8.3 The Atmosphere: The Cloud Factory

1. 8.3 The Atmosphere: The Cloud Factory • Clouds are made up of tiny water droplets- not water vapor (water vapor is invisible) • The Troposphere marks the location of the temperature inversion • The temperature inversion is a reversal in the direction of the temperature change with a change in height • The higher the air, the colder the temperature- until you reach the upper troposphere • Above the troposphere, the air begins to warm again

2. A recipe for clouds • Three ingredients are needed for cloud formation • Water, rising air, and dust are necessary for clouds to form • Water vapor provides water for clouds • Rising warm air from earth’s surface keeps the clouds in the sky • Microscopic particles of dust provide solid surfaces for condensation to form

3. Moving up in the world • Solar heating causes clouds to rise and move around the earth • Warm air rises and pushes clouds higher into the atmosphere • Sometimes mountains form obstacles and prevent clouds from moving into certain areas • Clouds can also be formed when warm air and cold air run into each other

4. Moving up in the world • The huge masses of air that collide in the middle latitudes form over source regions • A source region is a large area of land or ocean with the same temperature across its entire surface • The air above the source region takes on the characteristics of the ground below it • The air continues to change until it becomes an air mass- a single, large unit of air with uniform temperature and humidity characteristics

5. Moving up in the world • There are many different air masses • Continental tropical air masses form over dry continent regions- warm land • Maritime tropical air masses pick up moisture from the warm seas- warm water • Continental polar air masses have cold, dry air- cold land • Maritime polar air masses contain cool, wet air from cold regions- cold water • Arctic and Antarctic air masses develop over the poles and have very cold air and dry air

6. Moving up in the world • The United States experiences a mixture of different air masses • The boundary between two air masses is called a front • At a warm front, warm air pushes back the cold air • At a cold front, cold air pushes back the warm air