Total and tropospheric ozone changes: observations and numerical modelling

A survey has been made of total and tropospheric ozone dynamics in the context of its impacts on climate, human health and ecosystems. Observation data on total ozone content (TOZ) in the atmosphere and relevant numerical modelling results have been discussed as well as similar information for tropospheric ozone, whose formation and changes are being determined by quite different causes. A necessity has been emphasized to get more adequate global observational data on TOZ and tropospheric ozone (this is especially important in the latter case, because information on tropospheric ozone is far from being complete). Unsolved problems relevant to both total and tropospheric ozone have been briefly considered

Global total ozone dynamics - Impact on surface solar ultraviolet radiation variability and ecosystems. Part II: Dynamics of atmospheric chemical composition: The role of remote sensing. Part I: Global ozone dynamics and environmental safety (ESPR 3/96, pp. 153-157)

An overview of the ozone issues is given including the following aspects: 1. The impact of tropospheric ozone on climate as a greenhouse gas (GHG), 2. Solar activity effects on TO and ozone concentration vertical profiles in both the troposphere and stratosphere (in cases of solar radiation absorption by the stratosphere, an unexpected problem arises via a coupling between processes of increased absorption due to "bursts" of solar activity and an enhanced destruction of ozone molecules due to the same increase resulting in weakening UV radiation absorption) and 3. Surface ozone concentration variations under conditions of polluted urban atmospheres which lead to episodes of photochemical smog formation (dangerous for human health)

Global total ozone dynamics: Impact on surface solar ultraviolet radiation variability and ecosystems

An overview of the ozone issues is given including the following aspects: 1. The impact of tropospheric ozone on climate as a greenhouse gas (GHG), 2. Solar activity effects on TO and ozone concentration vertical profiles in both the troposphere and stratosphere (in cases of solar radiation absorption by the stratosphere, an unexpected problem arises via a coupling between processes of increased absorption due to 'bursts' of solar activity and an enhanced destruction of ozone molecules due to the same increase resulting in weakening UV radiation absorption) and 3. Surface ozone concentration variations under conditions of polluted urban atmospheres which lead to episodes of photochemical smog formation (dangerous for human health)

Global tropospheric ozone dynamics: Part II: Numerical modelling of tropospheric ozone variability: Part I: Tropospheric ozone precursors

Part I: An overview of the tropospheric ozone changes is presented focussing mainly on the tropospheric ozone precursors. The complexity of the problem is shown through the consideration of a great number of relevant substances, like nitrogen compounds, volatile organic compounds, peroxyacetyl nitrate, hydroxyl radical, carbon monoxide, alkyl nitrates. The up-to-date knowledge on the relevant numerical modelling is presented in Part II. Part II: Various causes of tropospheric changes have been considered in Part I in connection with the analysis of observation data. It is clear however, that the principal instrument for understanding numerous and often interacting causes of ozone changes is numerical modelling. A review of the current status of the numerical modelling has been made for the variability of the ozone concentration in the troposphere. Observation data on tropospheric ozone and relevant numerical modelling results show that a necessity exists to get more adequate global observational data

Atmospheric greenhouse effect in the context of global climate change

Great interest in the problem of the atmospheric greenhouse effect (not only in scientific publications, but also in mass media), on the one hand, and the undoubtfully overemphasised contribution of the greenhouse effect to the global climate change, on the other hand, motivate a necessity to analyse the role which the greenhouse effect plays as a factor of climate change. Significant progress in the analysis of existing observational data as well as succesful development of numerical climate modelling which have been achieved during the recent few years create a basis for a new survey of the atmospheric greenhouse effect in the context of global climate change. Such a survey is the principal purpose of this paper. After discussing a notion of the greenhouse effect, the detailed analysis of the present-day and paleoclimatic observational data has been conducted with subsequent consideration of numerical modelling results. A special attention has been paid to assessments of the greenhouse warming vs. aerosol cooling. Then possibilities of the early detection of a greenhouse climate signal have been analysed and a few comments on the global climate observing system have been made with the general conclusion that more observations and further numerical modelling efforts are necessary to more reliably assess the contributions of various mechanisms to the observed global climate changes. It is only in the context of a coupled totality of significant climate forming factors and processes that the contribution of the greenhouse effect may be estimated. © 1995 Società Italiana di Fisica

Long-term variation in surface ozone and its precursors in Athens, Greece: A forecasting tool

Intention, Goal, Scope, Background. Photochemical pollution is a very complex process involving meteorological, topographic, emission and chemical parameters. The most important chemical mechanisms involved in the atmospheric process have already been identified and studied. However, many unknown parameters still exist because of the large number of participating chemical reactions. Objective. The present study investigates the processes involved in the photochemical pollution effect of an urban station located in the greater area of the Athens basin and gives a plausible explanation for the different seasonal ozone development between that station and another rural one. Furthermore, the distribution of the mean monthly surface ozone observed at the urban station during 1987-2001 is examined in order to create a relevant forecasting tool. Methods. Averaged hourly data of O3 and NOx observations monitored at the above mentioned stations, during 1987-2001, have been used in order to derive the daytime (7:00-15:00) values. Trajectories calculated by using a 2D-trajectory code and meteorological data, during the period 1988-1996, have also been used. Results and Discussion. At the urban station, the percentage negative trend of NO and NOx data in winter and summer is higher than that in spring and autumn, while the percentage ozone trend is maximum in the summer. On the contrary, the negative surface ozone trend at the rural station exhibits a minimum in summer and a maximum in autumn and winter. The mean seasonal wind-rose for the selected months shows that the northward wind flow dominates during June, the month of the lowest negative ozone trend in the rural station. Finally, the development of the forecasting tool shows that the mean monthly surface ozone data during the period (1987-2001) demonstrates a semi-log distribution. Conclusions. Air transport effect on the air pollution of the rural station (not blocked by mountains) is deduced as a possible reason for the different seasonal ozone development observed between the rural and the urban station. Finally, the discrepancies between the theoretical probabilities deduced by the model and the empirical ones appear to be very small, and the corresponding correlation coefficient is 0.99. Recommendation and Outlook. However, to interpret the aforementioned statistical results about the negative trends in ozone and its precursors, additional parameters can be taken into account. Changes in NOx concentrations, for instance, can result not only from changes in emissions or meteorological conditions. There might also be a contribution through changes in the atmospheric composition. A study of the contribution of changes in atmospheric composition to trends of observed NOx concentrations requires that a series of steps be taken (removal of meteorological influence in the time series, calculation of trends in OH concentrations, etc.)

On the seasonal variation of the surface ozone in Athens, Greece

An attempt has been made to examine the seasonal variation of the surface ozone mixing ratio in Athens, Greece during the periods 1901-1940 and 1987-1998. The first finding is that in July and August while the daytime surface ozone mixing ratio from the beginning until the end of the 20th century has increased by approximately 1.8 times, the nighttime surface ozone mixing ratio remained approximately at the same level. The second finding is that the increase in the mean daytime mixing ratio during the transition period from winter to summer is equal to the increase in the maximum daytime mixing ratios, whilst the enhancement of the nighttime surface ozone maxima is stronger than that of the nighttime mean surface ozone mixing ratio. Plausible explanation for this finding is given through mechanisms like long-range transport and photochemical processes occurring in the boundary layer, free troposphere and lower stratosphere. An attempt has been made to examine the seasonal variation of the surface ozone mixing ratio in Athens, Greece during the periods 1901-1940 and 1987-1998. The first finding is that in July and August while the daytime surface ozone mixing ratio from the beginning until the end of the 20th century has increased by approximately 1.8 times, the nighttime surface ozone mixing ratio remained approximately at the same level. The second finding is that the increase in the mean daytime mixing ratio during the transition period from winter to summer is equal to the increase in the maximum daytime mixing ratios, whilst the enhancement of the nighttime surface ozone maxima is stronger than that of the nighttime mean surface ozone mixing ratio. Plausible explanation for this finding is given through mechanisms like long-range transport and photochemical processes occurring in the boundary layer, free troposphere and lower stratosphere. Copyright (C) 2000 Elsevier Science Ltd

An estimation of the surface solar ultraviolet irradiance during an extreme total ozone minimum

A simple theoretical algorithm has been employed to estimate the solar ultraviolet irradiance at Athens, Greece (38.7°N, 23.4°E) during, summertime 1993, a year of extreme total ozone minimum in the existing data record. This estimation has been performed by using total ozone measurements as derived by both ground-based and satellite instrumentation. The utilization of the present investigation will assist to the various assesments for the risk of human health from the biologically-effective doses of the solar ultraviolet radiation arrived at the earth's surface during that time period

On the relationship between total ozone and solar ultraviolet radiation at St. Petersburg, Russia

Daily total ozone observations made with the Total Ozone Mapping Spectrometer (TOMS) flown on the satellite Nimbus‐7 during 1978–1992, have been used in order to investigate the increase in the daily broad‐band and spectral solar ultraviolet radiation reaching the ground through a recently developed parametric model. Total ozone reductions of 3.0% during summer time and 11% during winter time per decade, at St. Petersburg (60°N, 30°E), Russia, cause an increase in erythematically active ultraviolet irradiance of at least 7% and 22%, respectively. Copyright 1995 by the American Geophysical Union

Long-term variation in surface ozone and its precursors in Athens, Greece: A forecasting tool

Intention, Goal, Scope, Background. Photochemical pollution is a very complex process involving meteorological, topographic, emission and chemical parameters. The most important chemical mechanisms involved in the atmospheric process have already been identified and studied. However, many unknown parameters still exist because of the large number of participating chemical reactions. Objective. The present study investigates the processes involved in the photochemical pollution effect of an urban station located in the greater area of the Athens basin and gives a plausible explanation for the different seasonal ozone development between that station and another rural one. Furthermore, the distribution of the mean monthly surface ozone observed at the urban station during 1987-2001 is examined in order to create a relevant forecasting tool. Methods. Averaged hourly data of O3 and NOx observations monitored at the above mentioned stations, during 1987-2001, have been used in order to derive the daytime (7:00-15:00) values. Trajectories calculated by using a 2D-trajectory code and meteorological data, during the period 1988-1996, have also been used. Results and Discussion. At the urban station, the percentage negative trend of NO and NOx data in winter and summer is higher than that in spring and autumn, while the percentage ozone trend is maximum in the summer. On the contrary, the negative surface ozone trend at the rural station exhibits a minimum in summer and a maximum in autumn and winter. The mean seasonal wind-rose for the selected months shows that the northward wind flow dominates during June, the month of the lowest negative ozone trend in the rural station. Finally, the development of the forecasting tool shows that the mean monthly surface ozone data during the period (1987-2001) demonstrates a semi-log distribution. Conclusions. Air transport effect on the air pollution of the rural station (not blocked by mountains) is deduced as a possible reason for the different seasonal ozone development observed between the rural and the urban station. Finally, the discrepancies between the theoretical probabilities deduced by the model and the empirical ones appear to be very small, and the corresponding correlation coefficient is 0.99. Recommendation and Outlook. However, to interpret the aforementioned statistical results about the negative trends in ozone and its precursors, additional parameters can be taken into account. Changes in NOx concentrations, for instance, can result not only from changes in emissions or meteorological conditions. There might also be a contribution through changes in the atmospheric composition. A study of the contribution of changes in atmospheric composition to trends of observed NOx concentrations requires that a series of steps be taken (removal of meteorological influence in the time series, calculation of trends in OH concentrations, etc.)