Showing papers on "Haze published in 2008"

Flood or drought: How do aerosols affect precipitation?

Abstract: Aerosols serve as cloud condensation nuclei (CCN) and thus have a substantial effect on cloud properties and the initiation of precipitation. Large concentrations of human-made aerosols have been reported to both decrease and increase rainfall as a result of their radiative and CCN activities. At one extreme, pristine tropical clouds with low CCN concentrations rain out too quickly to mature into long-lived clouds. On the other hand, heavily polluted clouds evaporate much of their water before precipitation can occur, if they can form at all given the reduced surface heating resulting from the aerosol haze layer. We propose a conceptual model that explains this apparent dichotomy.

Polarization-based vision through haze

Abstract: We present an approach for easily removing the effects of haze from passively acquired images. Our approach is based on the fact that usually the natural illuminating light scattered by atmospheric particles (airlight) is partially polarized. Optical filtering alone cannot remove the haze effects, except in restricted situations. Our method, however, stems from physics-based analysis that works under a wide range of atmospheric and viewing conditions, even if the polarization is low. The approach does not rely on specific scattering models such as Rayleigh scattering and does not rely on the knowledge of illumination directions. It can be used with as few as two images taken through a polarizer at different orientations. As a byproduct, the method yields a range map of the scene, which enables scene rendering as if imaged from different viewpoints. It also yields information about the atmospheric particles. We present experimental results of complete dehazing of outdoor scenes, in far-from-ideal conditions for polarization filtering. We obtain a great improvement of scene contrast and correction of color.

The 7–13 March 2006 dust storm over West Africa: Generation, transport, and vertical stratification

Abstract: Several studies have shown the importance of desert dust aerosols in weather forecast models. Nevertheless, desert dust has been poorly represented in such models and is the source of some prediction errors, in particular for tropical and subtropical regions. The purpose of this paper is to illustrate the formation and the three-dimensional transport of a severe dust storm which occurred in March 2006 over West Africa. An intense dust haze was transported southward over the Gulf of Guinea thereby generating an aerosol optical thickness (AOT) greater than 4 over Nigeria. The MesoNH mesoscale atmospheric model coupled with new dust parameterization schemes has been used to illustrate the three-dimensional transport of the dust plume and the vertical layering of this desert air mass above the lower atmosphere monsoon flux layer. It is modeled that more than 50 g m−2 of dust was emitted during this event from the surface by a strong Harmattan wind over the Sahel region. It is also shown that when the dust layer is located over the boundary layer, it can modify the atmospheric stability by as much as 9.5 K in terms of potential temperature in the lowest 2000 m of the atmosphere.

Ten years of multiwavelength Raman lidar observations of free-tropospheric aerosol layers over central Europe: Geometrical properties and annual cycle

Abstract: [1] We present geometrical properties and seasonal variations of appearance of aerosol particle pollution in the free troposphere over the central European lidar site at Leipzig, Germany. The data set has been acquired with Raman lidar in the past 10 years in the framework of the German Lidar Network (1997–2000) and since 2000 in the framework of the European Aerosol Research Lidar Network (EARLINET). In summary we analyzed 1028 measurements. Geometrical depth of the pollution layers was � 1k m in 33% of all cases. Geometrical depths >5 km were found in 10% of all cases. Traces of particle pollution were detected up to the height of the tropopause. Forest-fire burning in North America causes intrusion of particles into the stratosphere. Seven hundred seventeen of all observations were carried out on the basis of a regular measurement schedule which allows us to establish a statistic on the frequency of particle transport in the free troposphere. In 43% of the regular measurements we observed pollution above the continental boundary layer. The lofted particle layers largely result from intercontinental long-range transport. We use backward trajectory analysis to identify the main source regions of the lofted pollution layers. In 19% of all regular measurements, free-tropospheric pollution was advected from North America. Forest-fire smoke from Canada and anthropogenic pollution from urban areas of the United States of America and Canada were the sources of the particle layers. We find a strong seasonal dependence of occurrence of these layers with a peak in June–August of each year. In a few cases we observed forest-fire smoke advected from Siberia and east Asia with winds from westerly directions. Pollution advected from areas north of 70N presents another transport channel. That pollution consists of Arctic haze or mixtures of haze with anthropogenic pollution. The main occurrence of such particle layers is around springtime of each year. Import of mineral dust from the Sahara represents another transport path. Most of such cases are observed during late springtime and summertime. Free-tropospheric pollution advected from east and southeast Europe and Russia presents one transport channel from within the Euro-Asian continent.

Effects of meteorology, astronomical variables, location and human disturbance on the singing apes: Hylobates albibarbis.

Abstract: Gibbons are characterized by their species-specific calls. The frequency of singing is known to be affected by rainfall, with singing occurring less in the wet season. I investigate the hypothesis that gibbon singing is also affected by the natural light-dark cycle, and by the changing light intensity and air quality resulting from the smoke haze which blankets the Indonesian island of Borneo on a yearly basis. I compare three singing variables—onset of singing, average duration of singing bout and number of female great calls produced during the dry season of 2006 when there was no smoke haze (June–August) and when there was smoke haze present (September–November). I present evidence which indicates that the changes in singing behavior are affected by changes in rainfall and smoke intensity but not by other meteorological factors (i.e. wind and light intensity) or changing astronomical cues (light intensity, month, time of sunrise, time of moonrise, nocturnal illumination index, day length and night length). The possible long-term effects of this on gibbon behavior and territoriality are discussed. The need to carry out more research on the long-term effects of the smoke haze on wildlife behavior and possible solutions to the problem are discussed. Am. J. Primatol. 70:386–392, 2008. © 2007 Wiley-Liss, Inc.

Vision and the atmosphere

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.

Cloud effects from boreal forest fire smoke: evidence for ice nucleation from polarization lidar data and cloud model simulations

Abstract: Polarization lidar observations from the interior of Alaska have revealed unusual supercooled altocumulus cloud conditions in the presence of boreal forest fire smoke from local and regional fires. At temperatures of about −15 °C, the lidar data show ice nucleation prior to liquid cloud formation (i.e. below water saturation), as well as the occasional glaciation of the liquid layer. Thus the smoke aerosol appears to act as ice nuclei that become activated in updrafts before the liquid cloud forms, as the concentrated aqueous organic solutions are diluted sufficiently to allow them to freeze heterogeneously. This haze particle freezing process is similar to the production of cirrus ice crystals homogeneously at much colder temperatures. To test this hypothesis, cloud microphysical model simulations constrained by the measurements were performed. They indicate that this heterogeneous ice nucleation scenario can be supported by the cloud model. Although ice formation in this manner may generally act in the atmosphere, the boreal smoke particles produce an unusually dramatic effect in the lidar data. We conclude that smoke-induced ice nucleation occurs at moderate supercooled temperatures either through the effects of raised soil/dust particles embedded in the smoke droplets, coated soot aerosol or through the nucleation via certain organic solutions.

Local causes, regional co-operation and global financing for environmental problems: the case of Southeast Asian Haze pollution

Abstract: Lack of action on cross-border environmental problems in developing coun- tries is often ascribed to gaps in local capacity and resources, failure of regional cooperation and lack of financial support from rich countries. Using the case of the Southeast Asian Haze pollution from forest and peat fires in Indonesia, we explore the challenges posed by environmental problems whose causes are closely linked to local development and livelihood strategies, and whose impacts are local, regional (haze) as well as global (carbon emissions). We assess whether there are real opportunities to implement effectively the recent Association of Southeast Asian Nations (ASEAN) Agreement on Transboundary Haze Pollution. To address the deep determinants behind haze pollution, we propose signatories to the Agreement refocus their efforts to controlling peat fires rather than to strive for a zero-burning regime. We also recommend a new approach to financing sustainable development based on rules and incentives, with a regional pool of funds, contributed by rich countries through the Global Environment Facility and countries in Southeast Asia.

The Climatic Characteristics and Change of Haze Days over China during 1961-2005

Abstract: In the context of haze days during the period 1961-2005 over China,the characteristics and changes of temporal and spatial distribution of haze days as well as possible reason and the relationship with the trend of global solar radiation and sunshine duration are analyzed.Result shows that the spatial pattern of annual and seasonal haze days presents more in eastern and less in western China.There are three regions with the number of haze days coinciding with the economically developed regions:the lower and middle reaches of the Yangtze River,North China and South China.Apart from Northeast China,the Qinghai-Tibet Plateau and western part of Northwest China with small annual variation and less in values,the annual variation of haze days is obvious in most of the other regions.The haze days are maximum in winter and the minimum in summer.In recent 45 years,the national mean annual haze days exhibited obvious increasing trends with the maximum in 2004.In most parts of eastern China,the number of haze days shows increasing trends,particularly in areas such as the middle and lower reaches of the Yangtze River,Pearl River Basin and west of Henan Province with obvious trends and the increments of haze days are great,where the increasing air pollution caused by human activities and climate change are the possible reasons.In western China and Northeast China,the trend is decreasing.In North China,the middle and lower reaches of the Yangtze River and South China,the trends of haze days and sunshine durations are opposite.The increasing haze days may be one of the reasons leading to the decrease of global solar radiations.In Northeast China,Northwest China,Southwest China and Tibet-Qinghai Plateau,the trends of haze days show slight decrease and are identical to the change of sunshine duration.But in these regions the haze seldom occurs and the change of it will not greatly affect the change of sunshine duration and global solar radiation.

Dehazing an Image Using a Three-Dimensional Reference Model

Abstract: An image may be dehazed using a three-dimensional reference model. In an example embodiment, a device-implemented method for dehazing includes acts of registering, estimating, and producing. An image that includes haze is registered to a reference model. A haze curve is estimated for the image based on a relationship between colors in the image and colors and depths of the reference model. A dehazed image is produced by using the estimated haze curve to reduce the haze of the image.

Dust storm and black cloud influence on aerosol optical properties over Cairo and the Greater Delta region, Egypt

Abstract: We have analysed aerosol and cloud properties, obtained from moderate resolution imaging spectroradiometer (MODIS) data, over Cairo and the Greater Delta region during the spring months of March, April and May (MAM) and the autumn months of September, October and November (SON) in the years 2004, 2005 and 2006. During these two time periods, we have examined dust storms, dense haze and a smog-like phenomenon known, locally, as the 'black cloud'. Our work is based on the aerosol optical depth (AOD), fine mode fraction (FMF) and cloud properties (cloud top temperature (CTT), cloud top pressure (CTP), atmospheric infrared sounder (AIRS) temperature profiles and water vapour column). High anomalous water vapour is detected, which we believe is as a result of pollution aerosols rather than dust and is hence acting as cloud condensation nuclei (CCN). The CTT shows increasing and decreasing trends, corresponding to the dust occurring at ∼750-800 hpa and pollution episodes at >900 hpa, respectively as observed from the CTP. Temperature inversion conditions, as well as adverse weather conditions, contribute to the pollution observed by preventing pollutants from escaping to the higher atmosphere.

Diffuse greenhouse covering materials material technology, measurements and evaluation of optical properties

Abstract: At high irradiation levels, diffuse greenhouse coverings result in better light distribution, lower crop temperature, decreased transpiration, and increased photosynthesis and growth. Various greenhouse coverings (plastic films, glass panes and temporal coatings) can be used to transform direct light into diffuse light. However, light diffusing properties of materials are hardly known. Optical properties of a wide range of materials are being currently investigated, including direct light transmission under different angles of incidence, transmission for hemispherical light and haze. The potential of diffusing greenhouse covering materials is estimated by analyzing the global radiation data for different climatic regions: marine winter climate (The Netherlands), Mediterranean mild winter climate (Italy) and semi-arid climate (Arizona). The required optical properties differ for the various climates. With modern material technology, the optical properties (haze and light transmission) can be altered to meet the requirements for different climatic regions in order to optimize crop performance in the future.

A vertical profile of PM10 dust concentrations measured during a regional dust event identified by MODIS Terra, western Queensland, Australia

Abstract: Accurate determination of the spatiotemporal properties of dust plumes and their dust concentrations is essential for calibration of satellite products and the initialization and validation of numerical models that simulate the physical properties and affects of dust events. In this paper, we present a 500 m vertical profile of PM10 dust concentrations measured during a regional dust event in western Queensland, Australia. PM10 dust concentrations within the haze were found to be >20 times background ambient values and decreased with height following an exponential function. We apply an over-land algorithm to MODIS Terra satellite images of the dust haze to enhance its visual appearance against the bright land surface and define its size. In conjunction with the measured attenuation of dust concentrations with height we calculate the PM10 dust load of the plume to be ∼60% of that which would have been calculated assuming a constant dust concentration up to the dust ceiling height. Results extend previous findings from tower-based studies made close to the surface and confirm that atmospheric dust concentrations decrease rapidly with increasing height, thereby enabling more accurate calculation of atmospheric dust loads during synoptic-scale dust outbreaks.

Summer time haze characteristics of the urban atmosphere of Gwangju and the rural atmosphere of Anmyon, Korea

Abstract: An extensive visibility monitoring was carried out simultaneously in the urban area of Gwangju and the rural area of Anmyon, Korea. This study examines patterns of visibility impairment and haze-forming pollutant concentrations on both sites resulting from natural and anthropogenic sources of gases and particles. Optical visibility measurements by a transmissometer, a nephelometer and an aethalometer provide aerosol light extinction, scattering, and absorption coefficients for both sites. In order to investigate the physico-chemical characteristics of atmospheric aerosols, aerosol samples were collected by various aerosol samplers at GJVMS (Gwangju Visibility Monitoring Station) and at KGAWO (Korea Global Atmosphere Watch Observatory), respectively. In addition, haze characteristics causing visibility impairment at those two sites were analyzed to obtain source contributions by regionally transported aerosols using grid analysis and display system (GrADS) from NECP reanalysis data. During the intensive monitoring period, ammonium sulfate was dominantly responsible for the fine particle mass loading at GJVMS, whereas organic carbon was the largest contributor at KGAWO. Light scattering by particles accounted for 52.8 to 81.3% of the range at the urban site, GJVMS and for 72.1 to 94.2% of the range at the rural site, KGAWO. Light absorption by the EC and NO2 was between 14.5 and 34.8% at GJVMS, which was higher than the observed 1.1 ∼ 6.8% at KGAWO, respectively. Light scattering by aerosol was higher in the rural area than in the urban area. And organic carbon concentration was observed to be significantly higher than the concentration of elemental carbon at KGAWO. These haze-forming carbonaceous particles originate from anthropogenic pollutants at the urban atmosphere but they can be produced by natural environments such as marine and forest at the rural atmosphere.

Dust haze in Valles Marineris observed by HRSC and OMEGA on board Mars Express

Abstract: [1] We present analysis of a bright haze observed inside Valles Marineris, which formed in mid northern spring. The data were collected by the High Resolution Stereo Camera (HRSC) and the imaging spectrometer, Observatoire pour la Mineralogie, l'Eau, les Glaces et l'Activite (OMEGA), aboard Mars Express. This study provides a case example of the power of simultaneous multiple emission angle and hyperspectral imaging for study of aerosols and clouds in the Martian atmosphere. The haze appeared thinner after three days and disappeared in nine days. It was limited to a 2-km layer at the bottom of the canyon. The color was redder than the underlying surface. The analysis of the OMEGA spectra indicates that this haze was composed of dust particles. The dust layer appeared brighter with the HRSC stereo channels than the nadir channel due to longer scattering paths. We have estimated the optical depth of the haze by fitting both HRSC and OMEGA data with radiative transfer calculations. The retrieval of the optical depth is very sensitive to the aerosol scattering model used and the reflectance of the surface. Applying an aerosol scattering model derived from sky surveys at a constant elevation by the Imager for Mars Pathfinder, the optical depth of the haze is estimated from HRSC data to be within 1.7 to 2.3 at the wavelength (λ) of 0.675 μm. The wavelength dependence is obtained from OMEGA spectrum. It increases to 2.2–2.6 at λ = 1.35 μm and moderately decreases to 1.2–1.8 at λ = 2.4 μm.

Application of Wavelet Transform on Airborne Suspended Particulate Matter and Meteorological Temporal Variations

Abstract: Malaysia has experienced several haze periods since early 1980s in which suspended particulate matter (SPM) was the major components. The temporal variations observed are the result of interactions of various meteorological variables and pollutants emissions in different time scale. In order to study the relationship between particulate matter, temperature, rainfall and wind speed, non-decimated wavelet transform is applied to the time series. The low frequency components of the meteorological time series showed significant relationship with PM10 while the high frequency spectrums showed no significant relationship with PM10. The findings also support the suggestion that during the dry season, one of the major sources of particulates was from outside the country. Key-Words:PM10, Wavelet, Rainfall, Temperature, Wind speed, Non-decimated wavelet transform.

Study on Characteristics of PM 2.5 and Its Ionic Constituents in Chuncheon, Korea

Abstract: Fine particles () were collected and analyzed from November 2005 through August 2007 in Chuncheon, Korea to investigate the characteristics of and its ionic constituents. The average concentration during the study period was , which is almost two times higher than the annual US NAAQS standard of . concentrations were higher in spring and winter than in summer and fall. During spring, Asian Dust events dramatically enhanced concentrations, and long-range transport of emitted in industrial area of China often occurred during winter based on trajectory analysis. Contribution of to concentrations ranged from during Asian Dust events to , indicating that a large portion of was transported from China during Asian Dust events. Among the major ionic constituents showed the highest concentration, followed by , and . Chuncheon appeared to be rich environment, indicating that and were the predominant forms of and in . Haze has frequently occurred in Chuncheon since So-Yang dam was constructed in 1973. Haze events were observed on 23 days during sampling period, and the average concentration was approximately 1.6 times higher during haze events than during non-haze events. This result suggests that haze enhances the secondary aerosol formation because the aerosol spontaneously absorbs water to form a saturated salt solution, deriving a significant increase in the mass of the particle.

A shift in Jupiter's equatorial haze distribution imaged with the Multi-Conjugate Adaptive Optics Demonstrator at the VLT

Abstract: Jupiter was imaged during the Science Demonstration of the MCAO Demonstrator (MAD) at the European Southern Observatory's UT3 Very Large Telescope unit. Io and Europa were used as natural guide stars on either side of Jupiter, separated from each other by about 1.6 arcmin from 23:41 to 01:32 UT (2008 Aug 16/17). The corrected angular resolution was 0.090 arcsec across the entire field of view, as measured on background stars. The observations at 2.02, 2.14, and 2.16 micrometers were sensitive to portions of the Jovian spectrum with strong methane absorption. The data probe the upper troposphere, which is populated with a fine (~0.5 micrometer) haze. Two haze sources have been proposed: lofting of fine cloud particles into the stable upper troposphere, and condensation of hydrazine produced via ammonia photochemistry. The upper tropospheric haze is enhanced over Jupiter's equatorial region. Dramatic changes in the underlying cloud cover--part of the 2006/2007 "global upheaval"--may be associated with changes in the equatorial haze distribution now evident in the 2008 MAD images. Haze reflectivity peaked at 5 degrees N in HST/NICMOS data from 2005, but it now peaks at the equator. The observations suggest that haze variation is controlled by particle size, cloud source variation, diffusion, and horizontal transport.

Identifying Atmospheric Aerosols with Polarization Lidar

Abstract: A variety of types of aerosol particles, both natural and human-made, are commonly suspended in the atmosphere. Different aerosol types have characteristic shapes, but basically fall into two categories: spherical and irregular. Haze and forest fi re smoke particles are examples of the former, and desert dust and biogenic debris (e.g., pollen) of the latter. It is shown here that the capability of polarization lidar systems to sense the exact shape of particles makes it a powerful tool to remotely identify many types of aerosols. This is particularly important in the study of how aerosols may affect the properties of clouds.