Weather Basics What is Weather different weather bad weather often caused big problems It meant people either moved to a new area with better weather or faced starvation This still happens in areas of the world that lack access to safe food transportation People often choose to live in an area because of its climate Some people like living where it is warm all the time Others 8
Mild weather may make it easier to raise animals and grow crops for a living prefer to have seasons that change throughout the year Farmers and ranchers choose areas where the climate is right for their crops or animals People also avoid living in some areas because of the climate For example people might choose not to live in areas that get a lot of snow They may avoid moving to regions that get a lot of tornadoes hurricanes or droughts 9
atmosphere exosphere thermosphere mesosphere stratosphere troposphere Weather Is in the Atmosphere The air around Earth is called the atmosphere It is densest near the ground It becomes thinner at high altitudes From the ground upward the atmosphere has five layers the troposphere stratosphere mesosphere thermosphere and exosphere There is no clear boundary between the atmosphere and outer space One common dividing point is an altitude of 62 miles 100 km Above this there are still air molecules But the air is too thin for an airplane’s wings to generate lift The troposphere includes the air that makes life possible on Earth It is also where weather happens Weather phenomena happen in the lowest levels of the atmosphere 10
1 1 A device called a barometer measures atmospheric pressure Air is usually invisible but it has weight At sea level a inch 2.54 cm square on the ground has about 15 pounds 6.8 kg of air pushing down on it In other words that 1-inch column of air stretching from the ground to space weighs about 15 pounds 6.8 kg The force of the air pressing on the things around it is known as atmospheric pressure Atmospheric pressure does not stay the same all the time It is affected by heat and moisture When these things change the atmospheric pressure Earth’s weather also changes One of the biggest factors in these weather changes is the sun 11
