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Showing papers on "Haze published in 2002"


Journal ArticleDOI
TL;DR: This work studies the visual manifestations of different weather conditions, and model the chromatic effects of the atmospheric scattering and verify it for fog and haze, and derives several geometric constraints on scene color changes caused by varying atmospheric conditions.
Abstract: Current vision systems are designed to perform in clear weather. Needless to say, in any outdoor application, there is no escape from “bad” weather. Ultimately, computer vision systems must include mechanisms that enable them to function (even if somewhat less reliably) in the presence of haze, fog, rain, hail and snow. We begin by studying the visual manifestations of different weather conditions. For this, we draw on what is already known about atmospheric optics, and identify effects caused by bad weather that can be turned to our advantage. Since the atmosphere modulates the information carried from a scene point to the observer, it can be viewed as a mechanism of visual information coding. We exploit two fundamental scattering models and develop methods for recovering pertinent scene properties, such as three-dimensional structure, from one or two images taken under poor weather conditions. Next, we model the chromatic effects of the atmospheric scattering and verify it for fog and haze. Based on this chromatic model we derive several geometric constraints on scene color changes caused by varying atmospheric conditions. Finally, using these constraints we develop algorithms for computing fog or haze color, depth segmentation, extracting three-dimensional structure, and recovering “clear day” scene colors, from two or more images taken under different but unknown weather conditions.

1,325 citations


Journal ArticleDOI
TL;DR: Simpler models representing transport, limiting precursor pollutants, and gas-to-particle equilibrium should be used to understand where and when emission reductions will be effective, rather than large complex models that have insufficient input and validation measurements.
Abstract: The 1999 Regional Haze Rule provides a context for this review of visibility, the science that describes it, and the use of that science in regulatory guidance The scientific basis for the 1999 regulation is adequate The deciview metric that tracks progress is an imperfect but objective measure of what people see near the prevailing visual range The definition of natural visibility conditions is adequate for current planning, but it will need to be refined as visibility improves Emissions from other countries will set achievable levels above those produced by natural sources Some natural events, notably dust storms and wildfires, are episodic and cannot be represented by annual average background values or emission estimates Sulfur dioxide (SO2) emission reductions correspond with lower sulfate (SO4 2−) concentrations and visibility im-provements in the regions where these have occurred Non-road emissions have been growing more rapidly than emissions from other sources, which have remained

964 citations


Journal ArticleDOI
TL;DR: In this article, a haze optimized transformation (HOT) is developed and assessed for the detection and characterization of haze/cloud spatial distributions in Landsat scenes, which is derived from an analysis of a visible-band space where spectral response to diverse surface cover classes under clear-sky conditions is highly correlated.

308 citations


Journal ArticleDOI
TL;DR: In this paper, the effects of the south Asian haze on the regional climate are assessed using the National Center for Atmospheric Research Community Climate Model version 3 (CCM3) at the T42/L18 resolution.
Abstract: The effects of the south Asian haze on the regional climate are assessed using the National Center for Atmospheric Research Community Climate Model version 3 (CCM3) at the T42/L18 resolution. This haze, as documented during the Indian Ocean Experiment (INDOEX) campaign (1995‐2000), consists mainly of anthropogenic aerosols, and spans over most of south Asia and the north Indian Ocean. It reduces the net solar flux at the surface by as much as 20‐40 W m 22 on a monthly mean basis and heats the lowest 3-km atmosphere by as much as 0.4‐0.8 K day21, which enhances the solar heating of this layer by 50%‐100%. This widespread haze layer is a seasonal phenomenon limited to the dry period between November and May. The imposed haze radiative forcing leads to several large and statistically significant climate changes during the dry monsoon season, which include cooling of the land surface, and warming of the atmosphere. These temperature change features lead to the stabilization of the boundary layer that results in a reduction of evaporation and sensible heat flux from the land. The dynamical response to the aerosol forcing is surprisingly large. The aerosol forcing weakens the north‐south temperature gradient in the lower level, which results in an enhancement of the area mean low-level convergence and a northward shift of the ITCZ. The increase in low-level convergence leads to increased convective rainfall and latent heat release, which in turn leads to a further increase in lowlevel convergence. This positive feedback between the low-level convergence and deep convective heating increases the average precipitation over the haze area by as much as 20%. The ocean surface undergoes a suppression of evaporation. Because of this decreased evaporation accompanied by the increase in the hazearea precipitation, the precipitation over the rest of the Tropics decreases, with a large fraction of this decrease concentrated over the Indonesian and the western Pacific warm pool region. The prescribed dry monsoon haze effect affects the summertime wet monsoon too, but a detailed analysis has to await the availability of yearround aerosol data. The major inference from this study is that the effects of absorbing aerosols on the regional climate can be quite large. The simulated surface temperature response was very sensitive to the ratio ( R) of the surface aerosol forcing to the atmospheric forcing. The R itself varies from 21.5 in clear skies to about 20.5 in overcast skies over ocean, and available experimental data are not sufficient to constrain its value more narrowly.

144 citations


Journal ArticleDOI
TL;DR: In this paper, a cross-platform comparison resolved a number of measurement differences but also revealed that regional characterization from different platforms results in differences linked to variability in time and space, emphasizing the need to combine such efforts with coordinated satellite and modeling studies able to characterize large-scale regional structure and variability.
Abstract: converged on values of about 3.8 ± 0.3 m 2 g � 1 , providing a firm constraint upon the description and modeling of haze optical properties. MSE values trended lower with more dilute haze but became more variable in clean air or regions of low concentrations. This cross-platform comparison resolved a number of measurement differences but also revealed that regional characterization from different platforms results in differences linked to variability in time and space. This emphasizes the need to combine such efforts with coordinated satellite and modeling studies able to characterize large-scale regional structure and variability. These comparisons also indicate that ‘‘closure’’ between chemical, microphysical, and optical properties across platforms to better than about 20% will require significant improvements in techniques, calibration procedures, and comparison efforts. INDEX TERMS: 0305 Atmospheric Composition and Structure: Aerosols and particles (0345, 4801); 0345 Atmospheric Composition and Structure: Pollution—urban and regional (0305); 0394 Atmospheric Composition and Structure: Instruments and techniques; KEYWORDS: INDOEX, data comparison, optical properties, chemistry, microphysics, size distributions

138 citations


Journal ArticleDOI
TL;DR: In this paper, the authors used adaptive optics on the Gemini and Keck II telescopes to find a thin haze and discrete clouds in Titan's south polar troposphere, and they suggested that convection within this haze layer triggers methane condensation; subsequent latent heat release leads to vigorous convection and formation of transient clouds.
Abstract: Using adaptive optics on the Gemini and Keck II telescopes, we found a thin haze and discrete clouds in Titan’s south polar troposphere. The discrete clouds vary on timescales of a few hours. We propose a seasonal mechanism to explain the formation of this spring polar tropospheric haze. Assuming that the clouds are located in or above the haze, we suggest that convection within this haze layer triggers methane condensation; subsequent latent heat release leads to vigorous convection and formation of transient clouds. Our results have significant implications for planning the Cassini mission flybys of Titan. Subject headings: infrared: solar system — instrumentation: adaptive optics — planets and satellites: individual (Titan)

131 citations


Journal ArticleDOI
22 Aug 2002-Nature
TL;DR: A numerical simulation of Titan's atmosphere is described, which appears to explain the observed features of the haze, and includes a component of strong positive feedback between the haze and the winds.
Abstract: Titan, the largest moon of Saturn, is the only satellite in the Solar System with a dense atmosphere. Titan's atmosphere is mainly nitrogen with a surface pressure of 1.5 atmospheres and a temperature of 95 K (ref. 1). A seasonally varying2 haze, which appears to be the main source of heating and cooling that drives atmospheric circulation3,4, shrouds the moon. The haze has numerous features that have remained unexplained. There are several layers5, including a ‘polar hood’6,7,8, and a pronounced hemispheric asymmetry2. The upper atmosphere rotates much faster than the surface of the moon9,10, and there is a significant latitudinal temperature asymmetry at the equinoxes11,12. Here we describe a numerical simulation of Titan's atmosphere, which appears to explain the observed features of the haze. The critical new factor in our model is the coupling of haze formation with atmospheric dynamics, which includes a component of strong positive feedback between the haze and the winds.

131 citations


Journal ArticleDOI
TL;DR: In this article, the molecular and carbon isotopic compositions of Malaysian atmospheric polycyclic aromatic hydrocarbons (PAHs) in smoke haze from the 1997 Indonesian forest fire were measured.

127 citations


Journal ArticleDOI
TL;DR: A procedure for haze detection and removal from high-resolution satellite images using wavelet analysis (HAWAT) has been developed and visual inspection and statistical accuracy assessment show that the haze calibration is valid and robust.
Abstract: A procedure for haze detection and removal from high-resolution satellite images using wavelet analysis (HAWAT) has been developed. It involves the analysis of the low spatial frequency information content of a scene. The image contaminated by haze is decomposed into different spatial layers with wavelet transforms. Although haze is distributed in the lower frequency layer, this layer may also contain a component of land cover that is spatially and temporally relatively stable. A haze-free reference image of the same area is used to characterize land cover. The component of the characterized land cover is then subtracted with wavelet analysis. The residual wavelet coefficients are used to construct a spatially varying mask for subsequent haze detection and removal. After smoothing, the mask is subtracted from the contaminated image to obtain a corrected image with haze-off characteristics. Both visual inspection and statistical accuracy assessment show that the haze calibration is valid and robust.

118 citations


Journal ArticleDOI
TL;DR: In this article, the authors used a direct method which combines microphysics and photometric simulations of the Martian atmosphere to reproduce vertical profiles of the light scattered by the haze at the limb of Mars.
Abstract: [1] In this paper we use a direct method which combines microphysics and photometric simulations of the Martian atmosphere. This approach allows us to reproduce vertical profiles of the light scattered by the haze at the limb of Mars. Subsequent results are compared to a multiple-color image provided by the Viking Orbiter camera. The “free parameters” of our study are related to vertical transport and dust size distribution. A sensitivity study has been conducted, encompassing a relevant range of parameters, in order to obtain the most satisfying multispectral modeled profile with respect to the one inferred from data. Except for an unlikely distribution of submicron particles (reff ∼ 0.2 μm), no consistent fit can be obtained. This implies that size distributions of dust suggested by previous studies are not in agreement with the present analysis. This apparent discrepancy can be resolved by adding a separate peak of submicron particles to the size distribution previously extracted from Viking Lander images. Only in that case can spectral and vertical structures of haze be successfully matched. While a bimodal distribution would change the current picture of Martian dust, such distribution is a common representation of soil-derived aerosol size function in Earth deserts. We also attempted to derive information from the cloud shown in the Viking limb image. Our estimates suggest that cloud particle effective radius is around 1.2–1.8 μm, while the cloud visible opacity is 0.02.

108 citations


Journal ArticleDOI
TL;DR: In this article, the authors present an analysis of observed surface-temperature variations over the Indian subcontinent, which filters out effects of greenhouse gases and natural variability, revealing that absorbing aerosols have led to a statistically significant cooling of about 0.3°C since the 1970s.
Abstract: [1] Anthropogenic emissions over the Asian region have grown rapidly with increase in population and industrialization. Air-pollutants from this region lead to a brownish haze over most of the North Indian Ocean and South Asia during winter and spring. The haze, with as much as 10–15% of black carbon (by mass), is known to reduce the surface solar insolation by about 10% (−15 Wm−2) and nearly double the lower atmospheric solar heating. Here we present an analysis of observed surface-temperature variations over the Indian subcontinent, which filters out effects of greenhouse gases and natural variability. The analysis reveals that the absorbing aerosols have led to a statistically significant cooling of about 0.3°C since the 1970s. The seasonally asymmetric cooling, which is consistent with the seasonality of the South Asian aerosol forcing, raises the new possibility that the surface cooling underneath the polluted regions, is balanced by warming elsewhere.

Journal ArticleDOI
TL;DR: The status of aerosols in India is presented based on the research activities undertaken during last few decades in this region and the high particulate concentrations in most of the cities' atmosphere in India are of concern as it can cause deteriorated health conditions.

01 Jan 2002
TL;DR: Markowicz et al. as mentioned in this paper showed that absorbing mediterranean aerosols lead to a large reduction in the solar radiation at the surface, which is consistent with the south Asian haze observed over the Arabian Sea.
Abstract: of 17.9 W m 2 in the surface solar radiation, an increase of 11.3 W m 2 in the atmospheric solar absorption, and an increase of 6.6 W m 2 in the reflected solar radiation at the top-of-the atmosphere. Thus, the present data gives observational proof for the large role of absorbing aerosols in the Mediterranean. The negative surface forcing and large positive atmospheric forcing values observed for the Mediterranean aerosols is nearly identical to the highly absorbing south Asian haze observed over the Arabian Sea. INDEX TERMS: 0305 Atmospheric Composition and Structure: Aerosols and particles (0345, 4801); 0345 Atmospheric Composition and Structure: Pollution—urban and regional (0305); 0360 Atmospheric Composition and Structure: Transmission and scattering of radiation; 1610 Global Change: Atmosphere (0315, 0325). Citation: Markowicz, K. M., P. J. Flatau, M. V. Ramana, P. J. Crutzen, and V. Ramanathan, Absorbing mediterranean aerosols lead to a large reduction in the solar radiation at the surface, Geophys. Res. Lett., 29(20), 1968, doi:10.1029/2002GL015767, 2002.

Proceedings ArticleDOI
01 Dec 2002
TL;DR: In this article, the authors focus on attenuation due to scattering by haze, fog and low clouds droplets using the original Mie scattering theory and develop a computer-based platform, Simulight, which simulates infrared signal (750 nm-12 μm) propagation in haze, Fog, low clouds, rain and clear weather.
Abstract: One of the biggest challenges facing Free-Space Optics deployment is proper understanding of optical signal propagation in different atmospheric conditions. In an earlier study by the author (30), attenuation by rain was analyzed and successfully modeled for infrared signal transmission. In this paper, we focus on attenuation due to scattering by haze, fog and low clouds droplets using the original Mie Scattering theory. Relying on published experimental results on infrared propagation, electromagnetic waves scattering by spherical droplet, atmospheric physics and thermodynamics, UlmTech developed a computer-based platform, Simulight, which simulates infrared signal (750 nm-12 μm) propagation in haze, fog, low clouds, rain and clear weather. Optical signals are scattered by fog droplets during transmission in the forward direction preventing the receiver from detecting the minimum required power. Weather databases describe foggy conditions by measuring the visibility parameter, which is, in general, defined as the maximum distance that the visible 550 nm signal can travel while distinguishing between the target object and its background at 2% contrast. Extrapolating optical signal attenuations beyond 550 nm using only visibility is not as straightforward as stated by the Kruse equation which is unfortunately widely used. We conclude that it is essential to understand atmospheric droplet sizes and their distributions based on measured attenuations to effectively estimate infrared attenuation. We focus on three types of popular fogs: Evolving, Stable and Selective.

Journal Article
TL;DR: In this article, the authors found that the long duration of the haze, its black carbon content, the large perturbation to the radiative energy budget of the region and its simulated impact on the rainfall distribution, if proved correct, have significant implications to the regional water budget, agriculture and health.
Abstract: The south Asian brown haze covers most of the Arabian Sea, Bay of Bengal and the south Asian region. It occurs every year, and extends from about November to April and possibly longer. The black carbon and other species in the haze reduce the average radiative heating of the ocean by as much as 10% and enhance the atmospheric solar radiative heating by 50 to 100%. These findings are at variance with SG’s perceptions that the haze occurs only during January to March, and that the aerosol forcing used by UNEP was unrealistically large because it used 1999 values and ignored IR effects of aerosols. INDOEX and UNEP did not rely just on 1999 values, but used data for 1996 to 1999, and also accounted for the compensating IR effects. The long duration of the haze, its black carbon content, the large perturbation to the radiative energy budget of the region and its simulated impact on the rainfall distribution, if proved correct, have significant implications to the regional water budget, agriculture and health. The link between anthropogenic aerosols and reduction of monsoonal rainfall in south Asia also has been made by over fifteen model studies preceding the UNEP report. We do not find any reason to modify the findings, the recommendations and the caveats in the UNEP report. The press release, while its direct quotes of the report are accurate, should have given more emphasis to the caveats in the report. THE equatorial Indian Ocean is a unique natural laboratory for studying the impact of anthropogenic aerosols on climate, because pollutants from the northern hemisphere are directly connected to the pristine air from the southern hemisphere by a cross equatorial monsoonal flow into the inter-tropical convergence zone (ITCZ) 4

Journal ArticleDOI
TL;DR: In this article, the authors present direct radiometric observations of aerosol radiative forcing taken during the MINOS experiment (2001) at Finokalia Sampling Station located on North-Eastern shores of Crete, Greece.
Abstract: [1] We present direct radiometric observations of aerosol radiative forcing taken during the MINOS experiment (2001) at Finokalia Sampling Station located on North-Eastern shores of Crete, Greece. The mean value of aerosol optical thickness was 0.21 at 500 nm. Aerosols, mostly of anthropogenic origin, lead to a diurnal average reduction of 17.9 W m−2 in the surface solar radiation, an increase of 11.3 W m−2 in the atmospheric solar absorption, and an increase of 6.6 W m−2 in the reflected solar radiation at the top-of-the atmosphere. Thus, the present data gives observational proof for the large role of absorbing aerosols in the Mediterranean. The negative surface forcing and large positive atmospheric forcing values observed for the Mediterranean aerosols is nearly identical to the highly absorbing south Asian haze observed over the Arabian Sea.

Journal ArticleDOI
TL;DR: In this article, the authors discuss the role of economic incentives in managing forest fires and suggest a stakeholders approach to the possible sharing of costs in certain programs to combat the fires and haze.

Journal ArticleDOI
TL;DR: Single particle data show that carbonaceous aerosol with secondary ammonium, nitrate, and sulfate dominate the aerosol concentration during a stagnation period with a dramatic composition shift occurring to sodium type particles during the haze period.
Abstract: Particle and meteorological instrumentation were used to characterize ambient atmospheric conditions, aerosol size distributions, aerosol mass concentrations, and single particle size and chemical composition in Bakersfield, CA for the period January 9, 1999 through January 28, 1999. The sampling period included four distinct meteorological periods of stagnation, clearing, haze, and rain. Particle number and mass concentrations were the highest during the stagnation episode when a heavy and extensive fog developed. Mass and number concentrations also approached these high levels during the haze period. Single particle size and composition data from an aerosol time-of-flight mass spectrometer (ATOFMS) are used to provide unique continuous information on the diversity in types of particles present, the effects of meteorology on particle size and composition, and the distribution of important chemical species within individual particles. Aerosol composition and mixing state are found to vary with meteorological conditions. Single particle data show that carbonaceous aerosol with secondary ammonium, nitrate, and sulfate dominate the aerosol concentration during a stagnation period with a dramatic composition shift occurring to sodium type particles during the haze period. The aerosol is internally mixed with respect to carbon, nitrate, sulfate, and ammonium during the stagnation period. The mixing state changes significantly over the haze period when much greater diversity in the associations of chemical species within individual particles occurs.

Book ChapterDOI
01 Jan 2002
TL;DR: The Mexico City metropolitan area (MCMA) is located at the southern end of a semiclosed basin (19°25′N, 99°10′W), at a mean altitude of some 2200 m.
Abstract: On many sunny days, the residents of the Mexico City Metropolitan Area (MCMA) note that a thick gray haze builds up within this atmospheric basin impairing the visibility and the quality of the air. MCMA air quality has been recognized as among the worst in the world (WHO 1997). The MCMA is located at the southern end of a semiclosed basin (19°25′N, 99°10′W), at a mean altitude of some 2200 m. The average height of the surrounding mountain ranges is about 3200 m, with some peaks, including two volcanoes, exceeding 5000 m. Because of this irregular topography and the relatively light winds, ventilation of the basin is poor. In addition, surface as well as upper air temperature inversions occur frequently, trapping pollutant emissions close to the surface. During winter, inversions occur up to 25 days per month (DDF 1991). These climatological and topographical factors combine to provide plentiful sunshine which, in comparison to more northern latitudes, is enhanced in the ultraviolet (UV) radiation that drives atmospheric photochemistry to produce secondary pollutants such as ozone (03) and fine particles (Streit and Guzman 1996).

Journal ArticleDOI
01 Nov 2002-Icarus
TL;DR: In this article, the authors carried out a Titan tholin synthesis experiment and measured the time variation of the infrared spectrum of the product as a thin film developed, showing the progressive development of features characteristic of amines, aromatic and aliphatic hydrocarbons.

Journal ArticleDOI
TL;DR: In this article, the authors used HST images of Titan obtained in late 1996 to determine a three-dimensional map of haze optical depth in Titan's atmosphere, and solved for the total haze optical depths that best matched each HST image and then combined the results from each wavelength into a composite threedimensional map.
Abstract: We use Hubble Space Telescope (HST) images of Titan obtained in late 1996 to determine a three-dimensional map of haze optical depth in Titan's atmosphere. These images, taken at six wavelengths from 888 to 953 nm, probe Titan's atmosphere at various altitudes ranging from the surface to roughly 100 km. We solve for the total haze optical depths that best match each HST image and then combine the results from each wavelength into a composite three-dimensional map. The total optical depths due to haze in these maps range from 1.7 in the northernmost latitudes to 2.9 in the southernmost ones. The vertical haze profiles are roughly exponential except for a gap between 20 and 40 km, which may be a result of ethane or methane condensation onto tholins. There is a concentration of haze in the northernmost latitudes between 0 and 15 km above the surface.

Journal ArticleDOI
TL;DR: In this article, the authors showed that the optical haze properties of blown and cast polyethylene (PE) films were adversely affected (i.e., haze increased) as a result of enhanced surface roughness caused by the formation of distinct optically anisotropic "spherulitic-like" superstructures.
Abstract: In an earlier publication we showed that the optical haze properties of blown and cast polyethylene (PE) films were adversely affected (i.e., haze increased) as a result of enhanced surface roughness caused by the formation of distinct optically anisotropic “spherulitic-like” superstructures. In this report we have found that for a very wide variety of PE blown films, the total haze percent exhibited a complex parabolic relationship with the logarithm of the recoverable shear strain parameter, γ∞. At low values of γ∞, superstructures were developed (as discussed in our previous report) that increased surface roughness and hence total haze. As γ∞ increased, such superstructures were either significantly diminished in size or altogether absent, giving rise instead to an oriented, row-nucleated, stacked lamella texture that decreased surface roughness and hence total haze. However, at even higher γ∞ values, representing highly melt elastic behavior, fine-scale surface roughness due to high melt elastic instabilities was induced, thereby increasing surface roughness and consequently total haze as well. It was demonstrated in this work that two PE resins could exhibit the same level of total haze as a consequence of two completely different mechanisms or origins. Furthermore, we believe that this is the first time that both very low and very high melt elasticity have been shown as primary causative factors in yielding high haze in PE blown films, albeit for fundamentally very different reasons. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 2396–2411, 2002

Journal ArticleDOI
Janos Szanyi1
TL;DR: In this paper, the origin of haze was investigated in antimony-doped tin oxide thin films and in double-stack thin films, both deposited by chemical vapor deposition onto soda-lime-silica float glass substrates.

Journal ArticleDOI
Erik Andreassen1, Åge Larsen1, Katrin Nord-Varhaug, Merete Skar, Harry Oysaed 
TL;DR: In this paper, the authors define haze as the fraction of (nor-mal incident) transmitted light that deviates from the directly transmitted beam by more than 2.5 (1).
Abstract: he haze of a film is defined as the fraction of (nor-mal incident) transmitted light that deviates fromthe directly transmitted beam by more than 2.5 (1).The contrast of an object seen through a film de-creases with increasing haze. The resolution of detail,a second criterion of transparency, is usually referredto as clarity. From a light scattering point of view,haze corresponds to larger scattering angles than lossof clarity. Note that a reduction in haze not necessarilyleads to improved clarity. Haze due to surface rough-ness is in many cases inversely related to gloss, whichis another important optical property.Both bulk inhomogeneities and surface roughnessmay contribute to haze. The latter effect usually domi-nates for polyethylene (PE) films. The typical scale ofthe roughness relative to the wavelength of light ( )determines the scattering characteristics. The heightvariation of the surface is usually reported to follow aGaussian distribution (2), and optical surfaces areoften characterized by the root-mean-square deviation( ) from the mean surface height. Roughness values, , in the range 20–600 nm are typically reported forPE films, i.e. . The haze increases monotonouslywith increasing roughness. Various techniques havebeen used for characterizing the surface profiles.Atomic force microscopy (AFM), has been applied in anumber of recent studies (3–6).Many types of PE are available for film blowingprocesses. The three main types, low-density (LDPE),linear low-density (LLDPE) and high-density (HDPE),all have their advantanges and drawbacks, also whenit comes to optical properties. Early experimental liter-ature (up to 1981) on the haze of PE blown films wasreviewed by Willmouth (1). The main findings can besummarized as follows. Two main sources of surfaceroughness have been identified: 1) flow-induced irreg-ularities originating from the die, and 2) protrudingcrystalline structures (lamellae, stacks of lamellae orspherulites). The former is a well-known rheologicaleffect, and the resulting extrusion-induced haze isoften observed to increase with increasing melt elas-ticity, e.g. due to more long-chain branching (LCB) or broader molecular weight distribution (MWD). The melt elasticity of LDPE (containing LCB) can be

Patent
16 Jul 2002
TL;DR: In this paper, a container providing effective oxygen-scavenging functionality, while having low haze, is defined, where the container has at least one wall, wherein the wall comprises a populated area, and wherein the populated area comprises a film-forming polymer; and a population of particles comprising an effective amount of oxygen scavenging particles, such that the number of particles of said population does not exceed a concentration of about (6×107 particles÷T) per cubic centimeter of polymer.
Abstract: A container providing effective oxygen-scavenging functionality, while having low haze. The container has at least one wall, wherein the wall comprises a populated area, and wherein the populated area comprises a film-forming polymer; and a population of particles comprising an effective amount of oxygen-scavenging particles, wherein the number of particles of said population does not exceed a concentration of about (6×107 particles÷T) per cubic centimeter of polymer wherein T is the thickness of the populated area in mils; and wherein the wall has a transmission Hunter haze of up to about 1 percent per mil of the container wall.

Journal ArticleDOI
01 Jun 2002-Icarus
TL;DR: In this article, the authors quantify the charge states of submicrometer aerosols and aromatic macromolecules in Titan's organic haze and show that during the day, the dominant charge state for submicro-meter aerosols is positive.

Journal ArticleDOI
TL;DR: Spectral daytime aerosol optical depths have been measured at Sutherland, South Africa (32°22′S, 20°48′E), from January 1998 to November 1999, and the comparison of daytime and nighttime measurements for the years 1998-1999 makes it possible to validate the astronomical dataset of aerosol infrared depth ( τ a ) dating back to 1991 as mentioned in this paper.

Journal ArticleDOI
TL;DR: In this article, the spatial and temporal variations of the polarization of light scattered by Venus, as observed by the Pioneer Venus Orbiter between 1978 and 1990, was analyzed in terms of spatial and time variations of Venus upper haze properties.
Abstract: [1] The spatial and temporal variations of the polarization of light scattered by Venus, as observed by the Pioneer Venus Orbiter between 1978 and 1990, is analyzed in terms of spatial and temporal variations of Venus upper haze properties. Special attention is given to choosing maps with sufficiently accurate geometrical information. This selection involves multiple-scattering calculations for a number of reasonable models for the Venus atmosphere. For a set of observations in four wavelength bands of the Venus disk as a whole or a particular region thereof, observed values of Stokes parameters I and Q were used to obtain the average observed relative Stokes parameter qobs. Subsequently, the haze particle column density and the cloud top pressure were iteratively adjusted until values of qobs at two wavelengths were reproduced. For the planet as a whole, it was found that the haze particle column density decreased gradually during the Pioneer Venus Orbiter mission, whereas little significant temporal variability was found for the cloud top pressure. Similar long-term behavior was derived for selected regions of Venus. Regions at higher latitudes exhibited higher values of both the haze particle column density and the cloud top pressure than regions at lower latitudes. Something similar holds for regions with low solar elevations as compared to regions in which the Sun was close to the zenith.

Journal Article
TL;DR: It is suggested in the UNEP report that the impact of the haze assessed with the help of an atmospheric general circulation model is a decrease in rainfall in northwest Asia (including Saudi Arabia, Pakistan, Afghanistan), but it is found that the model simulation of the rainfall patterns over this region is particularly poor and hence the reliability of this projection is suspect.
Abstract: The wide publicity given to the release of a United Nations Environment Programme (UNEP) report on the so-called Asian Brown Cloud and its multifarious impacts on health, agriculture and climate on both regional and global scales, has led to considerable concern. We find that the UNEP news release (and hence the media reports based on it) is a blend of observations and scientifically sound deductions on the one hand and sensational statements with little scientific basis on the other. The UNEP report is based on the findings of an international programme called the Indian Ocean Experiment (INDOEX). The term Asian Brown Cloud was coined by leaders of INDOEX to describe the brown haze occurring during the period January to March, over the South Asian region and the tropical Indian Ocean, Arabian Sea and Bay of Bengal. It is important to note that, the haze is not a permanent feature of the atmosphere over the Asian region and the surrounding seas. It occurs only during January-March, in the season following the southwest monsoon and northeast monsoon seasons. It is suggested in the UNEP report that the impact of the haze assessed with the help of an atmospheric general circulation model is a decrease in rainfall in northwest Asia (including Saudi Arabia, Pakistan, Afghanistan). However, we find that the model simulation of the rainfall patterns over this region is particularly poor and hence the reliability of this projection is suspect. Also, the expected magnitude of the impact on crop yields is small and there is no basis for the statement in the UNEP news release that the 'vast blanket of pollution across South Asia is damaging agriculture'

Journal ArticleDOI
TL;DR: In this article, the microstructures of µc-Si films on textured SnO2 with different haze factors (from 13% to 65%) were observed with a scanning electron microscope and a transmission electron microscope.
Abstract: Microcrystalline silicon (µc-Si) films and solar cells were prepared by mercury-sensitized photochemical vapor deposition (photo-CVD). The changes in the structural properties of a series of µc-Si films grown under various H2 dilution and deposition pressure conditions were discussed. The results indicated that the properties of µc-Si films depend strongly on the atomic hydrogen. The microstructures of µc-Si films on textured SnO2 with different haze factors (from 13% to 65%) were observed with a scanning electron microscope and a transmission electron microscope. The observations revealed that the µc-Si layers grew from the initial stage of deposition with columnar grains and that they were conformal to the surface of textured SnO2. The grain boundary density of µc-Si film on SnO2 with higher haze factors was lower than that on SnO2 with lower haze factors. The effect of textured SnO2 with different haze ratios on p–i–n µc-Si cell characteristics was discussed and it was found that the higher haze factors showed a higher degree of light trapping in our µc-Si cells. We deposited µc-Si cells with an intrinsic µc-Si layer thickness of 430 nm on a textured SnO2 sample with a haze factor of 42% and achieved a conversion efficiency of 6.55%.