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Gulf Stream
Gulf Stream
A warm ocean current that begins in the Gulf of Mexico and then moves across the surface of the North Atlantic Ocean and nears the Atlantic coast of North America before turning east and spreading out to cross the Atlantic Ocean.
As soon as it begins to cross the Atlantic Ocean, it is called the North Atlantic Drift.
Gust
A short blast of air.
H
Haboob
Harmattan
A very hot wind that blows southwest from central Africa and can bring clouds of stinging dust.
Haze
A condition of the air in which visibility is reduced by the build-up of dust particles in it. It usually happens during dry conditions, because rainfall washes particles from the air. An extreme form of haze over cities involves particles of pollution and is called smog.
Heat
The part of the Sun’s energy that causes the temperature to rise.
 Hailstones – Hailstones are often pea-sized as here, but may be larger than the size of oranges.
 Heat island – Tall buildings trap heat, reflecting it back and forth and preventing the air from losing as much heat as in other parts of the city.
Heat island
The region in and around a city that remains up to several degrees warmer than the surrounding countryside on still summer nights and during calm spells in winter. The extra heat comes from buildings, industry and traffic.
The amount of warmth varies with the size of the city and with the speed of the wind. The extra heat tends to disappear when winds rise above 20km/h.
Very strong desert winds, usually accompanied by dust storms in the Sudan in Africa and in the Sonoran Desert of southern Arizona.
Hail, hailstones
A pellet of ice that is formed inside a tall cumulus cloud. A hailstone starts as a raindrop that has frozen when carried high enough by wind in the cloud. The falling hailstone collects moisture that forms a new layer of ice as the stone is again lifted through the cloud. Many layers of ice may be added until the hailstone is heavy enough to fall to the ground. Some hailstones have grown to weigh over half a kilo.
 Heat island – The thermometers show how the centre of a city is warmer than the countryside around it.
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