The Polluted Troposphere Programme was a 5-year NERC thematic research programme which was centred upon the study of polluted boundary layer air and its transport to the free troposphere. The programme focussed on the regional scale, defined as intermediate between urban and hemispheric.

Tropospheric ORganic CHemistry Experiment (TORCH) was a NERC Polluted Troposphere Research Programme project (Round 1 - NER/T/S/2002/00145. Duration 2002 - 2005) led by A. Lewis, University of York.

Organic compounds are found throughout the atmosphere and contribute to the generation of both fine aerosol and photochemical oxidants such as ozone. The project contains comprehensive and integrated programme of modelling and measurements to address three inter-linked areas of current uncertainty:

-To increase understanding of the role played by primary and partially oxidised organics in gas phase photochemistry.
-To develop thermodynamic and microphysical descriptions of organic aerosol and use them in improved models of behaviour in the atmosphere.
-To investigate the production, composition and evolution of organic aerosol and its links with gas phase organic oxidation.

The goals were to provide both a detailed data set on organic composition in the polluted atmosphere, and to develop theoretical and modelling tools which may be used in defining future air quality policy.
The Tropospheric Organic Chemistry experiment would formed a multi-institution consortium project with the Polluted Troposphere programme.

The TORCH project consists of two intensive measurement campaigns :

Writtle site TORCH 1
- Based at Writtle College, near Chelmsford, Essex between 27th July - 30th August 2003.
- The measurement site was located 20 miles from London and 10 miles from the M25 thus giving the opportunity to sample air recently outflowing from the London area.
- Over 50 scientists from 7 institutions were involved, using a comprehensive suite of instruments that measured: O3, CO, NO, NO2, C2-C8 hydrocarbons, C1-C4 oxygenated hydrocarbons, PAN, Peroxides (Organic and Inorganic), Organic nitrates, OH and HO2 radicals, Sum of RO2 + HO2 radicals, OH chemical lifetime, Photolysis frequencies (e.g. j(O1D), j(NO2), j (HCHO), Aerosol number and size distribution, Aerosol composition, Local meteorology, and 5 and 10 day back trajectories. Many of the instruments were also part of the Universities Facility for Atmospheric Measurement (UFAM).

TORCH 2
- This took place in April and May 2004 at Weybourne Atmospheric Observatory, on the north Norfolk coast.
- The same complement of instruments was used to sample air with a longer processing time (8-16 hours) Data is currently being validated and will be available shortly.

Over 50 scientists from 7 institutions were involved, using a comprehensive suite of instruments that measured: O3, CO, NO, NO2, C2-C8 hydrocarbons, C1-C4 oxygenated hydrocarbons, PAN, Peroxides (Organic and Inorganic), Organic nitrates, OH and HO2 radicals, Sum of RO2 + HO2 radicals, OH chemical lifetime, Photolysis frequencies (e.g. j(O1D), j(NO2), j (HCHO), Aerosol number and size distribution, Aerosol composition, Local meteorology, and 5 and 10 day back trajectories. Many of the instruments are also part of the Universities Facility for Atmospheric Measurement (UFAM).