On the intensity decay of tropical cyclones before landfall

It remains unclear how tropical cyclones (TCs) decay from their ocean lifetime maximum intensity (LMI) to landfall intensity (LI), yet this stage is of fundamental importance governing the socio-economic impact of TCs. Here we show that TCs decay on average by 25% from LMI to LI. A logistic decay model of energy production by ocean enthalpy input and surface dissipation by frictional drag, can physically connect the LMI to LI. The logistic model fits the observed intensity decay as well as an empirically exponential decay does, but with a clear physical foundation. The distance between locations of LMI and TC landfall is found to dominate the variability of the decay from the LMI to LI, whereas environmental conditions are generally less important. A major TC at landfall typically has a very large LMI close to land. The LMI depends on the heating by ocean warming, but the LMI location is also important to future landfall TC intensity changes which are of socio-economic importance.

Automated summary

The decay process of tropical cyclones from their ocean maximum intensity to landfall intensity remains unclear, but it is of fundamental importance in determining the socio-economic impact of these cyclones. This study presents a logistic decay model that connects the maximum intensity to landfall intensity based on energy production and surface dissipation. The distance between the maximum intensity and landfall location is found to be the dominant factor in the decay process, while environmental conditions are generally less influential.