摘要:

The Committee on the Award of the William Bowie Medal has requested me to give the reasons for the bestowal of the Medal this year to Felix Andries Vening Meinesz, Professor of Geodesy at the University of Utrecht in Holland, Director of the Royal Netherland Institute of Meteorology, Oceanography, and Geophysics at De Bilt, and Chairman of the Royal Netherland Geodetic Commission. For me to do this is a great honor and so great a pleasure that I shall consciously restrain myself in the use of laudatory adjectives.

ISSN:0002-8606    

DOI:10.1029/TR028i003p00359

年代:1947

数据来源: WILEY

摘要:

The author reports on the studies of the geoid made in the International Isostatic Institute during recent years. In order to be able to determine the undulations of the geoid we should know the gravity field over the Earth's entire surface, that is, the gravity anomalies. In the Isostatic Institute, Tanni has estimated the gravity field of the Earth as accurately as possible, taking into the consideration the isostatic reduction according to Hayford (T=113.7 km). These anomalies with the aid of Stokes' formula give the undulations of the geoid.

ISSN:0002-8606    

DOI:10.1029/TR028i003p00361

年代:1947

数据来源: WILEY

摘要:

The child later known to the world as General Georges Perrier was born October 28, 1872, at Montpellier, a university town in southern France, and christened Antoine Francois Jacques Justin Georges. He was the son of General Francois Perrier, internationally known for his work in geodesy, who reorganized the Service Géographique de l'Armée after the Franco‐Prussian War.The father died when young Georges was only sixteen, but by that time the lad had already decided to follow in his father's footsteps as far as possible. In 1892 he entered the École Polytechnique, which in no school for the dull or the lazy, and was graduated with distinction. The choice between a civil and a military career was open to him. He chose the army, and in particular the Artillery, but was soon assigned (1898) to the Geodetic Section of the Service Géographique de l'

ISSN:0002-8606    

DOI:10.1029/TR028i003p00366

年代:1947

数据来源: WILEY

摘要:

Part I of this paper was published in the April, 1947, issue of theTransactionspages 162 to 170.The principal questions upon which interest has centered are the origin of the shelf ice, the natural causes which have maintained it almost unchanged over the years, the causes and directions of its movement, and the causes for the persistence of the various breaks along the Barrier and of deeply crevassed areas at various points over the sheet.As a result of the scientific work of the Byrd Antarctic Expedition II from 1933 to 1935, information on most of these points is now available for about five thousand square miles of the Ross Shelf Ice. Using the geophysical equipment described in the first part of this paper, the author and his associates took soundings over an area extending from the Barrier south to latitude 80°07′ and in an east‐west direction from Kainan Bay to Discovery Inlet.Attempts to measure the rate of accretion of the shelf ice by snow gauges of various sorts must be regarded as unreliable. Widely as the records vary, it is quite apparent from the observations that the net accumulation on the surface of the ice in regions 100 miles or more from open water is only a small per cent of that occurring within 50 miles or less of open water.The two most important processes whereby the density of the shelf ice is changed are: First, settling, either slow, or rapid through snow tremors; and, second, recrystallization. Although the density at the surface may be only one or two tenths, the average for the first five feet will be about five‐tenths; but even at considerable depths the density is always appreciably less than that of solid ice.A modified McComb‐Romberg seismograph was used as a tilt meter, and a recurrent tilting of the ice was observed, having a period of about 25 hours and in the proper phase with the moon for a tidal effect. While it is impossible to determine the magnitude of the tide by this method, it is not unreasonable to suppose that a tide at least equal to that at Ross Island, namely, three feet, exists at the Bay of Whales.Triangulations made in 1934 on some of the markers established in 1929, combined with accurate fixes from star sights of the position of Little America, provide the data from which the shift in position of the ice surrounding the Bay of Whales during this five‐year period was determined.The contour map presented in the preceding Part is now extended to several thousand square miles. Most of the seismic records show marked stratification of the bottom and two cross sections (Figs. 12 and 13) have been constructed. The cross sections of the Ross Shelf Ice, one across the Bay of Whales to Roosevelt Island, and the other south into the shelf ice east of Lindbergh Inlet, throw a great deal of light upon the condition of equilibrium that exists today.A current of from one to three knots enters Okuma Bay and moves in a southwesterly direction, partly along and partly under the ice at Kainan Bay. It enters the Bay of Whales along the Barrier or emerges from under the shelf Ice on the east side of the Bay, particularly through Eleanor Boiling Bight, crosses the Bay in a southwesterly direction, and again goes beneath the ice along the west side of the Bay. The current then travels west under the ice past or south of Lindbergh Inlet and out from under the ice in a northwesterly direction through Discovery Inlet.The current underneath the ice where it projects out over the moraine causes a maximum amount of melting to occur along this path, thereby causing the major portion of the glacial material being carried by the shelf ice to be deposited on the forward edge of the moraine. This process is sufficient in itself to account for the origin of the Ross Shelf Ice.The present seismic measurements of the Ross Shelf Ice have provided the first real information,on its thickness, the thickness of the water layer under the floating portion, the contour of the bottom under the ice, the existence of large moraines and the contour of the undisturbed rock surface below. It has been shown that a much larger proportion of the shelf ice is actually or practically in contact with the bottom than has hitherto been suspected. These data have provided the answers to many of our questions relative to the origin of the shelf ice and the persistence of its characteristi

ISSN:0002-8606    

DOI:10.1029/TR028i003p00367

年代:1947

数据来源: WILEY

摘要:

By virtue of the Bernoulli effect, the wind blowing over the summit of Mt. Washington, New Hampshire, causes the station barometric reading to be less than the pressure at the same level in the free air near the summit but away from the influence of the mountain. The object of this paper is to determine the amount of pressure fall that results from the Bernoulli effect and to show how it may be compensated for to a good degree of approximation by use of a pitot tube connected to the barometer.The pressure deficiency produced by the wind at Mt. Washington has been ascertained by correlating barometric readings on the mountain with comparable data reported by surrounding low‐level radiosonde stations. The latter data were derived by interpolation from synoptic charts giving pressures of the 5000‐foot plane or heights of the 850‐millibar constant‐pressure surface. A curve of pressure correction to overcome the specified deficiency in barometric reading has been prepared, giving the correction as a function of wind velocity. This curve showed that the flow of air over the mountain causes the observed barometric pressure on the summit to decrease relative to free‐air pressure nearly in proportion to V2, where V = wind velocity observed on the summit. This fact suggested to the author that the impact pressure of the wind (ρV2/2, where ρ = air density) available from a pitot tube vaned into the wind might be used to compensate automatically for the pressure deficiency produced by the wind, since both impact pressure and pressure deficiency apparently are functions of V2. A vaned pitot‐tube assembly was built and mounted on the Observatory tower freely exposed to the wind. Tubing was used to connect the pitot tube to a fixed‐cistern mercurial barometer and to a pressure‐tight box containing a standard microbarograph. The impact pressure of the wind thus imposed directly on both the barometer and the microbarograph is found to compensate approximately for the deficiency in pressure due to the wind blowing over Mt. Washington. The pressure observed at the station, with the pitot tube connected to the barometer, was compared to the local free‐air pressure derived by interpolation from the upper‐air synoptic charts. Tables of frequency of various discrepancies between these two pressures are given. These tables show that zero (0) discrepancies occur with greatest frequency, although a discrepancy as large as eight millibars has been observed out of 176 comparisons. It is believed that a major proportion of each large discrepancy results from errors in location of the isograms on the upper‐air charts that served as a source for the comparative data. Judging by the data available, the mean discrepancy in station pressure found when using the pitot tube with the barometer at Mt. Washington is of th

ISSN:0002-8606    

DOI:10.1029/TR028i003p00385

年代:1947

数据来源: WILEY

摘要:

A modulator control device for radio reporting of wind speed and direction, as measured by standard instruments, is here outlined.

ISSN:0002-8606    

DOI:10.1029/TR028i003p00398

年代:1947

数据来源: WILEY

摘要:

Rainfall in Puerto Rico during the dry season (roughly December to April) varies markedly from year to year. In preliminary studies directed toward development of seasonal forecasting methods, the precipitation records have been analyzed to determine the synoptic types favorable for different seasonal rainfall totals during the months January to March, inclusive. Synoptic studies indicate that days with 0.25 inch or more of rainfall are usually the result of major synoptic disturbances, and that days with 0.20 or less represent undisturbed atmospheric flow with frequent light showers. An analysis of over 40 years of record on this basis shows that most of the heavier precipitation of the dry season is accounted for by major synoptic disturbances. Seasons of deficient rainfall tend to have a high frequency of days with 0.20 inch or less of precipitation; this correlation is appreciably greater than with the number of days having no rainfall.The data presented here are principally for San Juan on the north coast and Mayagüez on the west coast. Results obtained for both stations are in agreement, but correlation of rainfall between the two stations is not very good, indicating that, for forecast purposes, the effects of the broad‐scale circulation patterns must be correlated separately for different stations or are

ISSN:0002-8606    

DOI:10.1029/TR028i003p00401

年代:1947

数据来源: WILEY

摘要:

It can be considered well established that the observed periods of ocean swell are longer than the observed periods of the waves in the generating area. More recently it has been demonstrated that a wave spectrum is always present and that observed periods refer to the periods of the highest waves in the spectrum, the waves of maximum energy. These are called the significant waves. Furthermore, Munk has shown that at least the forerunners of swell have the character of impulsively generated waves in deep water which advance as conservative waves.Assuming that swell generally has these characteristics, it is shown that the air resistance which the swell encounters leads to a selective dissipation. The energy associated with the shorter period waves is dissipated more rapidly than that of the longer period waves, and consequently the energy maximum shifts toward longer periods, that is, the period of the significant waves increases. The effect is modified by following or opposing winds. Numerical examples are in satisfactory agreement with results from the semi‐empirical graphs of Sverdrup and Munk.The energy considerations indicate numerous new possibilities for the interpretation of records of swell, and it is hoped that these suggestions will further stimulate the effort to establish well located swell‐recording stations and to develop instruments for rapid analysis of wave records that give complete information as to the wave spect

ISSN:0002-8606    

DOI:10.1029/TR028i003p00407

年代:1947

数据来源: WILEY

摘要:

Determination of the ground‐water supply available from any aquifer or in any specified area requires not merely the application of specific quantitative methods but also a broad and accurate knowledge of the geologic, hydrologlc, and geochemical factors that are involved, and consideration of the economic and legal limitations. Further research is needed as to geologic texture and structure in relation to the occurrence and movement of the water; the precise nature of specific yield, which determines the effective storage capacities of the aquifers; the molecular physics involved in the downward and upward movement of water in the zone of aeration, and quantitative evaluation of ground‐water recharge and discharge; the hydraulics of ground water, as studied by pumping test methods, with special reference to boundary conditions; studies of perennial yield of aquifers of low permeability; the genesis of the mineral contents of ground water as determined through appropriate geologic, hydrologlc, and chemical studies; and methods of geophysical exploration and well logging for determining the occurrence of ground water. Serious study is also needed as to practicable methods of implementing the recently developed principles and methods of ground‐water hydrology in the production of water supplies and the economic and legal problems inv

ISSN:0002-8606    

DOI:10.1029/TR028i003p00418

年代:1947

数据来源: WILEY

摘要:

In the field of land‐use hydrology it is frequently of value to keep a chronological account or balance of the components of the water resource of a watershed. In this paper a time period for studying this balance is described. Essentially it is the annual period between times of maximum watershed storage at the end of the dormant season. Changes in ground‐water storage are taken into account, and by choosing the beginning and end points of the year at times of field capacity, water storage changes in the soil mass are eliminated. Sample data for an experimental watershed are gi

ISSN:0002-8606    

DOI:10.1029/TR028i003p00421

年代:1947

数据来源: WILEY