摘要:

Fassaite rims around spinel grains that are enclosed entirely by normally zoned cores of melilite crystals are interpreted as relict grains which predate the melting of Allende Type B1 refractory inclusions. Nonrelict, subliquidus fassaite did not begin crystallizing from melts of these compositions until the onset of precipitation of the reversely zoned melilite mantles around the same melilite crystal cores. Relict fassaite is fractionated and highly enriched in REE and other refractory lithophiles compared to subliquidus fassaite in the same inclusion. Mass balance suggests that the relict fassaite represents only 3% of the original premelt amount of fassaite, and that melilite and at least one other phase were additional condensate precursors of these inclusions.

ISSN:0094-8276    

DOI:10.1029/GL016i008p00775

年代:1989

数据来源: WILEY

摘要:

The solar Lyman‐α emission, the MgII core‐to‐wing ratio,R(MgIIc/w), the 10.7‐cm radio flux,F10.7, and the 1–8 Å X rays are compared during high solar cycle 21 activity from 1981–83. Daily variations of the Mg II and Lyman‐α ultraviolet (UV) lines are highly correlated. There is moderate linear correlation between these lines andF10.7and poor linear correlation with 1–8 Å X rays. Power spectral analysis indicates that all four fluxes have 27‐day periodicities due to solar rotation while theR(MgIIc/w) and Lyman‐α have noticeable 13‐day periods in the datasets.F10.7moderately represents the 27‐day solar UV variations and represents to a lesser degree variations shorter than or longer than rotation variations. X rays are not represented byF10.7on intermediat

ISSN:0094-8276    

DOI:10.1029/GL016i008p00779

年代:1989

数据来源: WILEY

摘要:

Measurements of ultraviolet solar spectra from Palmer Station, Antarctica have defined the surface radiation environment of the region during the Austral spring of 1988. At wavelengths where absorption by ozone is negligible, 335–345 nm, the noontime irradiances show the expected gradual increase from the first day of measurements, 19 September, through 21 December. Large variations related to cloudiness are imposed on this background. At wavelengths less than 310 nm the influence of the 1988 ozone “hole” is apparent. The noontime irradiance observed in the wavelength band 295–305 nm on 19 October, two months prior to summer solstice, exceeded any value measured through 21 D

ISSN:0094-8276    

DOI:10.1029/GL016i008p00783

年代:1989

数据来源: WILEY

摘要:

Emission features of HBr isotopes have been identified in high‐resolution far‐infrared emission spectra obtained with a balloon‐borne Fourier transform spectrometer in the spring of 1979 at 32°N latitude. When six single‐scan spectra at a zenith angle of 93.2° were averaged, two features of HBr isotopes at 50.054 and 50.069 cm−1were obtained with a signal‐to‐noise ratio of 2.5. The volume mixing ratio retrieved from the average spectrum is 2.0 × 10−11, which is assumed to be constant above 28 km, with an uncertainty of 35 percent. This stratospheric amount of HBr is about the same as the current level of tropospheric organic bromine compounds, 25 pptv. Thus, HBr could be the major stratospher

ISSN:0094-8276    

DOI:10.1029/GL016i008p00787

年代:1989

数据来源: WILEY

摘要:

A new balloon borne instrument called a backscattersonde has been used to study Polar Stratospheric Clouds (PSCs) at Alert, NWT (82°N, 61.5°W) during January and February of 1989. These measurements were supplemented with frost point, ozone and nitric acid vapor soundings. Type I PSCs were observed at temperatures and pressures generally consistent with present vapor pressure models of HNO3/H2O condensate, but some noticeable inconsistencies exist. It is suggested that these apparent problems, as well as some characteristic peculiarities in the PSC profiles, could be explained by the presence of two phases of the HNO3/H2O condensat

ISSN:0094-8276    

DOI:10.1029/GL016i008p00791

年代:1989

数据来源: WILEY

摘要:

The temperature record for the global surface air temperature indicates that six of the warmest years occurred in the period 1980–1988. Here we address the question on the likelihood that such an arrangement is simply a manifestation of the natural variability of the system. Our results indicate that the probability that such an arrangement will arise naturally is between 0.010 and 0.03

ISSN:0094-8276    

DOI:10.1029/GL016i008p00795

年代:1989

数据来源: WILEY

摘要:

The13C isotopic composition of methane emitted to the troposphere from Amazon capims (floating grassmats) ranged from −36.9 to −48.0‰, averaging −44.4 ± 4.2‰. All pools of methane associated with the grassmats were13C enriched; methane withdrawn from plant stems ranged from −39 to −49‰ while bubbles stirred from the root mat averaged −41.4‰. As the CH4flux from these habitats makes up some 40% of the total flux from the Amazon floodplain, CH4emissions from the region as a whole must be enriched in the heavy carbon isotope. Methane withdrawn from the stems of five genera of rooted macrophytes ranging in latitude from the Florida Everglades to the Alaskan Arctic exhibited13C enrichment relative to the sedimentary methane bubble reservoir. Several hypotheses based upon isotopic fractionation by methane transport, oxidation and production processes are proposed to exp

ISSN:0094-8276    

DOI:10.1029/GL016i008p00799

年代:1989

数据来源: WILEY

摘要:

In the course of studying Quasi‐biennial (QB) variations in the global sea surface temperature (SST) field, an apparent solar signal was detected. Specifically, the amplitude of variations in the QB frequency band appeared to be modulated at the 11 year solar cycle at least over the last four cycles. The sense of the relation is that high solar activity goes with low amplitude variations in the QB frequency band. In a series of recent papers, van Loon and Labitzke (1988a,b) and Libitzke and van Loon (1988) have found in the same frequency band a similar amplitude modulation in atmospheric fields of both Hemispheres also over the last four solar cycles. In an effort to study the apparent relation over more solar cycles, the analysis of the time series of SST was extended back to 1884. The solar‐SST relation found above was found to hold back to about 1925. Before that time, remnants of the SST signal can still be observed but the relation to the solar cycle becomes more confused. This lack of consistency through the 10 solar cycles examined here may be due to the fact that the apparent relationships are fictitious. They may also be partially due to poor SST data before 1920; the major failure in the solar‐SST relation occurring in the data sparse 1915–1920 period. It may also be that the weak solar variability at the turn of the century could not force an observable response in the SS

ISSN:0094-8276    

DOI:10.1029/GL016i008p00803

年代:1989

数据来源: WILEY

摘要:

Pressure oscillations having a narrow spectrum centered at 0.175 Hz have been measured in the deep sea at depths between 100 and 300 m. At these depths the nonlinear interaction between oppositely directed sea surface gravity waves causes pressure fluctuations, the intensity of which varies inversely with the square of the depth, uninfluenced by microseismic Rayleigh waves propagating on the seafloor below. The observed pressure fluctuations are consistent with the interaction between waves having a unimodel beam pattern whose half beam width is slightly larger than 90 degrees or with a shoreward propagating pencil beam of swells interacting with a small component reflected from the shore.

ISSN:0094-8276    

DOI:10.1029/GL016i008p00807

年代:1989

数据来源: WILEY

摘要:

Drifting buoy data for 1979–85 and meteorological fields for 1960–85 are used to assess sea ice motion in the Transpolar Drift Stream. Although the long‐term mean ice drift in this stream is toward the Fram Strait, three years (1979–81) with adequate drifting buoy data coverage show reversed ice motion over 30‐day periods in summer. This phenomenon is a response to seasonally changing win

ISSN:0094-8276    

DOI:10.1029/GL016i008p00811

年代:1989

数据来源: WILEY