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Dr Michael Cotterell

Dr Michael Cotterell

Dr Michael Cotterell
PhD, MSci

NERC Research Fellow

Area of research

Aerosol Optical Spectroscopy

Office E113
School of Chemistry,
Cantock's Close, Clifton BS8 1TS
(See a map)

+44 (0) 117 928 7665



Michael I. Cotterell is a NERC Independent Research Fellow in the School of Chemistry. He completed his PhD (2016) with Prof. Jonathan Reid (JPR) and Prof. Andrew Orr-Ewing FRS at the University of Bristol, where he developed an entirely new and accurate approach for measuring light extinction by single aerosol particles; an optical trap confined a single particle (SP) over indefinite periods in a controllable environment and its evolving extinction measured using cavity ring-down spectroscopy (CRDS). This SP-CRDS approach measures aerosol optical properties to an accuracy far superior to that achieved by other techniques. The size dependence in aerosol extinction can be measured for a range of hygroscopic and semi-volatile aerosol and Dr Cotterell 's research has demonstrated the accuracy in subsequent refractive index (RI) retrievals is better than ±0.05%. These measurements are key to understanding how aerosol evolves in the atmosphere with uptake/loss of water in response to humidity or the evaporation/condensation of semi-volatile species. Parameterisations of aerosol RI developed by Dr Cotterell are included in the University of Oxford Aerosol Refractive Index Archive. His PhD research was selected by the Aerosol Science and Technology journal for a video abstract based on an excellent peer review of a submitted manuscript (doi: 10.1080/02786826.2016.1219691).

Dr Cotterell's postdoctoral work, with Prof. Jim Haywood at the University of Exeter and Dr Justin Langridge at the Met Office, focussed on developing a new high capability Ensemble Cavity Ring-Down and PhotoAcoustic Spectroscopy (E-CRD-PAS) instrument for airborne studies of aerosol optical properties on the UK research aircraft (FAAM BAe-146). He performed airborne measurements of biomass burning aerosol over the South East Atlantic during the CLARIFY-2017 field campaign. Dr Cotterell continues to collaborate extensively with the UK Met Office, where he leads on using E-CRD-PAS to understand the evolution of atmospheric aerosol optical properties with changes in mixing state and on ageing through careful studies of laboratory-generated aerosol. These laboratory measurements have recently extended to brown carbon aerosol.


  • Aerosol optical properties
  • Cavity ring-down spectroscopy
  • Photoacoustic spectroscopy
  • Single particle trapping



Chemistry staff

Research sections

Recent publications

View complete publications list in the University of Bristol publications system

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