycle.

Abstract: Nitrogen and methane ices on the surface of Triton, Neptune's largest satellite, are exchanged between the summer and winter hemispheres on a seasonal time scale. Images of the satellite's sky obtained by the Voyager 2 spacecraft show the presence of several types of scattering materials that provide insights into this seasonal cycle of volatiles. Discrete clouds, probably composed of N2 ice particles, arise in regions of active sublimation. They are found chiefly poloward of 30 deg S in the southern, summer hemisphere. Haze particles, probably made of hydrocarbon ices, are present above most, but not all places. Recent snowfall may have occurred at low southern latitudes in places where they are absent. The latent heat released in the formation of the discrete clouds may have a major impact on the thermal balance of the lower atmosphere. Triton may have been less red at the time of the Voyager flyby than 12 years earlier due to recent N2 snowfall at a wide range of latitudes.

Haze and other aerosol components in late winter Arctic Alaska, 1986

Abstract: Three coarse and five fine aerosol components of different elemental compositions were identified at Barrow, Alaska, from March 17 to April 21, 1986, resolved by absolute principal component analyses of element concentrations in 280 sequential coarse and fine size fraction time step samples. In the coarse (> 2.5 μm), two components C-1 and C-2 had abundant Si, S, Cl, K, and Ca, but no Al, and together contained 85% of coarse S. Their compositions resembled expected products of carbonaceous fuel combustion, with Si being volatilized by carbon reduction and other metals volatilized perhaps as chloride salts. C-1, with high trace metal contents, might be from nonferrous smelting, whereas C-2, with high Fe, might be associated with conventional coal combustion. Both appeared semi-aged with respect to acidic gas uptake because the S chemical equivalents were less than those of metals contributing to alkalinity. When combined with Cl, S was close to the metal equivalents, indicating complete acid-base titration. A strong concentration rise of C-1 and C-2 occurred from March 25 to April 2 during a haze event, although C-1 was also present at other times. Air trajectories showed that air masses arrived at Barrow during the haze event from eastern or northern Europe. The third component C-3 was a dust aerosol rich in Al that contained high S but low Cl, suggesting saturation with H2SO4 and therefore aged and regional aerosols perhaps typical of the late winter Arctic. No major change in its concentration was observed to correspond to synoptic events. In the fine (< 2.5 μm), five components represent a sea-salt aerosol, an S-rich aerosol with some Si, K, Ca, and Fe, a trace metal aerosol, an Al-rich dust, and a marine product with Br, S, and Cl. The sea-salt was found only in three plumes when synoptic meteorology and air trajectories suggested origins in the North Pacific. The S-rich aerosol, accounting for 73% of S and 40% of Si, was enhanced during the haze event by 75%, and existed over the entire period at rather high levels and might be due to SO2 oxidation and condensation on fine Si-rich particles. The trace metal aerosol was always present and could have been generated from nonferrous smelters at lower latitudes. The Al-rich dust particles contained 7% of S and were similar to component C-3. The marine aerosol contained 74% of Br, 69% of Cl, and 20% of S, and could be from oxidation of marine biogenic Br and S gases. All but the sea-salt were present at Barrow throughout the period, with no clear relation to air trajectories or synoptic meteorology. The results show that certain winter meteorological conditions favor pollutant transport from lower latitudes to the Arctic. But while haze is related to industrial pollutants, other nonpollution products are present in the winter Arctic and may be important constituents of haze. They also show that by careful data reduction and meteorological analysis, the sources and transport pathways of haze may be better understood.

Effect of free radicals on haze formation in beer.

Abstract: An analytical method for determining proanthocyanidins by HPLC-electrochemical detection was developed, and the effect of free radicals on chill haze formation in beer was studied. Addition of H 2 O 2 and irradiation with 60 Co γ-rays accelerated the degradation of the proanthocyanidins and formation of chill haze in beer, while the addition of a metal scavenger, a H 2 O 2 decomposer, and free-radical scavengers inhibited these phenomena

Sulfur in particles in Arctic hazes derived from airborne in situ and lidar measurements

Abstract: Quantitative information is needed on arctic hazes in order to determine their effects on the radiation budget, clouds, the albedo and chemical properties of the arctic snowpack, and on ecosystems in the Arctic. Using airborne observations from lidar, and in situ measurements of particle light-scattering coefficients, aerosol size distributions and meteorological parameters, we have related backscattering measured by the lidar to the mass concentrations of particles in two mesoscale haze layers encountered in the North American Arctic. Assuming that the haze particles were composed of H2SO4 in thermodynamic equilibrium with the ambient air, good agreement is obtained between sulfur concentrations measured on filters and those derived from the particle size distributions and lidar measurements. Time-height cross sections are shown of the airborne concentrations of sulfur in particles derived from lidar backscatter measurements in a haze layer. The average concentrations of sulfur in accumulation mode particles in the two haze layers were 0.3 and 0.4 μg m−3, and the maximum concentration was ∼3 μg m−3, with substantial horizontal and vertical variability. We estimate lower limits for the total sulfur in particles in the two haze layers to be ∼3x;104 and ∼1x105 kg, respectively.

Reference wafer for haze calibration

Abstract: A standard for calibrating a wafer surface inspection optical scanner, particularly a system for measuring haze. The reference wafer (10) contains sections (12) divided into subsections (16), each subsection having a quasi-random pattern of light scattering features on an otherwise polished surface of the wafer. The quasi-random pattern of features is formed by creating a random pattern of pits (20) within tiny areas (18) of the subsection and repeating that pattern. The random pattern of pits covers an area less than the area of the spot of a scanning beam used by the wafer surface inspection system. By randomizing the pattern of pits within the scanning beam, the scattered light does not produce interference patterns and thus the scattered light is more isotropic. A direct measurement of the amount of haze on the reference wafer can be obtained from measuring the amount of scattered light caused by the pits. Since this level of scattering is known beforehand to correspond to a certain level of haze, the wafer surface inspection system can then be calibrated to accurately measure haze on surfaces of non-reference wafers.

An Analysis of Regional Haze Using Tracers of Opportunity

Abstract: A two-year record of hourly concentrations of halocarbon tracers (methylchloroform and perchloroethylene) and hourly averages of particle light scattering (Bsp) has been analyzed In an effort to understand the sources of haze In the U.S. southwestern deserts and mountains. Measurements were taken on top of Spirit Mountain in southern Nevada. In conjunction with photographs used to interpret visual quality, haze episodes at Spirit Mountain were usually coincident with elevated concentrations of tracers originating from urban sources. Haze obscured an 88-km-distant mountain 17 percent of the total observation time. Of those Incidents, 69 percent were associated with long-range transport of haze from the Los Angeles Basin.

Airborne Lidar Observations during AGASP-2

Abstract: Sample observations of the lower troposphere made by airborne lidar during the Arctic Gas and Aerosol Sampling Program-2 (AGASP-2) are shown for the area of Thule, Greenland. The lidar detected multiple haze layers, dense water clouds, ice crystal precipitation, and other features of interest over northern Greenland and the pack ice of Baffin Bay. The observations attest to the utility of a relatively simple airborne aerosol backscatter lidar in support of atmospheric studies in Arctic and Antarctic regions.

An Optical Device for the Detection of Clouds and Fog

Abstract: A simple, low-cost optical fog detector has been developed. The principle of operation lies in the detection of near-forward scattered light. The unconventional in-line arrangement of light source and detector, in combination with the centrally placed light stopper, enables the use of readily available devices in which optics and electronics are integrated, thus reducing manufacturing costs. The performance of the device is studied in the field as well as in a facility in which a well-defined fog can be produced. In addition, the response of the device as a function of fog droplet diameter is calculated. Both the experiments as well as the calculations show that the instrument has a good response to visibility reductions caused by water droplets within the size range encountered in fog and clouds, whereas the instrument is not sensitive to visibility reductions caused by larger droplets (drizzle or rain) or by haze.

An In-Depth Assessment of Internal Contamination in the Wide Field/Planetary Camera

Abstract: Following thermal vacuum/thermal balance testing, a gray haze was discovered on the corners of the Hubble Space Telescope Wide-Field/Planetary Camera aperture window. The phenomenon was suggested to be a result of molecular transport from a low-outgassig structural adhesive. Detailed analysis, both chemical and analytical, were conducted to assess the formation of the haze. Each material was considered individually, as it was not known if the actual contamination was a result of one, many, or possibly none of the materials considered. Results of the analytical assessment and the comparison with the chemical analyses provided incontrovertible evidence as to the cause of the window haze. The resultant cleanup and subsequent elimination of the problem are also addressed.

External effects correction of Landsat Thematic Mapper data

Abstract: A procedure has been developed to estimate and correct for external effects (haze level, solar zenith angle) in a Landsat Thematic Mapper scene. The procedure is based on the Dave model and uses a scatterplot-matching technique to estimate haze level directly from the scene data. A means for dealing with haze that spatially varies in density over a large scene is also included. The effectiveness of this procedure is demonstrated by showing that it permits a data screening algorithm with fixed thresholds to work on hazy areas as well as clear ones. An alternative formulation is proposed that would replace manual haze estimation with automated estimation based on a computed diagnostic feature.

Modelling of Radiation Transfer in Earth's Hazy Atmosphere and Calculation of Path Radiances in IRS LISS-I Bands

Abstract: A model (named ATMRAD) of radiation transfer in the Earth’s hazy atmosphere based on simplistic solution of radiation transfer equation and tropical model atmosphere is developed to estimate path radiance for correction of remote sensing multispectral data. The atmosphere is assumed to be cloud free and plane-parallel stratified with various quatities specified for 46 layers in its 100 km assumed thickness and model altitude profiles of haze aerosols specified for 23 km and 5 km visibility ranges. Altitude profiles of haze for any intermediate visibility ranges are deduced from linear mixing of the two profiles for 23 and 5 km visibilities. Deirmendjian size distribution function is assumed for aerosols. The radiation transfer calculations have been performed for 126 wavelengths in 0.25 to 3.0 μm range by considering Rayleigh and Mie Scatterings by air molecules and aerosols; and absorption by atmospheric gases. The model calculations have been carried out for path radiances in bands of IRS LISS-I sensor for different visibility ranges and solar illumination angles.

Internal Contamination in the Wide Field/Planetary Camera

Abstract: Following thermal vacuum/thermal balance testing, a gray haze was discovered on the corners of the Wide Field/Planetary Camera (WF/PC) aperture window. The phenomenon was suggested to be a result of molecular transport from a low outgassing structural adhesive. Detailed analyses, both chemical and analytical, were conducted to assess the formation of the haze. Each material was considered individually, as it was not known if the actual contamination was a result of one, many, or possibly none of the materials considered. Results of the analytical assessment and the comparison with the aforementioned chemical analyses provided incontrovertible evidence as to the cause of the window haze. The resultant cleanup and subsequent elimination of the problem are also addressed.

Haze in the Grand Canyon: An evaluation of the Winter Haze Intensive Tracer Experiment

Abstract: The Grand Canyon is one of the most spectacular natural sights on earth. Approximately 4 million visitors travel to Grand Canyon National Park (GCNP) each year to enjoy its majestic geological formations and intensely colored views. However, visibility in GCNP can be impaired by small increases in concentrations of fine suspended particles that scatter and absorb light; the resulting visibility degradation is perceived as haze. Sulfate particles are a major factor in visibility impairment at Grand Canyon in summer and winter. Many wintertime hazes at GCNP are believed to result from the accumulation of emissions from local sources during conditions of air stagnation, which occur more frequently in winter than in summer. In January and February 1987, the National Park Service (NPS) carried out a large-scale experiment known as the Winter Haze Intensive Tracer Experiment (WHITEX) to investigate the causes of wintertime haze in the region of GCNP and Canyonlands National Park. The overall objective of WHITEX was to assess the feasibility of attributing visibility impairment in specific geographic regions to emissions from a single point source. The experiment called for the injection of a tracer, deuterated methane (CD{sub 4}), into one of the stacks of the Navajo Generating Station (NGS), a major coal-fired power plant located 25 km from the GCNP boundary and 110 km northeast of Grand Canyon Village. A network of field stations was established in the vicinity -- mostly to the northeast of GCNP and NGS -- to measure CD{sub 4} concentrations, atmospheric aerosol and optical properties, and other chemical and physical attributes. 19 refs., 3 figs.

Cirrus cloud model parameterizations: Incorporating realistic ice particle generation

Abstract: Recent cirrus cloud modeling studies have involved the application of a time-dependent, two dimensional Eulerian model, with generalized cloud microphysical parameterizations drawn from experimental findings. For computing the ice versus vapor phase changes, the ice mass content is linked to the maintenance of a relative humidity with respect to ice (RHI) of 105 percent; ice growth occurs both with regard to the introduction of new particles and the growth of existing particles. In a simplified cloud model designed to investigate the basic role of various physical processes in the growth and maintenance of cirrus clouds, these parametric relations are justifiable. In comparison, the one dimensional cloud microphysical model recently applied to evaluating the nucleation and growth of ice crystals in cirrus clouds explicitly treated populations of haze and cloud droplets, and ice crystals. Although these two modeling approaches are clearly incompatible, the goal of the present numerical study is to develop a parametric treatment of new ice particle generation, on the basis of detailed microphysical model findings, for incorporation into improved cirrus growth models. For example, the relation between temperature and the relative humidity required to generate ice crystals from ammonium sulfate haze droplets, whose probability of freezing through the homogeneous nucleation mode are a combined function of time and droplet molality, volume, and temperature. As an example of this approach, the results of cloud microphysical simulations are presented showing the rather narrow domain in the temperature/humidity field where new ice crystals can be generated. The microphysical simulations point out the need for detailed CCN studies at cirrus altitudes and haze droplet measurements within cirrus clouds, but also suggest that a relatively simple treatment of ice particle generation, which includes cloud chemistry, can be incorporated into cirrus cloud growth.

Process induced defects controlled by lightscattering measurements

Abstract: The angular distribution of scattered light contains a lot of information about the investigated surface. Haze, oriented haze, time dependent haze, particles, subsurface damage, and other defects are detectable on semiconductor surfaces by appropriate lightscattering techniques. Calibration with reference to Total Integrated Scattered Intensity Measurements allows the conversion of intensity into rms roughness values. Chemo-mechanical polishing and subsequent epitaxy produce very smooth surfaces and lead to a regular arrangement of atomic steps at the surface. If the misorientation is less than 0.1° the existence and regularity of these steps can be demonstrated by angle-resolved lightscattering. Moreover, lightscattering monitors the performance of processing steps. It is demonstrated that thermal oxidation roughens smooth surfaces depending on oxidation parameters - long etching of Siwafers in HF can introduce surface roughness - storage of wafers may lead to time dependent haze - precipitation may introduce pronounced surface roughness and - ion implantation and plasma treatments roughen the surface and introduce subsurface damage, too. A threshold of more than 5 A rms interface roughness (Si-SiO 2 ) reduces the dielectric breakdown severly.