摘要:

The impact of non‐methane hydrocarbons of natural and anthropogenic origin on the photochemistry of the nonurban lower atmosphere has been studied using a photochemical model with detailed planetary boundary layer transport. The research was undertaken to evaluate the increase in peroxy radical concentrations due to hydrocarbon oxidation and their contribution to observed imbalances in the NOx, O3photostationary state (Parrish et al., 1986a). The results show that these hydrocarbons, at concentrations observed in the atmosphere, reduce the hydroxyl radical concentration in clean air and increase the peroxy radical concentration to levels that are needed to explain the observed imbalance in the photostationary state. For the conditions simulated here, natural hydrocarbons are the principal contributors to the increase in the peroxy radical concentration at low NOxmixing ratios. At higher NOxlevels the anthropogenic hydrocarbons that scale with NOxgain in importance. Model simulations that include the hydrocarbons reproduce the observed dependence of the concentration of ozone on various NOxconcentration

ISSN:0148-0227    

DOI:10.1029/JD092iD10p11879

年代:1987

数据来源: WILEY

摘要:

Using the resistance model for mass transfer, a formulation is derived for the dry deposition rate of a reactive, soluble gas depositing on a wetted, vegetative surface. The deposition velocity is expressed in terms of a dynamical resistance, which is a function of the physical state of the atmosphere, and a surface resistance, which is a function of the chemical and physical properties of the surface. This formulation is then used in a model to simulate the generation of acidic dew from the dry deposition of HNO3and SO2, as well as the SIVoxidants, H2O2and O3. Dewdrop pHs of about 4 are calculated by the end of the night, however these pHs can rapidly fall to potentially toxic levels soon after sunrise as the dewdrops evaporate. The deposition velocities to the dew for highly soluble species such as HNO3and H2O2are found to be entirely determined by the dynamical resistance; for the conditions adopted here a value of 0.4 cm s−1is calculated for these species. However, much smaller deposition velocities are predicted for SO2and O3because of their lower solubilities and hence larger surface resistances. In the case of SO2, a nocturnally averaged deposition velocity of only about 0.03 cm s−1is calculated for the standard model. Because the chemical lifetime of SO2in the dew is influenced by the atmospheric levels of H2O2, O3, and SO2, the SO2deposition velocity is found to be a strong function of these species' atmospheric abundances. These results imply that the deposition velocities of species such as SO2to wetted surfaces may be influenced by the chemical as well as the physical state of the atmosphere; the assumption typically adopted that dry deposition velocities are independent of the species' atmospheric abundance may not always be appropri

ISSN:0148-0227    

DOI:10.1029/JD092iD10p11895

年代:1987

数据来源: WILEY

摘要:

The “1½−D” model of Holton (1986a), which is actually a highly truncated two‐dimensional model, describes latitudinal variations of tracer mixing ratios in terms of their projections onto second‐order Legendre polynomials. The present study extends the work of Holton by including tracers with photochemical production in the stratosphere (O3and NOy). It also includes latitudinal variations in the photochemical sources and sinks, improving slightly the calculated global mean profiles for the long‐lived tracers studied by Holton and improving substantially the latitudinal behavior of ozone. Sensitivity tests of the dynamical parameters in the model are performed, showing that the response of the model to changes in vertical residual meridional winds and horizontal diffusion coefficients is similar to that of a full two‐dimensional model. A simple ozone perturbation experiment shows the model's ability to reproduce large‐scale latitudinal variations in total ozone column depletions as well as ozone changes in the chemically controlled upper stratosphere. Limitations of the model as a tool for perturbation studies are discussed, e.g., the fact that, as presently formulated, the model can only be used in a yearl

ISSN:0148-0227    

DOI:10.1029/JD092iD10p11909

年代:1987

数据来源: WILEY

摘要:

Simultaneous in situ measurements of NO, NO2, and O3were obtained from balloon flights near 50°N in August and December 1982. NOx(NO + NO2) was reduced by a factor of 10 in the 21‐ to 28‐km region in winter. Both NO and NO2exhibited very sharp vertical gradients in the vicinity of 29 km. NO, for example, increased by nearly 20 times over only a 1‐km increase in altitude. By considering air mass trajectories for the time of the winter flight, the reduction in NOxin the lower and middle stratosphere was determined to be consistent with photochemical conversion, principally t

ISSN:0148-0227    

DOI:10.1029/JD092iD10p11919

年代:1987

数据来源: WILEY

摘要:

Simultaneous in situ measurements of [NO], [NO2], [O3],jNO2, [CH4], [H2O], [CO2], pressure, and temperature in the 40 to 26‐km region of the stratosphere were made from Palestine, Texas (32°N), on October 16, 1986, using the Jet Propulsion Laboratory (JPL) Balloon‐borne Laser In Situ Sensor (BLISS) instrument, carrying a University of DenverjNO2instrument piggyback. Using tunable diode laser absorption spectroscopy over a long path length, measurements were made as follows during a 21‐hour flight: daytime [NO], [NO2], [O3], and NO2near 40 km; [NO], [NO2], and NO2through the sunset transition near 40 km; postsunset measurements of the rate of decay of [NO2] into the night over the 35 to 29‐km range; nighttime measurements of [NO2], [O3], [CH4], [H2O], and [CO2] at 27 km; and [NO]after sunrise. The NO, NO2, O3, CH4, H2O, and CO2concentration measurements generally show good agreement with previous observations, with a tendency for somewhat lower NO2amounts. Measured O3concentrations at 38 km agree well with comparable measurements from in situ UV photometers, but at 28 km they are lower by about 10% and agree more closely with solar backscattered ultraviolet data at this altitude. The observed change in [NO2] during the night over a 5‐km altitude range implies either lower [NO2] postsunset profiles, or significantly faster [NO2] decay than current model predictions using N2O5chemistry. Measurements of [NO], [NO2], [H2O], and [CO2] from an October 1985 flight are included for

ISSN:0148-0227    

DOI:10.1029/JD092iD10p11931

年代:1987

数据来源: WILEY

摘要:

Volume mixing ratio profiles of ethane (C2H6) in the lower stratosphere and upper troposphere and acetylene (C2H2) in the upper troposphere have been deduced from analysis of 0.01‐cm−1‐resolution infrared solar absorption spectra recorded between 25°N and 31°N latitude. The spectral data were obtained by the ATMOS (Atmospheric Trace Molecule Spectroscopy) Fourier transform spectrometer during the Spacelab 3 shuttle mission on April 30 to May 1, 1985. The investigation was based on nonlinear least squares curve fitting of the ν7; bandPQ3subbranch near 2976.8 cm−1and the ν9bandRQ0subbranch near 822.3 cm−1for C2H6and of the ν5bandR10 andR19 lines of C2H2at 755.0056 and 776.0818 cm−1, respectively. Improvements in the spectroscopic data base for the regions containing these absorption features are reported. The C2H6results indicate a nearly constant volume mixing ratio of 0.97 parts per billion by volume (ppbv) between 6 and 12 km and a decline to 0.1–0.2 ppbv at 18 km altitude. Measured C2H2mixing ratios are 0.070–0.092 ppbv between 7.7 and 12.6 km and 0.02 ppbv at 15.1 km. An upper limit of 0.02 ppbv is obtained for the average C2H2mixing ratio above 16.6 km. The retrieved profiles are compared with previous measurements an

ISSN:0148-0227    

DOI:10.1029/JD092iD10p11951

年代:1987

数据来源: WILEY

摘要:

The usual assumption by which chemical reaction rates are calculated in two‐dimensional atmospheric models is by using a product of zonal means of rate coefficients and constituent concentrations rather than the rigorous zonal mean of the corresponding products. This assumption has been tested for the reactions O + NO2→ NO+ O2and NO + O3→ NO2+ O2using mapped limb infrared monitor of the stratosphere data from the Nimbus 7 satellite and found to be quite satisfactory for winter 1979 at 60°N in the upper stratosphere. Relative differences between the two‐dimensional averaged rate and the more rigorous rate, calculated from the full, longitudinally varying temperatures and mixing ratios, were small (usually below 5%) and exceeded 15% only during times of strong dynamical activity. At those times or locations where stratospheric circulation is primarily zonal, the two averages agreed to within a few

ISSN:0148-0227    

DOI:10.1029/JD092iD10p11965

年代:1987

数据来源: WILEY

摘要:

A 1200‐day record from a perpetual‐January simulation with a general circulation model is analyzed for the presence of an oscillation resembling the 40‐ to 50‐day oscillation observed in the atmosphere. Representation of the global velocity potential at 200 mbar by empirical orthogonal functions (EOFs) reveals an eastward propagating disturbance having a principally zonal wave number 1 character. It is determined from power spectra of the velocity potential at points around the equator that the period of the oscillation is in the range of 28–31 days. Time series of the coefficients of the first two EOFs are used to define epochs for the compositing in equatorial latitudes of anomalies in zonal winds, in 500‐mbar convective heating, and in precipitation. Time‐longitude diagrams of the zonal wind anomalies indicate the presence of an eastward propagating disturbance characterized by two longitudinal scales. The principal anomalies in convective heating and precipitation appear as two stationary oscillations, one situated in a zone extending from 120°E to the dateline and the other in a relatively narrow

ISSN:0148-0227    

DOI:10.1029/JD092iD10p11971

年代:1987

数据来源: WILEY

摘要:

Weather station barograph records as well as infrasonic recordings of the pressure wave from the Mount St. Helens eruption of May 18, 1980, have been used to estimate an equivalent explosion airblast yield for this event. Pressure amplitude versus distance patterns in various directions compared with patterns from other large explosions, such as atmospheric nuclear tests, the Krakatoa eruption, and the Tunguska comet impact, indicate that the wave came from an explosion equivalent of a few megatons of TNT. The extent of tree blowdown is considerably greater than could be expected from such an explosion, and the observed forest damage is attributed to outflow of volcanic material. The pressure‐time signature obtained at Toledo, Washington, showed a long, 13‐min duration negative phase as well as a second, hour‐long compression phase, both probably caused by ejecta dynamics rather than standard explosion wave phenomenology. The peculiar audibility pattern, with the blast being heard only at ranges beyond about 100 km, is explicable by finite amplitude propagation effects. Near the source, compression was slow, taking more than a second but probably less than 5 s, so that it went unnoticed by human ears and susceptible buildings were not damaged. There was no damage at Toledo (54 km), where the recorded amplitude would have broken windows with a fast compression. An explanation is that wave emissions at high elevation angles traveled to the upper stratosphere, where low ambient air pressures caused this energetic pressure oscillation to form a shock wave with rapid, nearly instantaneous compression. Atmospheric refraction then returned part of this wave to ground level at long ranges, where the fast compressions were clearly au

ISSN:0148-0227    

DOI:10.1029/JD092iD10p11979

年代:1987

数据来源: WILEY

摘要:

We have found the dominance of a monochromatic inertia gravity wave with a vertical wavelength of approximately 5.6 km from middle and upper atmosphere radar observations of the mesosphere on February 8, 1985. By assuming linear dispersion and polarization equations for gravity waves, we have estimated the intrinsic period and propagation direction of the wave as 8 hours and northward, respectively. The minimum Richardson number for the atmosphere as modified by the inertia gravity wave was slightly negative near 72 km, which implies that the wave was saturated and generated turbulence through shear and convective instabilities. We observed an echo power enhancement near the altitude of the minimum Richardson number. At 68–78 km altitude we found intermittent fluctuations in radial wind velocities with a period of 9 min. Their phases rapidly reversed near 73 km, where their amplitudes reached a minimum and the Richardson number was less than 1. These fluctuations seem to be attributable to the shear or convective instabilities generated by the saturating gravity wav

ISSN:0148-0227    

DOI:10.1029/JD092iD10p11993

年代:1987

数据来源: WILEY