摘要:

The return of an ionospherically propagated radar pulse may be a combination of both specular reflection and diffuse scattering from the earth, and it is of some interest to estimate the structure of the return pulse due to this combination. In particular, it appears that specular reflections may occur between the transmitter and its co‐located receiver as a result of pulse reflection from suitably disposed geological and man‐made facets and that scanning over these specular areas may give some structure in the backscattered pu

ISSN:0148-0227    

DOI:10.1029/JZ071i002p00357

年代:1966

数据来源: WILEY

摘要:

Recent interest in the use of a multifrequency radar as a remote sensor for exploration of the earth and the moon has stimulated this study of the variation of radar backscattering with change in electromagnetic wavelength. The analysis of data has shown that radar cross sections of land and sea surfaces decrease with increasing wavelength and, on the average, follow approximately a λ−1behavior, although the exponent may vary from +2 to −6 in individual cases. Snow‐covered surfaces at all depression angles and sea surfaces at angles above 73° are the ones with positive values for the exponent. The wavelength dependence of the moon and the average values found on the earth in this study are quite similar. The combination of polarization and wavelength dependence versus depression angle may be characteristic features for distinguishing various terrain types by a multifrequenc

ISSN:0148-0227    

DOI:10.1029/JZ071i002p00361

年代:1966

数据来源: WILEY

摘要:

Improvements in the design and manufacture of the radiometersonde and in radiometersonde data processing since 1960 have produced new results and confirmed previous observations concerning long‐wave radiation in the atmosphere. Recent radiometric soundings are described which compare more accurate observations of total irradiance made with the ‘black disk’ and the conventional radiometersonde than those obtained in a similar experiment 5 years ago by Businger and Kuhn. The increased accuracy is the result of improved instrument design for both instruments and of better data‐processing techniques. The total irradiance measurements obtained with the standard radiometer agreed with those from the black disk radiometer within an rms difference of 4.9 watts meter−2after the random errors in the observational data were filtered by a least‐squares approximating polynomial. Comparison of infrared cooling observed with the conventional radiometersonde and with the black disk radiation detector illustrate the problems of measuring atmospheric radiative cooling with the disk radiometer in a purely gaseous atmosphere. Since the black disk is similar to the black ball, the latter has similar limitations. However, in a particulate atmosphere devoid of water vapor, there is observational evidence that it may be possible to approximate atmospheric long‐wave cooling by using the sounding of air temperature and that of the black ball or black disk

ISSN:0148-0227    

DOI:10.1029/JZ071i002p00367

年代:1966

数据来源: WILEY

摘要:

The infrared reflectivity of ice clouds, hoarfrost, and many other constituents was measured in the infrared. This paper relates the strong similarity in the over‐all spectral scattering for ice clouds and frost deposits. Infrared reflectivity of ice and water clouds is of importance in estimating the effective total albedo of the earth, since half of the energy in the solar constant lies in the infrare

ISSN:0148-0227    

DOI:10.1029/JZ071i002p00375

年代:1966

数据来源: WILEY

摘要:

The formal relationship is established between the geometric optic approach and the autocorrelation approach to the analysis of lunar and planetary radar echoes for a Gaussian autocorrelation function when the surface has Gaussian height statistics and introduces deep phase modulation on the incident wave. Similarly it is inferred that such an analogy also holds whenever the surface undulations contain structure no smaller than the wavelength of observation divided by the rms slope of the surface. If an appreciable amount of small‐scale structure is present, it is shown that (1) the range of scales responsible for the scattering will include an increasing amount of small‐scale structure with increasing angle of incidence and (2) no ample relationship appears to exist between the distribution of apparent surface slopes and the power backscattered as a function of angle of incide

ISSN:0148-0227    

DOI:10.1029/JZ071i002p00379

年代:1966

数据来源: WILEY

摘要:

The total massmα of the earth's atmosphere has been computed as precisely as possible from the present data on the atmospheric pressure and height distribution of the earth's land. The result ismα = (5.136 ± 0.007) × 1021g. The total mass of each of the principal constituents of the atmosphere was also compu

ISSN:0148-0227    

DOI:10.1029/JZ071i002p00385

年代:1966

数据来源: WILEY

摘要:

Equations for long waves in shallow water are derived systematically for an uneven bottom. With the basic assumption that the depth is small in comparison with a horizontal length scale, three regimes of approximation are presented according to the magnitude of the wave amplitude, (a) When the amplitude is of the same order of magnitude as the depth, the Airy equations are rederived as the first approximation, (b) When the amplitude is comparable to the cube of the depth, both lengths being nondimensionalized with respect to a common horizontal scale, two high‐order nonlinear equations are obtained which include the classical cnoidal wave as a special solution for a horizontal bottom. These equations may be transformed to a set of first‐order quasi‐linear hyperbolic equations with the characteristic curves in thex‐tplane directly related to the bottom profile. To facilitate numerical computations they are then written as differential equations along the characteristics. In the third regime (c) of extremely small wave amplitudes the appropriate linearized equations ar

ISSN:0148-0227    

DOI:10.1029/JZ071i002p00393

年代:1966

数据来源: WILEY

摘要:

The propagation of long‐period waves is determined by the first‐order linear small‐amplitude surface wave theory for regions away from the shore and by the first‐order nonlinear shallow‐water theory for regions near the shore. Calculations by the linear theory were made by using Friedrichs' second asymptotic representation, which is suitable for small beach slopes. Calculations by the nonlinear theory were made on a digital computer by a finite difference technique based on the method of characteristics. In the numerical method, the bore equations are coupled to the equations of the nonlinear theory, and a procedure for the calculation of the wave runup on the dry sloping beach is given. A primary objective of this study was the development of computer programs for the application of the nonlinear theory to periodic long waves. Instantaneous dimensionless wave profiles as functions of the distance from the shore are presented for several combinations of wave periods and bea

ISSN:0148-0227    

DOI:10.1029/JZ071i002p00401

年代:1966

数据来源: WILEY

摘要:

When the direction as well as the magnitude of the horizontal mean velocity (e.g., in a lake or ocean current) changes with the vertical coordinate, the horizontal diffusion of a batch of ‘marked’ fluid is greatly accelerated, as compared with diffusion in uniform flow. When, in addition, temporal changes are superimposed on this pattern, further dispersing effects appear. The net result is that, as observed during diffusion experiments in Lake Huron, apparent horizontal diffusivities increase steeply in complex currents. Theoretically some light may be thrown on this rather involved problem by several approximate measures: (1) by considering the kinematics of skewed, unsteady currents, (2) by calculating effective lateral or longitudinal diffusivities using a technique originated by G. I. Taylor in 1954, and (3) by calculating first and second moments of the concentration distribution in shear flow using the diffusion equation. Numerical estimates obtained in this manner of ‘acceleration’ effects show order of magnitude agreement with observations. From a practical point of view the interesting conclusion emerges that a low vertical eddy diffusivity tends to produce a high apparent horizontal diffusivity, owing to acceleration of diffusion by the greater complexity of the current, so that over‐all dilution rates vary less than one would otherwi

ISSN:0148-0227    

DOI:10.1029/JZ071i002p00411

年代:1966

数据来源: WILEY

摘要:

In conventional methods of aquifer tests homogeneous and isotropic aquifers are assumed. In many instances, however, the aquifers tested are anisotropic. Procedures are outlined for determining the principal directions of anisotropy and the hydraulic properties of homogeneous anisotropic aquifers. Data from pumping tests in leaky or nonleaky aquifers are used. The aquifers are uniform in thickness, and the flow therein during the period of the test behaves as if it were in an infinite aquifer. The collected data are from at least two groups of wells if the principal directions of anisotropy are known and from at least three groups of wells if these directions are not known. Each group of wells is located on a different radial line. When the pumped well partially penetrates the aquifer, the observation wells should either be completely screened throughout the aquifer or be located at distances from the pumped well of at least 1.5b(Kz/Kr)1/2, wherebis the uniform thickness of the aquifer, Kzis the vertical conductivity, andKris the directional conductivity in the horizontal planes of the aquifer. The procedures are illustrated by an example of computation.

ISSN:0148-0227    

DOI:10.1029/JZ071i002p00421

年代:1966

数据来源: WILEY