ISSN:0094-8276    

DOI:10.1029/GL009i006p00599

年代:1982

数据来源: WILEY

摘要:

Infrared photographs from the Atlantic Geosynchronous Satellite, enhanced to resolve cold anvil temperatures of tropical clouds, are analyzed statistically to determine their spatial‐temporal variability during the NASA‐U2 Flight Experiment of 1980. Diurnal dependence varies regionally, indicating topographic control via low level convergence and release of convective instability. Anvil growth rates, area covered and duration are discussed for individual and merging anvil systems. Gradients of anvil temperatures implied by infrared photographs are shown to be caused, in part, by radial decrease in anvil depth, i.e., to emissivities less than 1. An error in cloud top temperature of 10C is caused by 10% reduction in emissivity. Errors are near zero in dense, actively growing portions of the an

ISSN:0094-8276    

DOI:10.1029/GL009i006p00601

年代:1982

数据来源: WILEY

摘要:

Although mean circulations are generally credited with dehydration of the earth's stratosphere, convective instability in the tropics converts mean circulations to small residuals of local convective circulations. The effects of large cumulonimbus which penetrate the stratosphere and form huge anvils in the lower stratosphere are discussed with respect to hydration and dehydration of the stratosphere. Radiative heating at anvil base combined with cooling at anvil top drives a dehydration engine considered essential to explain the dry stratosphere. Seasonal and longitudinal variations in dehydration potentials are examined with maximum potential attributed to Micronesian area during winter and early spring.

ISSN:0094-8276    

DOI:10.1029/GL009i006p00605

年代:1982

数据来源: WILEY

摘要:

To investigate the possibility that significant amounts of tropical tropospheric air may be convectively introduced into the stratosphere, aerosol samplings over Panama were made at various altitudes using a wire impactor collector.Percentage of particle sizes less than the mean mode decreases with height above the tropopause, suggesting depletion of small particles, possibly due to coagulation. Larger aerosols (greater than 0.3 µm in diam.) are more abundant farther above the tropopause, indicating growth, mainly by condensation. The total particle concentration decreases with increasing height above the tropopause, and also with increasing temperature.Aerosols containing smaller‐size particles are thus found closer to the tropopause, and larger‐size, more‐evolved aerosols occur at higher altitudes. These data indicate that convective activity at the ITCZ may be a source mechanism for stratospheric ae

ISSN:0094-8276    

DOI:10.1029/GL009i006p00609

年代:1982

数据来源: WILEY

摘要:

A pair of particle size spectrometers was flown aboard the NASA U‐2 operating from the Canal Zone to make measurements of the aerosol and ice crystal budgets in cirrus produced by thunderstorms in the tropics. Measurements indicate that fairly large crystals up to 1 mm in size are injected into the stratosphere during cumulonimbus activity. Ice water contents range from a few thousandths to a few hundredths of a gram per cubic meter. Because the ambient temperature is typically around −80°C the mass of the larger crystals largely returns to lower altitudes before evaporating. Aerosol size distributions indicate a curious narrow growth mode between 0.15 and 0.2 µm in cirrus anvils which is absent outside these clouds. The presence of this narrow mode is attributed to near water saturation produced at cloud top. Nucleation of new ice crystals as well as aerosol is hypothe

ISSN:0094-8276    

DOI:10.1029/GL009i006p00613

年代:1982

数据来源: WILEY

摘要:

Total water was measured in the high troposphere and low stratosphere over Panama during ten aircraft flights. The results show that convective storms provide the means of transporting water into the stratosphere. From a consideration of the anvil heights over different areas of the tropical zone, it follows that a negative gradient of water vapor mixing ratio with altitude must exist over most of the lower stratosphere.

ISSN:0094-8276    

DOI:10.1029/GL009i006p00617

年代:1982

数据来源: WILEY

摘要:

An infrared radiometer with a pass band of 280 to 520 cm−1(35.7 to 19.2 µm) is employed on the NASA Ames Research Center U‐2 and C‐141A aircraft in the measurement of water vapor burden in the upper troposphere and stratosphere. Coincidentally with altitude changes the water vapor mass mixing ratio is also inferred by observing the change in optical depth over a known vertical distance. Data from the December 1980 U‐2 Water Vapor Exchange Experiment over the Panama Canal Zone adds to the concept that overshooting cumulonimbus towers “moisten” the lower stratosphere. The average mass mixing ratio in close proximity to or above such towers ranges from 3.5 to 5.0 parts per million above 18 km while the average background mass mixing ratio is only 2.9 parts per million. Generally the lowest background mixing ratios, averaging 2.6 parts per million occurred in the 18 to 21 km layer. For the same levels background Panama mass mixing ratios averaged from 1.0 to 3.0 parts per million higher than in midd

ISSN:0094-8276    

DOI:10.1029/GL009i006p00621

年代:1982

数据来源: WILEY

摘要:

Using P‐and S‐wave arrival times with the laterally varying P‐wave velocity structure derived from analysis of a refraction survey of the Imperial Valley, a hypocenter is ascertained for the October 15, 1979, Imperial Valley earthquake:Latitude 32° 39.50′N,Longitude 115° 19.80′W,Depth 8.0 km,Time 23:1

ISSN:0094-8276    

DOI:10.1029/GL009i006p00625

年代:1982

数据来源: WILEY

摘要:

The Geysers reservoir is situated in a 60–80 km‐wide right‐lateral shear zone associated with the North American‐Pacific plate boundary. A small fraction of the shear may be occurring as permanent aseismic creep, which is being converted to stick‐slip movement in The Geysers reservoir due to steam production. Two mechanisms could be responsible for the induced seismicity: a large (>100 bars) increase in effective rock pressure; and an increase in the coefficient of friction. The first mechanism requires that the initial state of the reservoir be predominantly liquid‐dominated. The second mechanism is a consequence of dehydration of the reservoir causing both the ‘hardening’ of clay and fault gouge, and the precipit

ISSN:0094-8276    

DOI:10.1029/GL009i006p00629

年代:1982

数据来源: WILEY

摘要:

Recently, seismic quiescence based on P.D.E. and I.S.C. data, has been reported in the Acapulco‐San Marcos region (16°–17.2°N, 98.5°–99.7°W) (McNally, 1981). In order to assess the seismic potential of this region we have estimated seismic moments and slips associated with 1957 (Ms= 7.5) and 1907 (Ms= 8.0) events which occurred in this area. Historical data suggest that earthquakes occurred in this region in 1845 (Ms≃ 7.9) and probably also in 1820 (Ms≃ 7.6). We find preference for the time‐predictable model in the data set which, if valid, forecasts the next large earthquake between now and 1993 with 1985 as the most likely year. Although this forecast can not be taken as definitive since it is based on several assumptions (each of which are reasonable but uncertain), the implications of reported quiescence and the results of this paper suggest a careful monitor

ISSN:0094-8276    

DOI:10.1029/GL009i006p00633

年代:1982

数据来源: WILEY