An Asymmetric Model of the Tropical Cyclone Surface Wind Field and Probabilistic Climatology of Structural Parameters

Abstract A new parametric model of a tropical cyclone’s (TC) surface wind field is proposed, in which parameters are calibrated on over 20 years of direct surface wind measurements from aircraft reconnaissance. The model extends previous formulations by representing structural asymmetries in the inner core and far field. The surface wind representation eliminates the need for uncertain aircraft flight (gradient) level-to-surface extrapolation or pressure gradient formulation conversions to wind speed. Parameters are expanded to wavenumber-1 asymmetric Fourier components around symmetric mean values; symmetric values are found to depend primarily on maximum wind speed and geographic location, while some asymmetric parameters show statistically significant relationships with motion and environmental vertical shear, consistent with recent studies. Finally, a probabilistic representation of the climatology of basin-wide TC wind field structure is constructed by fitting a multivariate statistical distribution to the optimized model parameters. The low-dimensional formulation is suitable for computationally efficient reconstruction of historical TC wind fields, from depression to Saffir–Simpson category-5 intensities, as well as for stochastic simulation in the context of catastrophe risk modeling.