摘要:

Nitrate flux has been determined in the snow sequence deposited at Windless Bight on the Ross Ice Shelf (Antarctica). The data were obtained from on‐site analysis of nitrate concentrations from a glaciological pit and a firn core spanning the time interval from midwinter 1971 to January 1986. The high resolution data can be combined with precipitation records collected from adjacent areas to provide a record of nitrate flux. The resulting time series contains a signal which corresponds to the two major solar events of 1972 and 1984. The concentration and flux profiles may be useful in studies of Antarctic ozone depletio

ISSN:0094-8276    

DOI:10.1029/GL013i012p01264

年代:1986

数据来源: WILEY

摘要:

Seasonal variation of vertical column density of stratospheric NO2was determined for the period of March 1983 to January 1984 by means of ground‐based visible absorption spectroscopy at Syowa Station (69.0°S, 39.6°E), Antarctica. The winter minimum of about 1×1015cm−2and the summer maximum of 7×1015cm−2were observed. These values are nearly equal to, or a little bit smaller than, those observed at northern high latitudes. The nighttime decay of column density was small from autumn to early spring. A rapid increase in column density occurred at the end of September before the minimum of total ozone content in mid‐October. This behavior suggests that both dynamical and photochemical processes may be involved in the Antarctic ozone depletion. The vertical profile of stratospheric NO2in early summer in Antarctica was revealed by three balloon‐borne measurements over Syowa Station in November 1982 and 1983. Above 25 km altitude, these profiles are basically identical to those observed at middle and high latitudes in the northern hemisphere. In the lower stratosphere below 25 km, variability in NO2density seems to be large due to dyna

ISSN:0094-8276    

DOI:10.1029/GL013i012p01268

年代:1986

数据来源: WILEY

摘要:

Measurements of CFCl3, CF2Cl2, CH3CCl3CCl4and N2O at Palmer Station, Antarctica (64°46′S, 64°04′W) from February 4, 1982 to November 30, 1985 are reported. For the week beginning January 1, 1984, the averages of the hourly measurements were 199.6 ppt for CFCl3, 329.0 ppt for CF2Cl2, 124.2 ppt for CH3CCl3, 150.2 ppt for CCl4, and 301.3 ppb for N2O. The mixing ratios increased at an annual rate of 5.87% y−1for CFCl3, 5.45% y−1for CF2Cl2, 5.31% y−1for CH3CCl3, 1.29% y−1for CCl4, and 0.2

ISSN:0094-8276    

DOI:10.1029/GL013i012p01272

年代:1986

数据来源: WILEY

摘要:

Measurements by the SAM II satellite instrument show that polar stratospheric clouds (PSC's) are a regular feature of the austral winter season in either nonvolcanically or volcanically disturbed periods. The tops of these clouds are observed above 20 km in early winter and descend in altitude over the course of the season to heights near 15 km in mid September. Typically, PSC's persist in the lowest stratospheric altitudes throughout September. Subsequently, October always represents a relative annual minimum in aerosol extinction above 15 km and in stratospheric column amount. In addition, volcanically produced aerosols in Antarctica peaked in early 1983 and, if linearly related to ozone losses, are probably not a contributing factor to the continued loss of total ozone in the Antarctic spring in 1984 and 1985.

ISSN:0094-8276    

DOI:10.1029/GL013i012p01276

年代:1986

数据来源: WILEY

摘要:

Simultaneous vertical profiles of O3, NO2and aerosol extinction obtained with the Stratospheric Aerosol Measurement II (SAM II), Stratospheric Aerosol and Gas Experiment (SAGE), and SAGE II satellite instruments across the southern polar vortex show that significant differences exist at all altitudes. Both gaseous species display lower concentrations within the vortex over measurement altitudes ranging from the tropopause to 60 km and 20 to 40 km for O3and NO2respectively. Aerosol extinction above 15 ‐ 18 km and total aerosol stratospheric column are also lower inside the vortex than outside. Total column amounts of O3and NO2are found to be strongly coupled to spatial location within the vortex, with minimum total values located around the vortex center. Vertical profiles selected to emphasize the observed difference across the circumpolar vortex are presented for October 13, 1981, and October 13, 1985, near 70° and 68°S latitude, respectiv

ISSN:0094-8276    

DOI:10.1029/GL013i012p01280

年代:1986

数据来源: WILEY

摘要:

Nitric acid and hydrochloric acid vapors may condense in the winter polar stratospheres. Nitric acid clouds, unlike water ice clouds, would form at the temperatures at which polar stratospheric clouds (PSCs) are observed and would have optical depths of the magnitude observed suggesting that HNO3is a dominant component of PSCs. ClO, N2O5and ClNO3may react on cloud particle surfaces yielding additional HNO3, HCl, and HOCL. In the vicinity of PSCs these reactions could deplete the stratosphere of photochemically active NOxspecies. The sedimentation of PSCs may remove these materials from the stratosphere. The loss of vapor phase NOxmight allow halogen‐based chemistry to create the ozone hol

ISSN:0094-8276    

DOI:10.1029/GL013i012p01284

年代:1986

数据来源: WILEY

摘要:

We describe measured properties of Antarctic polar stratospheric clouds and consider the possible relationship between the clouds and the formation of the ozone hole. We show that the ozone hole develops and the clouds dissipate in the same place and at the same time. There may be a causal relationship between cloud particle evaporation and ozone depletion. A heterogeneous mechanism involving chemical reactions in the cloud droplets is suggested.

ISSN:0094-8276    

DOI:10.1029/GL013i012p01288

年代:1986

数据来源: WILEY

摘要:

Theories have been proposed to relate the reduction of O3during antarctic spring to catalytic cycles involving chlorine and bromine species. A necessary condition for any chlorine‐catalyzed scheme is that a large fraction of the chlorine must be in the form of ClO in the lower stratosphere. It has been suggested that these high levels of ClO could be maintained by fast heterogeneous reactions, whose rates are not known at present. Model calculations based on the above mechanisms predict considerable amounts of OClO and Cl2O2, particularly during the night. We present results of calculations of the diurnal variations of ClO, OClO, and Cl2O2during antarctic spring, for different cases. Results from our calculations suggest that coincident measurements of the total column abundance and diurnal variation of ClO and OClO may help constrain key aspects of the proposed chemical mechanisms. Removal of O3by the catalytic cycle involving Cl2O2could be as important as that involving BrO for present levels of chlorine, provided that Cl2O2photolyzes rapidly to yield Cl and ClO2. We show that there is no synergy between these two cycles, since they both compete for the available Cl

ISSN:0094-8276    

DOI:10.1029/GL013i012p01292

年代:1986

数据来源: WILEY

摘要:

Chemical explanations for the spring decline of Antarctic O3involve reactions of ClO or interactions between BrO and ClO. Reaction schemes involving Br radicals have the highest efficiency for removal of O3. The chemical mechanisms require low levels of NOx. Recent cooling of the stratosphere may have triggered formation of HNO3monohydrate, removing NOxand setting the stage for enhanced loss of ozone over Antarctica.

ISSN:0094-8276    

DOI:10.1029/GL013i012p01296

年代:1986

数据来源: WILEY

摘要:

Analysis of October SBUV ozone profile data in the antarctic polar vortex shows that there was a decrease in ozone between 1979 and 1984 of between 15 and 30% at all levels from 30 mb to 0.7 mb. During spring of 1983 at 75° to 80°S the ozone mixing ratio at 1 mb decreases continuously from September through the summer solstice and then increases in late summer and fall, but we observe much less ozone at 1 mb in September and October than under similar conditions in the fall. This asymmetry between spring and fall ozone values may be the direct result of the sudden release of chlorine bound by meteoric material during polar night. Meteoric atoms, X, descending from the mesosphere react with the atmosphere to produce XOH, which will interact with HCl to form salts, XCl. Since these processes continue in the absence of sunlight, chlorine may accumulate during polar winter. The sudden release of this chlorine from photodissociation of these salts during spring could give rise to the loss of ozone in the upper stratosphere. At 30 mb ozone decreases substantially in mid‐September and remains at a low value until the mid‐October increase. Different mechanisms may be required to explain the ozone decreases in the upper stratosphere and in the lower stratos

ISSN:0094-8276    

DOI:10.1029/GL013i012p01300

年代:1986

数据来源: WILEY