摘要:

An airborne instrument suitable for measurement of the positive and negative small‐ion density of the atmosphere above 9 km has been developed. It is a self‐contained unit which can be attached externally to any subsonic aircraft. Access is required to the normal 28‐volt dc supply and to one channel of a recorder. Various nights during 6 months in 1965 have shown that over this period there was a gradual decrease in the stratospheric dust concentration, as evidenced by the return to equality of the polar ion densities by July. A series of vertical profiles obtained during a single 24‐hour period in July showed that any effect due to dust was confined to the troposphere and that, during this period at least, no significant time variation was apparent. Two long‐distance flights confirmed the dependence of small‐ion density on geomagnetic latitude for the two altitudes 1

ISSN:0148-0227    

DOI:10.1029/JZ071i008p01945

年代:1966

数据来源: WILEY

摘要:

Conditions resulting from a head‐on collision between two pressure jumps are considered. The atmosphere is assumed to consist of two incompressible layers and the motion to take place in one dimension only. In the final steady state it is found that two pressure jumps which are weaker and slower than the original jumps emerge from the region of collision. The process of collision results in a higher rate of loss of mechanical energ

ISSN:0148-0227    

DOI:10.1029/JZ071i008p01953

年代:1966

数据来源: WILEY

摘要:

The electromagnetic spectrum radiated from a typical lightning stroke has been calculated using a particular model of the return stroke. The main features of this model are that a uniform distribution of electrons, laid down by the leader discharge between cloud and ground, is relieved by a return stroke which has the form of a step‐function current‐pulse traveling from ground to cloud. Good agreement with experiment is found in the frequency region of maximum radiation intensity from approximately 1 to 15 k

ISSN:0148-0227    

DOI:10.1029/JZ071i008p01963

年代:1966

数据来源: WILEY

摘要:

The motion of air in a thunderstorm is described in terms of properties of vortex rings generated by shear in the updrafts around the axis of the storm. The upward linear momentum of the vortex filaments is altered by electrical forces in the storm in such a way that positive charges move to the axis of the storm and are convected upward while negative charges move to the periphery and remain below, once the process has been initiated in a downward directed electric field. The gravitational field tends to make the updraft with shear contract toward the axis of the storm.

ISSN:0148-0227    

DOI:10.1029/JZ071i008p01969

年代:1966

数据来源: WILEY

摘要:

A mathematical theory of ball lightning is presented. Ball lightning is considered to be an externally powered dc phenomenon that results from the funneling of cloud‐to‐ground current through a region of high temperature and high electrical conductivity. An approximate solution of the equations of current conservation and energy conservation with proper boundary conditions yields a luminous region of air. The predicted ball lightning diameters are in good agreement with observation for reasonable values of current, current density, electric field, and electrical conductivity inside and outside the ball. The luminosity, energy content, formation, locale, motion, and observed modes of disappearance of ball lightning are discussed. An explanation for the phenomenon of bead lightning is advan

ISSN:0148-0227    

DOI:10.1029/JZ071i008p01975

年代:1966

数据来源: WILEY

摘要:

The radioactive aerosol content of the surface air in Antarctica has been measured continuously since 1956, first at Little America station and later at the South Pole station. On‐site measurements were made daily of the radioactivity due to bomb‐produced fission products and to naturally occurring radionuclides of the radon and thoron series. Later, composite samples covering 3‐month periods were subjected to radiochemical analysis for such long‐lived radionuclides as Sr90, Cs137, Ce144, Pm147, and Pb210. The natural radioactivity was lower in Antarctica than has been observed at any other geographical location, as might be expected from, the small area of exposed land surface in the vicinity. Fission‐product concentrations, however, often exceeded those found in the southernmost part of South America and exhibited more well‐defined seasonal variations, with maximums in the antar

ISSN:0148-0227    

DOI:10.1029/JZ071i008p01985

年代:1966

数据来源: WILEY

摘要:

The following results have been obtained from a size‐distribution analysis of microparticles, 0.75 to 3.0 μ in diameter, contained in two firn cores collected during the Antarctic Peninsula traverse: (1) In both cores there is a distinct variation in particle concentration with depth. Twelve ‘cycles’ were interpreted from the microparticle distribution pattern between 4.2 and 21.0 m depth for Eights station, and seven ‘cycles’ were interpreted for K core between 3.2 and 19.0 m depth. (2) Assuming that each cycle represents about a 2‐year period (that is, 24–27 months), the annual accumulation for Eights station is between 37.4 and 42.1 g/cm2of water, and for K core it is between 56.3 and 63.3 g/cm2of water. (3) Microparticle cycles of a broad stratigraphic interval are generally preceded by ‘dirty’ layers, which may substantiate the theories of precipitation control by particle density in the atmosphere. (4) The character of‘dirty’ layers, or particle cycle maximums, changes with depth, indicating some fir

ISSN:0148-0227    

DOI:10.1029/JZ071i008p01993

年代:1966

数据来源: WILEY

摘要:

Further data are presented in support of our previous conclusion that the vertical distributions of Cs137and Sr90are in accord with the ocean mixing rates demanded by the distribution of natural radiocarbon in the sea. As of early 1963 no significant activity appears to have penetrated below 500 meters in either the North Atlantic or equatorial Pacific oceans. A method for shipboard separation of Cs and Sr from 200‐liter batches of seawater is outline

ISSN:0148-0227    

DOI:10.1029/JZ071i008p01999

年代:1966

数据来源: WILEY

摘要:

The transformation of progressive waves as they travel from deep water to the shore is analyzed using the Stokes theory at a fifth order of approximation and the method of conservation of energy flux. The approximation is not uniformly valid because the wave is traveling from deep to shallow water. The first, third, and fifth orders of approximation are compared with each other and with experiments. The differences between the predictions based on the three orders of approximation are small—of the order of 5%. For most practical purposes the third‐order theory would probably give the most reliable resu

ISSN:0148-0227    

DOI:10.1029/JZ071i008p02005

年代:1966

数据来源: WILEY

摘要:

During the past two years we have made a number of beach surveys in the course of terrain‐analytical studies in the Big Bend area of Florida (see Figure 1). The area of Alligator Spit and the islands to the southwest have been classified as a low‐energy environment [Tanner, 1960] on the basis of estimates of average breaker height (an inferred 6 cm at Alligator Spit). However, during these studies it became obvious that many beaches were eroded as much as several meters per year. The rate of erosion was greatest during the passage of hurricanes through the Gulf of Mexico, but it was not necessarily directly related to the passage of hurricanes through the Big Bend a

ISSN:0148-0227    

DOI:10.1029/JZ071i008p02013

年代:1966

数据来源: WILEY