The chemistry of the Atmosphere
Whether for understanding the causes and effects of global climate change or local air pollution, the chemistry of the gases and particles present in our atmosphere is a paramount area of research. To study this topic requires an approach that combines fundamental laboratory studies on the physico-chemical properties of atmospheric constituents with observations of the abundance and variability of these moities and numerical model simulations that integrate our understanding of the sources and fate of these compounds and with which we can test hypothesis on how they will change under different conditions.
My research involves the development and application of state-of-the-art chemistry-climate models. With these models we are trying to answer a number of questions relevant to society: (i) What are the impacts of changes in man made emissions on the composition of the atmosphere (ii) how does the changing composition of the atmosphere affect climate (iii) how will a changing climate impact the composition of the atmosphere.
- The mechanisms of oxidation of biogenic hydrocarbons
One of the main areas of research in my group is trying to better understand the mechanisms of oxidation of biogenic hydrocarbons - in particular the oxidation of isoprene. Isoprene enters the atmosphere via emissions from plants and trees. Every year a mass roughly equal to that of the entire human population is emitted into the atmosphere! Owing to this, and its high reactivity, it is paramount to include isoprene chemistry in chemistry-climate models. However, the details of the chemistry vary wildly between models and isoprene chemistry has been suggested as a major cause of disagreement between model predictions of secondary pollutants. The figure below highlights some of the chemistry of isoprene oxidation initiated by the hydroxyl radical.
- The impacts of fracking on air quality
In collaboration with the Met Office my group is also looking at the role of fracking in the UK, and the impacts of unconventional hydrocarbon extraction on air quality. For this work we use a version of the Met Office weather forecast model modified for simulating air pollution. The animation below shows the domain this model covers and the simulated levels of the pollutant ozone (O3) from the model.
- Long range transport of trace gases
Gases that have lifetimes against chemical reaction in the atmosphere greater than a few days can be transported over great distances. The animation below shows how the ozone depleting substance methyl chloride (CH3Cl) can be emitted from fires in Brazil and transported over several days and 100s of km across South America. Daily average observations of CH3Cl recorded at the AGAGE monitoring site in Barbados are plotted below the animation and you can see that there are several periods where "spikes" are seen in these data. We try to understand both the roles of atmospheric transport and chemistry over these long ranges to answer questions such as how will changes in emissions downwind of us impact the quality of the air we bretahe?
For more information about the groups published work see my publications below and my Google scholar page.
For more information about Alex check out his ORCID
Dr Kalberer and I lecture a part II course on chemistry in the atmosphere. For those interested in looking at some simple numerical problems concerning atmospheric chemistry, feel free to have a play with this simple R script: https://bitbucket.org/alex_archibald/atmos_chem_model
- 1 of 7