摘要:

During the period from August 25 to November 3, 1986, the r ≧ 0.15 μm and r ≧ 0.25 μm aerosol profiles were measured on six occasions at McMurdo Station (78°S) by balloon‐borne optical particle counters. In addition, condensation nuclei (r ≧ 0.01 μm) profiles were measured on three occasions between October 16 and November 3. Several of these measurements corresponded to times when McMurdo was located near the point of minimum springtime ozone, as indicated by ozone and temperature measurements conducted on 33 occasions during the period. The height of the stratospheric sulfate layer was observed to decrease over the period of measurement, indicating continued subsidence in the vortex during the period that ozone was decreasing. This observation suggests that upwelling in the vortex is not important in the ozone depletion process. Low concentrations of condensation nuclei in the region of the ozone minimum supports this conclusion. Enhanced condensation nuclei above 20 km in the vortex and the discovery of an apparent permanent layer in the springtime vortex at the top of the ozone depletion region suggests that they may be related to the ozone depletion process, although the nature of this relationship i

ISSN:0148-0227    

DOI:10.1029/JD093iD01p00665

年代:1988

数据来源: WILEY

摘要:

A series of aerosol soundings sensitive to particle sizes less than about 1 μm was made from McMurdo, Antarctica, beginning in August 1986, while the stratosphere was still cold, and continuing through the spring warming and polar vortex circulation breakdown. The statistical analysis of polar stratospheric cloud (PSC) occurrences at low temperature indicates that there was a combined high probability of sampling such a cloud on at least one of three occasions, but no unusual or definitve features in the profiles were noted that could unquestionably be associated with PSCs. Photographically documented ground observations indicate that there was very likely a PSC or unusual stratospheric aerosol condition present during the first sounding at about 20 km. These aerosol observations impact the present explanations of PSCs and indicate that the possibility of these clouds being made up of low concentrations of relatively large (greater than ∼5 μm) particles must be taken seriously. The low concentrations would effectively render the PSCs undetectable by the aerosol‐sounding equipment employed in this study. It is argued that the fall speed associated with the cloud particles would not measurably change the natural aerosol profile, but that there could be a tendency for some water vapor to be transported to lower altitudes. Because of atmospheric mixing and transport processes, the redistribution of water vapor may not be easily det

ISSN:0148-0227    

DOI:10.1029/JD093iD01p00677

年代:1988

数据来源: WILEY

摘要:

Aerosol size distribution in harmattan weather is studied, using a combination of the Yue‐Deepak size inversion procedure and the data from photographed aerosol filter samples, for a typical moderate episode in Lagos. Accuracy of retrievals by this method depends sensitively on knowledge of the complex index of refraction of the aerosol. At Lagos, some 1,500 km south of the harmattan dust source, about 57% of the extinction of solar radiation appears due to the particulate moder>1 μm, a modal extinction less than those obtainable at stations nearer the Saha

ISSN:0148-0227    

DOI:10.1029/JD093iD01p00687

年代:1988

数据来源: WILEY

摘要:

The mixing of droplets of different pH and acid‐neutralizing capacity that occurs when bulk samples of cloud, fog, and rainwater are collected yields solutions that are not in equilibrium with the atmosphere in which the droplets originally equilibrated. In most instances, bulk solutions are expected to outgas volatile solutes to reestablish equilibrium with the atmosphere, with concomitant changes in solution pH. This mixing‐induced gas exchange complicates equilibrium and kinetic modeling of pH‐dependent atmospheric processes and limits the use of bulk samples for estimation of atmospheric fluxes of volatile weak acids and bases (SO2(g), NH3(g), etc.). Calculations that attempt to interrelate bulk solution pH, bulk solution S(IV) concentration, and atmospheric SO2(g) partial pressure are shown to be fundamentally incorrect, unless the bulk sample has completely reequilibrated with the same atmosphere in which its component droplets were formed. A theoretical proof and several numerical examples are presented to show that droplet mixing at constant atmospheric partial pressures of soluble gases cannot occur without gas exc

ISSN:0148-0227    

DOI:10.1029/JD093iD01p00691

年代:1988

数据来源: WILEY

摘要:

Observations of winds in the upper mesosphere and lower thermosphere (∼80–110 km) measured at the geographically conjugate locations of Adelaide (35°S, 138°E) and Kyoto (35°N, 136°E) in the years 1983–1985 are used to study hemispheric differences in the behavior of the solar diurnal and semidiurnal tides. Comparisons of the tidal amplitude and phase parameters show that there are distinct hemispheric asymmetries. The diurnal tide is usually much larger in amplitude at Adelaide, and it exhibits a height structure which indicates a relatively larger contribution from the propagating (1, 1) mode at this location. Comparisons with recent theoretical work suggest that while some of these differences may be due to hemispheric differences in forcing and/or to interactions between the tide and the background winds in the middle atmosphere, it is also possible that they indicate weaker turbulent induced damping of the (1, 1) mode in the southern hemisphere. The characteristics of the semidiurnal tide agree well at the two locations. It is found that the zonal wind components are about 6 hours out of phase and the meridional components are in phase in all seasons. This behavior, taken together with the inferred vertical wavelengths, which are greater than 100 km in summer and ∼45–80 km in winter, indicates that there are strong contributions from the antisymmetric (2, 3) mode, probably forced by wind‐induced mode coupling from the symmetric (2, 2) mode. The phases near 90 km exhibit a “bimodal” or “two‐state” behavior with the phases being almost constant in one state near the June solstice and then making a rapid transition of between 4 and 6 hours to another phase‐stable state near the December solstice. The duration of the state near the June solstice (∼6–8 months) is longer than the duration of the state at the December solstice. Although the agreement between recent models and our observations is relatively good, better agreement may be expected when more realistic wind distributions, especially for the southern hem

ISSN:0148-0227    

DOI:10.1029/JD093iD01p00699

年代:1988

数据来源: WILEY

摘要:

In this work, stratospheric dc electric fields and conductivity measurements, associated with electrified convective clouds identified by satellite infrared imagery, are presented. These measurements were obtained at an altitude of 26 km by a balloon‐borne double‐probe detector, launched from Cachoeira Paulista (geographic coordinates 23°40′S, 45°W) on April 2, 1980. The electric fields are found to correspond to electrified convective clouds with charges of the order of a few coulombs. The conductivity measurements show variations by over a factor of 2 around the average value of 4 × 10−12mho/m. Such variations, which merit more investigation, did not show an apparent relation with the simultaneous electric field measurements. Using the vertical electric field and conductivity measurements, a current density is also estimated. Furthermore, a detailed original discussion on conductivity measurements in the atmosphere as well as a suggestion for estimating distances from the detector to the cloud, using the ratio between the magnitudes of the measured vertical and horizontal electric fields, i

ISSN:0148-0227    

DOI:10.1029/JD093iD01p00709

年代:1988

数据来源: WILEY

摘要:

Tandem mass spectrometric measurements of naturally occurring tropospheric ions have identified pyridine, methylpyridine, and ethylpyridine as the parent neutral species responsible for ions observed at mass 80, 94, and 108, respectively. High‐resolution mass spectra of natural ions observed over an extended mass range are also shown for two field study locations. At one site (Sapelo Island, Georgia), pyridine and its homologues dominated the positive spectrum. At Mount Evans, Colorado, the second site, pyridine along with a large number of more massive and presumably very alkali species were observed to dominate the positive spectrum. In addition, X ray‐produced ion spectra were also measured and used to make rough estimates of the pyridine concentrations at the Sapelo site (∼10 ppt) and the total concentration of alkali compounds, excluding NH3, at Mount Evans (∼0

ISSN:0148-0227    

DOI:10.1029/JD093iD01p00716

年代:1988

数据来源: WILEY

摘要:

The results of δ13C measurements of several types of major sources of atmospheric methane are as follows: rice paddies, −67‰; the peat bogs of the Lake Agassiz region of northern Minnesota, −67±5‰; swamps of the Florida Everglades, −55±3‰ and biomass burning, −24 to −32‰. In addition, results are presented of a study of the δ13C of CH4released from a slough, compared to the CH4in the bottom sediment. These isotopic values are used, together with previously published data, to make up a tentative budget of the fluxes of the major sources for atmospheric methane with an average isotopic composition matching the measured value for atmospheric CH4, taking into account the fractionation effect of the sink processes. This budget requires the existence of a significant flux from an anthropogenic source of heavy CH4, calculated to be 45±15 Tg yr−1if attributed to CH4from biomass

ISSN:0148-0227    

DOI:10.1029/JD093iD01p00725

年代:1988

数据来源: WILEY

摘要:

The full‐disk absolute solar irradiance was measured on December 7, 1983, and December 10, 1984. The first flight obtained data over the wavelength interval 150–260 nm, while the second obtained data from 150 to 340 nm. Absolute accuracy of the measurements varied from ±3 to ±9%, depending on the flight and the particular wavelength. Between 200 and 240 nm the results reported here are higher than previously reported irradiances, but there is good agreement over the other wavelength intervals. Near 150 nm the change in the solar flux between these two flights did not exceed 7%. Above 200 nm the change in the solar irradiance was not larger than the error bars of the measur

ISSN:0148-0227    

DOI:10.1029/JD093iD01p00735

年代:1988

数据来源: WILEY

摘要:

This article reviews the basic properties of sound waves and the nature of their interactions with cloud droplets. It is demonstrated through the use of a numerical model that a single‐frequency, high‐intensity sound wave can apparently alter the characteristics of a droplet population, leading to a more rapid development of precipitation in some cases. A consideration of the sound properties of thunder suggests that atmospheric effects are probably minor, however further research is recommen

ISSN:0148-0227    

DOI:10.1029/JD093iD01p00747

年代:1988

数据来源: WILEY