摘要:

Expressions are derived that allow the current in a lightning return stroke to be calculated from a measurement of either the magnetic flux density or the radiation field (electric field intensity or magnetic flux density) of the discharge. Published magnetic field and radiation field data are of insufficient time resolution to allow an adequate current determination to be made.

ISSN:0148-0227    

DOI:10.1029/JC075i027p05143

年代:1970

数据来源: WILEY

摘要:

Using the superposed‐epoch method, we statistically analyzed thunderstorm frequencies for 108 stations in eastern and central United States in relation to lunar positions for the years 1930–1933 and 1942–1965. The results are as follows. With full moon as key day, a peak in thunderstorm frequency occurs for 1953–1963 two days after full moon, the mean being 2.7σ above average level. This mean frequency is 4.8σ above the mean when computed only for the full moons as key days that have a declination of 17° north or more. We suggest that these increases near full moon may be related to the earth's magnetic tail and the neu

ISSN:0148-0227    

DOI:10.1029/JC075i027p05149

年代:1970

数据来源: WILEY

摘要:

The evaporation of a water reservoir may be reduced by increasing the reflectance of solar energy by the water surface. Such a change in reflectance will require a surface modification such as the application of a special surface film or monolayer with good reflecting properties. Since colored materials reflect at wavelengths at which the solar energy has its peak intensity, colored monolayers and artificially dyed monolayers were studied experimentally. A large number of dyes were investigated, but in no instance did the dyes color the monolayer or form a monolayer themselves. A yellow silicone oil film on a water surface was found experimentally to reflect solar energy about 1.7 times better than a plain water surface and also to reduce the evaporation rate. In addition, the film was extremely difficult to remove from a water surface. Its durability is a real advantage where there is the need to constantly resupply monolayers as in present evaporation suppression techniques. Analytical studies were conducted to determine the evaporation reduction resulting from increased solar reflectance. The transient energy equation for an element of a water surface was solved by numerical methods. The analytical model gave an average evaporation suppression by cetyl alcohol of 22.6%, which is consistent with previous experimental work. Results for monolayers with hypothetical reflectance properties and with the diffusion properties of a cetyl alcohol monolayer showed average evaporation reductions of 25 to 45%, depending on the reflection properties.

ISSN:0148-0227    

DOI:10.1029/JC075i027p05155

年代:1970

数据来源: WILEY

摘要:

The use of mean values of the drop number density in the coalescence equation is shown to lead to a system of ordinary differential equations that provide good approximative solutions with a minimum of computational effort. The coefficients in this system of equations are functions of the kernel and can be obtained by simple quadrature. Comparisons are made between numerical and analytic solutions for two types of kernels (constant and sum of arguments), using a Gaussian initial distribution of cloud droplets. Systematic deviations of the numerical results from corresponding analytic solutions are shown to depend on the choice of variables, and methods to suppress these deviations are discussed.

ISSN:0148-0227    

DOI:10.1029/JC075i027p05165

年代:1970

数据来源: WILEY

摘要:

The regular perturbation method with a small parameter is applied to solve a turbulent transfer equation in the lower atmosphere without the lateral effect. From this solution the effect of longitudinal diffusion on evaporation is shown to be negative but negligible for evaporating surfaces larger than, say, 100 cm in the direction of the wind.

ISSN:0148-0227    

DOI:10.1029/JC075i027p05173

年代:1970

数据来源: WILEY

摘要:

This paper presents some results from a field experimental program whose purpose was to determine, as quantitatively as possible, dust devil dynamics. The specific aspects considered here pertain to direction of dust devil rotation and the relation of this rotation to atmospheric vorticity. Direction of rotation data were obtained by stationing a number of observers over a prescribed area, which allowed close‐in observation of the dust devils. A concurrent measure of atmospheric vorticity was obtained by a specially constructed “vorticity” meter. It was found that, in general, there was almost no preference in direction of dust devil rotation but often, over short periods, one rotation direction would be strongly favored. A definite correlation existed between the sense of atmospheric vorticity and the direction of dust devil rotation. The results indicate that the earth's rotation, mesoscale phenomena, and shed eddies play little, if any, role in determining the direction of rotation. The source of the required vorticity appears to be produced primarily, if not entirely, by local processes. It is suggested that the responsible process is shear in the horizontal flows associated with convective activity in an unstable atmos

ISSN:0148-0227    

DOI:10.1029/JC075i027p05179

年代:1970

数据来源: WILEY

摘要:

Data on atmospheric transmission related to the stratospheric layer of aerosol from the explosion of the Agung volcano in March 1963 at Bali Island are discussed. In midlatitudes of the southern hemisphere the abnormal aerosol optical thickness at λ500 nm reached a peak of 0.3 during September 1963 but became very small after mid‐1965. Some pyrheliometric data require consideration of the λ dependency of attenuation on the volcanic dust to conform to spectral data. Over the northern hemisphere, the decrease of transmission due to Agung aerosol was marginal, and a strong seasonal variation that had been derived from pyrheliometric data seems questionable. Observations of the brightness of the eclipsed moon and analysis of brightness of the umbra are in good agreement with the above data if referred to the proper hemisphere. Indications on the size distribution of the volcanic dust from λ dependence of dust attenuation and sky light observations are discu

ISSN:0148-0227    

DOI:10.1029/JC075i027p05185

年代:1970

数据来源: WILEY

摘要:

The transfer of tritium from the atmosphere to the ocean and to continental water bodies by vapor exchange as well as by precipitation is generally accepted. Vapor exchange has been suggested as the dominant mechanism for transfer of tritium to small continental lakes. Evidence is presented here to suggest that input by precipitation can explain most of the tritium content of Crater Lake, Oregon. The hydrology of Crater Lake makes it ideal for this study because less than ½ of 1% of the lake volume is lost by seepage each year and because there is no surface outflow. Very little tritium can be lost from the lake by vapor exchange because the surface concentration is diluted by vertical mixing. If Crater Lake has retained nearly all its input tritium, and if less than half of this input was supplied by vapor exchange as derived from budget calculations, deep lakes with small drainage basins can provide good estimates of the total tritium rainout

ISSN:0148-0227    

DOI:10.1029/JC075i027p05195

年代:1970

数据来源: WILEY

摘要:

Passive microwave measurements of the sea surface were made in March and April 1969 from the Argus Island tower at 8.36 and 19.34 GHz over a range in wind speeds of from calm to 10 m/sec. These measurements show a definite dependence of microwave brightness temperature on wind speed and on sea foam. This dependence is the same at the two observational frequencies within the error of measurement.

ISSN:0148-0227    

DOI:10.1029/JC075i027p05209

年代:1970

数据来源: WILEY

摘要:

A new type of inexpensive accelerometer for the measurement of wave heights has been developed. It has been used as a self‐contained, free‐floating unit and as a part of a fixed system moored to a buoy. In the free‐floating mode it has measured waves in any depth of water; in the fixed mode it has been used in water depths up to 180 meters. It has measured wave heights up to 6 meters, with periods from 3 to 10 sec, and telemetered the data to a recording station up to 16 km away. The measurement error appears to be comparable to, or less than, that exhibited by other wave reco

ISSN:0148-0227    

DOI:10.1029/JC075i027p05215

年代:1970

数据来源: WILEY