摘要:

Fifteen heat‐flow values, representing the southernmost measurements made in the Atlantic, show a pattern of heat flow with tectonic features around the ridge‐fracture‐fracture triple junction which are explained by effects of hydrothermal circulation. High values (>4 μcal/cm²sec) on ridges which flank the axial valleys may either reflect a topographically controlled ascending limb of a hydrothermal circulation system, or result from conductive cooling of crust subsequent to the sealing of cracks generated at the spreading center. Intermediate to low values (0.4 to 1.8) in the depressions of fracture zones and axial valleys are consistent with a model of thermal cracking and subsequent hydrothermal circulation in the newly formed rocks. Low values (<1.3) over the ridge flanks may also be a consequence of secondary circulation in cracks re‐opened during dehydration of rocks previously hydrated near the spreading centers. If such secondary circulation is widespread, it would imply at least two, and perhaps more, minima in profiles of oceanic heat‐f

ISSN:0094-8276    

DOI:10.1029/GL002i006p00201

年代:1975

数据来源: WILEY

摘要:

We assume that a dilatant zone which develops as a precursor to an earthquake may be modeled by a zone of low‐velocity rock having the shape of a triaxial ellipsoid. For varying ellipsoid dimensions, velocity contrasts, and hypocenter distributions, we generate a synthetic data set of arrival times at surface stations. The artificial events are relocated using a constant‐velocity model to test for systematic hypocenter biasing. For all cases tested, the depth change for the distribution as a whole was not significant although individual events may move substantially. A downward migration of the ensemble of hypocenters was produced by a long, narrow ellipsoidal zone, however, the magnitude of migration for this case was only two perc

ISSN:0094-8276    

DOI:10.1029/GL002i006p00205

年代:1975

数据来源: WILEY

摘要:

Measurements were made of the helium concentration in the soil gases surrounding the Indian Hot Springs, Idaho Springs, Colorado. The helium concentration was shown to vary in a regular manner from the background level of 5.2 ppm to a high of more than 100 ppm near a warm (26°C) water seep, and more than 1,000 ppm near a hot (40°C) water seep. Such an association of helium in the soil gas with these hot waters near the earth's surface suggests the possible utility of helium surveys in locating hidden geothermal reservoir

ISSN:0094-8276    

DOI:10.1029/GL002i006p00209

年代:1975

数据来源: WILEY

摘要:

A new direction‐finding system is capable of tracking, from coastal stations, the drift of drogues more than 100 km from the shoreline. Frequency‐dependent transmitters on light, inexpensive drogues permit as many as fifteen widespread drogues to be monitored quasi‐simultaneously, enabling researchers to obtain mesoscale synoptic data at reasonable cost for the first time. Field tests on a moored drogue in Chesapeake Bay and on free‐drifting drogues at sea off Barbados show the system to be reliable and a

ISSN:0094-8276    

DOI:10.1029/GL002i006p00211

年代:1975

数据来源: WILEY

摘要:

Bromine may act as a catalyst for recombination of ozone and could be more efficient than either nitric oxide or chlorine. The lower atmosphere contains small concentrations of gaseous bromine produced in part by marine activity, in part by volatilization of particulate material released during the combustion of leaded gasoline, with an additional contribution due to the use of methyl bromide as an agricultural fumigant. Observations by Lazrus et. al. (1975) indicate small concentrations of bromine, ∼ 10−11(v/v) in the contemporary stratosphere and appear to imply a reduction of approximately 0.3% in the global budget of O3. Estimates are given for future reductions in O3which might occur if the use of CH3Br as an agricultural fumigant were to continue to grow at present ra

ISSN:0094-8276    

DOI:10.1029/GL002i006p00215

年代:1975

数据来源: WILEY

摘要:

We estimate the total concentration [ClX] versus altitude of Cl‐containing molecules, principally HCl, Cl and ClO. The predicted present stratospheric concentrations appear to be due to photolysis near 30 km of man‐made CF2Cl2and CFCl3, and CCl4from a ground‐level source, man‐made or natural. Based on preliminary measurements of CH3Cl at ground we estimate its contribution to stratospheric ClX through the major known loss mechanism for CH3Cl, abstraction by OH. Ground‐level sources of HCl and Cl2are large but tropospheric processes preclude significant impact on the stratosphere. Our computed profiles are consistent with first HCl concentrations measured byLazrus et al.[1974, 1975] in the 15–2

ISSN:0094-8276    

DOI:10.1029/GL002i006p00219

年代:1975

数据来源: WILEY

摘要:

A sensitive spectral radiometer system capable of measuring the atmospheric emission in the 6.5µm to 13.0µm region has been constructed for use on the WB57F aircraft used on the Department of Transportation Climatic Impact Assessment Program. The data obtained with this instrument on a number of flights have been analyzed to determine the total HNO3column density above the aircraft at various latitudes and seasons. Examination of these data indicate a definite variation of HNO3column density with latitude and possible seasonal variation

ISSN:0094-8276    

DOI:10.1029/GL002i006p00223

年代:1975

数据来源: WILEY

摘要:

Water vapor burden and in situ mixing ratios above and at high altitude flight levels were inferred from observations in the rotational water vapor spectral band (19.0–35.0 µm). Flight levels ranged from 15.3 to 20.0 km during 12 meridional traverses of a W‐B57‐F jet. The method of radiance observation, while radiometric, involved emission observations rather than absorption spectra analyses employed byMcKinnon and Morewood[1971]. The flights made during September, October, November 1973 and January 1974 provide profiles of lower stratospheric water vapor by overlapping tracks from 50°S latitude to 75°N latitude.The objective of the research is to describe the method of recovery of the water vapor burden and in situ mixing ratio by inference from infrared emission observations and to present the results as a latitudinal

ISSN:0094-8276    

DOI:10.1029/GL002i006p00227

年代:1975

数据来源: WILEY

摘要:

A new technique for observing directly the absolute concentration of atoms and radicals in the earth's upper atmosphere is discussed. Atomic resonance fluorescence in conjunction with a parachute borne flow‐through module deployed from a balloon at 40 kilometers is used to determine the ground state (³P) atomic oxygen concentration between 40 and 25 kilometers in the earth's atmosphere. Under daytime equilibrium conditions: 25 November 1974; 32°N latitude; solar zenith angle 56°, 10:30AM C.S.T., the absolute concentration of O(³P) is found to decrease from 1 × 109cm−3at 39 km to 6 × 107cm−3at 26 kilometers with statistically significant local structure evident in the altit

ISSN:0094-8276    

DOI:10.1029/GL002i006p00231

年代:1975

数据来源: WILEY

摘要:

Resolved spectra have been obtained from the ground of the O2(a¹Δg) emissions from the upper atmosphere utilizing a wide‐field interferometer with a cryogenically cooled germanium detector. The rotational structure of both the (0, 0) band at 1.27 µm and the (0, 1) band at 1.58 µm are clearly separable from the hydroxyl airglow. The decay rate of the O2(a¹Δg) during the twilight transition has been o

ISSN:0094-8276    

DOI:10.1029/GL002i006p00235

年代:1975

数据来源: WILEY