Understanding the Impact of Meridional Moisture Gradient on Tropical Cyclone Development Using Idealized WRF Simulations

Previous studies have hypothesized that horizontal moisture advection plays an important role in understanding rainfall variability and the growth of tropical waves, proposing a moisture-vortex instability (MVI), which includes meridional moisture advection and vortex stretching as the main mechanism in tropical wave growth and propagation (Russell 2019; Adames 2018). However, the process driving variability of tropical wave development by moisture meridional gradient has been less studied and remains unclear. Therefore, it is hypothesized that meridional moisture advection is the dominant mechanism responsible for generating strong vortex instability and triggering the development of tropical cyclones (TC). The focus is to examine the ability of a numerical model to reproduce this relationship and the mechanisms by which it is established to answer the following: Is the moisture gradient critical for the genesis, growth, and decay of TC? (2) Are these TCs more sensitive to reach the maximum potential intensity (MPI)?, and (3) Do Weather Research and Forecast Model (WRF) model idealized simulations support this hypothesis? This study aims to use the idealized WRF model, a 3D, nonlinear, non-hydrostatic, full-physics numerical weather prediction (NWP) model, to reproduce the essential features of a TC to gain more insights into understanding the TC development and impact of moisture gradients. The experiment to answer these questions will be configured with (1) horizontally homogeneous conditions, (2) a weak meridional moisture gradient, and (3) a strong meridional moisture gradient. This will allow us to thoroughly examine the meridional moisture gradient impacts on TC. The experiment with a strong meridional moisture gradient is expected to lead to a faster spin-up of the disturbance, yielding a stronger axisymmetric vortex supporting this hypothesis.