Showing papers on "Haze published in 1995"

The Arctic Haze Phenomenon

Abstract: The arctic atmosphere is the repository for surprisingly high concentrations of pollutants throughout the winter months. The polluted air mass in question includes virtually all the atmosphere above the Arctic Circle and also two great lobes that extend down over Eurasia and North America. In extent, this generally polluted airmass system is about as large as the African continent. The rather severe pollution throughout this airmass system in winter is, to a large extent, a result of the lowered rates of particle and gas removal in this cold, dark, and rather stable system. The arctic haze possibly has important climatic and ecological and global change implications that are coming under investigation in a number of planned studies.

Chapter 10 - Climatic effects of changing atmospheric aerosol levels

Abstract: This chapter discusses the various sources of atmospheric aerosols, their potential change in the future, and the effects that aerosols have on climate through perturbation of the radiation balance and through modification of cloud properties. Tremendous amounts of dust are mobilized by high winds in the desert regions of the globe, especially the Sahara, Gobi, and the Australian deserts. The dust plumes originating from these large deserts are the most conspicuous features in maps of the global distribution of atmospheric haze obtained from satellite data. The size of the desert regions and the intensity of the winds over them obviously have a great influence on the amounts of dust mobilized, and on the heights to which it is lofted. Changing mineral aerosol burdens have also been associated with climatic change in the past. Analysis of the mineral aerosol content of Antarctic ice cores shows elevated levels of soil dust during the ice ages, when large areas on the continental shelves were open to erosion by intense winds over the southern Hemisphere continents.

Simultaneous observations of the Saturnian aurora and polar haze with the HST/FOC

Abstract: Near simultaneous observations of the Saturnian H2 north ultraviolet aurora and the polar haze were made at 153 nm and 210 nm respectively with the Faint Object Camera on board the post-COSTAR Hubble Space Telescope. The auroral observations cover a complete rotation of the planet and, when co-added, they reveal the presence of an auroral emission near 80°N with a brightness of about 150 kR of total H2 emission. The maximum vertical optical depth at 210 nm is found to be located ∼5° equatorward of the auroral emission zone. The haze particles are presumably formed by hydrocarbon aerosols initiated by H2+ auroral production. In this case, the 3 × 1010 W of H2 emission observed with the FOC, combined with the deduced haze optical depth requires an efficiency of aerosol formation of about 7%. This result indicates that auroral production of hydrocarbon aerosols is a viable source of high-latitude haze.

Management of Late Corneal Haze Following Photorefractive Keratectomy

Abstract: Subepithelial corneal haze and myopic regression are potential complications following excimer photorefractive keratectomy (PRK). There are many medical and surgical methods of managing this haze. We present a 37-year-old male myope who underwent PRK and subsequently developed central corneal haze late in the postoperative course. The haze was managed initially with topical medications with limited success. Mechanical superficial keratectomy was done to remove the superficial scar tissue but the haze returned necessitating repeat excimer laser PRK, using a transepithelial technique. The haze did not recur. Both mechanical superficial keratectomy and repeat excimer laser ablation may ameliorate haze. Success of these procedures may depend on the morphology of the haze and the patient's individual wound healing response.

Capillary Zone Electrophoretic Determination of Heterocyclic Aromatic Amines in Rain

Abstract: Three carcinogenic heterocyclic aromatic amines, 3-amino-1-methyl-5H-pyrido[4,3-b]indole (Trp-P-2), 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhlP), and 2-amino-3,4,8-trimethylimidazo[4,5-f]quinoxaline (4,8-DiMelQx), have been detected by capillary zone electrophoresis in rain water and accompanying suspended particulates collected during haze episodes originating from major forest fires in Southeast Asia. The haze enveloped much of Southeast Asia, including Singapore, during August through October 1994. These compounds were not detected in rain samples collected in November 1994 after the haze had dissipated. This finding suggests that combustion of wood and vegetation is a likely source of these carcinogens in rain water.

Monsoon Shrinks With Aerosol Models

Abstract: New Delhi, India—Global climate models based on rising carbon dioxide levels predicted wetter monsoons in south Asia. But new models that incorporate an increase in the aerosol haze from pollution in south Asia reverse that prediction for parts of India and China, predicting a decrease in rainfall that could hurt agriculture.

Four micron infrared observations of the comet Shoemaker‐Levy 9 collision with Jupiter at the Zelenchuk Observatory: Spectral evidence for a stratospheric haze and determination of its physical properties

Abstract: We present preliminary results derived from low spectral resolution infrared spectra of the comet impact sites onto Jupiter. Fragments W/K were tracked several days after the collision at the SAO 6m-telescope on July 22 and 27. A systematic increase of the spectral radiance is observed for fragment W/K spectra as compared to undisturbed region spectra. This change is interpreted as the evidence for a stratospheric haze produced by the collision. From the spectral shape of this relative increase, the albedo of the haze can reach values as low as 0.06 but is constrained between 0.13 and 0.15 if the spot size is 3′. No stringent constraint is obtained for the altitude of this haze even if a 5–50 mbar level seems to be possibly the best estimate. The particles in the haze should play a significant role in the thermal balance over impact sites. The fragments W/K spectra between July 22 and July 27 show a high stability of the haze between both dates.

Spatial variations of Venus' cloud properties derived from polarimetry

Abstract: We study satellite polarization data of the clouds of Venus obtained by the Pioneer Venus Orbiter from 1978 through 1990. We present a new method for comparing these data to results of exact multiple scattering computations. This method has been applied to the analysis of a single disk distribution of the polarization at wavelengths 550 and 935 nm, using a simple model for the atmosphere of Venus. We find little variation in the cloud particle size distribution for the equatorial part of the disk. For this region, the effective particle radius is about 1.0 micrometers and the width of the size distribution decreases when approaching the terminator. However, our analysis of observations at higher latitudes suggests that for these regions a different explanation is needed. Here, an upper haze layer with smaller particles than those of the underlying cloud but having the same composition explains the observations well. The optical thickness of this haze is between 0.1 and 0.5 for an effective haze particle radius of 0.40 micrometers .

Induced spectra in planetary atmospheres

Abstract: Collision-induced absorption by H2 and He is the source of the dominant thermal opacity in the atmospheres of the major planets. As such, it is primarily responsible for the increase in temperature with depth in their tropospheres. In the visible and near infrared spectra of these planets, CIA in the fundamental and overtone vibrational bands of H2 probes the depth distribution of aerosol haze particles in the upper troposphere. This is important for studying tropospheric dynamics, such as condensation in a convective zone. The haze distribution also yields information on the meridional flow of the stratosphere and the precipitating byproducts of aeronomical chemistry. Rare emissions have been observed near the fundamental-band H2 quadrupole lines in spectra of Jupiter’s southern hemisphere. These may be due to the H2 dimer and might occur through the process of inverse predissociation.

A note on smoke concentration in urban Athens, using data measured by two different methods

Abstract: The relationships between smoke concentrations, measured at two monitoring stations in Athens by the ASTM (American Society for Testing and Materials) and the OECD (Organization for Economic Co-Operation and Development) methods are studied by using a sample of 738 mean daily values of simultaneous measurements during the period 1984–1986. It is shown that an exponential model, different for each monitoring station, with smoke concentrations in COH (coefficient of haze) as the independent variable and smoke concentrations in μgr/m3 as the dependent variable, was the most appropriate for transforming smoke data from COH to μgr/m3. Also it is shown that the transformation models can be applied independent of the prevailing meteorological conditions. Finally some tentative conclusions are derived concerning the long term variations of smoke concentrations in μgr/m3 for the period 1977–1990 and 1973–1990 at the two monitoring stations respectively. The trend analysis has shown that pollution abatement efforts resulted in an about 10% per year decreasing trend in smoke concentrations, during the period 1986–1990, at these two Athenian stations.

Backscatter haze measurement using a distributed light source

Abstract: System and method for in situ measurement of haze in a transparency, such as an aircraft windscreen, canopies, windows or the like are described which comprise an annular light source for illuminating a selected test area of the transparency along a selected optical axis, a photodetector, and a lens for projecting an image of the illuminated test area along the axis onto the photodetector.

Verification of lidar visibility

Abstract: The concept of a LIDAR, which is the short form of LIght etection &ndBnging, is the optical synonymofthe well known radar. It describes an optical remote sensingtechnique for the detection of the atmospheric pa-rameters like the optical density, etc.A main difference between LIDAR and RADAR is the wavelength of the emitted radiation, and therefore theinteractions between this radiaton and particles in the atmosphere. While a RADAR system detects particlesat the size of raindrops or snowflakes, a LIDAR system may even recognize smaller aeronautics like dust, haze,and fog particles. This better resolution is a consequenceof the smaller wavelength: the typical RADAR wave-length is in the order of millimetres or centimetres, while a LIDAR useslaser radiation which is in the order of

Analyses of haze and mist situations over Swiss lowlands during summer smog-periods with NOAA-AVHRR data

Abstract: Within the Swiss interdisciplinary summer-smog research programme POLLUMET (POLLUtion and METeorology), systematical analyses of haze and mist concentrations over the Swiss lowlands with digital weather-satellite data (NOAA-AVHRR) were made. The aim of this study was to learn about the temporal and spatial behaviour of haze and mist which is very important for air pollution situations. A model was created which is based on the calculation of the sky light reaching the satellite sensor in the visible and near-infrared channels. The sky light is caused by the particles in the lower region of the troposphere (haze and mist causing particles) and, therefore, the sky light can be considered proportional to the loading of haze and mist. Taking the sky light as an indicator of haze and mist, the main advantages are that no additional information concerning the atmosphere is needed and the parameter "sky light" is itself one part of the incoming radiation at the satellite sensor. With the model developed, this amount of the signal received at the satellite sensor can be calculated. With this new tool, time series of haze and mist concentrations during summer smog-periods over the Swiss lowlands could be calculated and analysed. The main interest focused on the behaviour of haze and mist quantities in different areal scales and over different objects on the earth's surface. The analyses showed interesting and even surprising results.

Ultraviolet observations of the Saturnian north aurora and polar haze distribution with the HST-FOC

Abstract: Near simultaneous observations of the Saturnian H2 north ultraviolet aurora and the polar haze were made at 153 nm and 210 nm respectively with the Faint Object Camera on board the Hubble Space Telescope The auroral observations cover a complete rotation of the planet and, when co-added, reveal the presence of an auroral emission near 80 deg N with a peak brightness of about 150 kR of total H2 emission The maximum optical depth of the polar haze layer is found to be located approximately 5 deg equatorward of the auroral emission zone The haze particles are presumably formed by hydrocarbon aerosols initiated by H2+ auroral production In this case, the observed haze optical depth requires an efficiency of aerosol formation of about 6 percent, indicating that auroral production of hydrocarbon aerosols is a viable source of high-latitude haze

Brume sèche dans le corridor Windsor-Québec Haze in the Windsor-Québec City corridor

Abstract: Haze frequencies in the Windsor-Quebec City corri­ dor have been analyzed for the period 1953-90 with hourly observations for 6 synoptic stations plus 2 other more remote ones for comparison. A southwestlnorth­ east frequency gradient is noted on the region, haze being more frequent in southwestern Ontario. Haze is observed more before noon, in summertime in a warm air mass ,. winter frequencies are nevertheless important at some stations. During the period, haze frequencies have declined after the 1970'5. The phenomenon varies with wind speed and direction, winds from the S being more favored at many stations while lowest frequencies are associated with N or NW directions everywhere. Haze episods were more frequent in the early 1970'5 and longer episods are more frequent than shorter ones. ln Montreal, higher ozone concentrations have been noted in the case where haze is reported.