Showing papers on "Haze published in 1975"

The effect of atmospheric haze on images of the Earth's surface

Abstract: The adding method to solve the equation of radiative transfer has been applied to a sunlit haze above a reflecting surface. The method was modified to include the effect of inhomogeneities on the underlying surface whose dimensions are less than the mean free path of the photons in the haze. Numerical examples of surface-feature contrast degradation due to haze are presented. This analysis renders it feasible to determine the optical thickness of hazes from haze-degraded images of the ground and also provides a technique to restore ground-image contrast, which has been obscured by haze, in photoelectrically scanned images.

The Life Cycle of Valley Fog. Part II: Fog Microphysics

Abstract: Extensive measurements were made of the microphysics of valley fog in the Chemung River Valley near Elmira, New York. This paper discusses data on drop size distributions, drop concentrations, liquid water contents, and haze and cloud nucleus concentrations obtained on eight fog nights. The behavior patterns of the microphysical variables were found to be extremely consistent. Shallow ground fog usually occurs prior to the formation of deep valley fog. The data show that ground fog is characterized by droplet concentrations of 100 to 200 per cubic centimeter in the 1 to 10 μm radius range with mean radii of 2 to 4 μm. As deep fog forms aloft, droplet concentration near the surface decreases to less than 2 cm−3 and the mean radius increases from 6 to 12 μm. Droplets of radii <3 μm disappear. Thereafter, droplet concentration and liquid water content increase gradually until the first visibility minimum at the surface when typical values range from 12 to 25 cm−3 and 50 to 150 mg cm−3, respectively....

Attenuation of Electromagnetic Radiation by Haze, Fog, Clouds, and Rain

Abstract: : The report assembles, under one cover, the values of aerosol attenuation coefficients of regions in the electromagnetic (EM) spectrum containing so-called 'atmospheric windows,' in which EM radiation suffers the least amount of atmospheric gaseous absorption. The purpose is to enable rapid quantitative assessment of target acquisition terminal guidance sensors using the windows during adverse weather. Both calculated and available measured values are presented. Being a compilation drawn from numerous sources, the report is intended more as a handbook for ready use than as a theoretical treatise.

On the determination of haze levels from Landsat data

Abstract: The paper describes two methods for determining haze levels (specified by haze optical depth at a wavelength of 0.5 microns) from Landsat multispectral scanner data. The channel correlation method relates the haze level to the y-intercept of the regression line through a plot of the data in the plane of the multispectral channels MSS 4 and MSS 5. The minimum value method relates haze level to the minimum value of individual lines in the MSS 4 data set.

Ultraviolet laser sounding of the troposphere and lower stratosphere

Abstract: WE report here measurements made with a ground-based, ultraviolet laser operating in the wavelength range 297–308 nm, which relate to the question of the atmospheric transmission between ground level and about 20 km, and particularly to the contributions of absorption by minor constituents. There has been considerable concern in recent years about the biological effects of increased solar ultraviolet radiation at ground level associated with a reduction in the concentration of atmospheric ozone1. It seems that wavelengths between about 300 and 310 nm are most likely to produce erythema (sun burn) and skin cancer2. The effects of aerosols, clouds, non-absorbing haze or fog and other absorbing atmospheric gases need to be considered in addition to the effects of ozone and of Rayleigh scattering when examining the penetration of these radiations to the Earth's surface3,4. Except for the Junge layer5 of aerosols which extends from about 12 to 22 km, and cirrus clouds, these scattering and absorbing agencies are probably located in the lower troposphere, below about 5 km.

Atmospheric effects for ground target signature modeling. 3: Discussion and application of the ASL scattering model

Abstract: : The aim of the atmospheric modeling project is to predict absorption and scattering effects of the atmospheric medium on the transmission of ground target electromagnetic (EM) signatures in the spectral region 0.4-14 micrometers, for a wide range of meteorological conditions. Special attention is being given to low visibility atmospheric states which can exist under battlefield conditions. Two important related aspects of the program are the atmospheric extinction and radiative transfer models. These models will be integrated into system performance models for the evaluation of terminal homing, surveillance, and target acquisition systems. This report will describe the Atmospheric Sciences Laboratory's (ASL) single scattering model, which was developed for input to multiple scattering codes for the determination of EM extinction caused by the atmospheric aerosol. Sample applications will be made to the cases of haze and dust.

Longwave radiation effects of the Harmattan haze

Abstract: Infrared in situ radiance observations at 8.0 to 14 microns and 9.5 to 11.5 microns of the West African Harmattan haze during the 1974 Global Atmospheric Research Project Atlantic Tropical Experiment field phase made possible the determination of some of the radiative properties of this tropospheric phenomenon. This in turn permitted development of a simple calculation model for radiative transfer through the haze. Radiometric observations of the dust haze, reaching from 600 m to 6.25 km, were analyzed for haze IR transmission. A transfer model incorporating these transmission properties gave an average calculated IR cooling rate of 0.09 C/h for the entire haze layer as compared to a haze-free cloudless-troposphere cooling rate of 0.06 C/h for the same levels. The haze volume-absorption coefficient was approximately 0.042/km for layers of all depths. This uniformity of the haze transmission was further evident in the direct correlation of its transmission and optical depth.

Estimation of sulphate in beer or water using a haze meter

Abstract: A rapid method is described for estimating the sulphate ion concentration in beer and water.

The thermal structure of Jupiter. II - Observations and analysis of 8-14 micron radiation. [ammonia haze distribution]

Abstract: Abstract Observations of Jovian limb structure at 8.11 and 8.45 microns are reported. These are used along with other limb structure and spectral data in the 8–14 micron region to derive a model of the thermal and cloud structure within the 1.0-0.01 bar pressure regime. The model is generally consistent with models derived from Pioneer 10 infrared radiometer data reported by Orton (1975b). The temperature is about 165K at 1.00 bar, 108K at 0.01 bar, and 143K at 0.03 bar. In zones, an optically opaque cloud of NH3 exists near the 143K (0.60 bar) level. A partly transparent haze of solid NH3 particles overlies the cloud. Belts are free of the cloud and have a much lower abundance of NH3 haze than the zones. The data are consistent with an NH3 gas abundance defined by saturation equilibrium, with a mixing ratio of 1.5 × 10−4 deep in the atmosphere, and with a CH4 mixing ratio of 2 × 10−3, about three times the currently accepted value.

Spectral Dependance of Inverse Problem in Radiant Energy Transfer Through Haze

Abstract: The spectral distribution of source intensity needed to obtain a prespecified irradiance at the receiver for different atmospheric haze condition has been calculated on the basis of semi-empirical expression due to Eldridge and Johnson (1962). Variations in the spectral distributions at the receiving end due to a general service lamp for different atmospheric condition are removable by use of matched filters in front of the source. For this study the scattering media are assumed to consist of uniform water dropl.ts of 0.1 (0.1) 0.6 micron radii with a concentration of 103 particles per c.c. The receiving distances are 0.25 (0.25) 1.0 (0.5) 4 0 Km. Attempt has been made to find out a suitable single matched filter for particular atmospheric haze condition to obtain uniform receiving illumination (with 5 percent variation) for all distances upto 1 Km.

Multiple scattered radiation emerging from continental haze layers. 1: Radiance, polarization, and neutral points

Abstract: The complete radiation field is calculated for scattering layers of various optical thicknesses. Results obtained for Rayleigh and haze scattering are compared. Calculated radiances show differences as large as 23% compared to the approximate scalar theory of radiative transfer, while the same differences are approximately 0.1% for a continental haze phase function. The polarization of reflected and transmitted radiation is given for various optical thicknesses, solar zenith angles, and surface albedos. Two types of neutral points occur for aerosol phase functions. Rayleigh-like neutral points arise from zero polarization that occurs at scattering angles of 0 deg and 180 deg. For Rayleigh phase functions, the position of these points varies with the optical thickness of the scattering layer. Non-Rayleigh neutral points are associated with the zeros of polarization which occur between the end points of the single scattering curve, and are found over a wide range of azimuthal angles.