WEATHER AND CLIMATE Unit #1 The Atmosphere CGF3M Physical Geography

WEATHER AND CLIMATE  In order to understand weather and climate we first must understand the characteristics of where weather and climate happen.  The Earth's atmosphere is a layer of gases surrounding the planet Earth and retained by the Earth's gravity.

WEATHER AND CLIMATE  The atmosphere has 4 main characteristics: It is fluid It is made up of various gases It has mass It consists of layers

 The atmosphere is fluid  Fluids are substances that can flow  Most fluids are liquid or gas  The atmosphere can flow from one place to another WEATHER AND CLIMATE

 When foreign substances (smoke, dust, pesticides, chemicals) enter the air the atmosphere can spread it considerable distances from the point of origin

WEATHER AND CLIMATE  The Atmosphere is made up of various gases  78% nitrogen  21% oxygen  0.93% argon  0.04% carbon dioxide  Trace amounts of other gases, in addition to water vapor

WEATHER AND CLIMATE  The Atmosphere has Mass  Fluids occupy space and have mass  The weight of air pushing down on the earth’s surface is referred to as air pressure

WEATHER AND CLIMATE  Air Pressure is affected by the heating and cooling of the earth’s surface.  Hot air rises, so the air pressure at higher elevations is less than that of the cool air at lower elevations  Air moves from areas of high pressure to areas of low pressure

WEATHER AND CLIMATE  When air rises, it leaves behind an area of low pressure, because the upward moving air is not pressing so hard on the surface. Areas of high pressure are formed where is sinking back down, and so pushing down harder.

WEATHER AND CLIMATE  Air pressure is measured in millibars or kilopascals.  On a weather map places across the country with the same air pressure are joined together with line, forming isobars

WEATHER AND CLIMATE  Weather associated with high and low pressure systems are very distinct  Lows: Relatively warm, moist air  Highs: Relatively cool and dry

WEATHER AND CLIMATE  The atmosphere consists of five layers with transitional regions between most  Each layer possesses individual characteristics  The most important differences between each layer are in the air pressure and temperature