Han, Y., & Ullrich, P. A. (2026). The Evolution of Tropical Cyclone Intensity and Size in Observations and HighResMIP Models. Submitted to Journal of Geophysical Research: Atmospheres.

Abstract

The destructive potential of a tropical cyclone (TC) depends on both its intensity and size, yet the coupled evolution of these properties remains insufficiently explored. This study investigates TC intensity–size relationships of TCs in observations and historical simulations from 12 HighResMIP models in the North Atlantic (NA) and western North Pacific (WNP). We apply the System for Classification of Low-Pressure Systems (SyCLoPS) to track TC life cycle and a novel quadrant wind radii calculation mirroring the IBTrACS format to enable consistent model–observation comparisons. SyCLoPS effectively removes weak tropical and extratropical systems misidentified as TCs in a conventional tracker, leading to improved TC tracking performance in ERA5 and models. TC track types are classified by their precursors and posterior scenarios based on SyCLoPS and IBTrACS labels. They are also grouped by intensity–size evolutionary pathways defined by peak intensity, size at peak intensity, and terminal size. Tropical depressions are more likely to intensify into intense but compact TCs, whereas monsoon depressions in the WNP and TCs undergoing extratropical transition tend to grow substantially in size as they evolve. In observations, the largest TCs are not the most intense and generally occur at higher latitudes. In contrast, most models have the strongest TCs reach peak size at lower latitudes. Only the highest-resolution (~20 km) model assessed captures intense, compact TCs that are common in observations. Despite this, the model ensemble mean performs comparably to ERA5 regarding TC track density, TC track type compositions, and differences in intensity and size characteristics between ENSO phases.

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