Grapes like to climb and hide their fruits below the leaf canopy. Makes it easier to find and harvest them if they are above our heads. Far as I can tell the difference between an arbor and a pergola is

The wind was howling with hellish fury. The stays’l up forward was reefed down to a little scrap of canvas, the mizzen above my head also reefed in hard. And the water. Mountains of jumbled, crazy breaking