〉 When fronts move through an area, the result is usually precipitation and a change in wind direction and temperature. air mass: a large body of air where temperature and moisture content are similar throughout front: the boundary between air masses of different densities and usually different temperatures

Clouds, rain, and sometimes snow can occur at fronts. Front types include warm fronts cold fronts stationary fronts

Lightning is a discharge of atmospheric electrical energy. Water droplets and ice crystals in thunderclouds build up electrical charges. Lightning is a big spark that jumps between clouds or between clouds and Earth to equalize the charge. Lightning heats the air so fast that the air expands faster than the speed of sound. The shockwave created is thunder.

Tornadoes are funnels of high-speed wind. Tornado winds are the most violent winds on Earth. Wind speeds may reach up to 500 km/h. Tornadoes typically form along a front between cool, dry air and warm, humid air. funnel cloud: a column of water droplets

Hurricanes are large, rotating tropical storm systems. These storms are called hurricanes in North America and the Caribbean cyclones in the Indian Ocean typhoons in the western Pacific tropical depressions: intense low-pressure areas that can become hurricanes

〉 Weather changes from day to day, but climate does not change as quickly. climate: the average weather conditions in an area over a long period of time. Two main factors are temperature and precipitation.

Temperatures tend to be higher close to the equator. Sunlight strikes the earth more directly close to the equator. The sun’s rays are less concentrated at the poles, and do not warm the atmosphere as much.

Earth’s tilt and rotation account for our seasons. When the North Pole is tilted toward the sun, the Northern Hemisphere experiences summer. There is more daylight, and the temperature increases. Earth is farthest from the sun on July 4. When the South Pole is tilted toward the sun, the Southern Hemisphere experiences summer.

Earth’s surface features affect climate. topography: the size and shape of the land surface features of a region, including its relief Variations in topography affect the climate of a region. Mountains can trap moisture on one side. Deserts may form on the dry side of a mountain. Broad flat surfaces allow winds to merge on the plains. Thunderstorms and tornados may form.

Determine whether each of the following statements describes a warm front or cold front. Warm air mass moves above slow cold air mass Thunderstorms and high winds characterize this type of front Cold air moves quickly under slow air mass Steady rain Grapes grow well in areas where climate is generally mild. Would you recommend planting grapes in California or North Dakota? Explain.

Global climate changes over long periods of time. Many factors produce changes in Earth’s climate, such as: eruptions of volcanoes shift of the continents changes in Earth’s tilt Scientists think that increases in human-made greenhouse gases have caused the recent increase in global average temperature.