Showing papers on "Haze published in 1978"
TL;DR: In this paper, the vertical structure of the size distribution and number concentration of particulates in atmospheric fog and haze near Grafenwohr, West Germany, were measured with a balloonborne light-scattering aerosol counter for periods spanning parts of eight days in February 1976.
Abstract: Vertical structure of the size distribution and number concentration of particulates in atmospheric fog and haze near Grafenwohr, West Germany, were measured with a balloonborne light-scattering aerosol counter for periods spanning parts of eight days in February 1976. For haze (∼5 km visibility) conditions, little vertical variation is seen; but for low visibility (<1 km) fog conditions, significant vertical increases in concentration of droplets with radii larger than 4 μm are seen over the first 150 m altitude. For haze, the particle size distribution is approximated by a log-normal with geometric mean radius rg≈0.2 μm and geometric standard deviation σg≈1.9. For fog, a bimodal distribution is found with a relative maximum for the larger particle mode at radii of 4 to 6 μm and corresponding values rg≈5 μm and σg≈1.6; the smaller particle mode has values of rg≈0.3 μm to rg≈0.6 μm and σg≈1.8 to σg≈2.5. Liquid water content values for haze and fog range from 10−4 to 0.45 g m−3. Extinction calcula...
77 citations
TL;DR: In this paper, an interactive computer graphics system is utilized showing that digital satellite data can obtain precise measurements of upward scattered solar radiation which is correlated to aerosol optical thickness and therefore to sulfate concentrations.
38 citations
TL;DR: The exact time dependent solution for hole boring through fog is obtained for pulsed high energy lasers, which includes scattering, absorption, and the effect of realistic particle distributions, which is applied to both haze burnout and fog hole boring.
Abstract: The exact time dependent solution for hole boring through fog is obtained for pulsed high energy lasers, which includes scattering, absorption, and the effect of realistic particle distributions. The results are applied to both haze burnout and fog hole boring. For the latter, at 10.6 microm, the calculated result is that 50% more laser pulse energy is required than that calculated from thermodynamic considerations alone. An absolute upper bound of 100% is also established. The results are compared to shorter wavelengths, e.g., 3.8 microm for which much larger fluences are required to evaporate fog or haze, and are also compared to other recent approximate results, which overestimate the required energy by a larger factor.
21 citations
TL;DR: Haze development in deproteinized juices was followed during incubation at 50°C. as discussed by the authors found that the materials, presumably flavonoids, most readily precipitating with gelatin are the quickest to form hazes in deprotcinized systems, Juices from different cultivars varied in their tendency to form haze.
Abstract: Haze development in deproteinized juices was followed during incubation at 50°C. Haze increased 15 times faster at pH 2.5 and 5 times faster at 3.0 than at pH 3.5. Salts enhanced haze formation, with their molar effectiveness in the order CaCl2 > MgCl2 > KCl > NaCl > Na2 SO4 > NaNO3. The rate of haze production in 0.7M NaCl was 16 times that found with no salt addition. The materials, presumably flavonoids, most readily precipitating with gelatin are the quickest to form hazes in deprotcinized systems, Juices from different cultivars varied in their tendency to form haze. Pectin and gum arabic (0.1%) retarded haze development.
14 citations
01 Jul 1978
TL;DR: In this article, the vertical structure of the size distribution and number concentration of particulates in atmospheric fog and haze near Grafenwoehr, West Germany, was measured with a balloon-borne light scattering aerosol counter for periods spanning parts of 8 days in February 1976.
Abstract: : Vertical structure of the size distribution and number concentration of particulates in atmospheric fog and haze near Grafenwoehr, West Germany, was measured with a balloon-borne light-scattering aerosol counter for periods spanning parts of 8 days in February 1976. The work was part of a US Army field exercise conducted for the purpose of determining the effect of atmospheric constituents on various night vision systems. For haze (approximately 5 km visibility) conditions, little vertical variation is seen; but for low visibility (1 km) fog conditions, significant vertical increases in concentration of droplets with radii larger than 4 micrometers are seen over the first 150 m altitude. Liquid water content values for haze and fog range from 0.0001 to 0.45 g/cu m. Extinction calculated from the particle size distributions shows an approximate 1/lamba wavelength dependence for haze conditions, but nearly neutral (wavelength independent) extinction for heavy fog. A correlation exists between calculated particulate extinction and calculated liquid water content, independent of particle size distribution, for the fogs and hazes studied.
9 citations
TL;DR: In this article, preliminary observations based on nephelometric measurements of the optical scattering coefficient of air over central London during June to August 1976, and evidence of haze formation in the London area as educed from the Daily Weather Reports (DWR) of the Meteorological Office (MO), and show how these relate to the occurrence of photochemical processes over Greater London.
Abstract: PHOTOCHEMICAL pollution in Greater London, as evidenced by unnaturally high ozone concentrations, has been reported on several occasions1–5. In Los Angeles, where photochemical activity has been experienced for many years, an obvious feature of this pollution is aerosol formation, which has been attributed to the participation of SO2 in the photochemical reaction sequence, with subsequent formation of sub-μm sulphate particles6. Although SO2 concentrations are higher in Greater London, there have been no reported measurements of photochemical haze, but Cox and Penkett7, by extrapolation of laboratory measurements of air samples from Harwell, have suggested that a conversion rate of 10% h−1 for SO2 to sulphate aerosol may be possible in Greater London; this would be sufficient to produce large quantities of sulphate aerosol. Identification of such processes is important because evidence suggests that photochemically produced sulphate aerosols can, in certain circumstances, account for a large proportion of total particlate mass in the 0.1–1.0 µm size range8. This size range is important in determining the optical scattering coefficient of polluted air9, and hence visibility, and potentially as a respiratory tract irritant because of its ability to penetrate deeply, in combination with its chemical nature10. We report here preliminary observations based on nephelometric measurements of the optical scattering coefficient of air over central London during June to August 1976, and evidence of haze formation in the London area as educed from the Daily Weather Reports (DWR) of the Meteorological Office (MO), and show how these relate to the occurrence of photochemical processes over Greater London.
8 citations
Patent•
30 Jan 1978
6 citations
18 Aug 1978
TL;DR: In this article, an intercomparison of all the OPAQUE aerosol counters was conducted at the Air Force Geophysics Laboratory and the results emphasized the need for proper maintenance and calibration.
Abstract: The objective of the NATO Project OPAQUE, a measurement program on the Optical Atmospheric Quantities in Europe, is to develop a data base of atmospheric optical and IR properties in Europe. An important part of this program is the measurement of the distribution of optical properties of aerosols as a function of time, geography and weather. Six OPAQUE stations are presently operational. The concentration and size distribution of aerosol particles is being measured with PMS and Royco particle counters. To verify comparability of these measurements an intercomparison of all OPAQUE aerosol counters was conducted at the Air Force Geophysics Laboratory. Results emphasized the need for proper maintenance and calibration. Properly maintained, all instruments appear to agree within a factor of two. In a supporting effort AFGL has been conducting airborne measurements of aerosol distributions in several of the OPAQUE areas. Measurements of concentration and size distribution have been conducted at altitudes between 300 and 5000 meters. Vertical profiles show very frequently a well defined low level haze layer of 1.5 to 2 km thickness, and a significant change in size distribution with increasing altitude.
3 citations
01 Jun 1978
TL;DR: In this article, it was shown that attenuation in the visible portion of the spectrum does not uniquely determine attenuation of other wavelengths and that the ratio of middle infrared attenuation to visible attenuation is determined mainly by the sizes of the drops in a fog.
Abstract: : It is generally agreed that propagation of electromagnetic energy is affected by fog drops and water vapor, but climatological probabilities of attenuation do not exist except for the visible range which has wavelengths from about 04 to 07 micrometer Unfortunately, attenuation in the visible portion of the spectrum does not uniquely determine attenuation of other wavelengths The ratio of middle infrared attenuation to visible attenuation is determined mainly by the sizes of the drops in a fog because water vapor attenuation is small in the middle infrared and negligible in the visible Water vapor is an important factor to be considered near one millimeter
1 citations