Showing papers on "Haze published in 1994"

Influence of plumes from biomass burning on atmospheric chemistry over the equatorial and tropical South Atlantic during CITE 3

Abstract: During all eight flights conducted over the equatorial and tropical South Atlantic in the course of the Chemical Instrumentation Test and Evaluation (CITE 3) experiment, we observed haze layers with elevated concentrations of aerosols, O3, CO, and other trace gases related to biomass burning emissions. They occurred at altitudes between 1000 and 5200 m and were usually only some 100-300 m thick. These layers extended horizontally over several 100 km and were marked by the presence of visible brownish haze. Air mass trajectories indicate that these layers originate in the biomass burning regions of Africa and South America and typically have aged at least 10 days since the time of emission. In the haze layers, O3 and CO concentrations up to 90 and 210 ppb were observed, respectively. The two species were highly correlated. The ratio concentrations in plume minus background concentrations of O3/CO is typically in the range 0.2-0.7, much higher than the ratios in the less aged plumes investigated previously in Amazonia. In most cases, aerosol (0.12-3 micrometer diameter) number concentrations were also elevated by up to 400/cu cm in the layers; aerosol enrichments were also strongly correlated with elevated CO levels. Clear correlations between CO and NO(x) enrichments were not apparent due to the age of the plumes, in which most NO(x) would have already reacted away within 1-2 days. Only in some of the plumes could clear correlations between NO(y) and CO be identified; the absence of a general correlation between NO(y) and CO may be due to instrumental limitations and to variable sinks for NO(y). The average enrichment of the ratio concentrations in plume minus background concentrations of NO(y)/CO was quite high, consistent with the efficient production of ozone observed in the plumes. The chemical characteristics of the haze layers, together with remote sensing information and trajectory calculations, suggest that fire emissions (in Africa and/or South America) are the primary source of the haze layer components.

Temporal and spatial variations of the atmospheric dust loading throughout West Africa over the last thirty years

Abstract: The dust haze conditions, typical of the African atmosphere south of the Sahara, are a result of wind-generated dust from arid lands. The magnitude of the dust haze is evaluated for the 30-year period beginning in 1957 by calculating the number of occurrences where the observed visibility was reduced below threshold values of 10 km and 5 km. The frequency of low visibility was several times greater for the 1977–1986 period than for the 1957–1966 period. Large decreases in visibility are observed after the severe droughts of 1972–1973 and 1982-1984. Contrasting regional differences of the dustiness evolution are noticed. These differences are closely related to the differences in the regional rainfall evolution. The increase in dustiness is believed to arise from dust produced in new desertic areas which result from rainfall shortages along the southern border of the Sahara.

Factors influencing atmospheric composition over subarctic North America during summer

Abstract: Elevated concentrations of hydrocarbons, CO, and nitrogen oxides were observed in extensive haze layers over northeastern Canada in the summer of 1990, during ABLE 3B. Halocarbon concentrations remained near background in most layers, indicating a source from biomass wildfires. Elevated concentrations of C2Cl4 provided a sensitive indicator for pollution from urban/industrial sources. Detailed analysis of regional budgets for CO and hydrocarbons indicates that biomass fires accounted for approximately equal to 70% of the input to the subarctic for most hydrocarbons and for acetone and more than 50% for CO. Regional sources for many species (including CO) exceeded chemical sinks during summer, and the boreal region provided a net source to midlatitudes. Interannual variations and long-term trends in atmospheric composition are sensitive to climatic change; a shift to warmer, drier conditions could increase the areas burned and thus the sources of many trace gases.

The Greenhouse and Anti-Greenhouse Effects on Titan

Abstract: Titan is the largest moon of Saturn and is the only moon in the solar system with a substantial atmosphere. Its atmosphere is mostly made of nitrogen, with a few percent CH4, 0.1% H2 and an uncertain level of Ar (less than 10%). The surface pressure is 1.5 atms and the surface temperature is 95 K, decreasing to 71 at the tropopause before rising to stratospheric temperatures of 180 K. In pressure and composition Titan's atmosphere is the closest twin to Earth's. The surface of Titan remains unknown, hidden by the thick smog layer, but it may be an ocean of liquid methane and ethane. Titan's atmosphere has a greenhouse effect which is much stronger than the Earth's - 92% of the surface warming is due to greenhouse radiation. However an organic smog layer in the upper atmosphere produces an anti-greenhouse effect that cuts the greenhouse warming in half - removing 35% of the incoming solar radiation. Models suggest that during its formation Titan's atmosphere was heated to high temperatures due to accretional energy. This was followed by a cold Triton-like period which gradually warmed to the present conditions. The coupled greenhouse and haze anti-greenhouse may be relevant to recent suggestions for haze shielding of a CH4 - NH3 early atmosphere on Earth or Mars. When the NASA/ESA mission to the Saturn System, Cassini, launches in a few years it will carry a probe that will be sent to the surface of Titan and show us this world that is strange and yet in many ways similar to our own.

How will dust from Shoemaker-Levy 9 alter Jupiter's stratospheric aerosol populations?

Abstract: Jupiter's stratospheric haze is most abundant in the polar regions. This polar stratospheric haze has a distinctive signature: bright polar caps are visible in methane absorption band images at 0.89 µm. The upcoming Shoemaker-Levy 9 impacts should significantly add to the stratospheric haze population, as a result of direct dust impact and perhaps as a result of a splash component of dust explosively ejected from the impact sites. The extra material will predominantly land in the southern hemisphere. Comet dust has a low albedo, and will generally lower Jupiter's brightness in continuum images, particularly near the limb. However, in the 0.89 µm methane absorption band images we expect Jupiter to brighten in dust impact regions, since the dust scatters light above most of the methane absorbers. Stratospheric sedimentation times are generally on the order of years, so this new haze component will be persistent.

Measurement and modeling of infrared imaging systems at conditions of reduced visibility (fog) for traffic applications

Abstract: This paper addresses the feasibility and operational application of different infrared (IR) imaging systems in road traffic to improve security of individual motor vehicles at conditions of low visibility, especially in fog. Extensive field measurements were carried out at different weather conditions, mainly fog and haze, utilizing three IR imaging sensors in different spectral bands in the near and thermal infrared. Additionally, a CCD camera in the visible band was used for comparison purposes. Measurements were performed on public roads and a test road which was equipped with heated and unheated radiation reference sources and thermal beacons. Furthermore, the atmospheric spectral transmission and relevant meteorological and aerosol parameters were measured. A mathematical model, SIMIS (simulation model for IR scenes), was developed and applied to generate and analyze thermal images of the test road. The spectral dependencies and radiation properties of fog and haze were modelled with LOWTRAN 7. Apparent radiances, temperatures, and contrasts of the references sources were simulated as a function of distance. The contrast transmission and effective IR visibility was derived and compared to the measured IR-imaging sensor data. From the analysis an assessment of the performance of IR-imaging sensors at fog conditions has been deduced.

Gram-Schmidt orthogonalization technique for atmospheric and sun glint correction of Landsat imagery

Abstract: A technique for correcting for haze and sunglint in Landsat Thematic Mapper imagery in coastal regions has been developed and demonstrated using Gram-Schmidt orthogonalization of the band covariance matrix. This procedure is an adaptation of Wiener filtering and noise cancellation stochastic signal processing. Using a covariance matrix constructed from an over water portion of the image containing haze and sunglint pixels, a transfer function between infrared (IR) bands (e.g. TM 5) and visible bands (e.g. TM 2) is derived. This transfer function is then applied to the entire image and the visible band contribution predicted by the IR is subtracted from the measured visible signal, pixel by pixel. A comparison between images with and without haze of the same scene indicates that the procedure allows the observation of underwater features not previously visible.© (1994) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Cloudiness stability measuring method for beer and measuring kit

Abstract: PURPOSE: To measure the cloudiness stability of beer quickly and accurately by measuring the content of Haze protein in a sample beer during and after production through immunoassay employing an antibody obtained from an antigen for Haze protein. CONSTITUTION: A commercial beer is reserved while being cooled by ice to produce Haze protein which is then filtered to obtain Haze protein having molecular weight of about 40000 and isoelectric point in the region of 4.0-5.0. An animal is then immunized using the Haze protein as an antibody and a polyclonal antibody having potency of 10000 units/mg produced in the body is sampled. The polyclonal antibody is employed in the measurement of Haze protein contained in a sample beer during and after production of beer through immunoassay, e.g. enzyme immunoassay. The cloudiness stability of beer can be measured accurately by measuring the content of substance causing cloudiness of beer, i.e., the Hazeprotein. COPYRIGHT: (C)1995,JPO