Daily Ozone Research Articles

The impact of human activities on the photochemical production and destruction of tropospheric ozone

AbstractThe spatial and temporal distribution of tropospheric ozone is controlled by transport processes, including advection, convection and dispersion and by stratosphere‐troposphere exchange, surface deposition to the earth's surface and by photochemical production and destruction within the troposphere itself. These processes have been represented in some detail in a global three‐dimensional Lagrangian chemistry (STOCHEM) model which has been used to construct global ozone budgets and identify the main features in the spatial distribution of daily ozone tendencies. The annually and spatially integrated net chemical production of ozone is about twice as large as the stratosphere‐troposphere exchange flux, so that the concentration‐dependent surface deposition balancing term is about three times larger than the stratosphere‐troposphere exchange term. The total production and loss terms for ozone by tropospheric photochemistry are much greater than the net chemical production, with total chemical production about five times larger than the net term. The ozone turnover time is therefore around 30 days, around one tenth of the turnover time due to stratosphere‐troposphere exchange alone. Human activities may influence future tropospheric ozone levels through at least two distinct mechanisms: first, increasing emissions of tropospheric ozone precursor gases: methane, oxides of nitrogen, carbon monoxide and hydrocarbons, leading to increased ozone levels; second, human‐induced climate change may lead to increased temperatures and water vapour concentrations, and hence increased ozone destruction and decreased ozone concentrations.

Statistical interpolation of ozone measurements from satellite data (TOMS, SBUV and SAGE II) using the kriging method

Abstract. This study demonstrates that ordinary kriging in spherical coordinates using experimental semi-variograms provides highly usable results, especially near the pole in winter and/or where there could be data missing over large areas. In addition, kriging allows display of the spatial variability of daily ozone measurements at different pressure levels. Three satellite data sets were used: Total Ozone Mapping Spectrometer (TOMS) data, Solar Backscattered UltraViolet (SBUV), and the Stratospheric Aerosol and Gas Experiment (SAGE II) ozone profiles. Since SBUV is a nadir-viewing instrument, measurements are only taken along the sun-synchronous polar orbits of the satellite. SAGE II is a limb-viewing solar occultation instrument, and measurements have high vertical resolution but poor daily coverage. TOMS has wider coverage with equidistant distribution of data (resolution 1° × 1.25°) but provides no vertical information. Comparisons of the resulting SBUV-interpolated (column-integrated) ozone field with TOMS data are strongly in agreement, with a global correlation of close to 98%. Comparisons of SBUV-interpolated ozone profiles with daily SAGE II profiles are relatively good, and comparable to those found in the literature. The interpolated ozone layers at different pressure levels are shown.Key words: Atmospheric composition and structure (middle atmosphere - composition and chemistry) - Meteorology and atmospheric dynamics (middle atmosphere dynamics)

Statistical interpolation of ozone measurements from satellite data (TOMS, SBUV and SAGE II) using the kriging method

This study demonstrates that ordinary kriging in spherical coordinates using experimental semi-variograms provides highly usable results, especially near the pole in winter and/or where there could be data missing over large areas. In addition, kriging allows display of the spatial variability of daily ozone measurements at different pressure levels. Three satellite data sets were used: Total Ozone Mapping Spectrometer (TOMS) data, Solar Backscattered UltraViolet (SBUV), and the Stratospheric Aerosol and Gas Experiment (SAGE II) ozone profiles. Since SBUV is a nadir-viewing instrument, measurements are only taken along the sun-synchronous polar orbits of the satellite. SAGE II is a limb-viewing solar occultation instrument, and measurements have high vertical resolution but poor daily coverage. TOMS has wider coverage with equidistant distribution of data (resolution 1° × 1.25°) but provides no vertical information. Comparisons of the resulting SBUV-interpolated (column-integrated) ozone field with TOMS data are strongly in agreement, with a global correlation of close to 98%. Comparisons of SBUV-interpolated ozone profiles with daily SAGE II profiles are relatively good, and comparable to those found in the literature. The interpolated ozone layers at different pressure levels are shown.Key words: Atmospheric composition and structure (middle atmosphere - composition and chemistry) - Meteorology and atmospheric dynamics (middle atmosphere dynamics)

Total ozone decrease in the Arctic after REP events

Abstract. Eight periods of relativistic electron precipitation (REP) with electron energies of more than 300 keV are identified from VLF data (10-14 kHz) monitored along the Aldra (Norway) - Apatity (Kola peninsula) radio trace. In these cases, anomalous ionization below 55-50 km occurred without disturbing the higher layers of the ionosphere. The daily total ozone values in Murmansk for six days before and six days after the REP events are compared. In seven of eight events a decrease in the total ozone of about 20 DU is observed. In one event of 25 March, 1986, the mean total ozone value for six days before the REP is bigger than that for six days after, but this a case of an extremely high ozone increase (144 DU during the six days). However, on days 3 and 4 there was a minimum of about 47 DU with regard to REP days, so this case also confirms the concept of the ozone decrease after REP. The difference between mean ozone values for periods six days before and six days after the REPs was found also for 23 points in Arctic on TOMS data. The difference was negative only in Murmansk longitudinal sector. Along the meridian of the trace it was negative at high latitudes in both hemispheres and was near zero at low latitudes.Key words: Atmospheric composition and structure (middle atmosphere - composition and chemistry) - Meteorology and atmospheric dynamics (polar meteorology)

Associations between ambient ozone, hydrocarbons, and childhood wheezy episodes: a prospective observational study in south east London

OBJECTIVESTo explore the hypothesis that hydrocarbon species and other air pollutants which accumulate at low and high concentrations of ozone are more directly associated with childhood wheezy episodes than ozone.METHODSProspective...

Effects of different ozone exposure regimes on photosynthesis, assimilates and thousand grain weight in spring wheat

The aim of the study was to compare two ozone exposure patterns with different peak concentrations under equal dose conditions. Spring wheat ( Triticum aestivum cv. ‘Nandu’) was ‘pre-cultivated’ under glasshouse conditions and exposed to two different ozone exposure scenarios (A: 1700–0900 h: 20 ppb, 0900–1700 h: 65 ppb; B: 1600–1200 h: 20 ppb, 1200–1600 h: 110 ppb) in large fumigation chambers for two weeks during anthesis. Control plants received charcoal filtered ambient air (<5 ppb ozone 24 h/day) (CF). Chlorophyll content as well as chlorophyll fluorescence (Fv : Fm ratio) and carbohydrate composition (hexoses, sucrose, starch) were monitored in flag leaves and in the case of carbohydrate content also in the penultimate internode during and after ozone exposure. Thousand grain weight (TGW) was determined for estimating yield effects. Photosynthesis decreased markedly in both treatments expressed as Fv : Fm ratio. In treatment B chlorophyll content (a + b) of leaves was reduced by 40% after 7 and 14 days of exposure ( p ≤ 0.001). Carbohydrate content decreased significantly as compared with CF-plants to 20% ( p ≤ 0.001) in the case of sucrose and starch. Effects were especially pronounced in treatment B (110 ppb for 4 h) and could be observed even seven days after exposure under CF conditions. After 14 days of exposure during anthesis, plants were incapable of recovery as shown by a significant reduction in thousand grain weight of ozone treated plants compared with CF-plants (treatment B: 22% at p ≤ 0.001). Effects on photosynthesis and carbon content even under moderate daily ozone peaks as in treatment A induced a significant yield loss of 11% ( p ≤ 0.001) as well, when applied during anthesis. It can be concluded that under equal dose conditions ozone treatments with comparatively high peak concentration induce more pronounced effects than ozone patterns with moderate peaks.

A new inversion algorithm to retrieve instantaneous values for the aerosol optical depth from spectral irradiance measurements

A new algorithm to determine both the instantaneous values of the aerosol optical depth /spl tau//sub /spl alpha//spl lambda// and the daily atmospheric ozone content Oz is presented. The algorithm is based on inversion methods and uses instantaneous experimental data of the total atmospheric optical depth /spl tau/T/sub /spl lambda//. A description of the method and an analysis of the Oz and /spl tau//sub /spl alpha//spl lambda// values for clear days in Valencia (Spain) is presented. The values estimated by means of this algorithm have been compared with those obtained by the algorithm proposed by Flittner et al. (1993) and by an algorithm, based on Flittner but employing the covariance matrix associated with the experimental errors in its calculations. Experimental measurements of direct spectral irradiance at normal incidence have been used as input parameters in these algorithms. The error analysis shows that the errors introduced by this method are small. Furthermore, the proposed method has the additional advantage of showing the variations of the aerosol optical depth with the optical air mass.

Measuring regional trends in ozone

We model maximum daily ozone concentration at a number of sites in Ontario in terms of weather classes, temperature, season and a moving average error term. In an effort to detect a regional trend in the remaining residuals, we develop a method related to principal components which obtains the linear combination of sites with greatest autocorrelation. We apply this method to data from sites in Southern Ontario and conclude that there was a regional trend in ozone during the period 1980–1992. A similar treatment does not find a general trend in temperature data but does reveal a widening gap in temperature between northern and southern sites.

Atmospheric volatile organic compounds (VOC) at a remote tropical forest site in central Amazonia

According to recent assessments, tropical woodlands contribute about half of all global natural non-methane volatile organic compound (VOC) emissions. Large uncertainties exist especially about fluxes of compounds other than isoprene and monoterpenes. During the Large-Scale Biosphere/Atmosphere Experiment in Amazonia – Cooperative LBA Airborne Regional Experiment 1998 (LBA-CLAIRE-98) campaign, we measured the atmospheric mixing ratios of different species of VOC at a ground station at Balbina, Amazonia. The station was located 100 km north of Manaus, SE of the Balbina reservoir, with 200–1000 km of pristine forest in the prevailing wind directions. Sampling methods included DNPH-coated cartridges for carbonyls and cartridges filled with graphitic carbons of different surface characteristics for other VOCs. The most prominent VOC species present in air were formaldehyde and isoprene, each up to several ppb. Concentrations of methylvinyl ketone as well as methacroleine, both oxidation products of isoprene, were relatively low, indicating a very low oxidation capacity in the lower atmospheric boundary layer, which is in agreement with a daily ozone maximum of <20 ppb. Total monoterpene concentration was below 1 ppb. We detected only very low amounts of VOC species, such as benzene, deriving exclusively from anthropogenic sources.

SMOGSTOP: a model for forecasting maximum daily ozone concentration in Belgium

Every summer, ground level ozone concentrations rise in Belgium and cause episodes of photochemical summer smog. This phenomenon is the cause of well recognised public health distress, especially for people suffering from respiratory diseases. To warn groups of sensitive people against forthcoming smog episodes, VITO (the Flemish Institute for Technological Research) and VMM (the Flemish Environmental Agency) have joined forces to create an ozone pollution forecasting model, called SMOGSTOP (Statistical Model Of Groundlevel Short Term Ozone Pollution). SMOGSTOP is used by Belgian government agencies to issue ozone reports and warnings in the media (TV, radio, internet, etc.). Ozone pollution levels, as well as concentrations of other air pollutants, are monitored in Belgium by the telemetric air quality measuring networks of the three Belgian regions: Flanders, Wallonia and Brussels. The major meteorological variables, such as the windvector, temperature, pressure, humidity and precipitation, are also monitored by the same networks. The historical time series of those variables, generated by the networks, are the source of input data for SMOGSTOP. Photochemical ozone pollution is the result of complex non-linear interactions between atmospheric pollutants and meteorology. As a consequence, it is extremely difficult to determine relationships between source emissions (ozone precursors) and ambient pollutant concentrations (ozone). To deal with this complexity, SMOGSTOP was constructed as an empirical model, applying a VITO tailor-made methodology called stratified pattern matching, to link meteorological and precursor information into ozone forecasts. In this paper, an overview of the process of ozone formation in Belgium is given, followed by the definition of the explanatory variables which will be used in the model. Then the methodology behind the model is reported and finally the results of the forecasting efforts in the period of 1.5.1995 till 31.8.1995 are presented.

Local and regional contributions to photochemical atmospheric pollution in southern France

In France, an important air quality surveillance network is organized by region. Each region has a number of measurement sites available. In southern France for each region studied, measurement sites show highly correlated variations of daily ozone maxima during the summer periods (from April to September). Thus, we can calculate a mean regional distribution representative of each region considered. We can notice a high level of correlation between mean regional distributions for different regions. The Marseilles and Martigues areas are neighboring regions that show high correlation between each other, but rather low with other regions. We observe in these two areas high levels of ozone and primary pollutants. This seems to be the result of phenomena from different scales. Indeed, at meso-scale, the land/sea breeze effect coupled with daily erosion of the stable layer brings ozone and sulfur dioxide polluted air masses over the ground. Lastly, at a synoptic scale, a Scandinavian anticyclone, spreading out over Western Europe and drifting over the European continent, seems to be necessary and sufficient to the formation of ozone episodes in the Marseilles and Martigues regions.

Studying ozone climatology with a regional climate model: 2. Climatology

The Canadian Regional Climate Model with oxidant chemistry (CRCM) has been used to study the climatology and transport of ground‐level ozone in eastern North America. The climatology is derived from simulations of five consecutive Julys from 1990 to 1994. Biogenic emissions are calculated each time step, while anthropogenic emissions are taken to be identical for each simulated July. Comparisons of daily ozone maximum for each individual month suggest that the model is simulating satisfactorily the month‐long periods and usually correctly reproduces the high and low ozone regimes associated with the different parts of the domain and/or the various synoptic conditions, the Ohio region being the exception. The climatological number of exceedences above 80 ppbv, calculated as the monthly average for the 5 years, yields better agreement with the number of exceedences calculated from the observed climatological O3 field than those for the individual months. This behavior suggests that a large fraction of the errors present in each simulation are randomly distributed. Thus it should be possible to obtain fields that are more representative of reality, for applications such as emission reduction scenario studies, by averaging over several long simulations.

An enhanced ozone forecasting model using air mass trajectory analysis

An enhanced ozone forecasting model using nonlinear regression and an air mass trajectory parameter has been developed and field tested. The model performed significantly better in predicting daily maximum 1-h ozone concentrations during a five-year model calibration period (1993–1997) than did a previously reported regression model. This was particularly true on the 28 “high ozone” days ([O 3]>120 ppb) during the period, for which the mean absolute error (MAE) improved from 21.7 to 12.1 ppb. On the 77 days meteorologically conducive to high ozone, the MAE improved from 12.2 to 9.1 ppb, and for all 580 calibration days the MAE improved from 9.5 to 8.35 ppb. The model was field-tested during the 1998 ozone season, and performed about as expected. Using actual meteorological data as input for the ozone predictions, the MAE for the season was 11.0 ppb. For the daily ozone forecasts, which used meteorological forecast data as input, the MAE was 13.4 ppb. The high ozone days were all anticipated by the ozone forecasters when the model was used for next day forecasts.

Daily ozone vertical profile model built on geophysical grounds, for column retrieval from atmospheric high‐resolution infrared spectra

The retrieval of column abundances of atmospheric gases from atmospheric infrared spectra necessarily depends on the choice of the a priori vertical profiles of the atmospheric species involved. Most commonly a standard profile is adopted, and some additional parameter is introduced in the retrieval algorithm for improving the final result. This parameter may be unrelated to geophysical arguments. For the retrieval of ozone columns, it is proposed here to use a model of a priori O3 vertical profiles which better reflect the real state of the atmosphere at the time and location of the measurement. The model profiles depend on the daily local thermal tropopause height and include a climatological seasonality. The model has been developed for the retrieval of ozone columns from high‐resolution Fourier transform infrared (FTIR) solar absorption measurements at the International Scientific Station of the Jungfraujoch in the Swiss Alps. It is demonstrated that the use of the model significantly improves the quality of the spectral fits while minimizing the need for adjusting additional nongeophysical parameters to compensate for atmospheric changes and that it enhances the accuracy of the retrieved O3 column data. Such is done by comparison of the retrieved FTIR O3 data with validated independent O3 data sets from co‐located Système d'Analyse par Observations Zénithales and nearby Brewer instruments. Contrary to some other approaches for improving the FTIR O3 retrieval, the model concept developed here can be applied to O3 observations at any midlatitude site, and it can be implemented in an operational retrieval procedure.

99/03385 Impacts from a fossil fuel power plant on ozone levels in Memphis, Tennessee

The Tennessee Valley Authority (TVA) Allen power plant is located on the Mississippi River in the southwest corner of Memphis, Tennessee. Allen has three coal-fired cyclone boilers with a rated capacity of 272 MW each. It is a Phase 2 plant under Title IV of the Clean Air Act and is the largest single source of NO{sub x} in the Memphis area. TVA plans to reduce Allen NOx emissions through a combination of burning low-sulfur coal (which has the benefit of reducing NO{sub x} emissions while also reducing SO{sub 2} emissions) and installing gas re-burn technology. A modeling study using the SAI, Inc., UAM-V photochemical model was conducted to examine the potential impacts of NO{sub x} reductions on ozone levels in the Memphis area. A series of four model simulations were made in which different Allen emissions scenarios were examined. The focus period of the photochemical modeling was 11--14 July 1995 when measurements in and near Memphis indicated peak hourly ozone levels of 135--140 ppb. This analysis primarily examined computed impacts within 50 km of Memphis. Allen was computed to contribute as much as 20--30 ppb to ground ozone levels 20-50 km downwind using its NO{sub x} emission rate beforemore » Title IV compliance. After compliance it was computed to contribute only about 10--20 ppb. At the same time, maximum daily ozone reductions due to Allen NO{sub x} titration of ozone were between 30 and 60 ppb. These benefits will be reduced by 30--50% after Title IV compliance, and are expected to occur within 30 km of the plant. More model grid cells indicated dis-benefits (net ground-level ozone increases) than benefits on three of the four episode days using the Title IV compliance emission rate. Significant ozone dis-benefits were expected because of the well-documented NO titration of ozone within plumes having a high ratio of NO to volatile organic compounds.« less

Health effects of photochemical smog: seasonal and acute lung function change in outdoor workers

We investigated effects of summer air pollution exposure on outdoor workers in the Fraser Valley, Canada. Fifty farm workers performed spirometry daily before and after each 12–16 h workday from 1 July to 18 August 1994. The mean daily maximum (1 h) ambient ozone concentration was 39 ppb (range 10–89 ppb) and the mean daily maximum 8 h average ozone concentration was 31 ppb (range 5–66 ppb). PM10 concentrations were low (mean 24 h average 16 μg m−3, range 6–30 μg m−3) and highly correlated with ozone. Due to the high level of correlation between ozone, temperature and PM10 it was not possible to separately analyse the effect of each of these variables on lung function. In regression models including daily maximum ozone (an indicator of photochemical smog), an individual's mean lung function level and the Julian date, decreased afternoon FEV1 and FVC, and the daily change (afternoon–morning) corrected for the morning measurement, were associated with ozone. These associations were still apparent the following morning, suggesting a persistent air pollution effect. These results reproduce our earlier finding of persistent lung function decrements in farm workers in the Fraser Valley associated with relatively low concentrations of ambient air pollution. In the subset of 12 individuals who participated in both studies, there was no correlation in individual responses to ozone between the two study periods. During both summer studies we observed a marked seasonal decline in lung function, although lung function levels improved to initial values between the two studies, suggesting a reversible seasonal effect of ozone on lung function. Copyright © 1999 John Wiley & Sons, Ltd.

New observations of ultraviolet radiation and column ozone from Socorro, New Mexico

Measurements of surface ultraviolet irradiances are presented for the period of June 1997 to December 1998 from Socorro, NM (34°N, 107°W). The observations are used with results of radiative transfer calculations to retrieve total column ozone. Mean differences between Socorro daily ozone measurements and Earth Probe TOMS satellite data are −1.8 DU and 0.6 DU for 1997 and 1998, respectively. Unusually low ozone was observed in late November and December of 1998, with levels near or below the lowest ozone in the 17‐year Nimbus‐7 and Earth Probe TOMS record for this location. The clear‐sky correlation between the UV Index at 60° solar zenith angle and total ozone is well described by a power law, with an exponent (Radiation Amplification Factor) of 0.97±0.16. One exception occurred during a 10‐day period in December 1997 and January 1998 in the aftermath of a heavy snow storm, when the UV Index exhibited clear‐sky enhancements of up to 30%. Increases in downwelling ultraviolet radiation were related to a higher effective surface albedo with maximum estimated values between 0.7 to 0.9.

A Hierarchical Approach to Multivariate Spatial Modeling and Prediction

We propose a hierarchical model for multivariate spatial modeling and prediction under which one specifies a joint distribution for a multivariate spatial process indirectly through specification of simpler conditional models. This approach is similar to standard methods known as cokriging and kriging with external drift,' but avoids some of the inherent difficulties in these two approaches including specification of valid joint covariance models and restriction to exhaustively sampled covariates. Moreover, both existing approaches can be formulated in this hierarchical framework. The hierarchical approach is ideally suited for, but not restricted for use in, situations in which known cause/effect' relationships exist. Because the hierarchical approach models dependence between variables in conditional means, as opposed to cross-covariances, very complicated relationships are more easily parameterized. We suggest an iterative estimation procedure that combines generalized least squares with imputation of missing values using the best linear unbiased predictor. An example is given that involves prediction of a daily ozone summary from maximum daily temperature in the Midwest.

Daily ozone patterns and AOT40 index on the East Coast of the Iberian Peninsula

The results from the Valencian Community air quality network show that within a natural pathway of air mass transport (e.g. a valley ) three different 03 diurnal patterns are clearly distinguished: high elevation (HE), midelevation (ME) and coastal sites (CE). HE are characterised by maintaining an almost constant high 03 level throughout the day (no diurnal cycle). CE have maximum levels coinciding with daylight hours and close-to-zero 03 levels at night (diurnal cycle). At ME the maximum values occur in the daylight hours; however, 03 levels never drop to zero. These different patterns occur within a spatial range of 50 to 60 Km, which implies a huge spatial variability in the area, and may strongly affect the values of several indices, e.g. the AOT40. Thus, AOT40 indices for 3 months are calculated as a running value through the year and compared for the different 03 patterns. Also, several daylight windows have been applied in the AOT40 calculations in order to check the sensitivity of the index to the daylight window choice and to the different daily ozone patterns, compared to the AOT40 calculated for hours with radiation>50W/m2 (real daylight period) and to the total exposure dose (TED, 24 h). It has been concluded that most windows estimate up to 90% of the TED in CE, and the estimations drop below 50% of the TED in non-diurnal cycle sites. This could be of importance for species whose period of stomatal conductance do not correspond to the daylight hours.

Total ozone and solar ultraviolet radiation, as derived from satellite and ground-based instrumentation at Dundee, Scotland

Daily ozone measurements from satellite sensor data (Total Ozone Mapping Spectrometer TOMS) over Dundee, Scotland (56.5 N, 3 W) during 1986-1992 with daily broad-band measurements of solar ultraviolet (UV) radiation reaching the ground deduced from ground-based instrumentation were used to investigate their correlation. The erythemally active UV radiation showed an increase of 35% during 1986-1992 while the total ozone amount showed a decrease of 10% during the same period. Furthermore, the ratio of the increase of UV radiation to the decrease in ozone concentration was maximum in July, showing that a small percentage decrease in total ozone during summer leads to a large percentage increase in solar UV radiation reaching the ground.