Identifying Air-Sea Processes That Relate to Momentum Flux and Surface Drag Variability in Tropical Cyclones

Many observational and modeling studies have highlighted that air-sea interaction plays a crucial role in tropical cyclone (TC) intensity change. One of the many ways the ocean and atmosphere interact is the transfer of momentum between the boundary layers. Numerical TC forecast models replicate this process through a surface drag coefficient that regulates the amount of momentum exchanged between the ocean and atmosphere. However, the few direct measurements and several indirect methodologies of estimating momentum flux and surface drag coefficient vary greatly amongst each other and have high estimation uncertainty. While there have been several prior observational studies in TC wind regimes to reduce this variability and uncertainty, resultant studies have been siloed to a particular boundary layer (air, ocean, or wave). Hence, there is a need to concurrently observe, examine, and quantify the relative contribution of processes that govern the exchange of momentum between the atmosphere, ocean, and wave boundary layers in a TC to discern if an accurate physical understanding of their interaction is being considered in modeled parameterizations. An attempt is made to identify the relative contribution of air-sea-wave processes governing the exchange of momentum within TCs using a suite of observations and distinguish which first-order processes amongst atmosphere, ocean, and wave fields that may contribute to the variability in momentum flux. Here, we present the diagnoses of contributing processes towards momentum flux within, and interactions between, the atmospheric and wave boundary layers.