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Air mass: a large body of air with the same temperature and humidity throughout.
Altitude: height above sea level; elevation. Temperature decreases as altitude increases, which is why high mountains have cool climates.
Cirrus clouds: high, wispy, feathery clouds made of ice crystals.
Climate: average weather conditions of a large area over a long period of time. Climate is determined by temperature and precipitation.
Cloud: a collection of tiny water droplets or ice crystals suspended in the air.
Cold front: a weather front where a cold air mass is moving in and replacing a warm air mass. The dense, cool air mass moves under the less dense warm air. Cold fronts often bring heavy rain or snow, followed by cooler temperatures.
Cumulus clouds: low, puffy clouds that resemble balls of cotton.
Equator: an imaginary line circling Earth and dividing it between the northern and southern hemispheres. The equator has the highest average temperatures because it gets the most direct sunlight.
Front: the boundary between two air masses that have different temperatures and densities. There are four types of fronts: cold front, warm front, stationary front, and occluded front. Fronts are the location of unsettled weather and are often where storms occur.
Hurricane: a large, rotating weather system that forms over warm, tropical oceans and has high wind speeds of at least 120 km/hr (75 mi/hr).
Latitude: the distance north or south of the equator.
Leeward: the side of a mountain range that faces away from the oncoming wind. Rain shadows occur on the leeward side of a mountain range.
Lightning: an electrical discharge between positively and negatively charged surfaces, either between clouds or between a cloud and the ground.
Occluded front: a weather front where a warm front is between two cold fronts. Occluded fronts may bring continuous rain or snow.
Polar zones: the climate zones near the north and south poles, where average temperatures are very cold.
Precipitation: any form of water that falls from clouds, including rain, sleet, snow and hail.
Rain shadow: the leeward side of a mountain range, which receives very little precipitation.
Stationary front: a weather front where a cold air mass and a warm air mass move toward each other. Stationary fronts often bring extended periods of rain.
Stratus clouds: low clouds that cover the entire sky.
Temperate zones: the climate zones between the polar zones and the tropical zone. Average temperatures in temperate zones have a wide range, and are warmer near the tropical zone and cooler near the polar zones.
Thunder: the sound caused by the rapid expansion of air during a lightning strike.
Tornado: a rapidly spinning column of air that appears as a funnel cloud and touches the ground.
Tropical zone: the climate zone near the equator, where average temperatures are warm.
Warm front: a weather front where a warm air mass is replacing a cold air mass. The less dense warm air mass moves over the denser, cold air. Warm fronts often bring light rain followed by clear, warmer weather.
Weather: short-term conditions of the atmosphere at a particular time and place; includes temperature, humididty, precipitation, wind and clouds.
Wind: movement of air caused by differences in air pressure.
Windward: the side of a mountain range that faces the oncoming wind.
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