General introduction of TEMIS

The changing composition of the Earth's atmosphere

The composition of the atmosphere has undergone dramatic changes since pre-industrial times due to increased emissions related to human activity, e.g. industry, transport, heating, changed land use and agriculture, biomass burning. These atmospheric changes are manifesting themselves through aspects like climate change (heating of the Earth related to greenhouse gases such as CO2 and CH4), air pollution (e.g. smog, acid rain), ozone depletion and the ozone hole. In response to this, several international agreements and protocols have emerged, such as the Montreal and Kyoto protocols.

Monitoring of atmospheric trace gases is of importance to quantify the concentrations of atmospheric trace gases. Based on solid observational data, and the global information provided by satellite instruments, top-down estimates can be made of the world-wide distribution of anthropogenic and natural emissions. The extension of the present-day monitoring network with new satellite observations will be important, given that emission inventories are characterised by large uncertainties. Observational data sets will provide the quantitative background knowledge to assess the implementation of present protocols, and they will form the basic source of information for future protocols.
 
Ozone and UV  
In the years following the discovery of the Antarctic ozone hole, the cause of the breakdown of ozone has been convincingly attributed to the emissions of chlorofluorocarbons (CFC's). The Montreal protocol and later amendments have led to a strong decrease in the production of man-made CFC's, which is expected to result in the recovery of the ozone layer in the coming decades. The amount of harmful ultraviolet (UV) radiation that will reach the Earth's surface is directly related to the thickness of the UV absorbing ozone layer (between 10-40 km altitude). Satellite monitoring of the ozone layer lies at the basis of UV analysis and UV index forecast.
 
Greenhouse effect  
Several gases in the Earth's atmosphere - such as carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O), ozone (O3) and the chlorofluorocarbons (CFC's) - trap infrared radiation, which leads to heating of the lower atmosphere and the Earth's surface: the greenhouse effect. Also small atmospheric particles, aerosols, have a large but difficult to quantify impact on the radiation budget. The Kyoto protocol discusses measures that would result in a reduction of the emissions of CO2 and other greenhouse gases.
 
Air pollution  
Air pollution has become a global issue. Much of the anthropogenic air pollution travels long distances and affects areas far from the emission source. Air pollution results in health effects for humans, has a damaging effect on flora and fauna, and causes acid rain. It is related to the large-scale fossil fuel combustion and fossil-fuel related activities, but also to biomass burning and changes in land use. The emissions of oxides of nitrogen (NO and NO2) and sulphur (SO2) leads to acid rain and result in photochemical smog and ozone formation.

Objectives of the TEMIS project

The TEMIS project contribute to the central issues mentioned above by generating data sets of several key species and by providing free access to these data sets via internet. Within the TEMIS project, long-term data sets are generated for ozone, UV, aerosols and several of the trace gases mentioned. Advanced retrieval techniques, chemistry transport modelling and data assimilation techniques are used to derive high-quality tropospheric products based on the mesaurements of UV-VIS satellites. These data sets are made freely available through a user-friendly interface.
Involvement of users  
The implementation of the TEMIS service results from direct interactions with parties interested in the tropospheric satellite data products. The choice of data sets that are delivered through the TEMIS internet service depend on the requests and requirements from these users.

TEMIS was a project within the Data User Programme (DUP) of the European Space Agency (ESA)