Role of diabatic heating on tropical cyclone structure and motion

Our past work has demonstrated the sensitivity of tropical cyclone track to cloud microphysical and cloud radiation assumptions (Fovell and Su 2007; Fovell et al. 2009, 2010). This work has utilized simulations made with a version of the real-data WRF model, modified to exclude land and possess a calm and initially horizontally homogeneous environment. Microphysics schemes ranging from simple to very sophisticated have been considered.

It was found that varying microphysics results in a significant spread of tracks, even in relatively short (72h) simulations. The symmetric and asymmetric structures of these storms evince distinct differences that are understood to influence storm speed and direction. However, this track diversity appears to emerge owing to cloud-radiative feedback (CRF), in which condensate particles are able to modulate long- and short-wave radiation. Different microphysical schemes produce different amounts and spatial distributions of radiatively active particles, such as cloud ice, snow crystals and cloud droplets. This results in different heating patterns with respect to intensity and radial, azimuthal and vertical structures.

Simple simulations using the Rotunno-Emanuel axisymmetric model with maintained heat sources and sinks will demonstrate the specific and general impacts of diabatic processes on storm structure, and ultimately storm motion in the fully 3D framework. This work strongly motivates more basic research in cloud-radiative processes and microphysical parameterizations, and highlights the need to validate numerical model products with available observations.