Potential Effect of Bio-Surfactants on Sea Spray Generation in Tropical Cyclone Conditions

Despite significant improvement in computational and observational capabilities, predicting intensity and intensification of major tropical cyclones remains a challenge. In 2017 Hurricane Maria intensified to a Category 5 storm within 24 h, devastating Puerto Rico. In 2019 Hurricane Dorian, predicted to remain tropical storm, unexpectedly intensified into a Category 5 storm and destroyed the Bahamas. The official forecast and computer models were unable to predict rapid intensification of these storms. One possible reason for this is that key physics, including microscale processes at the air-sea interface, are poorly understood and parameterized in existing forecast models. Here we show that surfactants significantly affect the generation of sea spray, which provides some of the fuel for tropical cyclones and their intensification, but also provides some of the drag that limits intensity and intensification. Using a numerical model verified with a laboratory experiment, which predicts spray radii distribution starting from a 100 μm radius, we show that surfactants increase spray generation by 20–34%. We anticipate that bio-surfactants affect heat, energy, and momentum exchange through altered size distribution and concentration of sea spray, with consequences for tropical cyclone intensification or decline, particularly in areas of algal blooms and near coral reefs, as well as in areas affected by oil spills and dispersants

CBLAST 2003 field work report

The long-range scientific objective of the Coupled Boundary Layer Air Sea Transfer (CBLAST) project is to observe and understand the temporal and spatial variability of the upper ocean, to identify the processes that determine that variability, and to examine its predictability. Air-sea interaction is of particular interest, but attention is also paid to the coupling of the sub-thermocline ocean to the mixed layer and to both the open ocean and littoral regimes. We seek to do this over a wide range of environmental conditions with the intent of improving our understanding of upper ocean dynamics and of the physical processes that determine the vertical and horizontal structure of the upper ocean. Field work for CBLAST was conducted during the summers of 2001, 2002, and 2003 off the south shore of Martha’s Vineyard, Massachusetts. The 2003 field work was conducted from the following platforms: heavy moorings, light moorings, drifters, F/V Nobska, CIRPAS Pelican aircraft, and an IR Cessna Aircraft. This report documents the 2003 field work and includes field notes, platform descriptions, discussion of data returns, and mooring logs. The 2003 Intensive Operating Period (IOP) was very successful and a high data return was seen.Funding was provided by the Office of Naval Research under contract numbers N00014-01-1-0029 and N00014-05-10090

Effects of Surfactants on the Generation of Sea Spray During Tropical Cyclones

Despite significant improvement in computational and observational capabilities, predicting intensity and intensification of major tropical cyclones remains a challenge. In 2017 Hurricane Maria intensified to a Category 5 storm within 24 hours, devastating Puerto Rico. In 2019 Hurricane Dorian, predicted to remain tropical storm, unexpectedly intensified into a Category 5 storm and destroyed the Bahamas. The official forecast and computer models were unable to predict rapid intensification of these storms. One possible reason for this is that key physics, including microscale processes at the air-sea interface, are poorly understood and parameterized in existing forecast models. Under tropical cyclones, the air-sea interface becomes a multiphase environment involving bubbles, foam, and spray. The presence of surface-active materials (surfactants) alters these microscale processes in an unknown way that may affect tropical cyclone intensity. The current understanding of the relationship between surfactants, wind speed, and sea spray generation remains limited. Here we show that surfactants significantly affect the generation of sea spray, which provides some of the fuel for tropical cyclones and their intensification. A computational fluid dynamics (CFD) model was used to simulate spray radii distributions starting from a 100 micrometer radius as observed in laboratory experiments at the University of Miami Rosenstiel School of Marine and Atmospheric Sciences SUSTAIN facility. Results of the model were verified with laboratory experiments and demonstrate that surfactants increase spray generation by 34% under Category 1 tropical cyclone conditions (~40 m s-1 wind). In the model, we simulated Category 1 (4 Nm-2 wind stress), 3 (10 Nm-2 wind stress), and 5 (20 Nm-2 wind stress) conditions and found that surfactants increased spray generation by 20-34%. The global distribution of bio-surfactants on the earth is virtually unknown at this point. Satellite oceanography may be a useful tool to identify the presence of surfactants in the ocean in relation to tropical cyclones. Color satellite imagery of chlorophyll concentration, which is a proxy for surfactants, may assist in identifying surfactant areas that tropical cyclones may pass over. Synthetic aperture radar imagery also may assist in tropical cyclone prediction in areas of oil spills, dispersants, or surfactant slicks. We anticipate that bio-surfactants affect heat, energy, and momentum exchange through altered size distribution and concentration of sea spray, with consequences for tropical cyclone intensification or decline, particularly in areas of algal blooms and near coral reefs, as well as in areas affected by oil spills and dispersants

Microscale to Mesoscale Modeling of the Ocean Under Tropical Cyclones: Effects of Sea Spray and Surfactants on Tropical Cyclone Intensity and Air-Sea Gas Exchange

Tropical cyclone intensity prediction remains a challenge despite computational and observational developments because successful intensity forecasting requires implementing a multitude of atmospheric and oceanic processes. Hurricane Maria 2017 and Hurricane Dorian 2019 serve as prime examples of rapidly intensifying storms that devastated communities in the Caribbean. A lack of understanding and parameterization of crucial physics involved in tropical cyclone intensity in existing forecast models may have led to these and other forecasting errors. Microscale physical processes at the air-sea interface are a major factor in intensification of tropical cyclones that are often unaccounted for in forecasting models since they are difficult to study in the field and laboratory and are therefore not well understood. An ongoing uncertainty in tropical cyclone dynamics is the sea spray generation function (SSGF). While multiple estimates of the SSGF have been produced, a lack of experimental data in high wind conditions makes it difficult to establish a confident SSGF for tropical cyclones. Surface active agents impact spray generation, causing variation in spray diameter and an increase in generation that may influence heat, momentum, and gas exchanges during tropical cyclones. To better understand these processes, a computational fluid dynamics model was developed that simulates spray generation under all five tropical cyclone category conditions and resolves spray with radii starting from 100-mm. The numerical results were validated with Category 1 data from a laboratory experiment at the University of Miami. SSGFs calculated from the model revealed an increase in the spray generation under all categories of tropical cyclone conditions except Category 4 and Category 5 conditions, where little to no impact of surfactants on spray generation was found. This phenomenon might be explained by a change in regime under major tropical cyclones. Additionally, small to mesoscale ocean circulation and characteristics, particularly in environments such as a western boundary current, lead to complex interaction between ocean circulation and tropical cyclones. Not only are ocean dynamics in the open ocean affected by tropical cyclones, but the impacts can extend to coasts outside of the predicted storm impact area, leading to unprepared coastal communities due to these poorly understood interactions. This can improve parameterizations of variables such as mixing and fluxes in tropical cyclone forecasting models. An additional computational fluid dynamics model has been developed that predicts and characterizes small to mesoscale ocean circulation and dynamics in a western boundary current. This body of work aims to further understand ocean circulation in the surface layer in western boundary currents and complex microphysics at the air-sea interface during tropical cyclones including spray and spume generation, evaporation, and related fluxes, air-sea gas exchange, and the effects of factors such as surfactants. The multitude of ocean dynamics and air-sea interaction processes to be studied in this work converge to strive for a more complete understanding of the ocean water column and the air-sea interface under tropical cyclones that could ideally be implemented into tropical cyclone prediction models to improve intensity forecasting

Geophysics and Ocean Waves Studies

The book “Geophysics and Ocean Waves Studies” presents the collected chapters in two sections named “Geophysics” and “Ocean Waves Studies”. The first section, “Geophysics”, provides a thorough overview of using different geophysical methods including gravity, self-potential, and EM in exploration. Moreover, it shows the significance of rock physics properties and enhanced oil recovery phases during oil reservoir production. The second section, “Ocean Waves Studies”, is intended to provide the reader with a strong description of the latest developments in the physical and numerical description of wind-generated and long waves, including some new features discovered in the last few years. The section is organized with the aim to introduce the reader from offshore to nearshore phenomena including a description of wave dissipation and large-scale phenomena (i.e., storm surges and landslide-induced tsunamis). This book shall be of great interest to students, scientists, geologists, geophysicists, and the investment community

NASA CYGNSS Mission Applications Workshop

NASA's Cyclone Global Navigation Satellite System, (CYGNSS), mission is a constellation of eight microsatellites that will measure surface winds in and near the inner cores of hurricanes, including regions beneath the eyewall and intense inner rainbands that could not previously be measured from space. The CYGNSS-measured wind fields, when combined with precipitation fields (e.g., produced by the Global Precipitation Measurement [GPM] core satellite and its constellation of precipitation imagers), will provide coupled observations of moist atmospheric thermodynamics and ocean surface response, enabling new insights into hurricane inner core dynamics and energetics. The outcomes of this workshop, which are detailed in this report, comprise two primary elements: (1) A report of workshop proceedings, and; (2) Detailed Applications Traceability Matrices with requirements and operational considerations to serve broadly for development of value-added tools, applications, and products