Identifying air-sea-wave processes that relate to momentum flux and surface drag variability in tropical cyclones
Abstract
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 and discern which processes are dominant. Therefore, the overarching objective for this particular proposal is to identify the relative contribution of processes governing the exchange of momentum between the atmosphere, ocean, and wave boundary layers within a TC using a suite of observations and distinguish which first-order processes amongst the three fields contribute most to the variability in drag coefficients. In doing so, we will also be able evaluate the Navy#s coupled TC model, COAMPS-TC, and provide guidance on how to improve momentum exchange using the findings. The proposed work builds off several previous Office of Naval Research field campaigns findings and methodologies and attempts to bridge the gap in understanding air-ocean-wave exchange as a complete system. It is hypothesized that variability between surface drag estimations amongst prior methods will be revealed when calculating momentum budgets inall three boundary layers. This hypothesis was formulated primarily on the basis that past studies still show large variability in surface drag coefficient despite using different methodologies. By undertaking the proposed research, we expect that future endeavors will be able to utilize the findings to improve and further validate momentum exchange in coupled TC models by either parameterizing or including any first-order processes that are currently not represented in two-way and three-way coupled systems. Tropical cyclones pose an annual significant threat to the Naval fleet and warfighter, since these storms spend the majority of their time over the tropical oceans, where Naval ships operate, and also influence the coastlines of Naval ports. Representing the accurate exchange of momentum stress between the ocean and atmosphere is crucial to accurately predicting TC intensity to protect Naval warfighter andcivilian life and property
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Mar 03, 2023
- Source ID
- N000142312112
Entities
People
- Johna E. Rudzin
Organizations
- Mississippi State University
- Office of Naval Research
- United States Navy