title: An improved dual channel PERCA instrument for atmospheric measurements of peroxy radicals.
abstract: This paper describes a new dual-channel PEroxy RadiCal Amplification (PERCA) instrument, which has been designed to improve the time resolution and signal to noise and to reduce the interference caused by variations in ambient ozone concentrations. The instrument was run at the Weybourne Atmospheric Observatory (WAO), North Norfolk, during WAOWEX (Weybourne Atmospheric Observatory Winter Experiment) in January/February 2002 and INSPECTRO (Influence of clouds on the spectral actinic flux in the lower troposphere) in September 2002. The performance of the instrument is assessed and compared to that of a single channel instrument. In particular, it is shown how the precision is greatly improved in fluctuating background ozone conditions. In addition the improved time response of the instrument allows changes in peroxy radical concentrations to be related to rapid changes in nitric oxide concentrations and the ozone photolysis frequency, j(O(1)D).
authors: School of Environmental Science, University of East Anglia, University Plain, Norwich, UKNR4 7TJ.
authors: Timothy J
authors: TJ
authors: Green
authors: Claire E
authors: CE
authors: Reeves
authors: Zoe L
authors: ZL
authors: Fleming
authors: Neil
authors: N
authors: Brough
authors: Andrew R
authors: AR
authors: Rickard
authors: Brian J
authors: BJ
authors: Bandy
authors: Paul S
authors: PS
authors: Monks
authors: Stuart A
authors: SA
authors: Penkett