摘要:

Density values were obtained in the stratosphere and mesosphere from measurements of impact pressure, velocity, and altitude on six X‐15 research airplane flights. A form of the Rayleigh pitot formula was used for density computations. Because of pressure‐instrumentation limitations and pressure lag, the maximum altitude for reasonably accurate density determination was considered to be about 65 km. For all six flights, four of which were made in summer, densities at altitudes above 40 km were higher than theU.S. Standard Atmosphere, 1962values. Temperatures calculated from density‐height profiles of two X‐15 flights agreed well with temperatures measured by rocketsondes launched from the Pacific missile range, Point Mugu, California, near the times of the

ISSN:0148-0227    

DOI:10.1029/JZ069i024p05123

年代:1964

数据来源: WILEY

摘要:

Estimated January and July zonal wind patterns are described to 120 km from the equator to 75°N. Time cross sections of mean monthly zonal winds to 120 km for latitudes 30° and 60°N are also shown. Day‐to‐day fluctuations of zonal and meridional winds between 25 and 65 km are greater in January than in July and appear larger during the day than at night. These data indicate that a monthly wind climatology prepared for various times of day would provide improved estimates of the wind for specific times and altitudes. Also, it is suggested that the large observed diurnal variability of zonal winds at heights between 90 and 120 km may be partially due to a nocturnal contraction and daytime expansion of the atmo

ISSN:0148-0227    

DOI:10.1029/JZ069i024p05131

年代:1964

数据来源: WILEY

摘要:

Measurements of intracloud lightning discharges are presented and discussed with particular emphasis on the relationships between potential gradient, potential gradient changes, andKchanges. An analysis of the intracloud lightning discharge is given in terms of an advancing streamer model. The observed variations of electric field with time and distance in theinitialpart of the discharge are consistent with a model which effectively lowers positive charge in the cloud, in agreement with the model proposed by Takagi but at variance with the earlier results of Smith. Thefinal, orJ‐type part of the discharge consists primarily of negative recoil streamers (Kchanges) which occur when the initial positive streamers contact regions of concentrated negative charge. The recoil streamers, as seen in photographs of cloud‐to‐air discharges, originate at the tip of the advancing streamer and travel back along the channel toward the source in a manner analogous to the development of the return stroke following the dart leader in the cloud‐to‐ground discharge. TheKchange is estimated to involve currents from 1000 to 4000 amp; aK‐change streamer velocity of 2×106m/sec

ISSN:0148-0227    

DOI:10.1029/JZ069i024p05141

年代:1964

数据来源: WILEY

摘要:

Electron densities between 1×1017cm−3and 5×1017cm−3are found for three lightning strokes by comparing the profiles of Stark‐broadened Hα lines with theoretical profiles. The results are discussed and compared with electron density determinations made from line intensity meas

ISSN:0148-0227    

DOI:10.1029/JZ069i024p05151

年代:1964

数据来源: WILEY

摘要:

Dispersion on the surface of natural waters is such as to suggest that the diffusion coefficient for pairs of particles varies as the 4/3 power of the particle separation for small time intervals. Similarity theory calls for a 2/3‐power variation when viscosity can be ignored. An explicit consideration of time may yet show that the 2/3‐power relationship is obeyed in nature so that the turbulence is characterized by the presence of an inertial subrange of eddies. Laboratory surface dispersion experiments were performed at low Reynolds numbers, and, in most cases, a 4/3‐power relationship was found. These results illustrate the necessity of using time as a parameter in all surface diffusion experiments before a judgment can be made on the nature of the turbu

ISSN:0148-0227    

DOI:10.1029/JZ069i024p05155

年代:1964

数据来源: WILEY

摘要:

Various criteria pertaining to the synoptic situation are presented in order to determine when a fully developed wind‐generated sea might be found in the North Atlantic Ocean. Four hundred and sixty wave records, corresponding to various synoptic situations, were digitized and analyzed spectrally as a first step in the preparation of a climatology of ocean wave spectrums. The wave records were taken by the ocean weather ships of the United Kingdom by means of a Tucker shipborne wave recorder. Selected subsets from the available spectrums based on these synoptic criteria were averaged in order to produce spectrums for various wind speeds. These selected subsets were examined to see if they came from the same population by means of the Kolmogorov‐Smirnov test, and the results show that, within the accuracy expected, the samples chosen represent fully developed seas. A second subset chosen at random without using these criteria was tested, and the results showed that wind speed alone does not properly characterize the sea state. A nested family of spectrums was obtained for wind speeds of 20, 25, 30, 35, and 40 knots in which the frequency of the maximum appeared to be inversely proportional to the wind speed and the significant height was proportional to the square of the wind speed. The spectrums and the results deducible from them yield results that appear to be a compromise among the various published theoretical forms for the spectrums and the equations for the significant height of a fully developed

ISSN:0148-0227    

DOI:10.1029/JZ069i024p05161

年代:1964

数据来源: WILEY

摘要:

The data for the spectrums of fully developed seas obtained byMoskowitz[1964] for wind speeds from 20 to 40 knots (10.29 to 20.58 m/sec), are used to test the similarity hypothesis and the idea proposed byKitaigorodskii[1961] that, when plotted in a certain dimensionless way, the power spectrums for all fully developed seas should be of the same shape. Over the important range of frequencies that define the total variance of the spectrum within a few per cent, the transformed plots yield a nondimensional spectral form that is nearly the same over this entire range of wind speeds within the present accuracies of the data. However, since slight variations of the wind speed have large effects on the location of this nondimensional spectral form, inaccuracies in the determination of the wind speed at sea allow for some latitude in the final choice of the form of the spectrum. Also, since the winds used to obtain the nondimensional form were measured at a height greater than 10 meters, the problem of relating the spectral form to a standard anemometer height arises. The variability introduced by this factor needs to be considered. The results, when errors in the wind speed, the sampling variability of the data, and the anemometer heights are considered, suggest a spectral form that is a compromise between the various proposed spectrums and that has features similar to many of them. A spectral form is recommended for tentative application to the problem of wave forecasting by spectral techniques. Improved wind speed measurements (taken at several elevations and averaged over longer time intervals) and better wave data (taken for longer time intervals and analyzed so as to better fit the procedures) are needed so that the form of the spectrums of fully developed wind seas and seas limited by either fetch or duration can be determined with even greater precision.

ISSN:0148-0227    

DOI:10.1029/JZ069i024p05181

年代:1964

数据来源: WILEY

摘要:

The variation of the mean wind with height (as a function of the variously proposed drag coefficients) affects the interpretation of wave spectrums for fully developed seas. It is found that the effect brings the results of Neumann, Wilson, and Moskowitz and Pierson into closer agreement. Further improvement in wave theory will depend on the solution of problems in turbulence and on more precise measurements of waves and winds at sea.

ISSN:0148-0227    

DOI:10.1029/JZ069i024p05191

年代:1964

数据来源: WILEY

摘要:

A line of oceanographic stations from 15°S to 5°N, taken aboard theArgoin July 1963 in the central Atlantic, has been compared with other Atlantic and Pacific transequatorial sections. In the Atlantic the two subsurface tongues of high salinity that extend equatorward from the tropical high‐salinity cells are approximately symmetrical about the equator and are separated by a high‐salinity core at the equator. In the Pacific the two tongues are not symmetrical about the equator: the boundary appears to be at about 6 to 8°N. The presence of an equatorial high‐salinity core in the Pacific has not been established and seems unlikely. At greater depths the Intermediate Waters that extend northward from the Antarctic show different salinity values at the salinity minimum beneath the surface at the equator: in the Pacific the minimum value is about 34.55‰ and in the Atlantic about 34.50‰. This is remarkable since the Atlantic is in general the more saline. The presence of the Equatorial Undercurrent in the Atlantic is indicated on theArgosection by weakening of the thermocline, the high‐salinity core, deep penetration of high oxygen concentration, and, within the limits of the method, geostrophic flow. The value of salinity at the core, the shape of the core, and the density distribution are markedly different from a section 278 km to the west made in April, 1961: these differences suggest that the Undercurrent was wider in July 1963. Between 5 and 12.5°S the section clearly indicates eastward geostrophic flow at a maximum speed of about 9 cm/sec near 200‐m depth. Such other data as are available do not preclude that this is a regular (perhaps seasonal) feature, and perhaps evidence of a South Equatorial Countercurrent in t

ISSN:0148-0227    

DOI:10.1029/JZ069i024p05205

年代:1964

数据来源: WILEY

摘要:

The 68‐cm radar echoes from the moon are interpreted with the approximation that the scattering can be described by the laws of geometric optics. The treatment relates the observed angular power spectrum directly with the distribution of surface normals, and no assumed functional dependence of the surface correlation function is required. A simple calculation gives a dielectric constant of 2.6 to 2.8, an average slope of 11° to 14°, and an rms slope of 15° to 23°. The depolarization data and the contour of the angular power spectrum are used in selecting these values from the different possible sets. The reduction technique has the added feature that the derived formulas can be used directly to calculate the microwave emissivity as a function of both angle and polariz

ISSN:0148-0227    

DOI:10.1029/JZ069i024p05217

年代:1964

数据来源: WILEY