摘要:

The minimum mantle viscosity in an earth accreting from planetesimals is estimated. A plausible distribution of planetesimal sizes deposits enough energy to melt the outer nine‐tenths of earth's mass; however, vigorous convection keeps temperatures near the solidus. Viscosity is significantly lower than prevails now. The temperature‐dependent viscosity provides self‐regulation so there is a continuing balance between accretional energy input and heat transfer out. This allows calculation of the minimum viscosity necessary to transfer out heat by a Nu/Ra‐number relation. Typical viscosities are 10−1to 106m²sec−1, lowest at mid‐accretion when the mass growth rate is largest. Terrestrial planets are compared, and minimum iron descent times to central lithospheres

ISSN:0094-8276    

DOI:10.1029/GL010i010p00925

年代:1983

数据来源: WILEY

摘要:

The mean of deep heat‐flow measurements in the interior of the Colorado Plateau (temperature measurements to depths>750 m) is about 5 mWm−2greater than the mean of shallow data. Although these data sets have remarkably similar means considering the experimental difficulties in measuring heat flow, the means never the less appear statistically different (59 mWm−2vs 64 mWm−2). If various lithospheric heating models are used to explain the uplift of the Colorado Plateau, a 5 mWm−2difference in surface heat flow will make the time of lithospheric heating very different. Deep heat‐flow data in the Colorado Plateau typically lack the large spatial variability that shallow data show. The deeper data should therefore relate better to regional geothermal trends caused by mantle thermal conditions and by crustal radioactivity. The deep heat‐flow data, where present, in the Colorado Plateau interior suggest a rather uniform heat flow and therefore rather constant mantle temperatures and crustal radioactivity. Continued concern with experimental data will be necessary to appreciate the uncertainties in the heat‐flow data and the resulting

ISSN:0094-8276    

DOI:10.1029/GL010i010p00929

年代:1983

数据来源: WILEY

摘要:

A seismic refraction profile utilizing shots at sea and receivers on land and on the ocean bottom lies on a north‐south line from the southernmost Coast Ranges, across the western Transverse Ranges, to the northern Borderland at the longitude of Santa Barbara. Computer ray tracing to model the data from this profile shows significant lateral P velocity variations extending to at least 15 km depth. Although fault dips cannot be resolved by these data, most major faults mapped on the surface have a signature in the deeper crustal structures. A deep low velocity trough underlies the Montalvo trend in the Santa Barbara Channel. A narrow high velocity ridge is associated with basement rocks south of the Santa Cruz Island fault. These lateral velocity variations suggest that earthquake hypocenters and fault plane solutions calculated assuming a laterally homogenous crust‐model may be significantly in er

ISSN:0094-8276    

DOI:10.1029/GL010i010p00933

年代:1983

数据来源: WILEY

摘要:

The large‐scale thermal structure of the California Current during 1982‐83 shows several anomalous conditions: warm sea surface temperature anomalies (∼1‐2°C), depression of the thermocline by 50 m or more, and pronounced subsurface warming (∼3‐4°C) relative to the 30‐year mean. The subsurface anomaly is much greater than the surface anomaly. These persistent (>6 months) structures, coupled with unusually high sea levels along the North American coast, show that a major Californian "El Niño" occurred during 1982‐83. The data support the conclusion that the expansion and intensification of the Aleutian low and the decrease in strength of the Pacific high produced an anomalous basin‐wide atmospheric circulation which coupled directly to the large‐scale oceanic wind‐driven circulation to produce the Californian "El Niño." The enhanced transport from the west (offshore California) and south (Baja California), which such a circulation would produce, is consistent with the observed water properties. The equatorial 1982‐83 El Niño is probably related to the Californian "El Niño" through an atmospheric teleconnection between equatorial sea surface temperature and the at

ISSN:0094-8276    

DOI:10.1029/GL010i010p00937

年代:1983

数据来源: WILEY

摘要:

In late January and early February 1983, observations made by the Stratospheric Aerosol Measurement (SAM II) satellite system showed that aerosol extinction profiles measured within the northern polar vortex differed significantly above 18 km from those measured outside the vortex. Values of the calculated optical depths above 18 km for February 1, 1983, are lower by approximately one order of magnitude within the polar vortex than those outside. Similar differences were found in the aerosol backscattering profiles obtained using an airborne lidar system when crossing the polar vortex. Since potential vorticity at a constant altitude is not conserved across the polar vortex, horizontal adiabatic transport does not occur.

ISSN:0094-8276    

DOI:10.1029/GL010i010p00941

年代:1983

数据来源: WILEY

摘要:

Nimbus 7 LIMS data and a photochemical model are used to show that the observed sharp latitudinal gradients in stratospheric wintertime NO2are consistent with the conversion of NO2to N2O5at high latitudes. This conversion, and the sharp gradients, are brought about by the interaction between transport and photochemistry. Calculated variations show good agreement with observations.

ISSN:0094-8276    

DOI:10.1029/GL010i010p00945

年代:1983

数据来源: WILEY

摘要:

The most abundant volatile sulfur compound found in the surface layers of the central equatorial Pacific Ocean (148°W to 170°E) was dimethyl sulfide (DMS). Concentrations of DMS ranged from 100‐400 ng DMS/L; the highest concentrations occurred at 2°N and 148°W. DMS accounted for more than 97% of the total volatile sulfur species present, and was significantly correlated with chlorophyll ‘a’. Elevated concentrations of DMS near the equator are related to nutrient eutrophication stimulated by equatorial upwelling and the horizontal transport from the east. Vertical profiles taken at 9 stations indicated that maximum DMS concentration occurred at 20‐40 m, with concentrations decreasing to<1 ng DMS/L at 150‐200 m.Flux calculations indicate that the central equatorial Pacific (6°N to 6°S between 148°W and 170°E) supplies about 1.0 Tg DMS/yr, assuming a mean surface concentration of 200 ng DMS/L and a piston ve

ISSN:0094-8276    

DOI:10.1029/GL010i010p00949

年代:1983

数据来源: WILEY

摘要:

The reaction of N2O5with water vapor, a potentially important nighttime loss reaction for NOxand formation pathway for nitric acid, has been investigated at 298 ± 1 K in two environmental chambers of 3800 and 5800 L volume. From the N2O5decay rates as a function of water vapor concentration, an upper limit to the N2O5+ H2O rate constant of less than 2.4 × 10−21cm³ molecule−1s−1is derived. However, while gas phase nitric acid was observed to be a major product, its yield, especially at low water vapor concentrations, was significantly lower than the value of 2 expected, indicating that the overall reaction in these chambers involved both homogeneous and heterogeneous components. After allowing for the contribution of the heterogeneous reaction, an estimate of the gas phase homogeneous rate constant for N2O5+ H2O of 1.3 × 10−21cm³ molecule−1s−1was obtained. While this value must still be regarded as an upper limit to the homogeneous rate constant, it is a factor of 10 lower than the only directly measured upper limit rep

ISSN:0094-8276    

DOI:10.1029/GL010i010p00953

年代:1983

数据来源: WILEY

摘要:

The phosphine photochemistry on Saturn is studied with a 1D photochemical model. The PH3concentration is rapidly depleted with height (scale height 3.5 km) in the upper troposphere. Formation of P, a probable precursor of P4, (a potential red chromophore in the atmosphere), is highly improbable unless the rate constant for the recombination reaction PH + H2+ M → PH3+ M is less than 10−41cm6molec−2sec−1. Coupling of PH3and hydrocarbon photochemistry, specifically the C2H2catalyzed photodissociation of CH4, is important. Column production rates of the organophosphorus compounds CH3PH2and HCP of ∼3 × 108cm−2sec−1are predicted, with potentially observable column densities o

ISSN:0094-8276    

DOI:10.1029/GL010i010p00957

年代:1983

数据来源: WILEY

摘要:

Evidence of lightning activity in the Venusian atmosphere has been obtained from the Venera 9, 11, and 12 spacecraft, and from the Pioneer Venus Orbiter (PVO). However, a search for optical pulses expected from Venusian lightning using the star sensor on the PVO did not detect any signals. It has been suggested that the star sensor did not detect lightning because Venusian lightning does not radiate in the 500‐ to 900‐nm spectral region detected by the star sensor. In this paper, we discuss spectra obtained from a laboratory simulation of Venusian lightning. Both the laboratory spectrum and the results of a theoretical calculation of line intensities show that Venusian lightning can be expected to radiate strongly in the 600‐ to 900‐nm spectral region. Hence, the failure of the star sensor to detect lightning must be caused by the low flashing rate or by the low intensity of Venusian li

ISSN:0094-8276    

DOI:10.1029/GL010i010p00961

年代:1983

数据来源: WILEY