Part of the UK's contribution to a Europe-wide programme of air monitoring under the UN Economic Commission for Europe's Convention on Long Range Transboundary Air Pollution. The monitoring is done under the auspices of EMEP (Co-operative Programme for Monitoring and Evaluation of the Long-range Transmission of Air Pollutants in Europe), and contributes data to a central European database (currently in Norway). The results are used to evaluate the levels of air pollution across Europe, to identify trends, and for comparison with computer model outputs. Harwell is also used as part of the the Automated Urban and Rural Network (AURN), the UK Precipitation Network, the UK Hydrocarbons Network, and the UK Heavy Metals Rural Network. A second EMEP site is located at Auchencorth Moss, which is run (on behalf of Defra) by CEH.