Trace Gas Distributions Research Articles

Effects of Solid‐Fueled Rocket Exhausts on the Stratospheric Ozone Layer

AbstractSpace transport systems often use solid‐fuel in boosters and this type of fuel is also very common for sounding rockets. One of the main components in the exhaust is hydrochloric acid. Photochemical model calculations have been performed to investigate local effects after such a rocket launch. Disturbances of the atmospheric trace gas distribution are possible; however, strong changes in the stratospheric ozone concentration are restricted to altitudes above 30 km and will only occur if the mixing of the exhaust gas with ambient air proceeds slowly.

Vertical distribution of aerosol particles, water vapor, and insoluble trace gases in convectively mixed air

Vertical distributions of submicrometer size aerosol particles, water vapor, and the insoluble gases (O3, CO, and NOy) were determined from measurements made during 12 aircraft flights conducted in June 1987 near Columbus, Ohio. Measurements extended from the surface to 290 mbar (∼9.5 km) and were made primarily in the vicinity of convective storms. The mixing ratio of aerosol particles decreased strongly with altitude, from an average value of 1800 scm−3 (SCM, standard centimeter) (at 20°C, 1 atm) near the surface to a value in the upper troposphere (30 scm−3, above 300 mbar) that was, on average, less than 2% of the near‐surface mixing ratio. This decrease was similar to that exhibited by water vapor. CO and NOy, in contrast, were more uniformly distributed. Average upper tropospheric mixing ratios were 128 and 0.8 ppb, 51 and 35%, respectively, of boundary layer values. Compact plumelike features were observed at high altitude in which concentrations of boundary layer constituents increased by 50% or more over a distance of several kilometers. These features are attributed to boundary layer air that had been transported upward in convective storms. Such boundary layer air encountered aloft could contain higher mixing ratios of water vapor and aerosol particles than found in adjacent regions, but on an absolute basis these soluble substances were always severely depleted relative to the insoluble gases, CO and NOy. We ascribe the qualitative difference between the vertical distributions of soluble and insoluble substances as being due to in‐cloud processes occurring during upward transport. The upward transport of soluble material is limited by dissolution in cloud water and subsequent conversion of cloud water to downward moving precipitation, whereas insoluble pollutants are not affected by this process.

Cloud draft structure and trace gas transport

Field observations obtained during the second NASA Amazon Boundary Layer Experiment (ABLE 2B), and two‐dimensional moist cloud model simulations are used to determine the dominant transport pathways within a continental tropical squall line. A surface‐based network triangle provided the focus for a multi‐instrumental sampling of the May 6, 1987, squall line which propagated through the central Amazon basin at a rate of 40–50 km h−1. Extensive use is made of the vertical distribution of specific trace gases that are representative of the prestorm and poststorm environment. One‐dimensional photochemical model results suggest the observed poststorm changes in ozone concentration can be attributed to convective transports rather than photochemical production. Two‐dimensional cloud model results detail the dynamic and thermodynamic attributes of the simulated squall convection. The well‐mixed moist troposphere in which the observed squall system developed may have hindered strong downdraft development. Parcel trajectory analyses are conducted to investigate the flow patterns of convective transports. A significant proportion (> 50%) of the air transported to the anvil region originated at or above 6 km, not from the boundary layer via undilute cores. The presence of a midlevel inflow and a strong melting layer at 5.5 km reduced the vertical development of the core updraft and aided in the maintenance of a rotor circulation. The predicted absence of more than one active cell in the model cloud field, the lack of a well‐organized downdraft in the presence of model estimated net upward mass flux, and the initial wind profile suggest the May 6 squall line was unicell in character.

New approaches to modelling the gobal distribution of trace gases in the troposphere

New approaches to modelling the gobal distribution of trace gases in the troposphere

Ageostrophic Effects on the Stratospheric Residual Circulation and Tracer Distributions

The behaviors of idealized geostrophic and ageostrophic circulations forced by differential heating and parameterized eddy mixing in the absence of boundary drag are examined for a range of mixing values and boundary conditions, using a nonlinear version of Holton's (1986) channel model. It was found that geostrophic and ageostrophic flows can have fundamentally different behaviors. This may have important implications for the circulation and trace gas distributions in the stratosphere. It is shown that, as eddy forcing vanishes, an ageostrophic system is not constrained to approach radiative equilibrium and may tend to the limit of an inviscid diabatic circulation under a range of boundary conditions.

Prospects for Aircraft‐Based Gas Exchange Measurements in Ecosystem Studies

Aircraft sampling of the planetary boundary layer can be used to measure trace gas distributions and fluxes directly on regional scales. Laser—based detection and in situ atmospheric sampling can be used for fast—response, accurate measurements of gas concentrations in a column of air over time. Lidar (light detection and ranging) techniques provide a unique method for determining the structure and dynamics of the boundary layer over time. Under stable atmospheric conditions, the combination of these techniques allows estimates of gas exchange between the biosphere and atmosphere.

U.S.‐Soviet climate research: More, better

The draft of an agreement for cooperative U.S.‐Soviet climate research contains a number of proposed projects that should lead to unprecedented knowledge of the worldwide atmospheric distribution of trace gases and their effect on climate change. Activities named in the document include the shared measurement of Antarctica's ozone hole, a joint experiment to investigate the relationship between aerosols and ozone in the Arctic stratosphere, and a program to measure biogenic methane produced in permafrost areas of the United States and the Soviet Union.The protocol, signed in preliminary form November 2, 1987, by representatives of both countries, is the latest update of a bilateral agreement in place since 1972. Ultimate approval of the protocol should come in the next few months, in the form of a final signing by Environmental Protection Agency (EPA) Administrator Lee Thomas and the head of the equivalent ministry in the Soviet Union, Yuri Izrael.

Seasonal and latitudinal distribution of trace gases in the stratosphere: Results from a 2D residual circulation model

Results for minor stratospheric constituents using a 2D model with self-consistent transport parameters are reported. The meridional circulation is obtained from the output of the MIT-GIT 3D stratospheric model (Cunnold et al., 1975). Consistent data from the same model are used to evaluate the diffusive tensors following the formalism of Holton (1981) and Tung (1982). Chemical damping is consequently taken into account, so that the entire model is built in a selfconsistent manner at the least with the 3D model and no ad hoc assumptions are made with respect of transport parameters. This version of the model represents a major improvement on previous work (Pitari and Visconti, 1984), which used to much too simple chemistry. Results are compared whenever possible with available experimental data, with particular emphasis on chemical reacting species. This comparison shows in general an agreement which is qualitatively similar to the one obtained from classical Eulerian models where transport parameters are often tuned to long-lived tracers without any sound physical basis.

Recent measurements of trace constituents from rocket and balloon probes

During the past few years several field campaigns each employing a number of different experiments and of different experimental techniques have given new insights into the behaviour of trace constituent distributions in the middle atmosphere. Results from the MAP/WINE and from the Energy Budget Campaings are presented and compared with results previously obtained. The measured trace gas distributions are often very structured in time and/or space. These variations cannot be understood if photochemical equilibrium conditions are assumed. It is therefore concluded that dynamical processes are of major importance to the trace constituent distributions even at altitudes where gases are believed to be in photochemical equilibrium.

Two‐dimensional tracer transport: Derivation of residual mean circulation and eddy transport tensor from a 3‐D model data set

Two‐dimensional distributions for long‐lived species, N2O, CFCl3, and CF2Cl2, have been calculated by using a 2‐D model extending from the ground to 70 km. The model utilizes a residual mean meridional circulation and a set of eddy diffusion coefficients. Both these fields have been obtained from the output of the MIT‐GIT three‐dimensional general circulation model of the stratosphere. The calculation of the residual mean circulation takes into account consistent fields of temperature and diabatic heating, meridional temperature advection, and vertical eddy fluxes. The diffusion tensor is obtained following Holton (1981) and utilizes the eddy field that is an output of the 3‐D model. The chemical source term is treated by introducing an additional tensor, following the suggestion by Tung (1982). This approach has the advantage of using the same matrix for all the chemical compounds. Values obtained for the residual mean meridional mass flux are in good agreement with similar results. The trace gas distributions obtained show a fairly good agreement in the equatorial regions but overpredict the concentration in the mid‐latitude stratosphere. This is a common modeling problem, especially with fluorocarbons, and is attributed, in our case, to values of the Kyy and Kzz components that are too large in the lower stratosphere. This particular result is probably due to the heating parameterization adopted in the original general circulation model.

Stratospheric H2O and HNO3 profiles derived from solar occultation measurements

Compact two‐channel radiometers for solar occultation experiments have been constructed in order to measure stratospheric trace gases. The instruments can be used as filter‐ or correlation‐type radiometers, depending on the trace gas under investigation. Within the LIMS correlative measurement program, balloon flights were performed with a payload of up to four of these two‐channel radiometers. From the filter‐type measurements, profiles of the trace gases H2O and HNO3 are inferred for the height region between the tropopause and the balloon float level. The data evaluation also includes a comprehensive analysis of the error sources and their effect on the accuracy of the trace gas profiles. The derived H2O and HNO3 profiles are assessed against the observations of other authors and are discussed in the light of the trace gas distributions calculated from photochemical models.

Statistical global and regional atmospheric models of temperature and gas components over the northern hemisphere

Statistical mid-latitude models of altitude distribution of temperature, water vapor, ozone, carbon dioxide and trace gases (CO, CH 4, N 2O, NO, NO 2) are considered. The mean characteristics of altitude profiles of these parameters, as well as their time and space variability, have been taken into account. The statistical regional models were constructed using a temperature-humidy complex. The considered statistical mid-latitude models have been constructed as applied to solutions of the problems on remote sounding of the atmosphere and underlying surface from outer space.

The Seasonal and Latitudinal Behavior of Trace Gases and O3as Simulated by a Two-Dimensional Model of the Atmosphere

Abstract A two-dimensional zonal-mean model with parameterized dynamics and an advanced photochemical scheme is used to simulate the stratospheric distributions of atmospheric trace gases including ozone. The model calculates the distributions of 37 species that are photochemically coupled via 140 reactions with rate data from WMO/NASA. A full diurnal treatment is used to calculate the diurnal variations of the short-lived species and the diurnal mean of the production/loss rates for the long-lived species. The calculated concentrations are compared with a wide range of observations with emphasis on the seasonal and latitudinal features. In this work, no post hoc adjustment of the dynamical parameters has been attempted to improve agreement with observations. In general, the model results are in good agreement with observations, although several discrepancies are noted. Rather than focusing on any individual species, we look for systematic agreements and discrepancies between model and observations for a ...

Accuracy and precision of the nitric acid concentrations determined by the Limb Infrared Monitor of the Stratosphere Experiment on NIMBUS 7

The LIMS is a six channel limb scanning IR radiometer flying on the NIMBUS 7 spacecraft. It measured radiances from October 24, 1978, to May 28, 1979, from which vertical profiles of temperature, ozone, water vapor, nitrogen dioxide, and nitric acid were determined. Nitric acid (HNO3) plays an important role in stratospheric chemistry, both as reservoir and as sink for the nitrogen compounds and because of its relationship to the hydroxyl radical. This paper describes the validation of the HNO3 results, beginning with an outline of the measurements and data reduction leading to the retrievals. The error sources due to instrumental effects and data reduction are described, and their effects on the results are calculated. The predicted random errors are shown to be somewhat larger than the observed values of ∼0.10 ppbv. The LIMS results are within 20% of a set of 15 correlative balloon‐borne measurements, obtained with several techniques over a range of season, latitude, and pressure between 100 and 20 mbar, the region of largest HNO3 mixing ratio. This is about the accuracy of the correlative measurements. The percent differences are larger at altitudes above 10 mbar. LIMS results agree with earlier measurements at all but the highest levels. Total overburdens above 200 mbar calculated from LIMS agree with those measured spectroscopically from aircraft. LIMS and other HNO3 measurements show similar agreement with model predictions. The consistency suggests that the major LIMS error sources are reasonably well understood. The HNO3/NO2 ratio also leads to reasonable OH concentrations. The global distribution of HNO3 in November shows strong latitudinal variation at the altitude of the maximum, with a large build up over the northern hemisphere pole at ∼40 mbar, but lower values over the southern pole. This reverses by early northern spring. Some characteristics and limits on the data are noted, but the LIMS HNO3 determinations are usually of comparable accuracy to other determinations. These results provide a valuable addition to our knowledge of the distributions of trace gases in the stratosphere. By themselves, but especially in conjunction with the LIMS measurements of temperature, ozone, water vapor, and nitrogen dioxide, they form the basis for a wide range of atmospheric studies.

Far infrared remote sounding of stratospheric temperature and trace gas distributions

The thermal emission spectrum of the Earth's stratosphere in the far infrared exhibits rotational transitions of a large number of trace constituents in addition to the magnetic dipole lines of molecular oxygen. Stratospheric lines that have been identified in the far infrared spectrum include H2O, O3, HNO3, N2O, CO, HCl, HF, HCN and OH. This paper discusses the potential usefulness of far infrared thermal emission measurements for simultaneous retrieval of temperature and constituent distributions. A description of the high-resolution Michelson interferometer currently employed for balloon-borne far infrared stratospheric studies is given, along with a summary of the mode of limbscan observations and an example of an observed spectrum. Numerical results based on synthetic limb radiance data for model atmospheres are presented. Formal inversion techniques with a radiative transfer model based on line-by-line transmittance calculations are employed.

Stratospheric trace gas distributions observed in different seasons

A newly developed balloon-borne cryogenic sampler has been used to collect large air samples in the midlatitude stratosphere (44° N). The samples were analysed for their content of several longlived trace gases. The vertical profiles of N 2O, CH 4, and CF 2Cl 2 derived from two balloon flights in winter 1982 and, as part of the MAP Globus Project, in fall 1983 indicate variations that are caused by large scale dynamic processes. Significant features of the profiles are discussed and compared with averaged profiles that were derived from a series of balloon sampling flights performed previously over the same location during the summer season. The temporal variation of the individual profiles is more detailed than predicted by model calculations.

Latitudinal distributions of trace gases in and above the boundary layer

Statistical analyses of global atmospheric concentrations provide evidence that C 2Cl 4, CHCl 3 and CH 3CCl 3 (methylchloroform) are more abundant in the tropical boundary layer than above it ( α ⩽ 0.09) by 27% (±27%), 21% (−21%, +12%) and 6.4% (±6%) respectively. The air samples on which these results are based were collected by cryogenic techniques during the June 1978 project GAMETAG flights and analyzed soon afterwards by gas chromatography (EC/GC and GC/FID), thus providing latitudinal concentrations of CO, CH 4, CCl 3F, CCl 2F 2, CH 3CCl 3 and light C 2-hydrocarbons, both in and above the boundary layer. In August 1980, after further development of analytical techniques, the stored air samples were re-analyzed to establish the latitudinal distributions of CH 3I, CHCl 3, C 2Cl 4, C 2F 3Cl 3 (F-113) and CHClF 2 (F-22) in and above the boundary layer. Stability studies, spanning a year, show that the concentrations of these gases do not change in the flasks.

The vertical distribution of stable trace gases at mid‐latitudes

Vertical profiles of H2, CH4, CO, N2O, CFCl3, and CF2Cl2 resulting from gas chromatographic analysis of air samples collected from altitudes between 1.5 and 35.3 km at a latitude of about 44°N are presented. Ten balloon flights were performed with a neon‐cooled cryogenic air sampler designed to collect large air samples at eight different stratospheric heights. Supplementary tropospheric air samples were taken aboard a chartered aircraft. Vertical profiles from 1978 and 1979 are compared with those derived from fights in 1977.

A two-dimensional model of the distribution of trace gases in the stratosphere and troposphere

We report the results of computations of the distribution of trace gases in the troposphere and stratosphere with a two-dimensional photochemical transport model. The region covered by the model extends from pole to pole and from 0 to 50 km. Atmospheric transport is included by using seasonal averaged values for mean meridional and vertical winds and eddy diffusion. The compounds transported in the model are N2O, NO x (NO+NO2), NO y (NOx+HNO3), N2O5, H2O, CH4 and H2O2. Odd hydrogen (OH+HO2+H) is assumed in photoequilibrium. A simple scheme is proposed to simulate the condensation of H2O and scavenging of other gases. Rayleigh scattering is included in the calculation of the photodissociation rates. The resulting distributions are compared whenever possible with experimental data. We attempt to discuss the stratospheric budget of water vapour taking into account photochemical sources (e.g. CH4 oxidation) and sinks. It is shown that similarly to other models serious disagreement seems to exist between the calculated and observed mixing ratios of NO x , NO y and the ratios of the different compound within the family. The amount of experimental data is, however, too sparse to draw any definite conclusion.

A two‐dimensional transport simulation model for trace atmospheric constituents

A two‐dimensional atmospheric transport simulation model is described which is designed to facilitate the interpretation of observed distributions of primary tropospheric trace gases. Transport by large‐scale advection is based on published meridional velocity fields, while the eddy diffusion component of the transport is based on published diffusion coefficients adjusted to produce agreement between model generated and observed global distributions of CCl3F. The observed CCl3F distribution presented here is useful in this context as it is based on recent multiple observations at six globally distributed background monitoring stations which use calibration gases based on a common standard. The model incorporates both northern and southern hemisphere CCl3F release estimates. It is found that in recent years the global rate of increase in tropospheric CCl3F concentration is higher than that consistent with available release data. The model results indicate interhemispheric exchange times (70°N to 70°S) of approximately 8 months.