The Atmosphere

1. The Atmosphere B3: Weather Factors Part 1 – Energy in the Atmosphere

2. Weather Factors – Part 1 • Heat – Heat is a major factor in weather • The movement of heat in the atmosphere causes temperatures to change, winds to blow, and rain to fall • Heat is a form of energy, and nearly all energy in the atmosphere comes from the sun

3. Energy from the Sun • Energy from the Sun– Energy from the sun travels in the form of electromagneticwaves • Classified according to wavelength • Radiation – transfer of energy by electromagnetic waves • Most of the energy from the sun travels to Earth in the form of visible light and infrared radiation • A small amount arrives as ultra-violet radiation

4. Energy in the Atmosphere • Before reaching the Earth’s surface, energy must pass through the atmosphere • Mesosphere – Blocks much of the UV radiation • Troposphere – Some energy is reflected or absorbed by the atmosphere, the rest passes through to the surface • Reflected - About 30% of sunlight is reflected back into space • About 25% is reflected by clouds, dust, and gases in the atmosphere • Scattering – the process in which sunlight is reflected in all directions by the air • About 5% is reflected the surface

5. Energy in the Atmosphere • Absorbed - About 80% of sunlight is absorbed • About 20% is absorbed by gases and particles in the air • About 50% is absorbed by the Earth’s surface • This energy heats the land and water

6. Energy at the Earth’s Surface • When Earth’s surface is heated, it radiates most of the energy back into the atmosphere as infrared radiation • Most of this radiation cannot travel all the way back into space • Instead, it is absorbed by water vapor and other gases in the air • These gases form a ‘blanket’ that holds heat in • Greenhouse Effect – process by which gases hold heat in the air

7. Energy at the Earth’s Surface • Natural and necessary process that keeps Earth’s atmosphere at a temperature able to support life • Also helps to keep Earth’s average temperature fairly constant • However, increasing the amount of greenhouse gases, increases the amount of heat retained • Global Warming – the increase in Earth’s averagetemperature due to increasing levels of greenhouse gases

8. Types of Heat Energy • What is the differencebetween temperature and thermal energy? • Temperature – a measure of how hot or cold a substance is • Thermal Energy – the total energy of motion in the particles of a substance • Example: Lit match and ice sculpture • Which has a higher temperature? • Match • Which has more thermal energy? • The swan because it has a lot more molecules

9. Measuring Temperature • Temperature is one of the most important factors in weather and is commonly measured with a thermometer • Thermometer – works because liquid expands when the temperature increases • Expansion causes the liquid to rise up the tube • As the liquid cools, it contracts and gets lower in the tube • Temperature Scales – temperature is commonly measured in Celsius or Fahrenheit

10. Measuring Temperature • Celsius Scale – In the Celsius scale, water freezes at 0o and boils at 100o • Fahrenheit Scale – In the Fahrenheitscale, water freezes at 32o and boils at 212o • Converting – The formula to convert Fahrenheit to Celsius is: • To get rid of the fraction – multiply both sides by 9 • 5 • oC = • (oF – 32) • X • 9 • What is the formula to convert Celsius to Fahrenheit? • 9oC • = • 5 • (oF – 32) • To get rid of the 5 – divide both sides by 5 • 5 • 5 • 9oC • Need to solve for F • = • oF – 32 • To get rid of the 32 – add to both sides • 5 • 9oC • + 32 • = • oF • 5

11. How Heat is Transferred • Heat is transferred in 3 ways: radiation, conduction, and convection • Radiation – transfer of energy by electromagnetic waves through the air • Cannot see radiation, but you can feel it • Examples: • Feeling warmth when standing in sunshine • Feeling heat when you hold your hand over a lamp or a flame

12. How Heat is Transferred • Conduction – The direct transfer of heat from one substance to another substance that is touching it • Occurs when faster moving molecules in a hot substance bump into slower moving molecules of a cooler substance • The faster molecules transfer some of their energy to the slower molecules ‘heating’ them up • The closer together the atoms or molecules are in a substance, the more effectively it conducts heat • Example: metal conducts heat better than water

13. How Heat is Transferred • Convection – The transfer of heat by the movement of liquid or gases • In fluid (liquid or gas) particles can easily move from one place to another • As particles move, they take their energy with them • Example: Pouring hot water into cold water. • The water molecules mix • causing the • cold water to heat up and the hot water to cool down

14. How Heat is Transferred • Convection Current – Movement of particles through fluid due to temperature • As particles heat up, they rise through the fluid • As particles cool down, they sink • The three types of heat transfer

15. Heating the Troposphere • Radiation, conduction, and convection all work together to heat the troposphere • During the day, the sun’s radiation heats Earth’s surface • The land becomes warmer than the air • The air near the surface is warmed by both radiation and conduction • Only the air touching the surface is heated by conduction • Within the air, heat is transferred through convection currents

16. Heating the Troposphere • Radiation • Conduction • Note: only the air touching the surface is heated – so it is much less air • Convection • Forms convection currents

17. In Closing • What is the difference between radiation, conduction, and convection?