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Gulf Stream Influence on Overlying Wind Field

Gulf Stream

The influence of the warm waters of the Gulf Stream on the winds in the atmospheric boundary layer (the lowest 3000–5000 feet of the atmosphere) has been recognized for several decades. A recent study suggested that the influence of this ocean–atmosphere interaction might extend throughout the entire troposphere that extends to a height of about 35,000 feet. This would have important implications for weather forecasting and climate modeling.

A project led by Dudley Chelton investigates the wind response to sea surface temperature (SST) from the surface to the top of the troposphere from satellite observations and compares the results with the wind fields from weather forecast models.

Chelton notes, “In combination with models and other observations, we’re trying to figure out how the influence of SST penetrates deep into the troposphere and affects weather patterns. Over the Gulf Stream, it is clear
that SST does infl uence winds high in the troposphere, probably more so than anywhere else in the world ocean. But
it’s a very important place, because a lot of storms form in the region, possibly because of this ocean–atmosphere
interaction.”

Satellite measurements of surface winds by the QuikSCAT Scatterometer and tropospheric winds inferred from atmospheric temperature profiles measured by the Advanced Microwave Sounder Unit (AMSU) are used to document the wind response to SST over the Gulf Stream at various atmospheric pressure levels from the surface to the top of the troposphere.

As the first step in this study, attention is focused on the period February 2007, during which winds blew strongly off the North American continent and approximately perpendicularly across the Gulf Stream.

The preliminary analysis provides strong observational evidence that the SST front associated with the Gulf Stream may indeed exert a strong influence on winds throughout the troposphere. As shown in the figure, vertical velocity has high vertical coherence, sometimes extending all the way from the surface to the top of the troposphere. This vertical velocity communicates the SST influence deep into the atmosphere.

This observed sea surface–temperature influence on atmospheric winds is grossly underestimated in weather forecast models and, by inference, in coupled climate models. Improving the accuracies of tropospheric winds in the models may therefore lead to improved weather forecasts and more accurate climate predictions.

Article courtesy of the College of Earth, Ocean, and Atmospheric Sciences 2010 Research Highlights

Photo courtesy of NOAA/OAR/OER

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