Showing papers on "Haze published in 1977"

XXXIX. The haze of Bayes, the aerial palaces of decision analysis, and the computerized Ouija board

Abstract: Most people prefer to avoid complicated problems. Politicians confronted with a complex, multi‐faceted dilemma will usually try to satisfy their constituents, rather than struggle with basic solutions to the dilemma. Judges asked to settle a major legal controversy will often make their decisions not by directly resolving the substantive issue, but by evading it, to reach a conclusion based on matters of technical procedure.

Ozone and Visibility Reduction in the Midwest: Evidence for Large-Scale Transport

Abstract: For June and July 1975, ozone concentrations throughout the Midwest showed a consistent dependence onwind direction with the highest concentrations associated with winds from the southeast. This systematicpattern suggests that large-scale transport rather than local sources control the general trends of the ozonelevel in the study area.Ozone and meteorological data covering an episode period 29 July-2 August have been analyzed usingweather maps, visibility reports, upper air soundings, trajectories and aircraft measurements to ascertainthe scale of the ozone problem. Results indicate that the highest ozone concentrations occurred within regions of reported haze, and that these regions had definite bounds which could be followed over the country.Moreover, distinct areas of reported obscured sky formed in the vicinity of St. Louis and Pittsburgh whichcould be followed over thousands of kilometers reducing visibilities substantially even in upper Ontario.Trajectories indicate that adverse conditions...

A maritime boundary-layer model for the prediction of fog

Abstract: A two-dimensional boundary-layer model is described. The model is designed to predict and study the effects of meteorological changes on the formation and dissipation of fog and stratus. Radiational heat loss along with the transport of static energy, moisture and momentum are treated. Cloud droplet distributions are parameterized using a gamma distribution from which radiative properties and droplet fall velocities are computed. Turbulent exchange coefficients are calculated using the Monin-Obukhov theory of similitude which accounts for variations in atmospheric stability. Although the boundary-layer depth depends only on turbulent intensity during stable atmospheric conditions, its growth during unstable conditions is determined from the capping inversion's intensity and the amount of turbulence generated at the surface. Several experiments are presented which demonstrate the effects of various meteorological parameters on the formation and duration of stratus and fog. Energy-budget analyses show the importance of each of the physical processes being modeled. Although not new, radiative transfer processes are shown to be extremely important in the transfer of heat from the boundary layer and in the process of fog formation. Fog formation location is highly sensitive to the moisture content upstream, whereas changes in wind speed had much less effect in the variance of fog location. Numerical experiments with other processes such as back radiation from the atmosphere, haze and cloud droplet population, are described and shown to have smaller effects.

The correction of Landsat data for the effects of haze, sun angle, and background reflectance

Abstract: A technique has been developed for simulating the effects of haze, sun angle, and background reflectance in Landsat data and correcting for them. The atmospheric model assumes a two-layer atmosphere: a Rayleigh scattering molecular layer and a Mie scattering haze layer next to the earth's surface. Reflection and transmission matrices describe the reflection and transmission properties of the plane parallel scattering layers. The multispectral scanner response is computed for various values of the parameters under evaluation. This yields expressions for Landsat gray-scale levels used for determining the effect of changes in any parameter. The Atmospheric Correction computer program is used to determine the haze level from the data, to compute the reflectance, and to interpolate in order to find the correction coefficients necessary to make the desired correction.

Aerosol research and technology

Abstract: Smoke, Dust and Haze: Fundamentals of Aerosol Behaviour By S K Friedlander Pp xvii + 317 (Wiley: New York and London, 1977) $1950; £1135

A Canadian haze climatology

Abstract: Maps of annual average haze frequencies for Canada show maxima in southwestern Ontario and around Sudbury, with a smaller maximum in the Vancouver area. Small maxima also exist in the Maritimes during summer and over the western Prairies in winter. The principal cause of these maxima appears to be the man-made emissions in and upwind of these areas. There are significant variations from summer to winter, both in time and space. In particular, there has been an increase in summer haziness in Ontario, southern Quebec and the Maritimes, and a general decrease in winter haziness in all regions, during the last twenty years.

Performance tests of signature extension algorithms

Abstract: Comparative tests were performed on seven signature extension algorithms to evaluate their effectiveness in correcting for changes in atmospheric haze and sun angle in a LANDSAT scene. Four of the algorithms were cluster matching, and two were maximum likelihood algorithms. The seventh algorithm determined the haze level in both training and recognition segments and used a set of tables calculated from an atmospheric model to determine the affine transformation that corrects the training signatures for changes in sun angle and haze level. Three of the algorithms were tested on a simulated data set, and all of the algorithms were tested on consecutive-day data.

Formation of photochemical aerosols. Final report

Abstract: The objective was to develop a better understanding of smog aerosol formation with particular reference to haze in the Southern California area. This study combined laboratory work with ambient air studies. Counting of particles by light scattering was the principle physical technique while infrared analyses was the major source of chemical information. A new reflectance spectroscopy technique was also developed. Infrared spectra of ambient aerosols have bands assigned to sulfate, nitrate, ammonium, and water which are completely removed by water washing of the sample but not by benzene. Synthetic aerosols generated by mixing ammonia with sulfuric and nitric acids produce similar spectra. Many ambient aerosol particles are hygroscopic or deliquescent so that they swell as the relative humidity increases and shrink as it decreases. This readily explains the heavy haze seen at high humidity days. A variety of reaction products (SO4(-2), NO3(-), organics) can potentially fulfill the requirement of water solubility and hygroscopicity to contribute to haze and loss of visibility. It is concluded that direct control of aerosol emissions will not markedly improve visibility in Southern California.

Arctic Haze: Natural or Pollution

Abstract: : Routine aerosol sampling at Barrow and Fairbanks continued. The basic four-year record of certain constituents in the Barrow aerosol showed distinct and reproducible seasonal variations. Cascade-impactor samples from Barrow and Europe were taken and analyzed for sulfate and trace elements. S02 at Bear Island during winter was found to be highly pulsed and associated mainly with cyclonic trajectories from eastern Europe and the USSR. On the basis of a wide variety of indirect meteorological and chemical evidence, Eurasia was strongly suggested to be the major source of Arcitic haze, with North America contributing only occasionally. Aerosol sampling at Iceland continued. A cooperative European Aerosol-Sampling Network was established and has proved highly successful. The hypothesis of the Eurasian source of Arctic haze was confirmed by the noncrustal Mn/V ratio, the first regional tracer for pollution aerosol; the dominance of Eurasian sources was further confirmed by a much more sophisticated seven-element tracer system which proved capable of discriminating among regional aerosols in Europe North America. Papers from the Second Symposium on Arctic Air Chemistry were published in a special issue of Atmospheric Environment (8/80); plans for the second symposium were made. A cooperative study with W. Berg of NCAR on Arctic bromine was begun.

An evaluation of the signature extension approach to large area crop inventories utilizing space image data

Abstract: The author has identified the following significant results. Two examples of haze correction algorithms were tested: CROP-A and XSTAR. The CROP-A was tested in a unitemporal mode on data collected in 1973-74 over ten sample segments in Kansas. Because of the uniformly low level of haze present in these segments, no conclusion could be reached about CROP-A's ability to compensate for haze. It was noted, however, that in some cases CROP-A made serious errors which actually degraded classification performance. The haze correction algorithm XSTAR was tested in a multitemporal mode on 1975-76 LACIE sample segment data over 23 blind sites in Kansas and 18 sample segments in North Dakota, providing wide range of haze levels and other conditions for algorithm evaluation. It was found that this algorithm substantially improved signature extension classification accuracy when a sum-of-likelihoods classifier was used with an alien rejection threshold.