The proposed research aims to develop a numerical tool for thorough predictions of production of aerosolized oil droplets at the sea-air interface, their transport within the marine atmospheric boundary layer (ABL) and deposition over a coastal region. The scientific goals of the proposed project are to: 1) understand the role of ABL structure and wave motion on aerosol generation at the sea-air interface; 2) investigate effects of transitioning from the ocean to the coast on aerosol concentration and distribution; 3) develop eddy-diffusivity models for regional meteorology algorithms by avoiding the typical assumption of a flat and homogeneous ocean surface and including a realistic wave motion. This project will be conducted through two interrelated tasks: one LiDAR measurement campaign will be performed in the Galveston area, TX, to generate unprecedented simultaneous and co-located observations of wind speed and aerosol concentration, while high-fidelity wind-wave coupled large eddy simulations (LES) will be performed to investigate aerosol dynamics, and finally reproduce the LiDAR observations.
A plume originated from oil spill rises following complex dynamics, which are affected by the multiphase plume composition, ocean currents and turbulence, and ultimately reaches the ocean surface generating aerosol. Plume gases are released in the atmosphere through bubble bursting, while oil droplets are aerosolized due to various mechanisms occurring at the sea-air interface that are affected by multiple parameters, such as wind stress, wind turbulence and wave dynamics. Once suspended in the atmosphere, aerosolized oil droplets are entrained within turbulent eddies and transported by the marine ABL. The aerosol residence time varies from days down to a fraction of a second, depending on the size and composition of the aerosol particles, velocity and turbulence in the ABL. Furthermore, when advected by wind, oil aerosol behaves in a more complicated fashion than passive scalars, which is a consequence of its non-negligible inertia and settling motion. The prediction of production, transport and deposition of aerosolized oil droplets for different wind and ocean conditions is still a great challenge due to the complex multiscale and multiphase nature resulting from the interaction between the ABL wind field and sea-surface waves. The proposed research will help to answer a number of key questions, including: 1) What are the dominant physical parameters, such as wave wavelength, wave phase velocity, wind shear, turbulence, relative direction between wind velocity and wave propagation, dominating the variability in aerosol flux at the sea-air interface? 2) What are the effects on aerosol distribution due to the transition from the ocean to the coast? 3) How significant is including in a transport model the wave motion and the characteristics of ABL structure? An important outcome of this research will be a numerical model for thorough aerosol predictions, which has been formulated based on unprecedented simultaneous co-located LiDAR measurements of wind speed and aerosol concentration, while an in-depth understanding of the dominating physical mechanisms governing aerosol dynamics will be achieved with high-fidelity wind-wave coupled LES.
Accurate predictions of production, transport and deposition of aerosol from the ocean surface to a coastal region can be advantageously leveraged to investigate transport of pollutants, their deposition and settling over a coastal area. An improved aerosol prediction model is important for a broad range of scientific and technological pursuits, such as for planning effective projects for environmental restoration. It will be possible to unveil under which atmospheric and wave conditions high pollutant concentrations will be observed, and which areas will mainly be affected. The developed numerical tool will be highly valuable to estimate the environmental impact of oil spill on the air quality, which is an essential information for medical research projects investigating respiratory diseases, such as asthma, for which enhanced morbidity has been observed in the Gulf area. Graduate students will be trained in an interdisciplinary fashion through LES and experiments performed with the UTD mobile LiDAR station, which is a unique facility for broadening participation of students from underrepresented groups and making them aware of important topics, such as oil spill in the Gulf of Mexico, environmental protection and climate change. The project will include outreach activities to connect the research with students in the region of Galveston, Houston and Dallas.