Warm air holds more moisture (humidity)
than cold air.
Remember that the ocean's
temperature, be it warm or cold, strongly influences the temperature
in the overlying mass of air.
You can see this in the diagram below by noting the difference in the
width of the red color band, representing air temperatures between 20
and 30oC on the western and
eastern sides of the ocean basins.
We shall first examine the impact of western
boundary currents -------
Let's Listen to Seaweb
Ocean Report about the western boundary current known as the Gulf
Stream (along the east coast of U.S.) -- remember western refers
to its position in the ocean -- the west side of the ocean.
Why is the ocean water warm at the beach south of Cape Cod, in Nantucket, but north of Cape Cod in Gloucester Massachusetts it is "freezing?"asks Laura. a listener of the Ocean Report.
The answer has to do with the Gulf Stream, which is the warm current that flows northward from the Gulf of Mexico along the U.S. east coast.
At first the Gulf SAtream flows close to shore, but by around Cape Hatteras, North Carolina, the prevailing winds push the Gulf Stream offshore. By the Massachusets, the Gulf Stream has been pushed far out to sea by the wind.
The very western edge of the Gulf Stream warms the water off Nantucket's beaches, but now by Cape Cod, the current heads northeast towards Europe, so that there is no way its warming effect can extend back west around Cape Cod to Boston or Gloucester.
Meanwhile, another major ocean current, called the Labrador current flows south from the Arctic and brings extra cold water to New England, including the beaches in Gloucester. .