Showing papers on "Haze published in 2005"

Rain, winds and haze during the Huygens probe's descent to Titan's surface

Abstract: The irreversible conversion of methane into higher hydrocarbons in Titan's stratosphere implies a surface or subsurface methane reservoir. Recent measurements from the cameras aboard the Cassini orbiter fail to see a global reservoir, but the methane and smog in Titan's atmosphere impedes the search for hydrocarbons on the surface. Here we report spectra and high-resolution images obtained by the Huygens Probe Descent Imager/Spectral Radiometer instrument in Titan's atmosphere. Although these images do not show liquid hydrocarbon pools on the surface, they do reveal the traces of once flowing liquid. Surprisingly like Earth, the brighter highland regions show complex systems draining into flat, dark lowlands. Images taken after landing are of a dry riverbed. The infrared reflectance spectrum measured for the surface is unlike any other in the Solar System; there is a red slope in the optical range that is consistent with an organic material such as tholins, and absorption from water ice is seen. However, a blue slope in the near-infrared suggests another, unknown constituent. The number density of haze particles increases by a factor of just a few from an altitude of 150 km to the surface, with no clear space below the tropopause. The methane relative humidity near the surface is 50 per cent.

Imaging of Titan from the Cassini spacecraft

Abstract: Titan, the largest moon of Saturn, is the only satellite in the Solar System with a substantial atmosphere. The atmosphere is poorly understood and obscures the surface, leading to intense speculation about Titan's nature. Here we present observations of Titan from the imaging science experiment onboard the Cassini spacecraft that address some of these issues. The images reveal intricate surface albedo features that suggest aeolian, tectonic and fluvial processes; they also show a few circular features that could be impact structures. These observations imply that substantial surface modification has occurred over Titan's history. We have not directly detected liquids on the surface to date. Convective clouds are found to be common near the south pole, and the motion of mid-latitude clouds consistently indicates eastward winds, from which we infer that the troposphere is rotating faster than the surface. A detached haze at an altitude of 500 km is 150–200 km higher than that observed by Voyager, and more tenuous haze layers are also resolved.

Raman lidar observations of aged Siberian and Canadian forest fire smoke in the free troposphere over Germany in 2003 : Microphysical particle characterization

Abstract: [1] Dual-wavelength Raman lidar observations were regularly carried out at Leipzig (51.3°N, 12.4°E) from May to August 2003. The measurements showed that particle backscatter and extinction coefficients in the free troposphere were higher compared to values in 2000–2002. Backward dispersion modeling indicates that intense forest fires that occurred in Siberia and Canada in spring/summer 2003 were the main cause of these free tropospheric haze layers. Measurements on 3 days were selected for an optical and microphysical particle characterization of these well-aged particle plumes. Particle lidar ratios measured at 532 nm wavelength were higher than at 355 nm. This property seems to be a characteristic feature of aged biomass-burning particles observed over central Germany. Mean particle Angstrom exponents calculated for the wavelength range from 355 to 532 nm varied from 0 to 1.3. Particle effective radii varied between 0.24 and 0.41 μm. Pollution advected from North America on 25 August 2003, in contrast, was characterized by considerably smaller particles. Mean effective radii were ≤0.2 μm, and Angstrom exponents were 1.8–2.1. Lidar ratios in that case were lower at 532 nm compared to those at 355 nm. Such signatures are characteristic for anthropogenic particles. At the moment, however, it cannot be completely ruled out that extremely hot forest fires in western areas of Canada generated comparably small particles. Except for this specific case the forest fire particles were considerably larger than what is usually reported from in situ observations of biomass-burning smoke. Possible explanations for this difference could be the kind of burning process, which could generate much larger particles in the source region, condensation of organic vapors on existing particles, and coagulation processes during the long transport time of more than a week. Relative humidity measured in these layers was very low. Hygroscopic growth of the particles therefore seemed to have little influence on the size of the particles. The forest fire smoke consisted of moderately absorbing material. Real parts of the complex refractive index of the particles were mostly <1.5, and imaginary parts were <0.01i. Single-scattering albedo in all cases varied between 0.9 and 0.98 at 532 nm.

Optical, physical, and chemical properties of tar balls observed during the Yosemite Aerosol Characterization Study

Abstract: [1] The Yosemite Aerosol Characterization Study of summer 2002 (YACS) occurred during an active fire season in the western United States and provided an opportunity to investigate many unresolved issues related to the radiative effects of biomass burning aerosols. Single particle analysis was performed on field-collected aerosol samples using an array of electron microscopy techniques. Amorphous carbon spheres, or “tar balls,” were present in samples collected during episodes of high particle light scattering coefficients that occurred during the peak of a smoke/haze event. The highest concentrations of light-absorbing carbon from a dual-wavelength aethalometer (λ = 370 and 880 nm) occurred during periods when the particles were predominantly tar balls, indicating they do absorb light in the UV and near-IR range of the solar spectrum. Closure experiments of mass concentrations and light scattering coefficients during periods dominated by tar balls did not require any distinct assumptions of organic carbon molecular weight correction factors, density, or refractive index compared to periods dominated by other types of organic carbon aerosols. Measurements of the hygroscopic behavior of tar balls using an environmental SEM indicate that tar balls do not exhibit deliquescence but do uptake some water at high (∼83%) relative humidity. The ability of tar balls to efficiently scatter and absorb light and to absorb water has important implications for their role in regional haze and climate forcing.

Health consequences of forest fires in Indonesia

Abstract: We combined data from a population-based longitudinal survey with satellite measures of aerosol levels to assess the impact of smoke from forest fires that blanketed the Indonesian islands of Kalimantan and Sumatra in late 1997 on adult health. To account for unobserved differences between haze and nonhaze areas, we compared changes in the health of individual respondents. Between 1993 and 1997, individuals who were exposed to haze experienced greater increases in difficulty with activities of daily living than did their counterparts in nonhaze areas. The results for respiratory and general health, although more complicated to interpret, suggest that haze had a negative impact on these dimensions of health.

High aerosol load over the Pearl River Delta, China, observed with Raman lidar and Sun photometer

Abstract: [1] Height-resolved data of the particle optical properties, the vertical extend of the haze layer, aerosol stratification, and the diurnal cycle of vertical mixing over the Pearl River Delta in southern China are presented. The observations were performed with Raman lidar and Sun photometer at Xinken (22.6°N, 113.6°E) near the south coast of China throughout October 2004. The lidar run almost full time on 21 days. Sun photometer data were taken on 23 days, from about 0800 to 1700 local time. The particle optical depth (at about 533-nm wavelength) ranged from 0.3-1.7 and was, on average, 0.92. Angstrom exponents varied from 0.65-1.35 (for wavelengths 380 to 502 nm) and from 0.75-1.6 (for 502 to 1044 nm), mean values were 0.97 and 1.22. The haze-layer mean extinction-to-backscatter ratio ranged from 35-59 sr, and was, on average, 46.7 sr. The top of the haze layer reached to heights of 1.5-3 km in most cases. Citation: Ansmann, A., R. Engelmann, D. Althausen, U. Wandinger, M. Hu, Y. Zhang, and Q. He (2005), High aerosol load over the Pearl River Delta, China, observed with Raman lidar and Sun photometer.

Dust storms and cyclone tracks over the arid regions in east Asia in spring

Abstract: [1] It has been argued that frequent dust storm developments in east Asia in spring are closely related to midlatitude synoptic-scale cyclone activity. This study investigates the relationship of springtime dust storms and other dust-related phenomena in east Asia to the tracks and locations of synoptic-scale cyclones by conducting statistical analyses of surface weather data, cyclone track data, and satellite data. Through these analyses, we discuss the role of cyclone activity on dust weather phenomena in east Asia. In the Gobi Desert and northeast China regions, strong cyclonic winds associated with strong cyclones are responsible for the dust weather developments, and the dust weather preferably occurs in the southwestern sector of the cyclone, where frontal activity and cold air action are significant. Despite the extremely dry climate, the formation of frontal cloud systems is evident particularly over the Gobi Desert, which will contribute to the higher frequency of severer dust weather. On the other hand, in the Taklamakan Desert severe dust weather (i.e., dust storm) is not so much affected by synoptic-scale cyclones, but weaker dust phenomena such as dust haze occur around the centers of cyclones that do not propagate farther eastward out of the Taklamakan region.

Arctic Study of Tropospheric Aerosol and Radiation (ASTAR) 2000: Arctic haze case study

Abstract: The ASTAR 2000 (Arctic Study of Tropospheric Aerosol and Radiation) campaign ran from 12 March until 25 April 2000 with extensive flight operations in the vicinity of Svalbard (Norway) from Longyearbyen airport (78.25°N, 15.49°E). It was a joint Japanese (NIPR Tokyo)–German (AWI Bremerhaven/Potsdam) airborne measurement campaign using AWI aircraft POLAR 4 (Dornier 228-101). Simultaneous ground-based measurements were done at the international research site Ny-Alesund (78.95°N, 11.93°E) in Svalbard, at the German Koldewey station, at the Japanese Rabben station and at the Scandinavian station at Zeppelin Mountain (475 m above sea level). During the campaign 19 profiles of various aerosol properties were measured. In general, the Arctic spring aerosol in the vicinity of Svalbard had significant temporal and vertical variability. A strong haze event occurred between 21 and 25 March in which the optical depth from ground-based observation was 0.18, which was significantly greater than the background value of 0.06. Airborne measurements on 23 March during this haze event showed a high aerosol layer with an extinction coefficient of 0.03 km −1 or more up to 3 km and a scattering coefficient from 0.02 in the same altitude range. From the chemical analyses of airborne measurements, sulfate, soot and sea salt particles were dominant, and there was a high mixing ratio of external soot particles in some layers during the haze event, whereas internal mixing of soot in sulfate was noticeable in some layers for the background condition. We argue that the high aerosol loading is due to direct transport from anthropogenic source regions. In this paper we focus on the course of the haze event in detail through analyses of the airborne and ground-based results. DOI: 10.1111/j.1600-0889.2005.00140.x

Atmospheric boundary-layer structure observed during a haze event due to forest-fire smoke

Abstract: During a haze event in Baltimore, U.S.A. from July 6 to 8, 2002, smoke from forest fires in the Quebec region (Canada), degraded air quality and impacted upon local climate, decreasing solar radiation and air temperature. The smoke particles in and above the atmospheric boundary layer (ABL) served as a tracer and provided a unique opportunity to investigate the ABL structure, especially entrainment. Elastic backscatter lidar measurements taken during the haze event distinctly reveal the downward sweeps (or wisps) of smoke-laden air from the free atmosphere into the ABL. Visualisations of mechanisms such as dry convection, the entrainment process, detrainment, coherent entrainment structures, and mixing inside the ABL, are presented. Thermals overshooting at the ABL top are shown to create disturbances in the form of gravity waves in the free atmosphere aloft, as evidenced by a corresponding ripple structure at the bottom of the smoke layer. Lidar data, aerosol ground-based measurements and supporting meteorological data are used to link free atmosphere, mixed-layer and ground-level aerosols. During the peak period of the haze event (July 7, 2002), the correlation between time series of elastic backscatter lidar data within the mixed layer and the scattering coefficient from a nephelometer at ground level was found to be high (R=0.96 for z =324 m, and R=0.89 for z=504 m). Ground-level aerosol concentration was at a maximum about 2 h after the smoke layer intersected with the growing ABL, confirming that the wisps do not initially reach the ground.

Experimental comparison between far‐ and near‐infrared wavelengths in free‐space optical systems

Abstract: We report an experimental comparison of three atmospheric transparency windows (800 nm, 1600 nm, and 10 μm) upon scattering attenuation from haze and fog. Our results prove that a 10-μm window is considerably better than the 1600 and 800 nm ones in dense and thick upslope fog conditions. © 2005 Wiley Periodicals, Inc. Microwave Opt Technol Lett 46: 319–323, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20976

Polishing slurry induced surface haze on phosphate laser glasses

Abstract: The effects of residual polishing slurry on the surface topology of highly polished, Nd-doped meta-phosphate laser glasses are reported. Glass samples were pitched polished using cerium oxide or zirconium oxide slurry at different pHs and then washed by different methods that allowed varying amounts of residual slurry to ‘dry’ on the surface. Upon rewashing with water, some of the samples showed surface haze (scatter), which scaled with the amount of residual slurry. Profilometry measurements showed that the haze is the result of shallow surface pits (100 nm–20 μm wide × ∼15 nm deep). Chemical analyses of material removed during rewashing, confirmed the removal of glass components as well as the preferential removal of modifier ions (e.g., K 1+ and Mg 2+ ). The surface pits appear to result from reaction of the glass with condensed liquid at the slurry particle–glass interface that produces water-soluble phosphate products that dissolves away with subsequent water contact. Aggressive washing, to remove residual slurry immediately following polishing, can minimize surface haze on phosphate glasses. It is desirable to eliminate haze from glass used in high-peak-power lasers, since it can cause scatter-induced optical modulation that can cause damage to downstream optics.

Laboratory studies of butane nucleation on organic haze particles: application to Titan's clouds.

Abstract: Titan, Saturn's largest satellite, has a thick nitrogen/methane atmosphere with various hydrocarbons present in minor amounts. Recent observations suggest that CH4 may condense to form clouds near the moon's tropopause. Titan's methane cloud formation is probably triggered by a sequential nucleation of hydrocarbons onto Titan's haze material as tropospheric convection occurs due to differential heating of the surface or as the haze settles through the lower stratosphere. To better constrain Titan's cloud formation mechanism, investigations of the nucleation of several hydrocarbons will be necessary. Butane was chosen for this study because it has a relatively high freezing point and is estimated to be present at 200 part per billion levels. If this amount of butane were to condense on each haze particle, a visible cloud would be observed. Laboratory measurements at T = 125 K were performed to determine the relative ease of solid butane nucleation onto laboratory-produced tholin particles having an element...

Surface haze and surface morphology of blown film compositions

Abstract: Reduction in surface haze is a very attractive way to improve the optical properties of most polyolefin films. This route becomes very viable for coextruded multilayer films where the inner layers may be utilized to provide the desired mechanical properties, such as high modulus, controlled shrinkage, and good tear strength while the outer 'skin' layers are utilized to give low surface and total haze values. This study summarizes the effect on surface haze of various such 'skin' layer compositions with a broader goal to produce high clarity and high modulus multilayer blown films. The surface roughness of multilayer films is measured using atomic force microscopy (AFM) and is directly correlated to the measured surface haze of the films.

The structure of the haze plume over the Indian Ocean during INDOEX: tracer simulations and LIDAR observations

Abstract: Three-dimensional, nested tracer simulations of a pollution plume originating from the Indian sub-continent over the Indian Ocean, in the framework of the Indian Ocean Experiment (INDOEX), between 5 and 9 March 1999, were performed with the Regional Atmospheric Modeling System (RAMS), to provide insight into the transport patterns of the pollutants, as well as to investigate the dynamical mechanisms controlling the vertical structure of the plume and its evolution in the vicinity of the Maldives Islands. Airborne and ground-based LIDAR observations of the structure of the haze plume made on 7 March 1999 were used to assess the quality of the simulations, as well as the impact of grid resolution on the vertical structure of the simulated plume. It is shown that, over the Arabian Sea, in the vicinity of the Maldives Islands, the pollutants composing the plume observed by the airborne LIDAR essentially originated from the city of Madras and that the vertical structure of the plume was controlled by the diurnal cycle of the continental boundary layer depth. A combination of tracer simulations and remote sensing observations (airborne LIDAR, ship-borne photometer, ground-based LIDAR in Goa) was used to analyse the diurnal evolution of the haze plume over the sea. We find evidence that the sea breeze circulation and orographic lifting taking place in the southern part of the Indian sub-continent during the daytime play a crucial role in the modulation of the continental boundary layer depth, and in turn, the haze plume depth. The eastward shift of the subtropical high from central India to the Bay of Bengal after 6 March lead to an increase in the tracer concentrations simulated over the Arabian Sea, in the region of intensive observations north of the Maldives, as transport pathways form Hyderabad and Madras were modified significantly. The nesting of a high horizontal resolution domain (5 km, with 39 vertical levels below 4000 m above mean seal level) allows for a better representation of local dynamics, the circulation of sea and mountains breezes, and therefore a noticeable improvement in the representation of the pollutants' plume in the simulation.

Methods and results from a new survey of values for eastern regional haze improvements.

Abstract: A contingent valuation survey was designed and implemented in 2003 to elicit the willingness to pay for haze reduction in scenic areas of the Eastern United States. This survey updated and enhanced a portion of a 1988 survey, Chestnut and Rowe’s Preservation Values Study, which is commonly used to estimate benefits of haze reduction policies. The 2003 survey incorporated features to address criticisms of the 1988 survey regarding its lack of budget constraints and its simplistic descriptions of changes in visibility. In preparing the new survey, we identified a fundamental error in the 1988 survey regarding the amount of visibility change that respondents were asked to value. When corrected, it reduces the estimates in that study of willingness to pay per unit of visibility change by ~40%. More importantly, we estimate that haze reduction benefits based on that study are overstated by ~70%. Results from our 2003 survey demonstrate that the distribution of willingness to pay is highly skewed, whic...

Reconciliation and Interpretation of Big Bend National Park Particulate Sulfur Source Apportionment: Results from the Big Bend Regional Aerosol and Visibility Observational Study—Part I

Abstract: The Big Bend Regional Aerosol and Visibility Observational (BRAVO) study was an intensive monitoring study from July through October 1999 followed by extensive assessments to determine the causes and sources of haze in Big Bend National Park, located in Southwestern Texas. Particulate sulfate compounds are the largest contributor of haze at Big Bend, and chemical transport models (CTMs) and receptor models were used to apportion the sulfate concentrations at Big Bend to North American source regions and the Carbon power plants, located 225 km southeast of Big Bend in Mexico. Initial source attribution methods had contributions that varied by a factor of ≥2. The evaluation and comparison of methods identified opposing biases between the CTMs and receptor models, indicating that the ensemble of results bounds the true source attribution results. The reconciliation of these differences led to the development of a hybrid receptor model merging the CTM results and air quality data, which allowed a nea...

Haze formation in model beer systems.

Abstract: The interaction of a haze-active protein (gliadin) and a haze-active polyphenol (tannic acid) was studied in a model beer system in order to investigate the principle mechanisms of haze formation at low temperatures. Low concentrations (g/L) of tannic acid, high concentrations of gliadin, and comparatively high temperatures lead to maximum haze values. When considered on a molar basis, the greatest haze levels are displayed at an approximate 1:1 equivalence of polyphenol and protein. The greater part of haze formation was completed within 0.5 h, irrespective of the concentration of gliadin, the concentration of tannic acid, and the temperature of the model solution.

Preface to special section on Global Aerosol System

Abstract: [1] This special issue brings together papers that were presented in a workshop of experts on the global aerosol system and its impacts on climate. Aerosols originate as urban haze and rural haze, and owing to long range transport of pollutants, becomes widespread aerosol layers across the globe. [2] Atmospheric aerosols play a dual role in the climate system and the hydrologic cycle (see reviews in the work of Ramanathan et al. [2001] and Kaufman et al. [2002]). Their first role is interaction with solar and thermal radiation: by scattering sunlight and reflecting a fraction of it back to space aerosols cool the climate system; by absorbing sunlight in the atmosphere aerosols further cool the surface but warm the atmosphere, changing the temperature and humidity profiles and the conditions for cloud development. [3] Aerosol particles play a second role by affecting the hydrologic cycle: serving as cloud condensation nuclei and ice nuclei, aerosols control the cloud droplet concentration and size. Higher number concentrations of submicron pollution aerosol tend to decrease the cloud droplet size and prevent or delay development of precipitation. Supermicron sea-salt particles can reintroduce precipitation and oppose the effect of pollution aerosol. These processes may cause changes in precipitation patterns to which the human civilization adapted during the last millennium, changes in cloud cover, and possible changes in the frequency of extreme events. [4] No less important is the aerosol effect on health, air quality, and agriculture that brought policy responses in Europe and North America in the last century and is affecting policy decisions in east and southern Asia today. Therefore advancements in aerosol science, together with research on the effect of greenhouse and trace gases and increased ability to predict the impact of human activity on the regional and global aerosol, can be expected to have direct impact on energy use and economic activities in nations around the world. [5] Unraveling these aerosol effects is still difficult because of the high spatial and temporal variability of sources, complex interaction of aerosol with atmospheric trace gases and clouds, and the short lifetime of aerosol of about a week, owing to wet and dry depositions. A single aerosol particle over the Mediterranean Sea can include anthropogenic sulfate and carbonaceous material from Europe, coating natural dust particle from Africa. [6] Today’s aerosol assessments of climate are based on aerosol chemical transport models and climate models that cannot yet resolve the aerosol interaction with clouds with their microscale physical and chemical exchanges. Models make good progress in capturing aerosol evolution, but source characterization is difficult. Accurate assessments of aerosol distribution and composition, the anthropogenic component, and the impacts on radiation and water cycle therefore require orchestrated observations of aerosol, precursor trace gases, clouds and precipitation from satellites, networks of surface-based instruments, laboratory studies, and dedicated field experiments. The observations require sufficient information content, accuracy, and global coverage to permit their integration into and testing of aerosol chemical transport, assimilation, and climate models [Intergovernmental Panel on Climate Change (IPCC), 2001]. [7] In the last decade, research of the global aerosol system was invigorated by an array of new measurements in several temporal and spatial scales, the fruits of which we start to see in this special issue, and the development of new models: [8] 1. Global, daily, and multidaily observations of aerosol, clouds, and their properties derived from satellite measurements of the scattered solar light, utilizing its spectral, angular, and polarization properties. [9] 2. Satellite measurements of the vertical distribution of aerosol, clouds, and precipitation using lidars and radars and thermal infrared and microwave radiometers. [10] 3. Surface networks that continuously measure in situ and remotely (both passive radiometers and active sensors) the aerosol physical and chemical properties, distribution of solar radiation, clouds, and precipitation. [11] 4. Intensive field campaigns that concentrate the measurement power in a given region for a limited period of time and help understand the aerosol sources and aerosol and cloud processes. [12] 5. Laboratory analysis of aerosol particles and measurements of aerosol processes. [13] 6. Development of transport models that start to mimic the aerosol distribution measured from satellite and surface networks. [14] 7. Assimilation of the aerosol models and measurements into climate models to study the effects of aerosol on JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 110, D10S01, doi:10.1029/2004JD005724, 2005

Reconciliation and interpretation of the Big Bend National Park light extinction source apportionment: results from the Big Bend Regional Aerosol and Visibility Observational Study--part II.

Abstract: The recently completed Big Bend Regional Aerosol and Visibility Observational (BRAVO) Study focused on particulate sulfate source attribution for a 4-month period from July through October 1999. A companion paper in this issue by Schichtel et al. describes the methods evaluation and results reconciliation of the BRAVO Study sulfate attribution approaches. This paper summarizes the BRAVO Study extinction budget assessment and interprets the attribution results in the context of annual and multiyear causes of haze by drawing on long-term aerosol monitoring data and regional transport climatology, as well as results from other investigations. Particulate sulfates, organic carbon, and coarse mass are responsible for most of the haze at Big Bend National Park, whereas fine particles composed of light-absorbing carbon, fine soils, and nitrates are relatively minor contributors. Spring and late summer through fall are the two periods of high-haze levels at Big Bend. Particulate sulfate and carbonaceous compounds contribute in a similar magnitude to the spring haze period, whereas sulfates are the primary cause of haze during the late summer and fall period. Atmospheric transport patterns to Big Bend vary throughout the year, resulting in a seasonal cycle of different upwind source regions contributing to its haze levels. Important sources and source regions for haze at Big Bend include biomass smoke from Mexico and Central America in the spring and African dust during the summer. Sources of sulfur dioxide (SO2) emissions in Mexico, Texas, and in the Eastern United States all contribute to Big Bend haze in varying amounts over different times of the year, with a higher contribution from Mexican sources in the spring and early summer, and a higher contribution from U.S. sources during late summer and fall. Some multiple-day haze episodes result from the influence of several source regions, whereas others are primarily because of emissions from a single source region.