International Fieldwork Intercomparison

Scientists from the Atmospheric and Planetary Chemistry group have participated in a major instrument intercomparison held at the large outdoor SAPHIR chamber in Germany between 5-17 October 2015.

Led by NCAS scientist Dr Lisa Whalley, the instrumentation was operated by PhD students Danny Cryer and Charlotte Brumby from the research groups of Professors Dwayne Heard and Paul Seakins, and supported by Dr Daniel Stone and another NCAS Scientist Dr Trevor Ingham.

Chemical oxidation in the atmosphere removes trace gases emitted by natural and anthropogenic processes, and is initiated primarily by the hydroxyl radical, OH. There are many 1000s of chemical species which react with OH, and hence it is very difficult during field studies to be confident that the majority of the OH sinks are measured. A new technique has emerged over the last decade which via a single measurement, called the OH reactivity, is able to quantify the total rate of removal of OH by reaction with its myriad of sinks.The intercomparison involved 8 separate instruments based on a number of distinct methods from the UK (Leeds), Germany, France, Finland and the USA, which simultaneously sampled from the SAPHIR chamber.

The University of Leeds FAGE OH reactivity instrument is part of the NCAS Atmospheric Measurement Facility (AMF). As well as a number of instrument tests, whereby fixed amounts of individual OH sinks were added to the chamber under a wide range of conditions, the experiments also involved sampling biogenic emissions from the adjacent Jülich plant chamber, and also a mix of typical urban emissions over a wide range of NOx. A large quantity of data was collected, and following a deadline of January 2016 for the submission of data, a workshop will be held in the spring of 2016 to compare and discuss the findings. For further information about the AMF see