Alan Plumb has performed pioneering work on atmospheric fluid dynamics, connecting fluid-dynamical insight and cutting-edge numerical simulation techniques with new observational information from high-resolution, multi-species chemical measurements. He has brought to bear original thinking about Lagrangian atmospheric transport leading to new insight into the interplay between chemical and dynamical effects, showing the way to a new generation of simplified global ‘ozone assessment models’ having far greater realism than current such models while demanding less computer power. This is of the highest importance in assessing the likely response of the ozone layer to, for example, future subsonic and supersonic passenger aviation. Throughout his career, Alan has consistently and repeatedly put his finger on key points about causal linkages in the atmosphere and made these points clear through outstandingly lucid papers and conference presentations, whilst upholding the highest standards of integrity and generosity to colleagues. One famous, influential and characteristic example is the work that led to the 1978 Plumb–McEwan experiment — the laboratory analogue of the quasi-biennial oscillation of the zonal winds in the equatorial stratosphere.