Weather Part 1

Solar Energy as Radiation Figure 1.1 Nearly 150 million kilometers separate the sun and earth, yet solar radiation drives earth's weather.

Weather and Climate Weather is defined as the state of the atmosphere at a particular time and place. Climate is the general pattern of weather that occurs in a region over a period of years. Weather is short term over a smaller area while climate is long term over a larger area.

Weather is the state of the atmosphere at a particular time and place. The six weather elements include: Atmospheric pressure Temperature Wind Precipitation Cloudiness Humidity Weather and Climate

Earth's Atmosphere The atmosphere is a thin layer of air that protects the Earth ’ s surface from extreme temperatures and harmful sun rays Figure 1.2 Thin Gaseous envelope

Gases in the Atmosphere This circle graph shows the percentages of the gases, excluding water vapor, that make up Earth's atmosphere.

Atmospheric Pressure Atmospheric gases have mass. Atmospheric gases extend hundreds of kilometers above Earth's surface. As Earth's gravity pulls the gases toward its surface, the weight of these gases presses down on the air below. Air pressure and air density are greatest at sea level and decrease with altitude.

Baseballs travel farther in higher-altitude air (Denver) than they do in lower-altitude air. Baseballs travel farther in higher-altitude air (Denver) than they do in lower-altitude air.

Fig. 1-8, p. 9

Structure of the Earth’s Atmosphere Five Layers: Troposphere Stratosphere Mesosphere Thermosphere Exosphere (not shown)

Structure of Atmosphere Troposphere: Lowest and thinnest layer but contains 90% of the atmosphere’s mass Where weather occurs —water vapor and clouds Temperature decreases with altitude; Most of the heat in this layer comes from the earth.

Structure of Atmosphere Stratosphere: Top of troposphere to 50 km above surface Ozone layer —Absorbs harmful UV radiation UV radiation splits O 2 molecules to single O atoms, which collide with O 2 molecules to create ozone, O 3 molecules In this layer, temperature increases with altitude because of ozone absorption of UV radiation. —Ranges from –50°C at base to 0°C at top

CFCs Chlorofluorocarbon molecules destroy ozone. When a chlorine atom from a chlorofluorocarbon molecule comes near a molecule of ozone, the ozone molecule breaks apart.

Structure of Atmosphere Mesosphere: Coldest Layer; Temperature decreases with altitude Thermosphere and Exosphere: These layers are not well defined. First layers to receive the sun rays.

Structure of Atmosphere Thermosphere : Temperature increases with altitude —Temperature is related to average speed of gas molecules—very high speed gives high temperatures Very low density of gas molecules means very little heat absorption —Very few air molecules collide with one another—low thermometer reading

Heating the Atmosphere Some energy is reflected back into space by clouds, particles, and Earth's surface. Some is absorbed by the atmosphere or by land and water on Earth's surface.

Heating the Atmosphere Energy flows from an object with a higher temperature to an object with a lower temperature Heat is transferred through the atmosphere by: Radiation: energy that is transferred in the form of rays or waves Conduction: energy that is transferred when molecules bump into each other Convection: energy that is transferred by flow of material Molecules move closer together, making air more dense, and air pressure increases Cold air sinks, pushing up warm air, which then cools and sinks, pushing up more warm air

Greenhouse Effect Solar energy that is absorbed by the Earth’s land and water is changed to heat that moves/radiates back into the atmosphere (troposphere) where gases absorb the heat, a process known as the greenhouse effect.

Greenhouse Animation