Showing papers on "Haze published in 1986"

The Ocean as a Source of Atmospheric Sulfur Compounds

Abstract: The impact of human activity on the global atmospheric sulfur cycle is easily seen in densely inhabited, industrialized regions: the degradation of visibility by haze, the acidity of atmospheric precipitation, and the damage to forest vegetation are among the more obvious symptoms of this impact. Atmospheric transport propagates these effects well beyond their source regions. The human perturbation of the atmospheric sulfur cycle results largely from the emission of sulfur dioxide (S02) from fossil fuel burning. A number of recent papers have reviewed these emissions and presented a detailed source allocation (e.g. Cullis and Hirschler, 1980; Moller, 1984). The estimates for man-made sulfur emissions fall into a relatively narrow range: about 2.5 ± 0.3 Tmol yr-1 (Tmol: 1 Teramole = 1012 mol = 32 x 1012 g).

Light diffusion through clouds and haze

Abstract: This paper describes an algorithm for approximating the single scattering model for light diffusion through clouds or haze of constant optical density. The clouds are contained between two single valued surfaces. The algorithm assumes that the sun is directly overhead, but gives convincing pictures for other sun directions. Its efficiency comes from approximating the exponential decay of transmitted light by a quadratic polynomial, and from vectorization on the Cray 1.

Interannual variability of global dust storms on Mars

Abstract: Global dust storms on Mars occur in some years but not in others. If the four Mars years of Viking data are representative, some distinguishing characteristics can be inferred. In years with global dust storms, dust is raised in the southern hemisphere and spread over much of the planet by an intensified Hadley circulation. In years without global dust storms, dust is raised in the northern hemisphere by relatively active mid-latitude storm systems but does not spread globally. In both cases the dusty season is winter in the north. Assuming that the cross-equatorial Hadley circulation plays a key role in the onset of global dust storms, it is shown from numerical simulations that a northen hemisphere dust haze weakens its intensity and, hence, its contribution to the surface stress in the southern hemisphere. This, in turn, reduces the possibility of global dust storm development. The interannual variability is therefore the result either of a competition between circulations in opposite hemispheres, in which case the variability has a random component, or it is the result of the cycling of dust between hemispheres, in which case the variability is related to the characteristics of global dust storms themselves.

The geography of dust storms

Abstract: Dust storms have a great many environmental implications in the world's dry lands where they are particularly common. Four main classes of dust event are identified and defined: dust storms, dust haze, blowing dust and dust devils. The geography of dust storms is analysed in each of eight major world regions: Africa, the Middle East, South-west Asia, Europe and the USSR, China, Australia, North America and Latin America. Terrestrially observed meteorological data and data from remote sensing platforms are employed to identify the major source areas in each region, their seasonality, diurnal patterns of activity and trajectories of long-range transport. Among the important controls on the frequency distribution of dust storm activity are the meteorological conditions that generate dust-raising winds, and a number of meteorological systems commonly cause dust storms in all global regions. These include low pressure fronts with intense baroclinal gradients, pressure gradient winds between moving or stationary air masses, katabatic winds and convectional cells. The nature of the surface upon which deflation occurs is also important; typical dust-producing geomorpholological units include alluvial spreads, lacustrine deposits, desert depressions, loess deposits and reactivated fossil dunes. Dust storm activity is prone to considerable variation. The seasonal characteristics are explicable with reference to the meteorological systems generating dust, the state of ground cover, particularly vegetation, and the effects of seasonal rainfall. Substantial variations also occur from year to year, and land use and climatic variations can substantially affect their occurrence.

Field Experiment for Measurement of the Radiative Characteristics of a Hazy Atmosphere

Abstract: Theoretical two-dimensional and three-dimensional solutions to the radiative-transfer equation have been applied to the earth-atmosphere system. A field experiment was conducted to test this theory. In the experiment the upward radiance was measured above and below a haze layer during simultaneous measurements of the haze characteristics. The measurements were conducted at a narrow near-IR channel (773 + or - 22 nm) which represents the visible and near-IR spectral region. The aerosol vertical optical thickness at eight wavelengths, as well as the vertical and horizontal profiles of the scattering coefficient, the temperature, and dew point were measured at several locations. These measurements quantified the vertical and spatial structure of the atmospheric haze and the atmospheric radiation. The result was a well-defined radiative-transfer experiment. The experimental data set is used to quantify the haze effect on upward radiance, including the adjacency effect (the effect of a bright area on the upward radiance measured above a dark adjacent area), and to test radiative-transfer models for a plane-parallel atmosphere above a nonuniform surface. A comparison is given between the theoretical prediction of upward radiance above the haze and the measurement. Agreement between theory and the experiment is discussed.

Estimation of atmospheric corrections from multiple aircraft imagery

Abstract: Remote-sensing techniques measure the radiance of the surface through a layer of atmosphere which both attenuates the signal and adds a path radiance. One class of solution can be found using the known dependence of transmittance on atmospheric path length. Multiheight measurements from aircraft enable the determination of transmittance and path radiance by linear regression. Multiangle measurements from overlapping aircraft scans have also been applied, but the difference of path lengths offered by the range of aircraft scan angles is insufficient to determine the atmospheric parameters with accuracy, especially with the uncertainties introduced by reflection from non-Lambertian surfaces. The atmosphere is not horizontally homogeneous in the presence of cloud or dense haze. Significant variations occur even at a distance from clouds and, on cloudless days, variations in optical depth can occur in dense haze layers. The variations are most significant at shorter wavelengths but have a coherent sp...

Calibration and evaluation of haze meters

Abstract: A survey of haze meters that are currently available has been carried out to find out whether an instrument(s) can be recommended for use by the brewing industry. There is a marked difference between values measured by instruments reading at 13° and 90° scatter. There are very minor differences in the haze values obtained using the various 90° instruments. Overall the Hach meter is recommended as a replacement for the Radiometer. Suspensions of styrene divinylbenzene beads were judged to be suitable as an alternative to Formazin for standardising haze meters.

The vertical structure of Jupiter's equatorial and tropical regions.

Abstract: The equatorial and tropical regions of Jupiter are presently treated in light of an inhomogeneous atmospheric model that encompasses both polarizing aerosols and methane gas, in keeping with Pioneer polarimetry and photometry data as well as the methane band data obtained by West (1979) The relative strengths of weak and strong methane bands are addressed by a two-cloud model with overlying stratospheric haze For all the regions considered, the best fit for polarization measurements is a negatively polarizing ammonia cloud beneath a positively polarizing haze Unlike the nearby features, the equatorial region and the Great Red Spot have a negative polarization at 80-deg phase angle, implying less gas above the clouds in these regions

Minimum detectable pollution levels from satellite imagery

Abstract: In this paper the detection of haze using satellite imagery is compared with simultaneous aircraft measurements of haze parameters. The vertical optical depths of the effective pollutant layers are compared with results from the satellite data in order to gauge a threshold for the detection of haze from satellites. This comparison indicates that in terms of the optical depth this threshold is approximately equal to 0.065. Regression analysis indicates that a ground aerosol SO4= concentration of ∼3 µgm−3 may be typical of such a value of optical depth.

The single scattering phase functions of Jupiter's clouds

Abstract: The determination of the single scattering phase functions of Jupiter's clouds and a thin upper haze by Tomasko et al. was refined and extended to seven latitudes in blue and red light. The phase function is well-constrained by the Pioneer 10 and 11 photometric data sets. Multiple scattering models were computed to match the limb darkening at each latitude at up to 15 phase angles from 12 deg to 151 deg. Ground-based observations were used for absolute calibration and to extend the data to lower phase angles. The phase functions were parameterized using the double Henyey-Greenstein function. The three Henyey-Greenstein parameters and the single scattering albedo were determined using a non-linear least squares method for the haze and the clouds below. The phase functions derived for the northen zone and belt are remarkably similar to the phase functions of the corresponding regions in the south, with most of the differences in brightness of the northern and southern features resulting from minor differences in single scattering albedo. Analysis of the Equatorial Region is complicated by the presence of numerous small features, but the phase function required is generally similar to that seen in the more homogeneous regions. Details of the phase functions of the haze and clouds are presented, and the differences between the cloud phase functions at low and high latitudes in red and blue light are discussed.

The Chemistry and Physics of Acid Fogs, Clouds and Haze Aerosol

Abstract: The chemistry of fogs, clouds, dew and rain at selected locations in California bas been observed over the last several years. Fog and cloud water in southern California often has extremely low pH values (i.e., 1.7 ≤ pH ≤ 4) and extremely high concentrations of sulfate, nitrate, ammonium ion and trace metals. A representative set of values reported by Waldman et al and Munger et al are given in Table I along with values reported for other sites around the world. Of special interest are the high values observed for SO_4^(2-), NO_3-, S(IV), CH_2O, Fe, Mn, Pb and Cu in fog water. These values and their time-dependent changes as shown in Figures 1 and 2 indicate that fogs provide a very reactive environment for the accumulation of HNO_3 and H_25O_4. Concomitant incorporation of NH_3 gas and calcareous dust into the droplet phase neutralizes some of the acidity.

Polyester film for membrane switch

Abstract: PURPOSE:To obtain the switch with high performance and market value in which low molecular weight-deposit is unnecessary to be wiped out, when conductive parts are screen-printed on a film, and the print-shifting due to shrinkage is eliminated by using, as constituting elements, polyethylene naphthalate in which shrinkage rate is OK a specified value or less and yet the inereasing rate of haze before its heat treatment to that after its heat treatment is equal to a specified value or less CONSTITUTION:Polyethylene naphthalate in which the haze increasing rate (defined by a formula I) at the heat treatment of 150 degC and 2hr is 20% or less, and its thermal shrinkage rate at that time is 05% or less in both longitudinal and transverse directions, has lowered mechanical property, when its polymerization rate is too low Therefore, ultimate viscosity is caused to be 040 or more, and preferably 045-090 When the increasing rate of haze is larger than 20%, low molecular weight substance adhere to the film surface, thereby not only making the transparency of the film worse, but also making the printed surface dirty or making the adhesion of the pint worse, when a conductive layer is print-coated When the thermal shrinkage rate exceeds 05%, and especially after Ag-paste has been printed when carbon paste of same pattern is printed, the pattern is shifted increasing rate of haze= H2-H1/H1X100% I (in the above formula, H1 represents the haze before heat treatment, and H2 the haze after heat treatment)

Further case studies on the impact of mesoscale convective systems on regional ozone and haze distributions

Abstract: The report is a continuation of an earlier effort to study the impact of mesoscale convective precipitation systems upon distributions of aerosol and photochemical oxidant pollutants in the planetary boundary layer (PBL). Analyses of surface visibility and ozone data revealed a dramatic response in the boundary-layer pollutant patterns to the passage of two very large convective storm systems. Regional visibilities, at times less than 5 km, increased dramatically over a multistate area to as high as 80 km. The resultant clean air region was termed a convective aerosol removal event (CARE). In the study, a well-defined CARE was found off the Georgia coast on 14 August 1980.

Local variation of haze thickness on the equatorial region of Venus

Abstract: The horizontal distribution of haze particles in the equatorial region of Venus was investigated using selected polarimetry maps obtained by the Orbiter Cloud Photopolarimeter (OCP) aboard the Pioneer Venus Orbiter, with five of these maps having been acquired on five consecutive terrestrial days. Nine sets of OCP polarimetry maps (PM) similar to PM 16 employed by Kawabata et al. (1980) were selected, and 935 nm data points were extracted to construct a cloud-haze model, from which the haze fraction f(h) within the cloud and the corresponding optical thickness tau(h) were determined for the period from December 1978 to October 1980. The results indicate that, in this period, the upper cloud layer of Venus had haze layers with tau(h) of about 0.02. Furthermore, the submicron particles present within the principal cloud contributed approximately 6 percent to the total scattering cross section per unit volume. Although no systematic time variations in the derived values of tau(h) and f(h) were noticeable, the consecutive five day observations indicated a presence of a large-scale horizontal inhomogeneity in haze particle distribution.

Environmental Conditions Associated with the Occurrence of Large Scale Dust Storms in Arid Regions of North Africa.

Abstract: : Dust storms are complex phenomena that are dependent on many meteorological and environmental factors. Because they normally occur in remote and in hospitable regions, they have been studied relatively little. Such studies are further hampered by the dearth of meteorological, climatological and geological data for such regions. In particular, the occurrence of the major storms seems to be related to identifiable meteorological conditions; such storms should be predictable with a fair degree of confidence. Likewise, it is clear that there are a wide variety of terrains that can serve as dust sources given the right meteorological conditions. However, the truly great storms appear to occur in a relatively well defined region of the western Sahara, west and southwest of the Ahaggar masif. There are many terrains in this region that can serve as dust sources. As a consequence, the dimensions of the storm appear to be controlled by the wind field and, hence, serves as a visible manifestation of the governing synoptic event. Nontheless, sources in these areas are clearly very important and could control the aerosol characteristics over a large area of West Africa and the tropical and subtropical North Atlantic. Keywords: Sand storm, Threshold wind velocity, Meteorology, Deserts, Sahara, Remote sensing, Haze, Deflation.

Relationships among Coefficient of Haze, Scattering Coefficient, and Visibility during an Agricultural Burn Season

Abstract: Evidence is presented that a relationship exists between prevailing visibility (PVIS) and a linear combination of the coefficient of haze (COH) and light scattering (BSCAT) during periods of agricultural burning as measured by a network of monitoring sites in the Sacramento Valley. The present study provides considerable hope that a combination of meteorological forecast and real-time air quality measurement, based upon an instrumental network comprised of readily available sensors, can be implemented successfully for purposes of ag-burn management. It has validated the importance of eliminating early morning and late afternoon observations from use in establishing predictive correlations. 13 references, 3 figures, 1 table.