摘要:

The geometry of lightning channels can be reconstructed from thunder data obtained with an array of microphones. In this acoustic technique we divide a thunder record into a series of short contiguous time periods and, by using cross‐correlation analysis, determine the direction of propagation of the predominant acoustic signal received during each of the time periods. If the atmospheric temperature and wind profiles are known, we can accurately trace the acoustic signals to their points of origin. The set of points generated in this manner from the complete thunder record delineate the geometry of the lightning channel. In application the accuracy of the channel reconstruction is limited by incomplete wind and temperature data; an example is given that reconstructs a lightning channel with an estimated error in the channel position of ≈10%. This technique is of particular value in investigating the nature of lightning channels inside clouds and in mapping the source regions supplying charge for lightn

ISSN:0148-0227    

DOI:10.1029/JC075i036p07517

年代:1970

数据来源: WILEY

摘要:

The results of an investigation of UHF radiation from linear lightnings over the frequency range 100–1300 MHz are reported. The amplitude distribution of UHF signals in the range 400–900 MHz is in close agreement with normal‐logarithmic law with a standard deviation of about 6 db. The flux intensity of radiation in this range is independent of frequency and equal to about 10−14w/m2Hz normalized to the distance from discharge of 1 km. The radiation over the decimetric wavelength is different from the common dipole emission of the lightning current. Over the range 10−5to 10−2sec the time‐dependence data conform to a distribution for which the probability of UHF pulses of length more thanTis propor

ISSN:0148-0227    

DOI:10.1029/JC075i036p07524

年代:1970

数据来源: WILEY

摘要:

Corona and spark discharges emitted from a large isolated positively stressed electrode have been studied. Currents have been measured with a time resolution of 0.01 μsec, and the current measurement has been correlated with the light yield along the trajectory of the discharge. A mechanism of forming the space charge distributions that causes an electric spark to propagate from a positively stressed electrode is described. An equation for the velocity of propagation for a leader discharge is derived from and related to other properties of the channel. It is concluded that the spark channel is formed primarily by electrostatic focusing in a propagating process, which lays down a charge similar to that of a leader stroke in lightning

ISSN:0148-0227    

DOI:10.1029/JC075i036p07531

年代:1970

数据来源: WILEY

摘要:

Some “best estimates” of collision efficiencies, including the influence of charges and fields from zero to those found in mature thunderstorms, have been made and incorporated into calculations of instantaneous mass accretion rates of the full range of cloud drop and raindrop sizes, an embryonic hailstone, and two larger hail stones. The implication drawn from these calculations is that instantaneous particles mass growth rate in the continued quasi steady‐state phase of precipitation growth in mature thunderstorms or electric fields of several hundred volts per centimeter can be speeded up by more than an order of magnitude by electrical forces when all particles involved are less than 100 μ. The effect decreases with increasing particl

ISSN:0148-0227    

DOI:10.1029/JC075i036p07547

年代:1970

数据来源: WILEY

摘要:

The theory of self‐preserving size distributions of Friedlander and Wang has been applied to particle formation after nuclear air bursts. The parameters at the start of coagulation are those derived from nucleation theory as applied by Stewart and by Edvarson. Brownian motion with and without slip correction has been considered. The results are compared with the log normal distribution having a logarithmic standard deviation of 2.0 such that both distributions have the same value of the geometric mean diameter. At constant mass 〈a〉 varies slowly with yield, namely, it varies asW−0.23. Contours of constant 〈a〉 as a function of mass and yield have been calculated. The results are compared with size distributions measured on cap and stem samples from eight air bursts of the 1962 Dom

ISSN:0148-0227    

DOI:10.1029/JC075i036p07559

年代:1970

数据来源: WILEY

摘要:

The collision of drops with diameters ranging from 2.0 to 4.5 mm was studied with the velocity differences of the drop pairs equal to those observed in nature. Breakup normally occurred and produced 4.2 fragments on the average. The original two droplets reappear as the larger fragments with very little change in size, and the smaller fragments were formed by the disruption of a joining neck. The collision and breakup are, therefore, basically temporary coalescence. Changes in surface tension did not affect the results. Calculations demonstrated the high frequency of occurrence of such collisions in natural rain. The experimental and numerical data, if expanded, will help to solve the problem of warm rain formation.

ISSN:0148-0227    

DOI:10.1029/JC075i036p07573

年代:1970

数据来源: WILEY

摘要:

The characteristics of the signal received in a long‐pulse bistatic laser radar system are examined with regard to the problem of contributions by multiple scattering from regions outside of the volume under consideration. The relative magnitudes of the doubly scattered radiation are computed for a wide range of observational heights and aerosol concentrations. Significant contributions due to doubly scattered energy are found for observation heights above about 40 km, even for relatively clear atmospheres. At higher altitudes and in more turbid atmospheres, doubly scattered energy can far exceed the energy from the region under stud

ISSN:0148-0227    

DOI:10.1029/JC075i036p07581

年代:1970

数据来源: WILEY

摘要:

A non‐Doppler method for determining the horizontal speeds of point targets crossing a circular radar beam is presented. It requires knowledge of only the range, the relative signal intensity variation with time, and the beamwidth of the radar. With a high‐range resolution FM‐CW radar the errors in speed range from a few per cent to about ±20% depending on the time resolution of the signals. With a low‐resolution pulsed radar the errors may be larger at short ranges but decrease rapidly with range. Speeds were measured with a vertical FM‐CW radar with 2‐meter range resolution. Dot angels, assumed to be insects, with observed 10‐cm cross sections of 10−5to 10−3cm2have speeds from 0.9 to 5.0 m sec−1. The high‐range resolution also permits accurate determination of the target vertical velocities from the time derivative of their height. Vertical velocities range from −0.86 to +0.75 m sec−1. The variation in both vertical and horizontal speeds of a selected group of insects correlates very well with the simultaneously observed radar heights of an atmospheric wave at about the same altitude as the insects. On the basis of phasing difference it is concluded that the insects are moving opposit

ISSN:0148-0227    

DOI:10.1029/JC075i036p07588

年代:1970

数据来源: WILEY

摘要:

The PRT5 was used for the remote measurement of ocean surface temperature. The correction for nonblackness of the ocean ranges from +0.6°C (under clear skies) to +0.1°C (under a low overcast). From an altitude of 300 meters the correction for absorption and emission in the intervening atmosphere can be approximated by 0.1(T−TA), whereTis the indicated radiometric temperature andTAis the air temperature at flight level. The influence of haze is investigated experimentally and found to be small. Absolute accuracy of the measurements when made carefully from low altitude is ±0

ISSN:0148-0227    

DOI:10.1029/JC075i036p07596

年代:1970

数据来源: WILEY

摘要:

Observations with bottom‐moored current meters in the Jungfern passage show that, contrary to previous conclusions, deep water in the Venezuela basin is being renewed. During a 5‐day record, the flow was mainly oscillatory at tidal frequency, with a net inflow by the tidal mechanism of only 6×103m3sec−1. During a single 11‐hour surge the inflow rate was 50 to 200 × 103m3sec−1. Steady‐state heat‐budget and oxygen‐budget calculations require a renewal rate of about 100×103m3sec−1. The sill depth is 1860 meters. STD observations near the sill reveal a sharp interface between Caribbean water above and oceanic water below sill depth. The north‐south hydrographic sections of IGY data show an abrupt change in vertical temperature gradient near 2600 to 2800 meters. This feature, also found in other basins, is interpreted to result from differences in renewal between tidal inflow and stronger sporadic surges, with the earth's rotation being an important

ISSN:0148-0227    

DOI:10.1029/JC075i036p07602

年代:1970

数据来源: WILEY