Have you ever been at the beach in early summer and had a day ruined by arrival of a cold seabreeze? I was attempting to have my first barbecue of the year last April 3rd in Morningside Park – the center of Manhattan – and an unusually brutal springtime seabreeze caused temperatures to drop from 68 to 52°F in less than two hours, though this change was not in the forecast. People were shivering, teeth chattering and cursing the cold strong winds, and my barbecue ended prematurely.
The seabreeze is an inland movement of relatively cool marine air that often arises on sunny, warm days. It is caused by mesoscale (2-500 km) atmospheric pressure differences that develop as a result of the different solar absorption properties of sea and land.
I just published a paper on the New York City area seabreeze in the science journal Geophysical Research Letters, highlighting a weeklong period where nearly every day had a strong seabreeze blowing northward from the coast. The observations showed that the seabreeze often traveled with a sharp cold front at its head, and traveled at least 70 km up the Hudson valley (Figure 2 in the paper).
I read more on the atmospheric science and quirks of the New York area seabreeze, and learned that the cool air “marine layer” that propagates inland is often only 100-500 m tall. On the west coast, due to the extremely cold offshore waters, the marine layer is often tagged with fog that makes it visible (picture the Golden Gate Bridge). Around New York City, it’s usually invisible, so I drew up the conceptual diagram below.
The seabreeze has characteristics of a gravity current, which is a flow of fluid caused by the fact that it has a different density (colder = more dense) from the surrounding fluid. It’s somewhat like what happens when you crack open a window on a cold winter’s day, and cool dense air rushes in and down along the floor by your ankles. Other forms of gravity currents are avalanches, mudslides, as well as many other environmental flows.
The southerly seabreeze is an integral part of New York City urban weather, often ameliorating the urban heat island effect that is caused by heat-retaining pavement and buildings. Sunbathers escape the hot city on summer days, to cool off at the beach or on piers along the Hudson. Sailors in the Hudson and Long Island Sound often take advantage of spring and summer afternoon winds. My paper was mostly about the impacts of the seabreeze on the Hudson River, but I hope to study the New York area seabreeze more in the near future with my new position at the Stevens Institute of Technology, where I study the New York area atmosphere and ocean.
Some interesting questions include:
Is the sea breeze Manhattan’s summertime air conditioning unit, or does it only have an impact on the waterfront?
Could things be done, in future decades of NYC development, to make use of the northward-flowing sea breeze … in terms of architecture of the waterfront skyline?
The seabreeze is surprisingly strong at New York Harbor, likely due to funneling by nearby topography — could a wind farm be installed outside the shipping lanes to help handle the large summertime power demand for air conditioning on hot days?