摘要:

An exact expression for the electric field intensity of an idealized lightning return stroke is derived, and from it the charge moment equation approximation is obtained. Exact criteria for the validity of the moment equation are given, and it is shown that for observation distances greater than 50 km the moment equation probably provides an adequate representation of the wave front rise time as well as of all other features of the electric field wave form.

ISSN:0148-0227    

DOI:10.1029/JC076i009p02101

年代:1971

数据来源: WILEY

摘要:

Forty thunder events from intracloud and cloud‐to‐ground lightning were analyzed by analog and digital power spectrum methods. Thunder exhibits a lowQ(0.5 to 2) spectrum with peak power observed at frequencies from<4 to 125 Hz. Significant differences are noted between thunder from intracloud and cloud‐to‐ground lightning. Intracloud thunder spectrums show a mean peak value of power at 28 Hz with a mean total acoustic energy of 1.9×1013ergs. Cloud‐to‐ground spectrums show a mean peak value at 50 Hz with a mean total acoustic energy of 6.3×1013ergs. The mean total acoustic efficiency for discharges to ground is calculated to be 0.18%. The thunder power spectrum is time varying. The mechanism of thunder production by a thermally driven expanding channel as described by A. A. Few appears to account for the dominant frequencies observed from many cloud‐to‐ground flashes, but cannot explain the high‐energy low‐frequency peaks of some cloud‐to‐ground and most intracloud discharges. The electrostatic mechanism of C. T. R. Wilson and of S. A. Colgate is proposed to explain the large energy peaks at fr

ISSN:0148-0227    

DOI:10.1029/JC076i009p02106

年代:1971

数据来源: WILEY

摘要:

Pulse trains of extremely low‐frequency (ELF) atmospherics were recorded at two widely separated stations, Hawaii and Arizona. The characteristics of the individual pulse trains indicate their probable origin to be multiple strokes in lightning flashes to earth. The 300‐Hz spectral amplitude ratios of first to subsequent pulses were computed from many pulse trains received simultaneously at both stations. The spectral amplitude ratios for the same pulse trains received at both stations were found to differ between stations in a random manner. The following possible contributions to the measured ELF amplitude ratio differences from two mechanisms are investigated in this report: (1) a horizontal component in the radiating elements in the lightning‐discharge channel, and (2) electron heating in the ionosphere by precursory very‐low‐frequency (VLF) components of the atm

ISSN:0148-0227    

DOI:10.1029/JC076i009p02116

年代:1971

数据来源: WILEY

摘要:

Depending on the value of the Prandtl number, the average velocity imparted to a layer of Boussinesq fluid by traveling thermal waves applied at the upper free surface is found, in the linear case, to be either in the same or opposite direction as that of the moving thermal source. Since the mean flow is in the opposite direction only when the Prandtl number is small, the 4‐day retrograde zonal motion of the Venus atmosphere may be evidence that the effective Prandtl number of the upper atmosphere is much less than unit

ISSN:0148-0227    

DOI:10.1029/JC076i009p02126

年代:1971

数据来源: WILEY

摘要:

Ozone distributions deduced from Umkehr observations are subject to error if the temperature dependence of ozone absorption has not been included in the development of an inversion system. An estimation of the error is made for the World Ozone Data Center Umkehr inversion system in the following way: Umkehr curves are computed for temperature dependent ozone absorption coefficients and for absorption coefficients at −44°C; then, ozone distributions are deduced from these curves and are compared for midlatitude summer and winter situations. Significant differences arise and their cause is discussed. It is suggested that any future work on the development of inversion systems for indirect observation of the vertical ozone distribution include a compensation for the temperature dependence of ozone absorpti

ISSN:0148-0227    

DOI:10.1029/JC076i009p02131

年代:1971

数据来源: WILEY

摘要:

An experiment was conducted to assess the performance of side‐looking air‐borne radar (SLAR) in mapping and identifying sea ice parameters. A Philco‐Ford AN/DPD‐2 (Modified) SLAR was installed on a Coast Guard C‐130 aircraft and flown on an experimental basis during September 1969 in conjunction with the S.S.Manhattan'stransit of the Northwest Passage. In addition to the research effort to determine its feasibility as an ice observational technique, the SLAR was also used as a routing aid to theManhattan. The results of this experiment indicate that SLAR can readily be used to detect ice concentrations, floe size and number, and water openings, and to identify, through careful image interpretation, ice age, ice drift, surface topography, fractures, and pressure characteristics. SLAR's broad areal coverage, all weather, day and night capability make it an effective means of observing sea ice, and for many purposes it provides observations superior to information obtained by a visual ice observer. SLAR imagery can be used in research efforts to study the formation, growth, and decay of sea ice and can be used operationally for ship routing and ice forecasting. It will be necessary to conduct similar experiments during other seasons of the year to determine whether there is a seasonal influence on the imaged appearance o

ISSN:0148-0227    

DOI:10.1029/JC076i009p02138

年代:1971

数据来源: WILEY

摘要:

An exact solution is given of the equations of motion of the atmosphere on the rotating earth, which yields a wind velocity pattern similar to that observed in the 90‐ to 150‐km region at midlatitudes through the use of chemical releases. Motivation for the particular form of the solution is indica

ISSN:0148-0227    

DOI:10.1029/JC076i009p02156

年代:1971

数据来源: WILEY

摘要:

During the austral summers of 1968 and 1969, the USCGCGlacierpenetrated the pack ice of the Weddell Sea to over 75°S in support of the International Weddell Sea Oceanographic Expedition (IWSOE). A total of 83 hydrographic stations were conducted during the two expeditions for analysis of temperature, salinity, dissolved oxygen, and nutrients. The data revealed a cold (−1.9°C) saline (>34.60‰) layer of water on the continental shelf below a depth of 200 meters in the southwestern Weddell Sea. We hypothesize that this water mass is formed by alteration of coastal current water as it flows along and beneath the vast ice shelves in the southern Weddell Sea. The altered coastal current water then mixes with warm deep water (>0.2°C,>34.67‰) along the continental slope in approximately 1∶2 to form antarctic bottom water (−0.4°C, 34.66‰). The mixing ratio is confirmed by using core values of preformed phosphate and preformed nitrate concentrations as conservative properties. Antarctic bottom water then flows out of the Weddell Sea between 50° and 15°W longitudes and 60° and 65°S latitudes. Bottom water (−0.26°C, 34.66‰) flows into the Weddell Sea from the east near the Coats Land coast and is entrained into the antarctic

ISSN:0148-0227    

DOI:10.1029/JC076i009p02164

年代:1971

数据来源: WILEY

摘要:

A steady state model for manganese distribution in calcareous sediment cores is presented. In this diffusion‐advection model, the chemical reactions involved are (1) Mn++is oxidized in the top of the core, and (2) Mn++is sorbed on the solid phase in the reducing conditions of the bottom. A general mathematical solution is given. A numerical statement is given for calcareous core

ISSN:0148-0227    

DOI:10.1029/JC076i009p02179

年代:1971

数据来源: WILEY

摘要:

Diborane (DB) has been released in twilight and produced brilliant greenish trails and puffs in the 90‐ to 150‐km altitude region. The emission was identified as the fluorescent solar scattering by BO2molecules. No chemiluminescence was observed, contrary to expectations from laboratory studies. The absence of chemiluminescence limits the use of DB as an atmospheric tracer to dawn and dusk periods. The radial spread of the gaseous DB releases was more confined than that of the liquid trimethylaluminum (TMA) releases; thus improved triangulation was possi

ISSN:0148-0227    

DOI:10.1029/JC076i009p02187

年代:1971

数据来源: WILEY