Abstract
Characterizing inflow structure is important to better represent tropical cyclone impacts in numerical models. While much research has considered the impact of storm translation on the distribution of inflow angle, comparatively less research has examined its distribution relative to the environmental wind shear. This study analyzes data from 3,655 dropsondes in 44 storms to investigate the radial and shear‐relative distribution of surface inflow angle. Emphasis is placed on its relationship with intensity change. The results show that the radial variation in the inflow angle is small and not significantly dependent on the shear magnitude or intensity change rate. In contrast, the azimuthal distribution of the inflow angle shows a significant asymmetry, with the amplitude of the asymmetry increasing with shear magnitude. The maximum inflow angle is located in the downshear side. The degree of asymmetry is larger in the outer core than in the eyewall. Intensifying storms have a smaller degree of asymmetry than steady‐state storms under moderate shear.
Plain Language Summary
The inflow angle represents the degree that the wind vector deviates from the tangential wind. It is an important factor for the successful modeling of tropical cyclone evolution and storm surge. Although the inflow angle in the storm‐relative framework and its variation with storm intensity have been documented in the past, it is still unknown how the inflow angle varies with intensity change in different variations of environmental wind speed and direction with height. This study uses the observational data from aircraft to investigate the characteristics of the radial and azimuthal distributions of inflow angle in storms with different values of environmental wind variation and intensity change rates. The results show minor differences in inflow angle with increasing radius from the storm center, but more significant differences in inflow angle moving around the storm. The degree of asymmetry increases with the magnitude of environmental wind variation and decreases with the storm intensity change rate. The inflow angle is more asymmetric in the outer core region than in the eyewall region.
Key Points
Intensifying storms have a lower degree of asymmetry of the surface inflow angle than steady‐state storms under moderate wind shear
The degree of downshear versus upshear asymmetry of the surface inflow angle increases with the shear magnitude
The degree of shear‐relative asymmetry of the surface inflow angle is larger in the outer core region than in the eyewall region
