摘要:

The Michelson interferometer experiment carried on the Nimbus 3 satellite has successfully obtained thermal emission spectra of the earth and atmosphere between 400 and 2000 cm−1with a resolution equivalent to 5 cm−1. Comparison of a measured spectrum with a spectrum calculated theoretically from near‐simultaneous radiosonde measurements indicates generally good agreement over most of the spectral range covered. A preliminary search for spectral features attributable to minor atmospheric constituents other than CO2H2O, and O3has resulted in a positive identification of only CH4thus far. Comparisons of temperature profiles estimated from selected spectra with those obtained from radiosonde measurements on an individual basis and in the form of maps for selected locations and times indicate that meaningful atmospheric temperatures can be obtained, even in the presence of clouds. Similar comparisons of water vapor estimates with radiosonde measurements demonstrate that good humidity profiles can be obtained under almost clear sky conditions, but, when clouds are present within the field of view, the estimates become unreliable. Total ozone amounts in an atmospheric column obtained from the spectra are in generally good agreement with Dobson spectrometer measurements, and the estimates are found to be insensitive to clouds within the field of view under most circumstances. A global map of ozone, constructed from data taken over a 24‐hour period, shows anticipated correlations with a conventional 300‐mb pressure height map in the northern hemisphere. The possibility of obtaining information on surface composition is investigated by using a spectrum obtained over Egypt that shows a depression of as much as 10°K in brightness temperature in parts of the atmospheric window. This effect can be attributed to reststrahlen due to the presence of SiO2in the d

ISSN:0148-0227    

DOI:10.1029/JC075i030p05831

年代:1970

数据来源: WILEY

摘要:

Using a computer and postulating highly idealized thundercloud conditions, we have modeled the interaction between a population of raindrops and a region of high electric field. Under favorable circumstances, the interaction produced a downward‐moving wave of potential gradient that intensified the preexisting field without apparent limit. The two major parameters that determined the intensification were the raindrop concentration and the amount of immobile negative charge produced by a stressed raindrop. Field intensification seems to depend critically on the peculiar characteristics of a water‐drop discharge at the altitude considered, namely the production of large numbers of highly charged negative droplets. Charged raindrops alone could not produce the required effect. It is suggested that the mechanism modeled here could be responsible for the initiation of cloud‐to‐ground lightning strokes. The mechanism should strongly favor a downward‐moving negative

ISSN:0148-0227    

DOI:10.1029/JC075i030p05858

年代:1970

数据来源: WILEY

摘要:

We attempt to explain the observed dependence of dart leader velocity on the interstroke time interval in a lightning flash in terms of the corresponding variation of electron density in the return stroke. The temperature decay in the return stroke channel calculated by Uman and Voshall is used in conjunction with the conductivity measurements of Yos to yield an order of magnitude for the electron density. The percentage change in the dart leader velocity, calculated as a function of the interstroke time interval, shows a reasonably good agreement with the experimental data of Brook and Kitagawa. Certain limitations inherent in Loeb's formula for dart leader velocity are briefly discussed.

ISSN:0148-0227    

DOI:10.1029/JC075i030p05868

年代:1970

数据来源: WILEY

摘要:

Cloud drop charge and size have been measured with tethered balloon‐borne equipment in the lower few hundred meters and at an early stage of a forming thunderstorm by photographing the droplets in a combined sound wave and electrostatic field. The drop size distribution shows a peak at 7 to 8 microns in diameter, and the charge distribution at each of several drop sizes shows an average negative charge of −18×10−8esu, and a mean absolute charge 〈|q|〉 =K0r2, whereK0= 1.72 esu cm−2. At an observed average of 200 to 300 drops cm−3, this corresponds to a space charge concentration of about −5×10−5esu cm−3or 105el

ISSN:0148-0227    

DOI:10.1029/JC075i030p05873

年代:1970

数据来源: WILEY

摘要:

A solution to the problem of cloud drainage leading to lightning strokes that involve the corona streamer mechanism in raindrop‐laden clouds had never been delineated in detail. Recent studies, especially the work of G. A. Dawson on the disruption and discharge from raindrop‐size water droplets, have now permitted the completion of the picture by giving a basis for the early and rapid generation of the high fields' near the cloud base initiating the stepped leader and permitting the drainage to proceed as the leader forges its way to gro

ISSN:0148-0227    

DOI:10.1029/JC075i030p05882

年代:1970

数据来源: WILEY

摘要:

Radon 222 (Rn) vertical soundings were made on five different days over Illinois from 150 meters to as high as 5 km above the surface. The Rn concentration ranged from 60 to 300 pc m−3at 150 meters above the surface and decreased exponentially by approximately one‐half with every 700‐meter increase in elevation. The Rn soundings were compared with earlier theoretical Rn profiles and with actual Rn measurements taken by several other investigators. The Rn concentration was found to decrease more rapidly with increasing altitude than had been calculated theoretically. Possible explanations for this disagreement are pres

ISSN:0148-0227    

DOI:10.1029/JC075i030p05890

年代:1970

数据来源: WILEY

摘要:

The Gerstner solution (1809) for waves on the surface of a semi‐infinite homogeneous fluid is extended for an incompressible vertically stratified fluid in a rotating system. For oceanic surface waves on the earth the frequency and vertical wave number differ only negligibly from their nonrotating values. The particle orbits, while still circular, now lie in a plane slightly tilted from the vertical. This has important consequences when one considers the second‐order drift currents associated with surface waves. These waves, which are rotational, can be generated by irrotational forces in a rotating sys

ISSN:0148-0227    

DOI:10.1029/JC075i030p05895

年代:1970

数据来源: WILEY

摘要:

A one‐dimensional internal wave antenna was maintained in the main thermocline at Bermuda for 10 months. The antenna consists of three temperature sensors 1 km apart at a depth of about 600 meters plus engineering sensors. The signals are generally incoherent until periods approaching 12 hours are reached, when the sensors become coherent at zero phase. A large, variable, internal semidiurnal tide was measured. The diurnal tides appear to be generally absent, but there is an unexplained energy rise at periods of about 19 hours, which may be related to the inertial period at 22 hours. Much of the high‐frequency incoherence is ascribed to the presence of a strong local microstructure, possibly generated on the island its

ISSN:0148-0227    

DOI:10.1029/JC075i030p05899

年代:1970

数据来源: WILEY

摘要:

Passive microwave radiometric measurement of salinity variations were made at the south and southwest passes of the Mississippi River on September 27, 1969. The passive microwave system mounted on the NASA/MSC P3A aircraft can measure radiometric energy in four bands centered on 1.4, 10.6, 22.2, and 31.4 GHz. No radiometric temperature change (within instrumental limits) was observed with the 10.6‐, 22.2‐, or the 31.4‐GHz radiometers. We did observe a radiometric change of 13–18°K with the 1.4‐GHz radiometer. This observed change and the absence of an observed change by the other channels agrees (within experimental limits) with the theoretically predicted radiometric temperature variation for water at 25°C. This measurement demonstrates that an airborne passive microwave radiometer operating at 1–1.5 GHz can rapidly measure salinity and variations in salinity ove

ISSN:0148-0227    

DOI:10.1029/JC075i030p05909

年代:1970

数据来源: WILEY

摘要:

Simultaneous field measurements of wave and current parameters in the surf zone and the resulting longshore transport of sand have been made on two beaches under a variety of conditions. The direction and flux of wave energy was measured from an array of digital wave sensors placed in and near the surf zone. Quantitative measurements of the longshore sand transport rate were obtained from the time history of the center of gravity of sand tracer. The measurements have been used to test two models for the prediction of the longshore transport rate of sand. The first model gives the immersed weight longshore transport rate of sand,Il, as proportional to the longshore component of wave energy flux (power),Il=K(ECn)bsin αbcos αb, whereEis the energy density,Cnis the wave group velocity, and αbis the breaker angle. The second model assumes that the waves provide the power to move and support the sand and that the superimposed longshore current 〈νl〉 provides a longshore component that results in the longshore transport of sand according to the relationshipIl=K′ (ECn)bcos αb〈νl〉/um, whereumis the magnitude of the maximum horizontal component of orbital velocity near the bottom under the breaking wave, assumed to be proportional to the rate of energy dissipation by friction on the beach bed. The measurements show that both models successfully predict the sand transport rate, with values of the dimensionless coefficientsK= 0.77 andK′ = 0.28. The coherence of the models implies that they are interrelated, their common solution giving the relation as 〈νl〉 =K″umsin αb, whereK″ is a dimensionless constant equal to 2.7. This relation can be obtained directly by equating the longshore current and the longshore component of the momentum flux (radiation stress) of the breaking waves. Thus, the coherence of the models appears to be based on the generation of the longshore currents by the longshore radiation stress. The models will not be equivalent if 〈νl〉 owes its origin to some other generating

ISSN:0148-0227    

DOI:10.1029/JC075i030p05914

年代:1970

数据来源: WILEY