Introduction
Understanding the composition of the troposphere is the overarching theme of our research. The holy grail for tropospheric chemistry modellers is to understand and quantify tropospheric O₃. Tropospheric O₃ is a greenhouse gas with a radiative forcing comparable to that of CH₄. It is produced by the photochemical oxidation of carbon monoxide and natural and anthropogenic volatile organic compounds (VOCs) in the presence of nitrogen oxides. It is also one of the main ingredients of photochemical smog, that often plagues large cities such as Los Angeles, and at elevated concentrations cause respiratory illnesses and reduced yields of agricultural crops. There are many aspects to understanding tropospheric O₃ some of which we tackle in this group and are described in these webpages

Smog over Houston TX

General Areas of Current Research

• Data analysis
  Ground-based and aircraft observations of atmospheric composition have been central to our understanding of chemistry in the troposphere [1,2]. Progressively more important is the use of satellite data in putting local and regional-scale data on a global scale [3,4,5,6].
• Numerical modelling of atmospheric and oceanic chemistry
  We use a heirachy of chemistry models to analyse atmospheric and oceanic measurements: from simple chemical mass balance [6], to balanced carbon model of the terrestrial biosphere [7] to sophisticated chemical transport model [8,9]. We are involved with the development of the TOMCAT chemistry transport model that uses assimilated ECMWF meteorology. In collaboration with Professor Mike Pilling (University of Leeds) we are also involved with helping to evaluate small subsets of the Master Chemical Mechanism using field measurements.
• Surface flux estimation
  We apply formal and ad hoc inverse methodologies to estimate the magnitude and uncertainty of surface fluxes of anthropogenic, pyrogenic and biospheric gases and particles using a range of datasets [3,10,11]. This is also known as the "top-down" emission inventory approach. We are also actively involved with the development of "bottom-up" parameterizations of biospheric VOC fluxes [12].
• In situ chemical processing of gases and particles
  We have used the ratio of long- and short-lived (or soluble and insoluble) trace gases to quantify the export efficiency of black carbon [13] and also the sink of cloud condensation nuclei against wet deposition [14]. A better quantitative understanding of these processes improves our estimates of their radiative forcing on climate. We are extending this analysis to more reactive chemical species that require more detailed chemistry.