摘要:

A computer code for calculating radiation flow and hydrodynamic motion has been used to investigate the radial‐temperature and time‐temperature profiles of an air channel heated by a single return stroke of lightning. The investigation used a novel model in which input heat releases were computed from calculated electrical conductances of channel zones and from the experimentally determined information on the electrical current in a single return stroke. Although no experimental information on profiles was available for comparison, apparently realistic temperature profiles of the lightning channel were deduced. However, the magnitudes of the theoretical channel temperature and of its variation with time are in good agreement with experimental observations. The calculated total energy dissipation per unit length of channel is also in fair agreement with experimental estima

ISSN:0148-0227    

DOI:10.1029/JC076i003p00637

年代:1971

数据来源: WILEY

摘要:

Radionuciide concentrations for89Sr,90Sr,144Ce, and137Cs were sequentially sampled from two rainstorms to study fallout behavior as a function of rainfall rate and type of storm approximately 7 months after the eighth Chinese nuclear explosion of December 27, 1968. Great time variability in the89Sr/90Sr ratio was found in conjunction with a well‐developed storm on July 21, but a nearly steady ratio was observed in a stratified stable‐type storm on August 14. Tapping of stratospheric air appeared to be the cause of the ratio changes. For both storms, a strong trend was found for concentrations of radioisotopes to decrease with increase in rainfall rate. Detailed discussions on meteorological factors, including a dilution effect, are given to interpret the experimental d

ISSN:0148-0227    

DOI:10.1029/JC076i003p00646

年代:1971

数据来源: WILEY

摘要:

A mechanism is proposed for the formation of ice fog particles in the city and environs of Fairbanks, Alaska. Equations are developed for calculating the size distribution resulting from growth by deposition of water vapor. The equations are numerically solved with a computer for three major types of ice fog sources: (1) automobile exhaust, (2) exhaust from heating plants, and (3) open water. The size distribution produced by an individual source is determined by the cooling rate of water vapor injected into the environment. The cooling rate is a function of the source characteristics and the ambient temperature. The proposed mechanism adequately represents the observed size distribution if the cooling rate of the water vapor injected into the environment is not too large (source types 2 and 3). Because of the large cooling rate of the water vapor injected into the atmosphere by source type 1, the size distribution from this source is not adequately represented by the model. In agreement with observations, the computational results predict a decrease in the size of ice fog particles with decreasing ambient temperature for source types 2 and 3.

ISSN:0148-0227    

DOI:10.1029/JC076i003p00657

年代:1971

数据来源: WILEY

摘要:

The hydrodynamic and thermodynamic equations for the upper layers of the ocean are solved by expanding the variables in Fourier series and by making use of the mean field approximation. Solar radiation heating is introduced as a time‐dependent source term in the heat conduction equation, and surface cooling processes are represented by a constant heat flux out of the top of the ocean. Wind mixing is represented by eddy coefficients of viscosity and conductivity. The calculations show that convection is inhibited by the solar radiation during the day, but usually soon after sunset the water column became unstable, and convection took place near the sea surface. As night progressed, the convection penetrated more deeply until nearly isothermal conditions in the upper layers prevailed. The convection ceased soon after sunrise. The horizontal spacing of convection cells increased with increasing eddy coefficients. When the eddy coefficients became very large, convection did not take place. The turbidity of the water had only a slight effect on the convection proces

ISSN:0148-0227    

DOI:10.1029/JC076i003p00666

年代:1971

数据来源: WILEY

摘要:

We analyzed the process maintaining the seasonal heat storage in the 0–250 meter surface layer of the North Pacific Ocean by using 140,000 bathythermograph observations. Horizontal mixing contributes less than 10% to the local monthly change in heat storage throughout the North Pacific except in the areas east of Japan, west of Vancouver Island and south of the Aleutian Islands. In these areas mixing contributes up to 38% of the local monthly change in heat storage. Horizontal advection of heat is calculated from the heat conservation equation by using estimates for net surface heat exchange. Advection is equal or greater in importance than the net surface heat exchange in determining the local thermal structure. Advection also leads the net surface heat exchange by an average of 2 months. A numerical model of the seasonal change in heat storage is developed by using the heat conservation equation to further examine the influence of horizontal mixing and advection on the seasonal changes in the local heat storage. The results show that a horizontal circulation of 42 million m3sec−1is required in the large subtropical anticyclonic gyre in the central Pacific. In addition, an eastern Pacific gyre southeast of the Hawaiian Islands of 12 million m3sec−1is required. By using the numerical model, we also examined the behavior of heat storage anomalies in the North Pacific Ocean. The results show that the heat storage in the areas east of Japan and in the western and eastern tropical Pacific are primarily affected by changes in the circul

ISSN:0148-0227    

DOI:10.1029/JC076i003p00676

年代:1971

数据来源: WILEY

摘要:

Mean hourly dispersion coefficients are predicted by using a first‐order Markov chain model developed from continuous hourly current meter records at a fixed point. Dispersion coefficients compare favorably with other studies. The Eulerian data are assumed equivalent to Lagrangian because the Reynolds numbers were large, and because the velocity field was homogeneous over the distances considered. A conventional dye injection study at Port Maitland on Lake Erie verified the Eulerian to Lagrangian data conversion. Concentrations as a function of distance for a constant continuous point source of a passive contaminant are computed. A method for determining the maximum, mean, and minimum probable distances traveled by a particle in a period of hours is presente

ISSN:0148-0227    

DOI:10.1029/JC076i003p00688

年代:1971

数据来源: WILEY

摘要:

When the air temperature drops below the water temperature under a floating ice sheet, thermal cracks often occur. To acquire quantitative information on these cracks from an analytic point of view, the ice has been represented as a homogeneous elastic floating plate. The effect of thermal contraction then becomes equivalent to a lateral surface load. After the problem has been formulated in general terms, three special conditions which lend themselves to analytic treatment are considered: the wide ice sheet under conditions of plane strain, the narrow ice sheet under plane stress conditions and the axisymmetric ice sheet. The first two lead to simple solutions that illustrate general effects, the third is of more practical significance. Typical stress distributions prior to cracking are shown and for particular numerical values, some of which are applicable to arctic sea ice; typical crack spacing is related to the temperature difference between the upper and lower surface. Finally, the assumptions on which the analysis rests are examined critically with regard to establishing the validity of the results and to indicate ways in which improvements in the analytic treatment can be made.

ISSN:0148-0227    

DOI:10.1029/JC076i003p00694

年代:1971

数据来源: WILEY

摘要:

The mass physical properties (shear strength, porosity, and density) of 32 cores from the northern part of the Middle America Trench have been determined. A stability analysis using the shear strength data (determinations made with a vane shear device) indicate that the sediments are generally stable except on the landward flank of the trench where slumping is possible under the slope conditions observed. Comparisons of gravity‐piston core pairs indicate differences in porosity and shear strength that are the result of the coring procedure. The corer used in this study was designed to minimize sample disturbance, but clearly better coring devices are needed before in situ conditions are approached. Porosity and the log of shear strength are inversely related, and porosity has a positive relationship to per cent clay. The specific gravity of the sediments is 2.66 gm/cm3(at zero porosity), a value similar to that of other areas with a high rate of terrigenous depositio

ISSN:0148-0227    

DOI:10.1029/JC076i003p00704

年代:1971

数据来源: WILEY

摘要:

On steep‐faced beaches where waves break and swash at an angle to the shoreline the littoral drift of beach material results from the saw‐tooth motions of the sediment in the longshore direction. The sand moves forward obliquely to the shore under the incoming wave swash and then moves normal to the shoreline under the return flow. For such transport conditions a rational derivation leads to the relationshipIi=K(ECn)bsin αbcos αb, whereIiis the longshore transport rate of sediment expressed as an immersed weight, (ECn)bis the flux of wave energy at the breaker zone, αbis the angle the breaking wave makes with the shoreline, andKis a dimensionless proportionality coefficient. This often applied relationship, previously only intuitive, is therefore more rigorously established for special saw‐tooth transport. It has recently been shown to also apply when the sediment is transported by a longshore current proportional toumsin αb, whereumis the orbital velocity under the breaking waves. These are the two most important mechanisms by which sediment is transported along the shore under wave action, and hence the successful application of the above relationship can be expected. Deriving the relationship by two different approaches suggests that the ratio tan β cos αb/cfmay be constant, where tan β is the beach slope, andcfis the coefficient of bottom friction. This helps to explain the observation that the longshore current is proportional toumsin αband to account for the lack of dependence of the sand transport relationships on the beach slope. The profiles of variation of the longshore sand transport as a function of the distance seaward of the swash line are examined theoretically. The results conform with the field

ISSN:0148-0227    

DOI:10.1029/JC076i003p00713

年代:1971

数据来源: WILEY

摘要:

We used an in situ oceanographic system to measure the degree of saturation (IP/Ksp′) of calcium carbonate. Results of two profiles measured in the eastern Pacific Ocean off southern California are described and compared with data obtained by conventional chemical techniques. From this preliminary study it appears that the waters investigated become undersaturated with calcite at a depth of approximately 400 meters and remain so to a depth of about 1600 meters, where they move towards saturation. Below 2500 meters they appear to become undersaturated again and probably remain so to the depth of the ocean floo

ISSN:0148-0227    

DOI:10.1029/JC076i003p00722

年代:1971

数据来源: WILEY