Does the vertical wind shear profile matter to tropical cyclone intensity change?

Vertical wind shear is commonly measured as the difference of horizontal winds between 200 hPa and 850 hPa averaged in an annulus between 500-700 km radii. Vertical shear is regarded to be detrimental to tropical cyclone (TC) development and intensity and generally weakens an existing TC. However, both observations and numerical studies show that strong TCs can resist moderate vertical shear. Our recent observational studies demonstrate that the effect of vertical shear on TC intensity depends strongly on the vertical profile of the shear. Nevertheless, the effect of vertical shear on TC intensity change is still the least understood issue. This could be one of the reason why the improvement in TC intensity forecast has been very slow in the past 2-3 decays. In this study, we attempt to address why the vertical wind shear profile matters to TC intensity change based on idealized numerical experiments using a full-physics, cloud-resolving TC model (TCM4). I this talk, special attention will be given to the conceptual interactions between a TC vortex and the vertical wind shear in different layers (namely in a deep layer, in the mid-upper troposphere, or in the mid-lower troposphere). We will also show how sensitive the dependence on the vertical shear profile is to the size of the TC itself. The implications of the results to the improvement of TC intensity forecast will be briefly discussed.