An easterly wind, interrupting the (North East) Trade winds off the Atlantic coasts at North Africa, across the Gulf of Guinea and the Cape Verde Islands. It is called Doctor sometimes, because it is supposed to have healthful properties. It occurs in the winter, between November and February. Dust parts cause a haze, which can cover large coastal areas. They can reduce the visibility to 45 metres (50 yards). It is called Doctor sometimes, because it is supposed to have healthful properties.