Dynamical controls on intensity-duration characteristics of heatwaves in an idealised model

An idealised climate model is used to study the contribution of the atmospheric circulation to the intensity-duration characteristics of heatwaves. Using the observed correlation between near-surface temperature and lower tropospheric dry static energy (DSE), we study the energetics of the lower troposphere during heatwaves in the model. We observe that, remarkably, the intensity-duration characteristics of heatwaves are primarily controlled by zonal advection of DSE, parallel to the climatological gradient of DSE. In regions of non-zero climatological lower tropospheric winds, this leads to a phenomenon which we term as a heatwave "conveyor belt" where DSE anomalies advected by the climatological winds lead to DSE accumulation profiles which determines heatwave intensity and duration. We show that changes in intensity-duration characteristics by latitude are primarily determined by changes in the magnitude of the zonal winds. Our results propose a new, circulation focused viewpoint to study heatwave characteristics.