Ozone Buildup Research Articles

An analysis of ozonesonde data for the lower stratosphere: Recommendations for testing models

I present an analysis of ozonesonde data with a focus on using these data to evaluate stratospheric models of transport and chemistry. Ozonesondes are the only instruments that provide year‐round profiles of ozone throughout the lowermost stratosphere for middle and high latitudes of the Northern Hemisphere. I show vertical profiles and the annual cycle of ozone at selected pressure levels and stations and use TOMS data to evaluate the spatial bias of the sonde stations with respect to zonal mean values of column ozone. Between 10 and 30% of the ozone column is located between 100 hPa and the tropopause at middle and high latitudes, and this region drives much of the seasonal variation of the ozone column. The sonde data allow quantification of the buildup of ozone in the lowermost stratosphere of the Northern Hemisphere in winter and of its loss in late spring and summer. The amount of ozone between the tropopause and 100 hPA in the Northern Hemisphere decreases from 175 to 75 Tg from March to September, with the maximum rate of decrease in May to June; about half of the decrease is caused by the increase in the height of the tropopause. There is a lag of about a month in the time when ozone starts to accumulate in the lowermost stratosphere, from September near 40°N to October or November near 80°N, and a similar lag in the time when ozone starts to decrease, from February or March near 40°N to March or April near 80°N. I propose that the sonde data be used to provide a test of transport in two‐ and three‐dimensional models in addition to those provided by long‐lived tracers, such as N2O, CFCs, CO2, CH4, and their correlation patterns, and age of air. The annual variation of the ozone content of the lowermost stratosphere in the Northern Hemisphere is suggested as a particularly useful constraint on transport parameterizations. I make recommendations for the use of particular stations and provide summary statistics for ozone concentrations and for the mean tropopause height for each station.

Daytime buildup and nighttime transport of urban ozone in the boundary layer during a stagnation episode

A 3‐day period of strong, synoptic‐scale stagnation, in which daytime boundary‐layer winds were light and variable over the region, occurred in mid July of the 1995 Southern Oxidants Study centered on Nashville, Tennessee. Profiler winds showed light and variable flow throughout the mixed layer during the daytime, but at night in the layer between 100 and 2000 m AGL (which had been occupied by the daytime mixed layer) the winds accelerated to 5–10 m s−1 as a result of nocturnal decoupling from surface friction, which produced inertial oscillations. In the present study, we investigate the effects of these wind changes on the buildup and transport of ozone (O3). The primary measurement system used in this study was an airborne differential absorption lidar (DIAL) system that profiled O3 in the boundary layer as the airplane flew along. Vertical cross sections showed that O3 concentrations exceeding 120 ppb extended up to nearly 2 km AGL, but that the O3 hardly moved at all horizontally, instead forming a dome of pollution over or near the city. The analysis concentrates on four meteorological processes that determine the 3‐D spatial distribution of O3 and the interaction between urban and rural pollution: (1) daytime buildup of O3 over the urban area, (2) the extent of the drift of pollution cloud during the day as it formed, which controls peak O3 concentrations, (3) nighttime transport by the accelerated winds above the surface, and (4) vertical mixing of pollution layers the next day. Other consequences of very light‐wind conditions were intra‐regional differences in daytime mixed‐layer depth over distances of 50 km or less, and indications of an urban heat‐island circulation.

Atmospheric fine structure during GTE TRACE A: Relationships among ozone, carbon monoxide, and water vapor

A major focus of the Global Tropospheric Experiment/Transport and Chemistry Near the Equator‐Atlantic (GTE TRACE A) experiment was to determine whether the seasonal tropospheric ozone (O3) buildup over the tropical South Atlantic, observed by both satellites and sondes, is due to photochemical production of O3 from biomass burning effluents or from transport of O3 from the stratosphere. During this expedition, fast response in situ measurements were made of O3, carbon monoxide (CO), and dew point (DP) from aboard the NASA DC‐8 aircraft. Numerous vertical profiles were obtained over Brazil, Africa, and the South Atlantic to determine the origin of the observed O3 enhancement. Fine structure in these data was examined by (1) investigating differences in the species concentration (5‐s averages) and its 2 km vertical running mean during altitude profiles, (2) calculating Fishman‐Seiler coefficients for all vertical profiles with altitude range greater than 3 km, and (3) calculating linear regressions between species across short time intervals (2.5 min) using time series data. The fine structure holds information about the recent history of an air mass and therefore can indicate the “source” of tropospheric O3 enhancement: either transport from the stratosphere (negative correlation with CO and DP) or from photochemistry in the troposphere (positive correlation with CO). All three methods indicate that within the tropical South Atlantic during the TRACE A experiment, net in situ photochemical production is significantly more important than transport from the stratosphere.

Multivariate analysis of a 1992 SONTOS data subset

Statistical analysis of observations made between 7 and 31 August 1992 at a rural site in Southern Ontario, Canada, is presented using principal component analysis (PCA), as well as rank and partial correlation analyses. Data for ozone, CO, SO 2, NO, NO y , (NO + NO 2 including NO x , PAN and HNO 3), ethane, ethylene, propane, acetylene and isoprene are employed, as well as such meteorological information as temperature, relative humidity, wind speed and direction. The analysis involved several scenarios classifying the data according to daytime, nighttime and wind direction. A normal correlation analysis suggests that isoprene might be important in the build-up of ozone in the S-W sector, whereas it is not important in the N-E wind sector. PCA show that the chemical and the meteorological variables interact differently within the different scenarios. Finally, the relationships between ozone and isoprene for both wind sectors are found to be the same when the data are subjected to a partial correlation analysis including the meteorological parameters and it is concluded that the S-W ozone-isoprene relationship might be biased by temperature.

Total ozone measurements made with the Brewer ozone spectrophotometer during STOIC 1989

The Canadian Atmospheric Environment Service participated in the Stratospheric Ozone Intercomparison Campaign (STOIC) by operating a Brewer ozone spectrophotometer at the Table Mountain Observatory from July 19 to August 2, 1989. Frequent direct Sun measurements of total column ozone were made throughout most days during the 2 weeks of the intercomparison. Results of the Brewer instrument total ozone measurements are given. They show that there is a diurnal variation of total ozone with values increasing on average by 6.6±2.4 Dobson units between early morning and late afternoon. Comparing the total ozone measurements with ozone concentration measurements made at ground level suggests that the daytime increase is a result of a buildup of surface ozone during the day. The total ozone measurements made by the Brewer instrument during STOIC are compared with total ozone measurements made by the National Oceanic and Atmospheric Administration (NOAA) Dobson instrument, the NASA/Wallops electrochemical concentration cell ozonesondes and the total ozone mapping spectrometer satellite instrument.

Observations of H 2O 2 and PAN in a rural atmosphere

Measurements of gaseous H 2O 2 and peroxyacetyl nitrate (PAN) concentrations in air are given for a site in rural southern England over an approximately 4-year period. In both cases the data show both diurnal and seasonal patterns. Temperature and wind direction had clear influences on the recorded concentrations of both species. There was an indication of increasing H 2O 2 concentrations with time. The use of a two-dimensional global model confirmed that this would be expected to occur alongside growth in ozone formation. It is suggested that, during photochemical episodes, the sequential build-up of ozone, PAN and H 2O 2 could be important in influencing the ability of vegetation to resist the effects of aggressive pollutants.

Ozone generation in the 214-nm photolysis of oxygen at 25.degree.C

Ozone formation in the 214-nm photolysis of oxygen at pressures ranging from 380 to 1300 Torr was investigated. The rates of ozone formation increase with the square of oxygen pressure mirroring the pressure dependence of the absorption cross sections of oxygen. This observation demonstrates the importance of the collision-induced changes in oxygen absorbance and points to a need to examine the role of oxygen dimer (O/sub 2/) in reactions initiated by its photodissociation. Because of the high dilution of ozone, its formation was found to be linear with time even though, on the average, its rate of photolysis exceeded the rate of its generation from oxygen. The quantum yield of ozone formation was 1.86 /plus minus/ 0.17 independent of O/sub 2/ pressure. From this result the quantum yield of the primary process O/sub 2/ + hv (214 nm) ..-->.. 2O(/sup 3/P) is estimated as being equal to 0.93 /plus minus/ 0.08 (2sigma). Based on the observed linear buildup of ozone and on model calculations, an upper limit of about 0.03 is estimated for O/sub 3/ photolysis via a channel which leads to O(/sup 3/P) and an excited O/sub 2/ species that can regenerate ozone in its reaction with oxygen.

A study of global ozone transport and the role of planetary waves using satellite data

Global ozone fluxes and flux divergences within the region between 30 and 0.4 mbar are computed for the period from December 1, 1978, to November 30, 1979, using Nimbus 7 solar backscattered ultraviolet ozone profiles and meteorological data derived from National Oceanic and Atmospheric Administration satellites. The annual cycle of ozone transports in the northern and southern hemispheres is presented and discussed. It is found that planetary scale waves are responsible for initiating the high‐latitude ozone buildup in winter. The time of occurrence and the position of the annual maximum ozone are found to be closely related to the planetary wave activity in both hemispheres.

Ozone formation behind pulsed-laser-generated blast waves in oxygen

The formation of ozone behind blast waves in oxygen generated by a pulsed laser has been investigated both experimentally and theoretically, over cell pressure range of 0.68–27 atm. Ozone buildup formed by successive pulses was monitored by recording UV absorption at 2540 Å. It was found that, as the number of pulses increase, the rate of ozone formation decreased until finally an equilibrium concentration was reached. This equilibrium magnitude was determined by the condition that the number of ozone molecules produced by the wave equals the number decomposed by the same wave. The decomposition and formation of O3 during a single pulse were monitored by time-resolved UV absorption measurements. In order to provide a fundamental basis for interpretation of the mechanism of ozone formation, a mathematical model was developed. Although qualitatively measurements and theory agree, the data, mainly on the number of O3 molecules produced per pulse, is in significant disagreement. Several possible explanations of this discrepancy are given.

Numerical Experiments with a General Circulation Model Concerning the Distribution of Ozone in the Stratosphere

The distribution of ozone below 60 km altitude has been simulated in two experiments employing a nine-layer quasi-geostrophic spectral model and linear parameterization of ozone photochemistry, the first of which included thermal and orographic forcing of the planetary scale waves, while the second omitted it. The first experiment exhibited a high latitude winter ozone buildup which was due to a Brewer-Dodson circulation forced by large amplitude (planetary scale) waves in the winter lower stratosphere. Photochemistry was also found to be important down to lower altitudes (20 km) in the summer stratosphere than had previously been supposed.

Photochemical ozone formation in urban and point source plumes

Results are presented of aerial measurements in plumes from large urban areas, petroleum refineries, automotive-painting operations, fossil-fuel power plants, and the controlled burning of forest slash. The field monitoring studies, which were carried out during the summer months between 1974 and 1980, emphasized the collection of data on in-plume ozone buildup and associated precursor concentrations. With the exception of power-plant emissions, photochemical ozone formation in excess of ambient background levels was documented in all the plumes studied. An examination of NMHC/NO/sub x/ suggests that ozone production (or, in the case of power-plant effluents, depletion) is consistent with the traditional HC-NO/sub x/-UV light model. The urban nonmethane hydrocarbon composition is found to be similar for the cities monitored, but marked variation is seen between the plumes from other sources.

Photochemical ozone formation from petroleum refinery emissions

Atmospheric emissions from the Marathon oil refinery at Robinson, Illinois were investigated during June and July 1977. Surface and aerial measurements were used to provide an integrated, three dimensional monitoring network. Concentrations of ozone, oxides of nitrogen, sulfur dioxide, methane, carbon dioxide, individual non-methane hydrocarbons and halocarbons were recorded on a routine basis. In addition, meteorological parameters such as wind speed, wind direction, solar radiation and mixing height were also measured. The field monitoring study focused on three major areas: 1. (1) characterization of gaseous components within the refinery effluent, especially nonmethane hydrocarbons and nitrogen oxides; 2. (2) natural sunlight bag irradiation experiments to examine ozone forming potential of refinery emissions and 3. (3) aerial measurements of changes in plume chemistry during the first six to eight hours of transport. Results indicate levels of hydrocarbons and nitrogen oxides were elevated downwind of the refinery. Concentrations within the effluent exceeded background values by as much as 300- and 10-fold, respectively. Irradiations of captured refinery emissions suggest excess photochemical ozone can be produced in the first 6 h, with amounts varying according to NMHC/NO x , ratios and initial NMHC concentrations. Real-time measurements on board the aircraft documented instances of ozone buildup in the refinery plume as it drifted downwind.

The transport of trace substances in the atmosphere and their implications for the general circulation of the stratosphere

Considerations concerning the distribution of artificial radioactive substances in the troposphere point to the occurrence of stratospheric-tropospheric exchange in the region of the discontinuity between the tropical and middle latitude tropopause. Computations of the horizontal flux of ozone in the lower stratosphere and examination of the distribution of the tracer tungsten 185 in the stratosphere suggest that the trace substances are transported northwards from the tropical stratosphere by the action of transient eddy processes in which northward moving parcels of air are sinking and southward moving parcels are rising. The amount of ozone transported varies seasonally and is a maximum in the late winter and spring. The total transport appears sufficient to account for the observed spring build-up of ozone in middle and high latitudes. The eddies invoked are shown to be consistent with the observed countergradient transport of heat in the lower stratosphere, the pattern of stratospheric isentropes and the covariance values found from meridional and vertical velocities. The combined results indicate a new view concerning the mechanics of stratospheric motions as contrasted with the classical ideas of mean meridional motions.