BIOSPHERE-ATMOSPHERE INTERACTIONS

My research interests lie in exploring the nature and magnitude of interactions between the biosphere and atmosphere resulting from the emissions of reactive trace gases from vegetation. I am particularly interested in the role that such gases may play in governing the response of the Earth system to future changes in climate and land use.

Tropospheric ozone and aerosol particles have significant impacts on air quality and climate. The biosphere is a major source of both tropospheric ozone and fine particulate matter (e.g. PM_2.5) through emissions of precursor trace gases or biogenic volatile organic compounds (bVOCs). The composition of the atmosphere is also known to impact the biosphere through, for example, increased primary productivity under high atmospheric concentrations of CO₂, highlighting the potential for strong coupling within the system. While climate change directly alters bVOC emissions, atmospheric composition (i.e. the mixing ratio of CO₂ but also O₃) also affects the bVOC flux both directly, by stimulating or inhibiting VOC synthesis and release, or indirectly via plant productivity. These interactions result in feedbacks between the biosphere and atmosphere that can mitigate or exacerbate the initial perturbations, on both local and global scales.

CURRENT RESEARCH

I am currently in the third year of a PhD entitled “Atmospheric impacts of biofuel cultivation” which explores the potential effects of the cultivation of biofuel feedstock crops on atmospheric composition, air quality and climate through associated changes in emissions of bVOCs. I use realistic small-scale changes in planting that reflect the projected global demand for biofuels for transportation in the near future (2020s). When current vegetation is replaced with biofuel crops, such as oil palm and short rotation coppice (species such as willow and poplar) the flux of bVOCs to the atmosphere is altered in magnitude, spatial distribution and precise compound mix, leading to changes in the abundance of climate and air quality relevant species such as ozone and secondary organic aerosols in the troposphere.

Figure showing projected changes in mean surface ozone concentrations (ppbv) over Europe in July using the HadGEM2 model. These changes are the result of alterations in isoprene emissions due inter-planting current crops and grasses with short rotation coppice for use as biofuel feedstocks.

My research involves the use of a range of FORTRAN models to simulate the changes in emissions and the subsequent changes in atmospheric composition. These include a bVOC emissions model MEGAN (Model of Emissions of Gases and Aerosols from Nature), a chemistry transport model FRSGC/UCI, and the UK Met Office’s Earth system model, HadGEM2.

My research is funded through a studentship from NERC (the Natural Environment Research Council).

Publications

Ashworth K., Hewitt C.N., Wild O. (2010) Sensitivity of isoprene emissions estimated using MEGAN to the time resolution of input climate data, Atmospheric Chemistry and Physics, 10, 1193-1201, 2010 (pdf, supplement)