Here you can read more about some of the things that we have discovered in the Chemistry Modelling group. Selected highlights are listed under six themes which span the our research.

Stratospheric Ozone Layer

The stratospheric ozone layer shields the Earth's surface from damaging ultraviolet radiation. It also plays an important role in the Earth's climate balance.

• Arctic Ozone Depletion: We investigate the processes responsible for polar ozone depletion use our models to quantify the extent of this loss. Our model showed record depletion in the Arctic winter 2010/11 due to exceptionally cold temperatures.
• Stratospheric Brewer-Dobson Circulation: Air is transported very slowly through the stratosphere in the so-called Brewer-Dobson circulation. We have used our models to improve how this circulation is treated in weather forecast models.
• Chemical Data Assimilation: The technique of data assimilation is used routinely in numerical weather prediction to create meteorological analyses. We have included a sequential chemical data assimilation in our model that has the ability to assimilate many species simultaneously and preserve tracer correlations.
• Solar Variability: Radiation from the sun varies naturally over an 11-year cycle. We study the effect of this solar variation on stratospheric ozone and the lower atmosphere.
• Recovery of the Ozone Layer: Our research involves detecting and understanding chlorine/bromine trends and predicting the extent and timing of ozone layer recovery as a result of the Montreal Protocol. We are also interested in the climate impact of the recovering ozone layer.

Tropospheric Composition

The oxidizing capacity of the troposphere determines the lifetime of many pollutants (e.g. CO) and greenhouse gases (e.g. CH₄). The primary oxidant OH is continually produced and destroyed in the troposphere through complex gas-phase chemistry.

• Short-Lived Halogenated Species: Natural emissions of compounds from the oceans are an important source of bromine and iodine in the troposphere. Some of this may reach the stratosphere. 
• Dimethyl Sulphide (DMS): DMS is an important precursor for clouds and changes to the DMS budget may have implications for climate. We investigate the oxidation of dimethyl suiphide by halogens.

Atmospheric Chemistry and the Earth system

• Forest fires: Fires emit trace-gases and aerosol to the atmosphere which affect climate and air quality. We have shown that the intensity of forest fires in the boreal regions is related to El Nino climate variability, and these fires dominate the interannual variability of Arctic CO.
• Ozone-vegetation interactions: Vegetation cover affects tropospheric ozone through providing an efficient surface for dry deposition and through biogenic isoprene emissions. We demonstrate the sensitivity of pre-industrial ozone to land cover change in an Earth system model.

Air Quality

We work with the Met Office to study UK Air Quality

• AQUM:The Met Office use the AQUM to produce short-term forecasts of chemical weather and air quality. We are currently using satellite observations to validate the AQUM, as well as surface observations.
• Ozone and Crops: Ozone in the troposphere can damage crops. We quantify for the first time how ozone produced in one continent destroys crops in other continents.
  

Greenhouse Gases and Carbon Fluxes

We use our models in both 'forward' and 'inverse' mode to investigate the global sources and sinks of important greenhouse gases such as CO₂ and CH₄.

• CH4

Mesospheric Chemistry

In collaboration with Prof. John Plane in the School of Chemistry we also research into metal chemistry and meteor smoke particle deposition in the mesosphere.

• Satellite Observations and Global Modelling of Metal Layers: We have made new satellite retrievals of the metal layers near 80 km, and studied them by adding new chemistry schemes to a chemistry-climate model.
• Modelling of Smoke Particle Transport and Deposition: We use our global 3-D models to study the interaction of meteoric smoke particles with stratospheric sulphuric acid particles and how the smoke particles are deposited at the Earth’s surface.