An Open-Source, Physics-Based, Tropical Cyclone Downscaling Model With Intensity-Dependent Steering

An open-source, physics-based tropical cyclone (TC) downscaling model is developed, in order to generate a large climatology of TCs. The model is composed of three primary components: (a) a random seeding process that determines genesis, (b) an intensity-dependent beta-advection model that determines the track, and (c) a non-linear differential equation set that determines the intensification rate. The model is entirely forced by the large-scale environment. Downscaling ERA5 reanalysis data shows that the model is generally able to reproduce observed TC climatology, such as the global seasonal cycle, genesis locations, track density, and lifetime maximum intensity distributions. Inter-annual variability in TC count and power-dissipation is also well captured, on both basin-wide and global scales. Regional TC hazard estimated by this model is also analyzed using return period maps and curves. In particular, the model is able to reasonably capture the observed return period curves of landfall intensity in various sub-basins around the globe. The incorporation of an intensity-dependent steering flow is shown to lead to regionally dependent changes in power dissipation and return periods. Advantages and disadvantages of this model, compared to other downscaling models, are also discussed. Tropical cyclones (TCs) are rare and extreme weather systems that can cause a lot of damage to society. Because the most intense of TCs are exceedingly rare, it is difficult to ascertain not only the frequency with which they occur, but how this frequency might change in the future. This problem is also compounded by the fact that even state-of-the-art climate models have trouble representing strong TCs. This study presents the development of a new, physics-based, TC model. The model can rapidly simulate a large number of TCs given a mean climate, and is shown to reasonably reproduce the general behavior of TCs observed over the past 43 years. The model is open-source and freely available online. The development of an open-source physics-based tropical cyclone (TC) downscaling model, based on random seeding, is describedSteering of the TC that is intensity-dependent can change TC hazard on both local and regional scalesThe model reproduces the observed climatology of TCs, including the seasonal cycle, inter-annual variability, and hazard

Automated summary

An open-source, physics-based tropical cyclone downscaling model is developed to generate a large climatology of TCs. The model can reproduce observed TC climatology, including seasonal cycle, inter-annual variability, and hazard. The model is driven by large-scale environment and captures the variability in TC count and power-dissipation. It can also assess the regional TC hazard and its changes over time. The advantages and disadvantages of this model compared to other downscaling models are discussed.