Ozone and NO2

Example of assimilated OMI NO2 data into the LOTOS-EUROS model (project MACC)

The groundlevel concentrations of ozone, especially in rural areas, and of NO2, especially in the urban environment, are an important policy issue in terms of human health, eco-system exposure and the corresponding attainment of air quality and deposition standards. There is a need for detailled modelling of NO2 and O3, both in operational air quality forecasting and in analysis to determine the contributions of different sources like traffic, industry, agriculture to the occuring concentrations and deposition. Using observations from ground level and from satellites and combining them with modelling by data assimilation will improve the resulting concentration fields.

High in the atmosphere, so in the stratosphere, ozone acts as a sunscreen shielding humans, animals and plants from UV radiation coming from the sun, where as at groundlevel, in elevated concentrations, ozone is harmfull. So, there is "good" ozone in the stratosphere and "bad" ozone at groundlevel, although it is the same molecule, O3. Ozone, as a principal constituent of photochemical smog, "summersmog", and which is formed by reactions between NO2 and VOC under the influence of sunlight, is harmful for human health, especially for children, elderly people and those with chronic respiratory diseases, and causes damage to vegetations like trees and crops.

In Europe, nitrogen oxides pollute the air as a results of traffic and energy production. NOx is also a precursor for a number of harmful secondary air pollutants including nitric acid, the nitrate part of secondary inorganice aerosols and photo oxidants including ozone. Concerning health risks, NOx at the occuring concentration levels, might be more an indicator than directly harmful itself.
Example of modelled NO2-column for the Netherlands in July

Chemical interaction
Because of the close interrelation between ozone and nitrogen oxides, the research and applications involving ozone often involve that of nitrogen oxides and visa versa. Combined research, for example simulation by LOTOS-EUROS in combination with satellite observations of NO2 is applied to deliver specific products for the regional monitoring of ozone and nitrogen oxides concentrations and deposites, as well as operational forecasting of smog across Europe.