Influence of Model Resolution on Simulated Extreme Wildfire Plume Heights During the 2019/2020 Australian New Year Event

Pyrocumulonimbus (pyroCb) events, smoke-infused thunderstorm clouds triggered by intense wildfires under suitable meteorological conditions, are an efficient pathway for transporting smoke to elevated altitudes. In some cases, smoke reaches the upper troposphere and lower stratosphere region, where it can persist for extended time periods and influences climate, air quality, and atmospheric composition. The initial injection height of a wildfire plume is a key parameter in wildfire modeling. Plume-rise models are commonly employed to determine injection heights, yet they often underestimate the heights reached during extreme events. This bias is amplified in global simulations with relatively coarse spatial resolution, where key dynamical processes cannot be adequately resolved. This leads to biases such as a reduced aerosol lifetime and changes in smoke transport patterns. One way to address this is by taking the sensible heat release of the fire and the resulting feedback onto its surrounding atmosphere into consideration. We investigate the 2019/2020 Australian New Year wildfire event, which featured significant pyroCb activity, using simulations at three different horizontal resolutions. We show that the inclusion of the sensible heat release makes the plume rise model outcomes more resolution-dependent, and the plume rise model still fails to reproduce the highest observed plume heights. To improve accuracy, we develop a resolution-dependent enhancement to the sensible heat release term that improves agreement with satellite observations of plume height. Our findings highlight the need to account for resolution effects when taking feedbacks via the sensible heat release into consideration.