Showing papers on "Haze published in 2007"

Revised Algorithm for Estimating Light Extinction from IMPROVE Particle Speciation Data

Abstract: The Interagency Monitoring of Protected Visual Environments (IMPROVE) particle monitoring network consists of approximately 160 sites at which fine particulate matter (PM2.5) mass and major species concentrations and course particulate matter (PM10) mass concentrations are determined by analysis of 24-hr duration sampling conducted on a 1-day-in-3 schedule A simple algorithm to estimate light extinction from the measured species concentrations was incorporated in the 1999 Regional Haze Rule as the basis for the haze metric used to track haze trends. A revised algorithm was developed that is more consistent with the recent atmospheric aerosol literature and reduces bias for high and low light extinction extremes. The revised algorithm differs from the original algorithm in having a term for estimating sea salt light scattering from Cl(-) ion data, using 1.8 instead of 1.4 for the mean ratio of organic mass to measured organic carbon, using site-specific Rayleigh scattering based on site elevation and mean temperature, employing a split component extinction efficiency associated with large and small size mode sulfate, nitrate and organic mass species, and adding a term for nitrogen dioxide (NO2) absorption for sites with NO2 concentration information. Light scattering estimates using the original and the revised algorithms are compared with nephelometer measurements at 21 IMPROVE monitoring sites. The revised algorithm reduces the underprediction of high haze periods and the overprediction of low haze periods compared with the performance of the original algorithm. This is most apparent at the hazier monitoring sites in the eastern United States. For each site, the PM10 composition for days selected as the best 20% and the worst 20% haze condition days are nearly identical regardless of whether the basis of selection was light scattering from the original or revised algorithms, or from nephelometer-measured light scattering.

Aerosol optical properties and their radiative effects in northern China

Abstract: [1] As a fast developing country covering a large territory, China is experiencing rapid environmental changes. High concentrations of aerosols with diverse properties are emitted in the region, providing a unique opportunity for understanding the impact of environmental changes on climate. Until very recently, few observational studies were conducted in the source regions. The East Asian Study of Tropospheric Aerosols: An International Regional Experiment (EAST-AIRE) attempts to characterize the physical, optical and chemical properties of the aerosols and their effects on climate over China. This study presents some preliminary results using continuous high-quality measurements of aerosol, cloud and radiative quantities made at the first EAST-AIRE baseline station at Xianghe, about 70 km east of Beijing over a period of one year (September 2004 to September 2005). It was found that the region is often covered by a thick layer of haze (with a yearly mean aerosol optical depth equal to 0.82 at 500 nm and maximum greater than 4) due primarily to anthropogenic emissions. An abrupt ‘‘cleanup’’ of the haze often took place in a matter of one day or less because of the passage of cold fronts. The mean single scattering albedo is approximately 0.9 but has strong day-to-day variations with maximum monthly averages occurring during the summer. Large aerosol loading and strong absorption lead to a very large aerosol radiative effect at the surface (the annual 24-hour mean values equals 24 W m � 2 ), but a much smaller aerosol radiative effect at the top of the atmosphere (one tenth of the surface value). The boundary atmosphere is thus heated dramatically during the daytime, which may affect atmospheric stability and cloud formation. In comparison, the cloud radiative effect at the surface is only moderately higher (� 41 W m � 2 ) than the aerosol radiative effect at the surface.

Influences of Winter Haze on Fog/Low Cloud Over the Indo-Gangetic Plains

Abstract: [1] The aerosol loading in south Asia has increased considerably because of the growing population, urbanization, and industrialization in recent years. To understand the effects of aerosols on cloud properties in this region, we have analyzed an extensive collection of aerosol and cloud properties, obtained from the Moderate resolution Imaging Spectroradiometer (MODIS) data, over the Indian subcontinent during winter 2000–2006. During these winter months, the Indo-Gangetic (IG) plains, in the northern part of India, are subjected to dense haze and fog on the basis of MODIS climatology of aerosol optical depth and cloud properties (cloud effective radius, cloud top pressure, and cloud fraction), respectively. We derive a fog/low-cloud detection scheme from MODIS level 2 data to generate distribution of fog/low cloud on a daily basis for December–January 2000–2006. Interactions between winter haze and fog/low cloud over the IG plains were analyzed by minimizing the effect of dynamical processes associated with fog formation. On the basis of the interannual variability of meteorological parameters, winter 2004–2005 was associated with favorable conditions for fog formation in terms of comparable values of relative humidity with respect to previous years. However, significantly lower fog occurrences were found in winter 2004–2005 over the IG plains from MODIS and ground observations, while higher aerosol loading was observed in 2004–2005 compared to previous years. Thus the role of higher aerosol loading in 2004–2005 was investigated, combined with the high concentration of black carbon (BC) aerosols over the IG plains, indicated by aerosol transport model, suggesting that the BC aerosols may have significant impact on the fog/low-cloud formation over the IG plains and hence less fog in winter 2004–2005.

Have Australian rainfall and cloudiness increased due to the remote effects of Asian anthropogenic aerosols

Abstract: [1] There is ample evidence that anthropogenic aerosols have important effects on climate in the Northern Hemisphere but little such evidence in the Southern Hemisphere. Observations of Australian rainfall and cloudiness since 1950 show increases over much of the continent. We show that including anthropogenic aerosol changes in 20th century simulations of a global climate model gives increasing rainfall and cloudiness over Australia during 1951–1996, whereas omitting this forcing gives decreasing rainfall and cloudiness. The pattern of increasing rainfall when aerosols are included is strongest over northwestern Australia, in agreement with the observed trends. The strong impact of aerosols is primarily due to the massive Asian aerosol haze, as confirmed by a sensitivity test in which only Asian anthropogenic aerosols are included. The Asian haze alters the meridional temperature and pressure gradients over the tropical Indian Ocean, thereby increasing the tendency of monsoonal winds to flow toward Australia. Anthropogenic aerosols also make the simulated pattern of surface-temperature change in the tropical Pacific more like La Nina, since they induce a cooling of the surface waters in the extratropical North Pacific, which are then transported to the tropical eastern Pacific via the deep ocean. Transient climate model simulations forced only by increased greenhouse gases have generally not reproduced the observed rainfall increase over northwestern and central Australia. Our results suggest that a possible reason for this failure was the omission of forcing by Asian aerosols. Further research is essential to more accurately quantify the role of Asian aerosols in forcing Australian climate change.

Effect of Atmospheric Haze on the Deterioration of Visibility over the Pearl River Delta

Abstract: The studies on the effect of atmospheric aerosol on climate and environment are hot issues in the current circle of international science and technology In recent years the pollution of aerosol is getting worse and worse over the Pearl River Delta The clouds of aerosol occur all year round, with heavy pollution area located at the western side at the mouth of Pearl River The haze weather mainly occurs from October to April next year, resulting in visibility deterioration From the beginning of 1980s, visibility dramatically deteriorated, obviously increasing haze weather, in which there are three big fluctuations, showing the periods of pollutions of dust, sulphate and dust,fine particle from photochemical process and sulphate and dust accompanying with the development of economy respectively The long-term tendency of visibility caused by fog and light fog does not show a tendency due to human activities or economic development, which mainly shows the interannual and interdecadal variation of climate The deterioration of visibility has close relation to the fine particles over Pearl River Delta, with half of PM10 overpass the limited value set by national second graded standard (150 μg m-3), meanwhile, all values of PM25 overpass the day-mean limited value of American national standard (65 μg m-3), especially from October to January next year, monthly mean values of PM25 almost reach two times of standard value, indicating the fine particle concentration is very high The ratio of PM25 to PM10 is also very high, reaching 58%-77%, higher especially in dry season than in rainy season Thus it is the fine particle pollution in aerosol pollution over the Pearl River DeltaCompared with the data of 15 years ago, the ratio of ne particle to aerosol has obviously increased

The Burning Issue

Abstract: Neither governments nor civil society have been able to mitigate the annual shroud of haze that blankets Southeast Asia

Haze removal for high-resolution satellite data: a case study

Abstract: In the framework of a land cover study of a reclamation area, a high-resolution IKONOS scene characterized by an extremely non-homogenous haze cover was processed in order to reduce haze and calculate some vegetation indices (VIs). Haze removal was performed by means of a technique based on the haze optimized transform (HOT). As HOT is also sensitive to components other than haze, with respect to the original procedure we introduced a second step in which the haze component estimated from HOT was masked both for water bodies (as in the original approach) and urban features (responsible for high HOT values). Interpolation was finally performed in order to reconstruct haze in such areas. Dark-object subtraction (DOS) was then performed on the dehazed scene in order to estimate approximate soil reflectances necessary to calculate VIs. Their calculation for original and dehazed data illustrates the beneficial effects of the haze removal process and shows that, in the case of severe haze cover, even so-called atmospherically resistant VIs require a preliminary haze removal procedure.

A case study on biomass burning aerosols: effects on aerosol optical properties and surface radiation levels

Abstract: . In spring 2006, biomass burning aerosols from eastern Europe were transported extensively to Finland, and to other parts of northern Europe. They were observed as far as in the European Arctic. In the first part of this paper, temporal and spatial evolution and transport of these biomass burning aerosols are monitored with MODIS retrieved aerosol optical depth (AOD) imagery at visible wavelengths (0.55 μm). Comparison of MODIS and AERONET AOD is conducted at Toravere, Estonia. Then trajectory analyses, as well as MODIS Fire Mapper products are used to better understand the type and origin of the air masses. During the studied four-week period AOD values ranged from near zero up to 1.2 at 0.55 μm and the linear correlation between MODIS and AERONET was very high (~0.97). Temporal variability observed within this four-week period was also rather well explained by the trajectory analysis in conjunction with the fire detections produced by the MODIS Rapid Response System. In the second part of our study, the surface measurements of global and UV radiation at Jokioinen, Finland are used to study the effect of this haze episode on the levels of surface radiation. We found reductions up to 35% in noon-time surface UV irradiance (at 340 nm) as compared to typical aerosol conditions. For global (total solar) radiation, the reduction was always smaller, in line with the expected wavelength dependence of the aerosol effect.

Improved Monitoring of Rainforests Helps Pierce Haze of Deforestation

Abstract: Deforestation produces a significant amount of greenhouse gas emissions through burning, clearing, and decay. But exactly how much? (Read more.)

Titan's Organic Factory

Abstract: Researchers have identified molecules in the atmosphere of one of Saturn's moons that are responsible for its smog-like haze.

System and method for dehazing

Abstract: Outdoor imaging is plagued by poor visibility conditions due to atmospheric scattering, particularly in haze. A major problem is spatially-varying reduction of contrast by stray radiance (airlight), which is scattered by the haze particles towards the camera. The images can be compensated for haze by subtraction of the airlight and correcting for atmospheric attenuation. Airlight and attenuation parameters are computed by analyzing polarization-filtered images. These parameters were estimated in past studies by measuring pixels in sky areas. However, the sky is often unseen in the field of view. The invention provides methods for automatically estimating these parameters, when the sky is not in view.

Study on the visibility reduction caused by atmospheric haze in guangzhou area

Abstract: In recent years the pollution of aerosol is getting worse and worse in Guangzhou area. The haze weather mainly occurs from October to April of the following year, resulting in visibility deterioration. From the beginning of the 1980’s the visibility dramatically deteriorated, obviously increasing haze weather, in which there are three big fluctuations, respectively showing the periods of pollution of dust, sulphate and dust, fine particle from photochemical process and sulphate and dust accompanying the development of economy. The long-term tendency of visibility caused by fog and light fog does not have the tendency due to human activity or economical development and the variation mainly show the inner interannual and interdecadal variation of climate. The deterioration of visibility has close relation to the fine particles in Guangzhou area, with half of PM10 surpassing the limits set by national second graded standard, meanwhile, all values of PM2.5 rise above the day-mean limits of American national standard, indicating very high fine particle concentration. The ratio of PM2.5 to PM10 is also very high, reaching 62% – 69%, especially higher in dry seasons than in rainy seasons.

Phase behavior of methane haze.

Abstract: Methane aerosols play a fundamental role in the atmospheres of Neptune, Uranus, and Saturn's moon Titan as borne out by the recent Cassini-Huygens mission Here we present the first study of the phase behavior of free methane aerosol particles combining collisional cooling with rapid-scan infrared spectroscopy in situ We find fast (within minutes) phase transitions to crystalline states directly after particle formation and characteristic surface effects for nanometer-sized particles From our results, we conclude that in atmospheric clouds solid methane particles are crystalline

Highly Transparent Polypropylene Cast Films: Relationships Between Optical Properties, Additives, and Surface Structure

Abstract: Polypropylene homopolymer and ethylene/propylene-random-copolymer cast films formulated with various amounts of slip and antiblocking aids as well as acid scavengers and produced under different processing conditions were characterized with respect to surface structure and optical properties. The topographical analysis was done by atomic force microscopy (AFM). Optical properties were determined using a hazemeter and an UV/Vis/NIR spectrophotometer. AFM height images revealed a significant influence of processing conditions on the development of surface structures. Besides the occurrence of scratches displaying the replica of the metallic chill roll, particularly characteristic eight-shaped superlamellar crystalline features were affected by the cooling conditions. Relationships between surface enrichment of additives and vertical and lateral roughness parameters were established. In general, film types formulated without additives exhibit better optical properties. For film types formulated with polymer-processing aids, the diffuse-scattering power is reduced by low molecular weight, high amounts of acid scavenger aid, and antiblocking agents with low porosity. A separation of haze into its bulk and surface components indicated that total haze is dominated by surface haze. The comparison of haze and the vertical roughness parameters exhibited a tendency of a linear correlation. POLYM. ENG. SCI., 47:1021–1032, 2007. © 2007 Society of Plastics Engineers

The Influence of Meteorological Factors on PM 10 Concentration in Incheon

Abstract: In this study, we have analyzed concentration measured at Incheon Regional Air Monitoring Network (10 stations) and meteorological data at Incheon Weather Station to investigate factors (i.e. wind direction, wind speed, relative humidity, major meteorological phenomenon, and sea-land breezes existence) influencing concentration in Incheon during 2005. Statistical differences among meteorological factors were assessed by Kruskal-Wallis test or Mann-Whitney U test. The main conditions causing high concentration are summarized below; 1. When westerly wind prevailed (however, decreased when winds were blowing from the east or north). 2. When the winds were calm, owing to accumulation of nearby emissions under stagnant conditions, or when the wind speed is in excess of 6 m/s, which shows the effect of fugitive dust produced by wind erosion. 3. Under the condition of high relative humidity and poor diffusion based on meteorological phenomenon such as fog, mist, and haze. 4. When the Sea-Land breezes existed, which occurred 70 days in Incheon during 2005 and contributed significantly to high concentration in the coastal urban area. In conclusion, we have found that the meteorological factors have influence on concentration in Incheon.

FSO systems: Rain, drizzle, fog and haze attenuation at different optical windows propagation

Abstract: This paper presents an experimental comparison of three optical transparency windows of the Earth's atmosphere along a period of 12 months. Rain, drizzle, fog and haze scattering attenuation were simultaneously measurements in side by side parallel free space optical communication links, operating at 0.78 mum, 1.55 mum and 9.1 mum (near-IR, mid-IR and far-IR). Results include a real time measurement of the optical signals received of the three wavelengths links used versus visual range and rainfall acquitted and a comparison with the Carbonneau rain rate relation.

Particulate matter dispersion and haze occurrence potential studies at a local palm oil mill

Abstract: The emissions from palm oil industry through incineration and open burning are the major sources of air pollutions contribution in Malaysia. The consequence of increasing the particulate concentration, the particulate matter dissolves with vapour and grows into droplets when the humidity exceeds approximately 70% and causing opaque situation known as haze. This work focuses on the dispersion particulate matter from palm oil mill. Gaussian Plume Model from a point source, subject to various atmospheric conditions is used to calculate particulate matter concentration then display the distribution of plume dispersion using geographic information system. Atmospheric Stability, mixing height, wind direction, wind speed, natural and artificial features play an important role in dispersion process. Study on the dispersion of particulate matters and the haze potential are presented as a case study in this paper. The data obtained will be served as the purpose of modeling the transport of particulate matter for obtaining permits and prevention of significant deterioration to the environment.

Influence of environmental components on haze growth

Abstract: With the use of 193nm lithography, haze growth has increasingly become a critical issue for photomask suppliers and wafer fabs. Recent photomask industry surveys indicate the occurrence rate of haze is 10 times higher on 193nm masks compared to 248nm masks. Additionally, work has been presented that shows strong relationship between environmental conditions around the photomask and the occurrence of haze at 193nm. This underscores the need to better understand the basic mechanisms of haze and the measures such as environmental airborne molecular contamination (AMC) control which can be employed to reduce the occurrence of haze in use. A custom excimer laser test system capable of 193nm and 248nm wavelengths was built to accelerate haze growth and to better understand haze formation mechanisms. Work on materials impact on haze growth, such as pellicles and reticle compacts, as well as preliminary findings on environmental impacts have been presented previously. Results indicate even on pristine surfaces haze can grow when contaminants are present in the storage and use environment. The test system has been upgraded to include tight control on the concentration of specific airborne contaminants of concern. The impact of these contaminants and their relative concentrations will be examined in this paper and are presented to aid the industry in determining the level of environmental control needed over the life of a reticle.

Physical, chemical and optical properties of aerosol particles collected over Cape Town during winter haze episodes

Abstract: Airborne measurements were conducted in the winter months of July and August 2003 over the metropolitan area of Cape Town to characterize physical, chemical and optical properties of aerosol particles during intense brown haze episodes. Particles were collected on highly temporally and spatially resolved samples and investigated using a high-resolution scanning electron microscope (SEM). From morphology and elemental composition, particles were categorized in terms of seven groups: aggregated soot particles, mineral dust, sulphates (SO 4 2 ), sea-salt, tar balls/fly ash, rod-shaped particles associated with soot agglomerates, and those that could not be attributed to any of these groups. Refractive indices of aerosols were derived from chemical distributions obtained from SEM analysis and combined with in situ measurements of number–size distributions to determine optical properties of dry particles in the size range 0.1–3.5 µm. Particles exhibited marked spatial and temporal variability in chemical composition. They were externally mixed with highly absorbing soot particles. From number concentrations, light extinction and absorption coefficient ranges were ep = 19–755 Mm –1 and ap = 7–103 Mm –1 , respectively (at wavelength = 550 nm). Single scattering albedo, 0, varied from 0.61 to 0.87 with a mean value of 0.72 ± 0.08; this value was much lower than generally reported in the literature, a result that was attributed to high concentrations of highly absorbing soot (fractional number concentrations of up to 46% were observed in the SEM). The haze could be attributed to extinction of light by fine aerosols composed mainly of anthropogenic particles. High extinction coefficients and low single scattering albedo computed here demonstrate quantitatively the contributions of particulate matter to visibility reduction and the brown haze phenomenon in Cape Town.

Contrarian approach to and ultimate solution for 193-nm reticle haze

Abstract: Despite ample phenomenological evidence of reticle haze in IC manufacturing fabs, the mechanism of reticle haze formation is not well understood. Many attempts to control reticle haze formations are driven by trial-and-error approach and results are frequently contradicting and confusing. The authors apply extensive expertise of airborne molecular contamination (AMC) measurement and control and DUV optics protection [1,2] to develop a potential solution to the issue of 193-nm reticle haze. The authors outline the common mechanism of reticle haze formation and show that chemical modification of the reticle surface during mask manufacturing procedure is largely responsible for mask reticle susceptibility to AMC and surface molecular contamination (SMC). A proposed mechanism well explains available experimental and phenomenological data and the differences seen in chemical compositions of the haze particles observed at different fabs. The authors propose a single elegant solution for controlling multiple types of haze. Effectiveness of this solution is demonstrated through the field data obtained from production fabs.

Haze Detection and Removal in Remote Sensing Images Based on Undecimated Wavelet Transform

Abstract: A new approach for detecting and removing haze from panchromatic high-resolution remote sensing images based on undecimated wavelet transform is proposed.It involves detecting the haze areas and estimating its thickness from the scene by analyzing the low frequency information content,and rectifies the high frequency content by different amplitude according to different haze optical thickness.In our experiments,both visual inspection and statistical data show that the approach is valid.

Substrate effects on the characteristics of haze defect formation on the photomask surface under exposure condition

Abstract: We have explored substrate effects upon the characteristics of haze creation on the mask surface by performing surface analysis for each of Cr, MoSiON, and Qz substrates of the mask before and after laser exposure. We found out chemical ions such as sulfur and ammonium ions should have different mobility behavior towards haze defect creation depending on each substrate during laser exposure. This fact can partially clarify the reason why haze occurrence on the mask in real mass production mainly comes up with Qz substrate surface even though it has the lowest level of chemical residue on it. We also realized that sulfur ions are penetrating into a sub layer of Qz substrate and even deeper during laser exposure, which signifies that we may have to remove a thin surface layer from Qz substrate to further improve haze issue from the current standpoint.

A practical solution to the critical problem of 193 nm reticle haze

Abstract: The authors have developed and successfully implemented a practical, yet effective solution to help eliminate haze formation in the production fab. Based on a novel mechanism of haze formation described earlier, along with a thorough understanding of the reticle surface chemistry changes during the manufacturing process, the authors found an unexpectedly simple and straightforward way to prevent haze formation. This is possible regardless of the origin of the reticle, by controlling the purity of the immediate reticle environment.

Assessment of the dehydration‐greenhouse feedback over the Arctic during February 1990

Abstract: The effect of pollution-derived sulfuric acid aerosols on the aerosol-cloud-radiation interactions is investigated over the Arctic for February 1990. Observations suggest that acidic aerosols can decrease the heterogeneous nucleation rate of ice crystals and lower the homogeneous freezing temperature of haze droplets. On the basis of these observations, we hypothesize that the cloud thermodynamic phase is modified in polluted air mass (Arctic haze). Cloud ice number concentration is reduced, thus promoting further ice crystal growth by the Bergeron–Findeisen process. Hence, ice crystals reach larger sizes and low-levkel ice crystal precipitation from mixed-phase clouds increases. Enhanced dehydration of the lower troposphere contributes to decreased water vapour greenhouse effect and cools the surface. A positive feedback is created between surface cooling and air dehydration, accelerating cold air production. This process is referred to as the dehydration-greenhouse feedback (DGF). Simulations performed using an Arctic regional climate model for February 1990 are used to assess the potential effect of the DGF on the Arctic climate during February. Results show that the DGF has an important effect on cloud, atmospheric dehydration, and temperature over the Central and Eurasian Arctic, which is the coldest part of the Arctic. Cloud ice is significantly reduced and the total atmospheric water path is decreased by as much as 12%. This results in a surface cooling ranging between 0 and − 3 K. Moreover, the lower tropospheric cooling over the Eurasian and Central Arctic strengthens the atmospheric circulation at the upper level, thus increasing the aerosol transport from the mid-latitudes and enhancing the DGF. Over warmer areas, the increased aerosol concentration (caused by the DGF) leads to longer cloud lifetime, which contributes to warm these areas. Copyright © 2006 Royal Meteorological Society

Haze generation effect by pellicle and packing box on photomask

Abstract: ArF exposure tool have been implementing as a main work force of lithography. And haze generation by high actinic wavelength energy is big issue to be resolved. Many studies have been reported to remove or minimized ion residual on photomask surface and PKL developed haze free process. Even though the surface of photomask is free from ions generating haze defect by haze free process, but the ions from environment like pellicle and packing box make worsen to keep cleanness of photomask. The evaluation of environment effect like outgas from pellicle and packing box have been reported, but it was hard to know pure environmental effect because the surface of photomask was not enough clean to test it. Several pellicles and boxes with different material from supplies were tested in terms of outgas, contamination of ion and threshold energy generating haze. Some material of packing box and pellicle showed very sensitive to keep haze free photomask surface. Keyword: Haze, Pellicle, Storage & package material, Box, Outgas, Storage atmosphere, Sulfate Free Cleaning