YIP Sea spray-induced fluxes at high wind conditions: Synergistic experiments and data-driven modeling
Abstract
Project Abstract (Approved for Public Release)Research Problem: Coastal areas of the US are home to almost 130 million Americans, profoundly impacted by weather and climatic patterns. The air-sea fluxes of mass, momentum, and energy are fundamental components that drive short-term weather events and long-term climate trends. At the ocean interface, particularly under high wind speed conditions, surface waves frequently break and generate sea spray that controls these air-sea exchanges within the coupled atmospheric and oceanic boundary layers; thus, they must be fully integrated into weather forecasting models. Despite recent advancements in measurement technology and numerical simulations, our current understanding and ability to predictively model spray-mediated fluxes still lagsubstantially behind actual needs, especially in strongly forced conditions. For instance, no air-sea flux parameterization is currently able to accurately account for sea-spray dynamics. This project aims to advance the present understanding of sea spray dynamics and their influence on air-sea flux transfers with an overarching objective of reducing uncertainties in strongly forced wind-wavepredictions. Objectives and Technical Approach: Theoretically, the process of spray generation at the ocean surface can be described using the so-called spray generation (or source) function. However, direct measurements of source function and the resulting spray-induced fluxes are typically extremely difficult in the field, particularly in strong winds that produce larger spume droplets. Numerical simulations are equally challenging due to the difficulty of resolving a wide range of relevant length and time scales involved. This limits our understanding of spray generation mechanisms and their role in atmosphere-ocean coupling, which impedes progressin developing physics-based parametrizations of spray-mediated fluxes for improved weather and sea state predictions. To bridge this gap, a synergisticresearch program based on laboratory measurements and high-fidelity simulations is proposed to evaluate the dynamics of spume droplets at high wind speeds. This will be accomplished by a combination of novel experiments based on high-speed shadow imaging to concurrently measure drop size distribution and production/deposition velocities and a digital-twin modeling frameworkto augment measurements with near-surface turbulence statistics and droplet-flow interactions. The resulting dataset enables the development of sea-state-dependent parameterizations of spray source function and spray-mediated fluxes using physics-aware machine learning algorithms with superior generalizability features.Outcome and Impact: In recent years, ONR has been mainly focused on advancing the understanding of air-sea interactions and enhancing predictive capabilities by expanding detailed cross-cutting measurementsto address previously unquantified dimensions of small-scale, near-surface air-sea interactionprocesses. In that regard, sea spray and its impact on air-sea fluxes are among the least understood processes, while their reliable parametrizations are crucial for theaccurate prediction of extreme events. The proposed research program will allow for the first-ever concurrent measurements of size-dependent spray dynamics and direct quantification of spray-induced fluxes under strong wind conditions. These unique measurements will provide a dataset for significant advancements in understanding the spray generation process and developing sea-state-dependent models for spray source function and spray-mediated air-sea fluxes, enhancing the predictive modeling capabilities of weather and climate models.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Feb 24, 2025
- Source ID
- N000142512151
Entities
People
- Kianoosh Yousefi
Organizations
- Office of Naval Research
- United States Navy
- University of Texas at Dallas