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144064 - atmospheric modelling of grass pollen.pdf (3.24 MB)

Atmospheric modelling of grass pollen rupturing mechanisms for thunderstorm asthma prediction

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posted on 2023-05-20, 22:58 authored by Emmerson, KM, Silver, JD, Thatcher, M, Wain, A, Penelope JonesPenelope Jones, Dowdy, A, Newbigin, EJ, Picking, BW, Choi, J, Eber, E, Bannister, T
The world's most severe thunderstorm asthma event occurred in Melbourne, Australia on 21 November 2016, coinciding with the peak of the grass pollen season. The aetiological role of thunderstorms in these events is thought to cause pollen to rupture in high humidity conditions, releasing large numbers of sub-pollen particles (SPPs) with sizes very easily inhaled deep into the lungs. The humidity hypothesis was implemented into a three-dimensional atmospheric model and driven by inputs from three meteorological models. However, the mechanism could not explain how the Melbourne event occurred as relative humidity was very low throughout the atmosphere, and most available grass pollen remained within 40 m of the surface. Our tests showed humidity induced rupturing occurred frequently at other times and would likely lead to recurrent false alarms if used in a predictive capacity. We used the model to investigate a range of other possible pollen rupturing mechanisms which could have produced high concentrations of SPPs in the atmosphere during the storm. The mechanisms studied involve mechanical friction from wind gusts, electrical build up and discharge incurred during conditions of low relative humidity, and lightning strikes. Our results suggest that these mechanisms likely operated in tandem with one another, but the lightning method was the only mechanism to generate a pattern in SPPs following the path of the storm. If humidity induced rupturing cannot explain the 2016 Melbourne event, then new targeted laboratory studies of alternative pollen rupture mechanisms would be of considerable value to help constrain the parameterisation of the pollen rupturing process.


Publication title

PLoS One










Menzies Institute for Medical Research


Public Library of Science

Place of publication

United States

Rights statement

Copyright 2021 Emmerson et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

Repository Status

  • Open

Socio-economic Objectives

Atmospheric processes and dynamics; Natural hazards not elsewhere classified; Public health (excl. specific population health) not elsewhere classified

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