Showing papers on "Haze published in 2000"

Reduction of Tropical Cloudiness by Soot

Abstract: Measurements and models show that enhanced aerosol concentrations can augment cloud albedo not only by increasing total droplet cross-sectional area, but also by reducing precipitation and thereby increasing cloud water content and cloud coverage. Aerosol pollution is expected to exert a net cooling influence on the global climate through these conventional mechanisms. Here, we demonstrate an opposite mechanism through which aerosols can reduce cloud cover and thus significantly offset aerosol-induced radiative cooling at the top of the atmosphere on a regional scale. In model simulations, the daytime clearing of trade cumulus is hastened and intensified by solar heating in dark haze (as found over much of the northern Indian Ocean during the northeast monsoon).

Chromatic framework for vision in bad weather

Abstract: Conventional vision systems are designed to perform in clear weather. However, any outdoor vision system is incomplete without mechanisms that guarantee satisfactory performance under poor weather conditions. It is known that the atmosphere can significantly alter light energy reaching an observer. Therefore, atmospheric scattering models must be used to make vision systems robust in bad weather. In this paper, we develop a geometric framework for analyzing the chromatic effects of atmospheric scattering. First, we study a simple color model for atmospheric scattering and verify it for fog and haze. Then, based on the physics of scattering, 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 "true" scene colors, from two or more images taken under different but unknown weather conditions.

Impact to lung health of haze from forest fires: the Singapore experience.

Abstract: Objective: From late July to the beginning of October 1997, countries of Southeast Asia experienced severe smoke haze pollution from uncontrolled forest fires mainly in the Indonesian states of Kalimantan and Sumatra. In Singapore, the impact of the 1997 haze was felt in the period from the end of August to the first week of November 1997 as a result of prevailing winds. Methodology: The Ministry of the Environment monitors ambient air quality by a country-wide telemetric air quality monitoring and management network, with 15 stations located throughout the island, linked via a public telephone network to a central control station at the Environment Building. The monitoring methods used are the United States Environmental Protection Agency (USEPA) reference methods. The Pollutant Standards Index (PSI) developed by the USEPA is used for the reporting of daily air pollution concentrations. Intervals on the PSI scale are related to the potential health effects of the daily measured concentrations of the five major air pollutants: sulfur dioxide, particulate matter (PM10), nitrogen dioxide, ozone and carbon monoxide. Public sector health facilities which come under the Ministry of Health, have computerized patient care systems which enable the routine ongoing surveillance of disease conditions for the period of the haze. Attention during the period of the haze was focused on conditions related to health effects of the haze. Data sources for the monitoring of the lung health effects of the haze included morbidity from public sector outpatient care facilities, accidents and emergency departments, public sector inpatient care facilities and national mortality data. Results: Findings from the health impact of the haze showed that there was a 30% increase in outpatient attendance for haze-related conditions. An increase in PM10 levels from 50 μg/m3 to 150 μg/m3 was significantly associated with increases of 12% of upper respiratory tract illness, 19% asthma and 26% rhinitis. Supplementary findings from scanning the electron microscopic sizing of the haze particles showed that 94% of the particles in the haze were below 2.5 μm in diameter. This was consistent with emissions from combustion sources originating over 500 km from Singapore. This has been of some concern because particles smaller than 2.5 μm in diameter can easily bypass normal body defence metabolism and penetrate deeply into the alveoli of the lungs. During the same period, there was also an increase in accident and emergency attendance for haze-related conditions. There was no significant increase in hospital admissions or in mortality. Conclusion: The present study found that the health effects from the 1997 smoke haze in Singapore were generally mild.

Origin of carbonaceous aerosols over the tropical Indian Ocean: Biomass burning or fossil fuels?

Abstract: We present an analysis of the carbon, potassium and sulfate content of the extensive aerosol haze layer observed over the tropical Indian Ocean during the Indian Ocean Experiment (INDOEX). The black carbon (BC) content of the haze is as high as 17% of the total fine particle mass (the sum of carbonaceous and soluble ionic aerosol components) which results in significant solar absorption. The ratio of black carbon to organic carbon (OC) (over the Arabian Sea and equatorial Indian Ocean) was a factor of 5 to 10 times larger than expected for biomass burning. This ratio was closer to values measured downwind of industrialized regions in Japan and Western Europe. These results indicate that fossil fuel combustion is the major source of carbonaceous aerosols, including black carbon during the events considered. If the data set analyzed here is representative of the entire INDOEX study then fossil fuel emissions from South Asia must have similarly contributed to aerosols over the whole study region. The INDOEX ratios are substantially different from those reported for some source regions of South Asia, thus raising the possibility that changes in composition of carbonaceous aerosol may occur during transport.

Air quality in Malaysia: impacts, management issues and future challenges.

Abstract: Objective Observations have been made on the long-term trends of major air pollutants in Malaysia including nitrogen dioxide, carbon monoxide, the ozone and total suspended particulate matter (particularly PM10), and sulfur dioxide, emitted from industrial and urban areas from early 1970s until late 1998. Methodology The data show that the status of atmospheric environment in Malaysia, in particular in highly industrialized areas such as Klang Valley, was determined both by local and transboundary emissions and could be described as haze and non-haze periods. Results During the non-haze periods, vehicular emissions accounted for more than 70% of the total emissions in the urban areas and have demonstrated two peaks in the diurnal variations of the aforementioned air pollutants, except ozone. The morning 'rush-hour' peak was mainly due to vehicle emissions, while the late evening peak was mainly attributed to meteorological conditions, particularly atmospheric stability and wind speed. Total suspended particulate matter was the main pollutant with its concentrations at few sites often exceeding the Recommended Malaysia Air Quality Guidelines. The levels of other pollutants were generally within the guidelines. Since 1980, six major haze episodes were officially reported in Malaysia: April 1983, August 1990, June 1991, October 1991, August to October 1994, and July to October 1997. The 1997 haze episode was the worst ever experienced by the country. Short-term observations using continuous monitoring systems during the haze episodes during these periods clearly showed that suspended particulate matter (PM10) was the main cause of haze and was transboundary in nature. Large forest fires in parts of Sumatra and Kalimantan during the haze period, clearly evident in satellite images, were identified as the probable key sources of the widespread heavy haze that extended across Southeast Asia from Indonesia to Singapore, Malaysia and Brunei. The results of several studies have also provided strong evidence that biomass burning is the dominating source of particulate matter. The severity and extent of 1997's haze pollution was unprecedented, affecting some 300 million people across the region. The amount of economic costs suffered by Southeast Asian countries during this environmental disaster was enormous and is yet to be fully determined. Among the important sectors severely affected were air and land transport, shipping, construction, tourism and agro-based industries. The economic cost of the haze-related damage to Malaysia presented in this study include short-term health costs, production losses, tourism-related losses and the cost of avertive action. Although the cost reported here is likely to be underestimated, they are nevertheless significant (roughly RM1 billion). Conclusions The general air quality of Malaysia since 1970 has deteriorated. Studies have shown that should no effective countermeasures be introduced, the emissions of sulfur dioxide, nitrogen oxides, particulate matter, hydrocarbons and carbon monoxide in the year 2005 would increase by 1.4, 2.12, 1.47 and 2.27 times, respectively, from the 1992 levels.

Impact of haze from forest fire to respiratory health: Indonesian experience.

Abstract: Objective This paper will describe the impact on the human lung of haze from forest fires in Indonesia based on data collected from different provinces. Methodology Data were collected from personal reports from pulmonologists working in the area as well as from province/district health offices and hospitals. Results These data show that there was a significant impact of haze to the human lung. There was a significant increase in respiratory conditions, lung function complaints and other related impacts. Conclusion Further studies, especially cohort studies, should be undertaken so that the long-term' impact of pollution from forest fires can be known.

Color perception through atmospheric haze.

Abstract: The radiance of most objects seen at a distance through the atmosphere is dominated by scattered light of a blue hue that should make the landscape appear predominately blue. However, common experience shows that people can see colors at a distance. A possible explanation of this paradox is that the visual system splits the light into a haze layer and the background landscape. A straightforward mathematical description of this splitting explains the results of a color matching study in the Great Smoky Mountains National Park. In this study, hues of objects seen through haze were found to be constant with changes in optical depth while colorfulness decreased exponentially.

Reduction of Tropical Cloudiness by Soot

Abstract: Measurements and models show that enhanced aerosol concentrations can augment cloud albedo not only by increasing total droplet cross-sectional area, but also by reducing precipitation and thereby increasing cloud water content and cloud coverage. Aerosol pollution is expected to exert a net cooling influence on the global climate through these conventional mechanisms. Here we demonstrate an opposite mechanism through which aerosols can reduce cloud cover and thus significantly offset aerosol-induced radiative cooling at the top of the atmosphere on a regional scale. In model simulations the daytime clearing of trade cumulus is hastened and intensified by solar heating in dark haze (as found over much of the northern Indian Ocean during the northeast monsoon).

Seasonal variation of aerosols in the Martian atmosphere

Abstract: Reanalysis of Viking Lander (VL) visible and Viking Orbiter infrared optical depth measurements shows that the visible to infrared ratio of total extinction opacity varies with season. The ratio is near to its previously reported constant value, 2.5, during dust storm periods and higher during northern spring and summer. The increase in ratio is hypothesized to be due to seasonally varying water ice haze, which produces a higher optical depth in the visible than in the infrared. This differs significantly from previous analyses of VL visible opacities which have assumed that only dust contributes to the optical depth measured during the early afternoon. Consequently we suggest that the Martian atmosphere is clearer of dust, especially during northern spring and summer, than previously suggested based upon VL data. We find dust visible optical depths of 0.1–0.4 during the northern spring and summer seasons, compared to previous estimates of 0.4–0.6. We also find that water ice hazes can provide roughly 50% of the total visible opacity in these seasons. For southern spring and summer, dust optical depths are more variable, but generally ≥0.4, with water ice opacity ≤0.1. The data suggest water ice optical depths are slightly higher and peak earlier (Ls = 80°–90°) at VL1 than at VL2 (Ls = 115°–130°). We estimate average northern summer water (daytime minimum) ice masses to be roughly 0.1–0.5 precipitable microns, depending on the assumed particle size distribution and hence 1–5% of the total water column. The observation of significant and previously unrecognized amounts of water ice haze suggests a larger role for water in controlling atmospheric heating rates and the vertical distribution of dust and water vapor than has been widely accepted to date.

LASE measurements of aerosol and water vapor profiles during TARFOX

Abstract: The Lidar Atmospheric Sensing Experiment (LASE) was operated autonomously from the NASA high-altitude ER-2 aircraft on nine flights during July 10–26, 1996, as part of the Tropospheric Aerosol Radiative Forcing Observational Experiment (TARFOX). LASE measured high-resolution profiles of water vapor and aerosols in regions of urban haze plumes over the U.S. eastern seaboard. Real-time LASE aerosol measurements were used to guide the in situ aircraft to sample haze layers. In this paper the vertical and horizontal distributions of aerosol backscatter measured by LASE are presented along with the temporal evolution of the haze layers. The aerosol backscatter data also identify the presence of gradients in the aerosol plumes, the presence of low-altitude clouds, and optically thin cirrus. This information is useful for many of the radiometeric observations made during TARFOX and can help explain observational differences among ground, airborne, and satellite observations. An iterative procedure is discussed which was used to invert lidar data to retrieve aerosol scattering ratios, extinction, and total optical depths from the LASE measurements. The sensitivity of these retrievals to assumed parameters is discussed and the results of retrievals are also compared to the well-known Bernoulli method. LASE water vapor measurements were made across the entire troposphere using a three “line pair” method to cover the range of water vapor mixing ratio from < 0.01 g/kg near the tropopause to ∼ 20 g/kg near the surface in a single aircraft pass over the experiment region. These measurements also show two-dimensional distributions of large spatial gradients in water vapor in the lower and upper troposphere. These observations are useful in the calculation of IR radiation fields and relative humidity fields, since relative humidity has a strong influence on the growth of aerosols and their scattering properties. Water vapor profiles, aerosol scattering ratios, aerosol extinction coefficients and aerosol optical depths were derived using the methodology presented in this paper from LASE measurements during TARFOX. These measurements are compared with other in situ and remote measurements during TARFOX in the companion papers [Ferrare et al., this issue (a, b)]

Sorbent treating of lubricating oils to remove haze precursors

Abstract: A base oil feed having a tendency to form a haze at ambient or sub-ambient temperatures is contacted with a solid adsorbent to remove at least a portion of the haze precursors, thereby reducing the haze-forming tendency of the base oil feed.

Modelling the effects of 'haze' on oil palm productivity and yield.

Abstract: * 21 Hurrell Road, Cambridge CB4 3RQ UK. A n increasing incidence ofatmospheric pollution in the Southeast Asian region leading to substantial reductions in solar radiation has promoted concern over the possible long term effects on oil palm yields. Previous models of oil palm growth and production have emphasized the importance for yield of adequate radiation but effects of reduced radiation on yield are not immediately apparent due to the long time required for bunch morphogenesis, the complexity of the process and-the presence of assimilate stores which serve to buffer the palm against periods of adverse conditions. Because climatic factors other than radiation influence the physiological processes on which productivity is dependent, models were deueloped to take into account the other main factors, namely, temperature, atmospheric oapourpressure deficit (VPD) and soil water auailability. Temperature had only a small effect because variations in mean temperatures were small. Soil water availability had a larger influence but VPD was the most important factor influencing yields. A lower VPD, lower temperature and improved soil water supply associated with reduced radiation tended to offset yield reductions due to lower light intensity. Under certain conditions, predicted yields were higher under low or moderate than under high radiation. High radiation was associated with high euapotranspiration (ET) rates and lower rainfall, leading to increasing likelihood ofsoil water

Techniques for identifying dust devils in Mars Pathfinder images

Abstract: Image processing methods used to identify and enhance dust devil features imaged by IMP (Imager for Mars Pathfinder) are reviewed. Spectral differences, visible red minus visible blue, were used for initial dust devil searches, driven by the observation that Martian dust has high red and low blue reflectance. The Martian sky proved to be more heavily dust-laden than pre-Pathfinder predictions, based on analysis of images from the Hubble Space Telescope. As a result, these initial spectral difference methods failed to contrast dust devils with background dust haze. Imager artifacts (dust motes on the camera lens, flat-field effects caused by imperfections in the CCD, and projection onto a flat sensor plane by a convex lens) further impeded the ability to resolve subtle dust devil features. Consequently, reference images containing sky with a minimal horizon were first subtracted from each spectral filter image to remove camera artifacts and reduce the background dust haze signal. Once the sky-flat preprocessing step was completed, the red-minus-blue spectral difference scheme was attempted again. Dust devils then were successfully identified as bright plumes. False-color ratios using calibrated IMP images were found useful for visualizing dust plumes, verifying initial discoveries as vortex-like features. Enhancement of monochromatic (especially blue filter) images revealed dust devils as silhouettes against brighter background sky. Experiments with principal components transformation identified dust devils in raw uncalibrated IMP images and further showed relative movement of dust devils across the Martian surface.

Haze-free lubricating oils

Abstract: A base oil feed having a tendency to form a haze at ambient or sub-ambient temperatures is contacted with a solid adsorbent to remove at least a portion of the haze precursors, thereby reducing the haze-forming tendency of the base oil feed.

Satellite Image Processing for Haze and Aerosol mapping (SIPHA): code description and presentation of results

Abstract: The monitoring of aerosol concentrations becomes a high environmental priority particularly in urban areas. The aerosol optical thickness in the visible spectrum is a surrogate for fine aerosol concentrations, especially under pollution conditions with low mixing height, and can be measured with high ground sampling density with the help of satellite sensors. The SIPHA code was developed for such application on high-resolution satellite images and allows quantification of the aerosol optical thickness over land, snow and sea. The code compares multitemporal satellite data sets and evaluates radiometric alterations due to the optical atmospheric effects of aerosols. A novel feature of this code is the decoupling of the radiometric alterations due to optical atmospheric effects from those due to ground temporal variations. A real-scale application of the code on time series of Landsat data was carried out over European urban sites.

In situ observations of aerosol properties above ice saturation in the polar tropopause region

Abstract: In the polar winter tropopause region (T≅ 200 K, p = 200 hPa) over northern Europe, the occurrence of a haze-mode aerosol in the diameter range 0.75 μm 10 μm where found in regions with Swν > 0.57 (Sice ≥ 1.17). Hence, a range of Swν values existed between 0.5 and 0.57, where the haze mode was present outside of cirrus clouds. The ratio of number densities of haze-mode particles to Aitken-mode particles reached ∼1.25% inside and <0.3% outside of ice-supersaturated regions. In descending air parcels a continuous decrease in the number density of haze-mode particles was observed. This suggests a deliquescence transition in rising air parcels and evaporation of liquid haze droplets without recrystallization in sinking air parcels. Consideration of the possible chemical composition, phase, and growth timescales of the haze-mode particles leads to the conclusion that they are likely to contain ammoniated sulfates in the liquid phase. On the basis of measured particle sizes and calculated extinction values, the observed haze mode may be a candidate for subvisible cirrus cloud particles.

Apparatus and method for measuring haze value

Abstract: PROBLEM TO BE SOLVED: To provide a means easily adjusted in positional movement in a lateral, longitudinal or oblique direction with respect to the surface desired to be measured of a sample corresponding to various forms and surface properties of the sample becoming a measuring object and capable of confirming the coincidence of the surface desired to be measured and the surface of a predetermined opening by the naked eye and a haze measuring method capable of confirming the accuracy of an apparatus due to the contamination of an integrating sphere and the deterioration of a photodetector to correct the same to ensure a reliable measuring result. SOLUTION: In the haze vaolue measuring method, the substrate on which a collimator lens and a reflecting mirror are arranged in the haze value measuring apparatus is constituted so as to be revolvable centering around the rotary shaft arranged to one corner of the substrate by 90 deg. and a confirming work space is provided in front of the opening of the integrating sphere and a haze standard plate to which a haze value (H) and a real value of total light transmissivity (Tt) are applied is measured during a measuring process to calculate a correction factor of the total light transmissivity and diffused light transmissivity and this correction factor is used in the measuring operation of the sample.

Filtering lubricating oils to remove haze precursors

Abstract: A dewaxed oil having a tendency to form a haze at ambient or sub-ambient temperatures is contacted with a solid adsorbent to remove at least a portion of the haze precursors, thereby reducing the haze-forming tendency of the dewaxed oil.

Modeling of potential power plant plume impacts on Dallas-Fort Worth visibility.

Abstract: During wintertime, haze episodes occur in the Dallas-Ft. Worth (DFW) urban area. Such episodes are characterized by substantial light scattering by particles and relatively low absorption, leading to so-called “white haze.” The objective of this work was to assess whether reductions in the emissions of SO2 from specific coal-fired power plants located over 100 km from DFW could lead to a discernible change in the DFW white haze. To that end, the transport, dispersion, deposition, and chemistry of the plume of a major power plant were simulated using a reactive plume model (ROME). The realism of the plume model simulations was tested by comparing model calculations of plume concentrations with aircraft data of SF6 tracer concentrations and ozone concentrations. A second-order closure dispersion algorithm was shown to perform better than a first-order closure algorithm and the empirical Pasquill-Gifford-Turner algorithm. For plume impact assessment, three actual scenarios were simulated, two with c...

Determination of Haze API From Forest Fire Emission During the 1997 Thick Haze Episode in Malaysia using NOAA AVHRR Data

Abstract: The results of a study conducted at the UTM Centre for Remote Sensing is reported to quantify haze from forest fire emission using NOAA AVHRR data. In this study, NOAA AVHRR LAC data dated 22 September 1997, one of the worst thick haze episode in Malaysia were used. The relationship between measured Air Pollution Index (API) of the measurements were carried out by Alam Sekitar Malaysia Sdn. Bhd. (ASMA) at five selected air pollution stations in Peninsular Malaysia. These relationships were shown as the best regression model. Finally, these models were used in generating maps of haze-intensity for individual haze components, namely carbon monoxide (CO), Ozone (O3), PM10, sulphur dioxide (SO2) and nitrogen dioxide (NO2) in order to predict haze API from NOAA AVHRR data. The results indicated that NOAA AVHRR data are very useful in reporting regional haze occurrence continuously.