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| Airflow
separation is thought to be one of the
factor contributing to very high wind
speeds in hurricanes. We observe and
measure separation above surface gravity
waves in the lab and the field and directly
measure the surface stress. |
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The coupled air-sea boundary layers play an
important role in the multiple fluxes between the ocean
and the atmosphere. In particular the stress (drag) on the
ocean's surface is a crucial parameter for both short term
forecasting and the modeling of long-term global climate
trends. However, the effects of airflow separation are not
well understood. For example, while hurricane track forecasts
have significantly improved in the past few years, hurricane
intensity forecasts are essentially unchanged since 1970!
This is in part due to our lack of understanding of the
complex physics involved in the air-sea fluxes of momentum
when airflow separation is present. The proposed research
program is concerned with the role of airflow separation
in influencing the air-sea momentum flux. Specifically,
we perform laboratory and field experiments and examine
the detailed structure of the separated airflow above the
waves in order to determine
- What processes and factors (wavelength, slope,
phase, asymmetry...) lead to airflow separation,
- And assess the impact of airflow separation on
the air-sea momentum balance.
The figure above shows the velocity magnitude above a wind
wave measured using high resoltuion particule image velocimetry
(PIV) in the laboratory. We can clearly identify a separated
region on the less side of the wave.
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