Impacts of environmental humidity on concentric eyewall structure

The tropical cyclone (TC) secondary eyewall (SE) is an important aspect of TC intensity and structure forecast, because it largely affects the horizontal scale of destructive winds and heavy rainfall. Hence, it is important to understand the possible factors that influence the structure and size of SE. Idealized simulations suggest that the environmental humidity is one of the key factors. It is favorable for TC to establish a SE in a moist environment. Furthermore, the SE is likely to be located at a larger radius, thereby leads to a wider moat area. Consequently, the structure of SE would affect TC intensity change during the eyewall replacement cycle. This study strongly motivates further researches with respect to how the environmental conditions influence the storm dynamics and thermodynamics.