摘要:

The chemistry of atmospheric CH4, CO, and CO2is treated with a one‐dimensional model incorporating the effects of eddy diffusion in the altitude region of 0–120 km. Methane is well mixed up to about 20 km, and its mixing ratio declines steadily at higher altitudes. Carbon monoxide is well mixed in the troposphere. Its mixing ratio decreases initially in the lower stratosphere, reaches a minimum value of the order of 10−8near 30 km, and increases steadily at higher elevations. Carbon dioxide is well mixed in the troposphere. Its mixing ratio declines somewhat in the stratosphere, and this decline reflects the importance of anthropogenic production of CO2and the relatively long time constants for stratospheric diffusion. Mixing ratios of CO and CO2are comparable near 120 km. Combustion is a minor source of CO in comparison with oxidation of CH4. Oxidation of CH4also provides a significant source of stratospheric H2O and H2. The principal sinks for CO and CH4involve reactions with OH. Carbon dioxide is removed at the surface and to a lesser extent in the atmosphere by photolysis. Mean atmospheric residence times for CO and CH4are 0.3 and 7 years, respect

ISSN:0148-0227    

DOI:10.1029/JC077i024p04477

年代:1972

数据来源: WILEY

摘要:

Data from aircraft measurements of the atmospheric content of sulfur (SO2and sulfate on participate matter) over a rural area in southern Sweden are presented and discussed. Some 30 flights have been performed with measurements at four to eight different altitudes up to 3 km. Most of the sulfur was found to be in the form of SO2. Mean values of concentrations of both SO2sulfur and sulfate sulfur decreased by a factor of roughly 2 from the ground up to 3 km. Although there is a rather large scatter in the data, systematic seasonal variations (with a minimum in summer) and dependence on static stability are demonstrated. The observed relation between SO2and sulfate concentrations and the rate of decrease of SO2with height indicate that the mean turnover time for SO2before oxidation is at least of the order of tens of hours in this area.

ISSN:0148-0227    

DOI:10.1029/JC077i024p04494

年代:1972

数据来源: WILEY

摘要:

Short duration increases in the concentration of atmospheric ozone have been observed beneath active New Mexican thunderstorms in the vicinity of an exposed and grounded sharp metal rod. These ozone transients immediately follow the emission of charge into the air from the metal point under the influence of atmospheric electricity. The increases are greater when they are associated with negative charge emission than when they are associated with positive; the maximum ozone concentration above lightning‐induced emission of negative charge has been about 6.4 times that of the fine weather concentration (about six ozone molecules per hundred million air molecules). Longer duration increases in the atmospheric ozone to about 1.5 times the prestorm concentration are found above a collection of natural grass points when overhead clouds are electrified with a net positive charge. Our comparison of the ultraviolet radiation pulses from negative and positive point to plane discharges suggests to us a photochemical explanation for the relatively large production of ozone by negative charge emission. Whereas much of the ozone found aloft appears to have been transported by updrafts from the surface, the concentrations observed in an electrified cloud were greater than those near the earth. We find that ozone is produced by the point discharge from the surfaces of water droplets under intense electric fields; this process may account for some of the ozone observed in thundercloud

ISSN:0148-0227    

DOI:10.1029/JC077i024p04500

年代:1972

数据来源: WILEY

摘要:

Measurements of charge versus size of drops within warm thunderstorm clouds indicate that the mean specific charge per gram decreases dramatically as the size increases. Because coalescence between smaller and larger drops occurs with an approximately geometric cross section, the charge neutralization length (the distance in which the smaller drops of one charge sign could neutralize the charge of the larger drops by coalescence) becomes small in comparison with cloud dimensions and hence ensures that any effective charge separation mechanism rapidly approaches steady state. The downward, steady‐state, large drop mass flux averaged over the cloud is usually less than the upward, convected, small drop mass flux. At the interior of the cloud, quasi steady‐state charge separation requires an equal and opposite charge flux carried by smaller and larger drops. The two conditions are inconsistent with current drop charge versus size measurements by several orders of magnitude. Currently, the assumption of equal and opposite charge flux, is not substantiated and hence charge separation by differential ‘falling’ of larger and smaller drops within the cloud should be a small contribution to the total charge tr

ISSN:0148-0227    

DOI:10.1029/JC077i024p04511

年代:1972

数据来源: WILEY

摘要:

The radar cross section of a cloud‐to‐ground lightning stroke is calculated for the two limiting cases of overdense and underdense plasma. By using a model of the decaying channel and smoothly joining these limiting cases, curves of the temporal variation of the radar cross section can be obtained. Results are presented for wavelengths of 3.2, 10, 23, and 150 cm. Comparison with radar noise levels shows that radars of wavelength 10 cm or greater can be used to monitor the conditions within lightning strokes for up to about 100 msec after stroke incidence. Radars with wavelengths much less than 10 cm are not so suitable. With radar it should be possible to determine the lightning channel conditions conducive to dart leader formation, the relationship between initial ionization density and dart leader speed, the ratio of the diameters of leaders and return strokes, some information on the electron density inside leaders and its temporal variation, and also, with radars of smaller wavelength, (3 cm or less) the initial shock expansion rate of the return stroke. The radar cross section of the dielectric discontinuity of the hot air of the channel is shown to be negligible, in agreement with Browne (19

ISSN:0148-0227    

DOI:10.1029/JC077i024p04518

年代:1972

数据来源: WILEY

摘要:

A statistical technique for deriving size distribution models of tropospheric air‐borne particles is described. The technique provides an estimate of the probable average size distribution for any total particle concentration between 0.1 and 10.0 cm−3for three different geographical locations. The size distribution data obtained by Blifford and Ringer (1969), and Blifford (1970) are used to derive models of particle size distribution for three locations: Scottsbluff, Nebraska; Death Valley, California; and the Pacific Ocean, 250 km west of Santa Barbara, California. As a special application, these models are fitted by an optimization procedure to the modified Γ distribution function used by Deirmendjian. Some optical scattering properties of these particle models are estimated by use of Mie's solution, and the results are discu

ISSN:0148-0227    

DOI:10.1029/JC077i024p04529

年代:1972

数据来源: WILEY

摘要:

The distribution of lapse rates observed with a high resolution temperature sonde on two summer balloon flights is presented. Shallow layers of relative instability are observed in the stratosphere as well as the troposphere. Ten percent of the troposphere sounding had lapse rates in excess of 9.5 deg/km, and 10% of the stratosphere sounding had lapse rates in excess of 6.5 deg/km. This fraction of relatively unstable lapse rates must play a large role in determining the over‐all diffusivity of the stratospher

ISSN:0148-0227    

DOI:10.1029/JC077i024p04539

年代:1972

数据来源: WILEY

摘要:

An experimental study of gravity wave behavior near a straight caustic was carried out in a wave tank that was 4.26 meters (14 feet) square and 30.48 centimeters (1 foot) deep. A uniform wave train was generated in shallow water of constant depth and propagated toward a portion of the tank where the depth increased linearly to a value equivalent to deep water. The straight line at which the depth started to increase was at 50° to the wave crests at the generation source. The waves propagated up to this line, then refracted, totally reflected, and turned back toward the shallow water. The results of the experiment show that the experimental model not only successfully produces a caustic but also verifies the theoretical results near the caustic derived by Chao (1971) within the framework of a linear theory. The same bottom model was used to examine the refraction of transient wave groups. The transients were recorded at several places in the tank in such a way as to compare two alternative hypotheses: one that the waves refracted according to refraction equations involving their spectral phase speeds, and the other that group velocities were involved. The measurements show that the wave groups were refracted according to the phase speeds of the spectral components

ISSN:0148-0227    

DOI:10.1029/JC077i024p04545

年代:1972

数据来源: WILEY

摘要:

A sequence of double‐peaked open‐ocean wave spectra was observed simultaneously with eddy correlation estimates of momentum flux and atmospheric stability over a 15‐hour interval at Argus Island tower (near Bermuda) on March 22 and 23, 1967. The wave spectra were associated with a generating sea and advecting swell in the fetch of the warm sector of an advancing cyclone. The equilibrium range constant for these wave spectra was estimated at (7.8 ± 1.6) × 10−3. The Miles‐Phillips exponential growth parameter was in reasonably good agreement with other field investigations, and observations support predicted amplification factors given by Phillips (1966) over the range 20 ≤C/U* ≤ 32 whereCis wave phase speed andU* is the friction velocity. Two observations of both linear and exponential growth parameters associated with spectral frequencies of 0.13 and 0.14 Hz were available to compare predicted and observed wave growth, with good results after correction for residual wave background. Observed temporal overshoot‐undershoot of a particular wave component is interpreted in terms of an energy balance between wind input, wave‐wave interactions, and wave breaking as a wave component evolves to its equilibrium condition. An example of spectral growth associated with advecting lower‐frequency swell illustrates wave‐induced fluctuations associated with momentum transfer from the sea to the atmosphere. Peaks in the horizontal and vertical wind‐velocity spectra and the cospectra and quadrature spectra associated with wave spectral peaks are clearly evident when ocean swell propagates thr

ISSN:0148-0227    

DOI:10.1029/JC077i024p04555

年代:1972

数据来源: WILEY

摘要:

The initial state of stress in fallen snow is calculated by considering incremental gravity loading of the accreting snow slab. It is then postulated that slab avalanche release is initiated by a reduction of shear strength on a critical layer to a value below that of the existing shearing stress. The manner of top tensile failure, side shear failure, and either buckling or shear compression failure at the lower end of the slab is then described. These results provide avalanche dimensions that are lower bounds on those occurring naturally.

ISSN:0148-0227    

DOI:10.1029/JC077i024p04570

年代:1972

数据来源: WILEY