摘要:

An electrostatic mechanism for the generation of thunder, originally suggested by Wilson (1920), is applied to a model of a thundercloud in which the charge needed to produce a lightning flash is drained from within the cloud, either from a relatively thin horizontal layer or from a cylindrical volume. The mutual repulsion of the charged water droplets causes the atmospheric pressure to be reduced within the charged regions of the cloud. An acoustic rarefaction pulse is generated following a lightning discharge as atmospheric pressure equilibrium tends to be restored in the region from which charge is removed. If the acoustic waves are generated over a flat region that is several (viz., 4–10) wavelengths wide, the principal acoustic signal that is generated is beamed straight up and straight down. This signal can be observed only if the detector is placed directly below (or above) the cloud. The signal amplitude is estimated to be in the range 0.5–50 × 10−6atm, and the spectral peak should occur within the range 0.2–2 Hz. Somewhat similar results are obtained if it is assumed that the charge for the lightning flash is drained from a cylindrical volume within the cloud. The beamed acoustic signal can reach the ionosphere with negligible attenuation and perhaps produce a detectable interaction. In addition to the beamed signals, a weaker but isotropic compressional pulse should be radiated by the release of the electrostatic stress between the principal charge distributions inside the cloud and between the cloud electric dipole moment and the ground. These pulses should have a lower dominant frequency and a lower pressure amplitude than the acoustic signals radiated from the volume that supplies charge for the lightni

ISSN:0148-0227    

DOI:10.1029/JC078i012p01889

年代:1973

数据来源: WILEY

摘要:

Distribution and time constants of the exchangeable carbon on the earth's surface are discussed in terms of a two‐box model and a three‐box model. Emphasis is given to the question of the functional relationship of the14C level in the atmospheric CO2to the cosmic ray production rateQ. It is shown in a quantitative way that relatively slow changes (with a time constant of more than 30 years) of the atmospheric14C content can be described adequately by a two‐box model. More rapid changes require more complicated models. The most appropriate definition of ‘residence time’ of14C (and CO2) in the atmosphere depends on the time scale of the phenomenon under consideration. The observed fluctuations of the14C content of atmospheric CO2during the past 7000 years can be explained by assuming production rate variations due to geomagnetic and heliomagnetic modulations of the cosmic ray flux, as long as these fluctuations occur on a time scale longer than ∼100 years. More rapid fluctuations with amplitudes in excess of 1%, if they exist, will require a different

ISSN:0148-0227    

DOI:10.1029/JC078i012p01897

年代:1973

数据来源: WILEY

摘要:

Theoretical effects of atmospheric state, nadir angle, cloud amount, cloud height, and random noise on temperature data from the NOAA series satellites are investigated. These satellites have a dual‐channel (visible and infrared) scanning radiometer. Temperature departures for nadir viewing range from 2.2°K for a dry winter atmosphere to 10.5°K under moist subtropical summer conditions. An 8°K temperature difference at the sea surface when viewed at zero nadir angle through the 30° N‐July standard atmosphere registers less than 3°K at the satellite and is further compressed to 1°K when viewed at a 60° nadir angle. A 10% cloud cover can introduce errors that range from 0.5°K to 4°K depending on cumuloform cloud height; hence clouds must be completely eliminated in the analysis. Random noise in radiosonde data can introduce errors greater than 1°K for any given sounding; however, compositing and smoothing will eliminate most of this error source. A correction scheme for cloud‐free conditions is developed that is essentially free of bias. A reasonable error estimate for the total system is of t

ISSN:0148-0227    

DOI:10.1029/JC078i012p01909

年代:1973

数据来源: WILEY

摘要:

Micrometeorological data obtained at ocean station Papa during May and June 1970 are analyzed to determine the variation of the stress, drag coefficient, and wave energy in relation to the synoptic weather system. Two periods associated with the passage of high wind speed disturbances are examined. The drag coefficientC10, determined by the dissipation technique, has an average value of (1.63 ± 0.28) × 10−3for wind speeds up to 17 m sec−1and is observed to have a possible dependence on spectral shape of the wave field. The development of the wave field during the two storms is disc

ISSN:0148-0227    

DOI:10.1029/JC078i012p01917

年代:1973

数据来源: WILEY

摘要:

The mean length of runs of high wave heights and the mean number of waves between the exceedance of one level by a group of waves to the next exceedance of the same level by the succeeding group of waves have been investigated for a range of spectral widths. Asymptotic forms for both these statistics are obtained for narrow band spectra. Approximate expressions for these statistics are evaluated for one spectral form and a range of spectral widths and the results compared with data from numerical wave simulation experiments.

ISSN:0148-0227    

DOI:10.1029/JC078i012p01933

年代:1973

数据来源: WILEY

摘要:

The dynamics of rip currents is investigated using a set of shallow water equations with a horizontal eddy viscosity term. A boundary layer analysis is introduced based on the observed fact that rip currents are rather narrow. Similarity solutions of the model equations are found which seem to give reasonable representations of the velocity profile and other characteristics of rip currents. The mechanisms that are believed to be responsible for the formation of rip heads are studied. The turning of rip currents due to the longshore momentum carried by the entrained fluid is analyzed.

ISSN:0148-0227    

DOI:10.1029/JC078i012p01937

年代:1973

数据来源: WILEY

摘要:

Directional antennas at Cape Kennedy were used to passively detect radio noise emitted by storm clouds. With the antenna programmed to automatically raster‐scan an area of the sky, a slaved display provided a picture or map of the electrical activity. A number of such pictures are shown, including a sequence indicating high‐altitude electrical activity in a tornado‐producing thunder

ISSN:0148-0227    

DOI:10.1029/JC078i012p01944

年代:1973

数据来源: WILEY

摘要:

A success‐failure time series analysis was carried out on 3653 data points derived from 10 years of meteorological data acquired at White Sands Missile Range revealing a 7‐day period in daytime visibility data. A ‘success’ was classified as a day during which two consecutive visibility observations of less than 80 km were recorded, the surface wind speed was less than 5 m sec−1for at least 12 hours prior to the visibility observation, and the relative humidity was less than 50%. These criteria were employed to minimize the influence of dust generated by locally high winds and to reduce the influence of relative humidity in increasing atmospheric particulate concentration or size. The periodicity did not appear to be caused by anthropogenic

ISSN:0148-0227    

DOI:10.1029/JC078i012p01948

年代:1973

数据来源: WILEY

摘要:

This paper describes the results of an analysis of 13.3‐GHz single‐polarized scatterometer data collected during NASA/MSC mission 135, flown on March 16, 1970. Data were gathered over a crude oil spill on the Gulf of Mexico (test site 128) off the Mississippi delta. With the aid of RC‐8 camera photographs the scattering cross section was correlated with the extent of the oil spill. The scattering cross section at higher incidence angles (25°–50°) decreased by 5–10 db in the presence of the oil spill. This was attributed to the damping by oil of small gravity and capillary waves. The composite scattering theory and the scatterometer‐acquired data were used to obtain an expression of radar scattering over ocean surfaces with oil spills. The study demonstrates that the presence and extent of oil spills can be detected with high‐frequenc

ISSN:0148-0227    

DOI:10.1029/JC078i012p01952

年代:1973

数据来源: WILEY

摘要:

Two‐wavelength radiometric measurements of heat flux as developed by McAlister require corrections under rough sea conditions. One correction stems from the increase in sea surface area compared with a horizontal plane. Another correction due to sea surface roughness and nadir angle of viewing is required to obtain the temperature gradient normal to the interface. For example, these errors combined amount to 8% for 10‐m/sec wind and 20° nadir angle. Vertical advection associated with convergence and divergence due to wave motion and turbulence generally have negligible effect on the two‐wavelength radiometric measurement of heat flux but can possibly become significant for capillary waves and strong conv

ISSN:0148-0227    

DOI:10.1029/JC078i012p01964

年代:1973

数据来源: WILEY