摘要:

The so‐called yellow clouds which occur in the Martian atmosphere are generally believed to consist of granular material which has been swept from the surface by atmospheric winds. Three questions relating to these clouds are considered in this paper: the surface winds required to initiate grain motion, the particle grain sizes which may be primarily responsible for the surface obscuration, and the effects such material movement may have on the surface. It is found that unless the Martian surface is extremely rough, which appears unlikely, the wind velocities necessary to initiate grain movement are considerably greater than on the earth. If the surface atmospheric pressure is 80 mb, the required velocities do not generally exceed those observed. This is not the case if the surface pressure is 25 mb. Compatibility, for 25 mb, can be achieved, however, if the required high‐velocity winds are of such short duration as to have escaped detection or if they are associated with relatively small cyclonic disturbances. It is also found that the vertical wind velocities required to maintain particles aloft are less than those required in the terrestrial atmosphere over a rather large grain size range (1 to 300 μ for 80 mb; 4 to 200 μ for 25 mb) and that particles significantly larger than generally quoted in the literature could be responsible for most surface obscurations. The possible effects of yellow cloud formation on the surface are noted. In particular, the presence or absence of dune formations can be used as an indirect indication of the surface grain

ISSN:0148-0227    

DOI:10.1029/JZ069i018p03759

年代:1964

数据来源: WILEY

摘要:

Emission spectrums of mineral suspected to exist in the lunar crust are calculated by using reflective spectrums and the Planck‐Wien radiation law. A severe error in temperature measurement of these materials results when the emissivity is assumed to be independent of wavelength. The magnitude of this error is dependent upon the method of calculation and the composition examined. The results of detailed calculations for a series of minerals which include typical suspected lunar assemblages of granite, obsidian, dunite, chondritic meteorite, and tektite are presented. The average emissivity calculated over the 2‐ to 25‐μ, wavelength interval at 350°K from reflectance measurements on polished specimens gave values ranging from 0.78 to 0.86. These deviations from blackbody behavior give rise to calculated lunar temperatures low by 3.5 to 5.5%. The calculated temperature dependence of the average emissivity of these materials is pr

ISSN:0148-0227    

DOI:10.1029/JZ069i018p03771

年代:1964

数据来源: WILEY

摘要:

The backscattering properties of a smoothly undulated surface are discussed by means of a joint distribution of heights and surface slopes. It is shown that only those regions which are tilted so as to be normal to the incident radiation are effective in the backscattering. When this fact is properly accounted for, it is shown that the previously accepted scattering formulas have to be modified somewhat. It is also shown that the difference between the scattering properties of the two principal linear polarizations with respect to the mean surface must be exceedingly small for this kind of surface model.

ISSN:0148-0227    

DOI:10.1029/JZ069i018p03779

年代:1964

数据来源: WILEY

摘要:

Analytical expressions are developed for the direct computation of infrared transmission as a function of the amount, pressure, and temperature of the absorber. The parameters that are necessary for the application of the expressions are tabulated over the wave number range between 25 and 2150 cm−1(400 to 4.65 microns in wavelength) in intervals of 25 cm−1. Sample computations of the transmission described by the model have been shown to be comparable to recently published data. In its present form the model provides a practical tool for the numerical treatment of many radiation probl

ISSN:0148-0227    

DOI:10.1029/JZ069i018p03785

年代:1964

数据来源: WILEY

摘要:

Techniques are described for the measurement of atmospheric ozone, using the chemiluminescent reaction between ozone and rhodamine B. Details are given for a balloon sonde, for an aircraft‐installed ozone meter, and for a surface ozone recorde

ISSN:0148-0227    

DOI:10.1029/JZ069i018p03795

年代:1964

数据来源: WILEY

摘要:

Results from an analysis of data obtained by means of the chemiluminescent ozone sonde in a series of observations at various stations in North America indicate that the vertical distribution of ozone is closely related to the thermal properties of the air masses through which the sounding is taken. Significant changes in temperature lapse rate or in the wind field frequently are associated with correspondingly significant changes in partial pressure of ozone. When the tropical high‐level tropopause overlaps the extratropical tropopause, the ozone sounding frequently appears to be a composite of the upper part of a typical tropical sounding and the lower part of a typical middle‐latitude sounding extending through the extratropical tropopause. Preliminary results are presented showing a comparison of the seasonal variation of the ratioQ1/Q2of the amount of ozone in a lower layer of the atmosphere (300 to 100 mb) to that in an upper layer (100 to 40 mb) with the seasonal variation of the tropical‐extratropical tropopause structure as indicated by monthly mean temperature soundings. It is shown that for selected stations at different latitudes the variation in the ratioQ1/Q2is related to the variation in thickness of the layer of polar stratospheric air that intrudes into the subtropical tropos

ISSN:0148-0227    

DOI:10.1029/JZ069i018p03801

年代:1964

数据来源: WILEY

摘要:

A number of thermal fronts have been observed in the southern Sargasso Sea between latitudes 22°N and 32°N. Across all fronts the temperature changed 1°C or more within a distance of 10 km, with the colder water on the northern side. The fronts extend in depth from the surface to at least the bottom of the mixed surface layer. One front, surveyed for a distance of 150 km, appeared to run generally east‐west, although there was considerable meandering. Surface currents of as much as 60 cm/sec have been measured flowing eastward along the frontal edge. Calculations for one front indicate that the front is in approximate geostrophic equilibrium. Little or no frontal activity has been observed during the summer mo

ISSN:0148-0227    

DOI:10.1029/JZ069i018p03809

年代:1964

数据来源: WILEY

摘要:

A gravity meter read on floating ice, such as pack ice, shelf ice, or ice islands, shows a typical oscillation of about 20‐ to 60‐sec period corresponding to motions of the order of a few hundred microns. This phenomenon has been reported in the literature by Crary, Hunkins, and others. The motion of an ice‐covered ocean is related to long‐period gravity waves on the open ocean. The motion of the ice is no doubt due to the combined effect of waves entering the ice field from the open ocean and local winds. Power spectrums over the band 10‐ to 100‐sec period were computed for several records made at stations on pack ice (1 to 3 m thick), ice islands (20 to 50 m thick), and shelf ice (250 m thick). The spectrums have the same general form for the three different ice covers, and they show a sharp increase in spectral density with period in the band 10 to 100 sec. Records made during a storm and during a quiet period show an increase in wave motion due to local winds, especially at lon

ISSN:0148-0227    

DOI:10.1029/JZ069i018p03815

年代:1964

数据来源: WILEY

摘要:

A narrow‐beam or lateral echo sounder was towed near the ocean bottom to survey a 2.5‐ by 3‐km area on the continental rise. A lateral echo sounder transmits a beam of acoustical waves that is very narrow in the horizontal direction and relatively wide in the vertical direction. Irregularities on the ocean bottom reflect and scatter some of the energy back to the receiving transducer. The bottom is scanned by moving the transducer along a direction perpendicular to the beam of acoustical waves. The survey determines the geographical location and shape of small bottom irregularities. The bottom near 41°45′N, 64°56′W, has depths greater than 2400 m and slopes down to the south. It has numerous spurs and valleys in the north‐south direction. The region studied included a valley and crest of a spur. The relief along the east‐west direction is about 40 m. The instrument was towed about 60 m above the bottom, crossing the area with many tracks. The records were adjusted and a mosaic ‘picture’ of the bottom constructed, showing the geographical location of many features. In the valley the features were generally irregular. Several reflections were observed that appeared to be from sets of parallel ridgelike features. The spacing between the ridgelike features w

ISSN:0148-0227    

DOI:10.1029/JZ069i018p03823

年代:1964

数据来源: WILEY

摘要:

It is suggested that the correction of sea gravity data for submarine topography be computed for a datum surface coinciding with the surface of a standard oceanic crust and with the surface of a standard continental margin. The standard continental margin is a transitional zone between the standard continental and oceanic crusts. Every column of it, including the upper part of the mantle down to the isopiestic level, is in isostatic equilibrium with similar columns of the standard continental and oceanic crusts. Two models of the standard continental margin are given. Sea gravity anomalies reduced in the manner given in the paper are called ‘modified free‐air anomalies.’ They are free of the gravity effect of submarine topography; consequently they represent the gravity effects of the deviations of the actual crust from the standard crust. Over continental margins a correction for the edge effect of the continent must be applied. A unified world‐wide isogal map over continents, oceans, and continental margins can be constructed by using Bouguer anomalies on land and modified free‐air anomalies over the sea if both types of anomalies are corrected for the edge effects of the continents. The modified free‐air anomalies are directly related to the deviations of the actual crust from the standard crust; thus the interpretation of sea gravity data is simplified. The interpretation of modified free‐air anomalies along a profile is illustrated

ISSN:0148-0227    

DOI:10.1029/JZ069i018p03837

年代:1964

数据来源: WILEY