Thermal Response of Climate System

1. Thermal Response of Climate System • Weather Update • Seasonality • Solar Elevation at Noon • Heat Transfer Processes • Latent Heat Transfer • Heating Imbalances • For Next Classs: Read Christopherson Ch. 4 available on AsUlearn

2. Annual March of the Seasons • Winter solstice – December 21 • Subsolar point Tropic of Capricorn • Spring equinox – March 21 • Subsolar point Equator • Summer solstice – June 21 • Subsolar point Tropic of Cancer • Fall equinox – September 21 • Subsolar point Equator

3. Annual March of the Seasons Figure 2.15

5. 11:30 P.M. in the Antarctic Figure 2.16

6. Midnight Sun Figure 2.17

7. Insolation at Top of Atmosphere Figure 2.10

8. Solar Elevation at Noon Figure 2.18

9. Solar Elevation at Noon (SEN) • SEN is the angle of the noon sun above the horizon • SEN = 90˚ - ArcDistance • ArcDistance = number of degrees of latitude between location of interest and sun’s noontime vertical rays • If the latitude of location of interest and sun are in opposite hemispheres, add to get ArcDistance • If they are in the same hemisphere, subtract from the larger of the two values

10. SEN Example • What is the SEN on June 21 for Boone (36 N) • SEN = 90 – ArcDistance • Where are the sun’s noontime vertical rays? • ArcDistance = 36 – 23.5 • ArcDistance = 12.5 • SEN = 90 – 12.5 • SEN = 77.5˚

11. Analemma

12. Driving Question • What are the causes and consequences of heat transfer within Earth’s climate system?

13. Heat Transfer Processes • Radiation • Both a form of energy and a means of energy transfer • Radiational heating: object absorbs radiation at a greater rate than it emits radiation • Internal energy increases, temperature rises • Radiational cooling: object emits radiation at a greater rate than it absorbs radiation • Internal energy decreases, temperature drops

14. Heat Transfer Processes • Conduction and Convection • Conduction: the transfer of kinetic energy of atoms or molecules via collisions between neighboring atoms or molecules • Heat Conductivity: the ratio of the rate of heat transport across an area to the temperature gradient • Substances with a higher heat conductivity have greater rates of heat transport • Solids are better conductors than liquids, liquids are better conductors than gases

15. Heat Transfer Processes • Conduction and Convection • Convection: the transport of heat within a fluid via motions of the fluid itself • Generally only occurs in liquids or gases (fluids) • Convection in the atmosphere consequence of differences in air density • Sensible Heating: combination of conduction and convection

16. A fresh layer of snow is a good heat insulator Convection currents transport heat conducted from Earth’s surface into the troposphere

17. Phase Changes of Water Water occurs naturally in all three phases (solid, liquid, gas) Depending on phase changes, either absorbs or releases heat to or from environment Latent heat: quantity of heat involved in phase changes of water Latent heating: the transport of heat from one location to another as a consequence of changes in the phase of water Heat Transfer Processes

18. Phase Changes of Water Heat absorbed from environment during changes to higher energy states melting, evaporation, sublimation Heat released to environment during changes to lower energy states freezing, condensation, deposition Heat Transfer Processes

20. Thermal Response and Specific Heat • Specific Heat: amount of heat that will raise the temperature of 1 gram of a substance by 1 Celsius degree • Measured relative to liquid water • Water has the greatest specific heat of any naturally occurring substance • Variation in specific heat from one substance to another implies that different materials have different capacities for storing internal energy

22. Thermal Response and Specific Heat • Thermal Inertia • Resistance to a change in temperature • The input (or output) of equal amounts of heat energy causes a land surface to warm (or cool) more than the equivalent surface area of a body of water over a given span of time • Water exhibits a greater resistance to temperature change than land

23. Maritime and Continental Climates Maritime climates: immediately downwind of the ocean, and experience much less contrast between average winter and summer temperature Continental Climates: well inland, experience a much greater contrast between winter and summer temperature Thermal Response and Specific Heat

24. Heat Imbalance: Atmosphere vs. Earth’s Surface • Figure below displays how solar radiation intercepted by Earth interacts with the atmosphere and Earth’s surface • Numbers are global annual averages, normalized so that units represent a percentage of the average solar radiation incident at the top of the atmosphere

25. Heat Imbalance: Atmosphere vs. Earth’s Surface • Latent Heating • Transfer of heat energy from one place to another as a consequence of phase changes of water • Heat is transferred from Earth’s surface to the troposphere through latent heating • Large quantities of heat are required to bring about phase changes of water as compared to phase changes of other naturally occurring substances

26. Heat Imbalance: Atmosphere vs. Earth’s Surface • Latent Heating • Latent heat of fusion: amount of heat required to convert a solid at its melting point to a liquid without a change in temperature • Latent heat of vaporization: amount of heat required to convert a liquid to a gas without a change in temperature

27. Sensible Heating Transport of heatfrom one location or object to another via conduction, convectionor both Often combines with latent heating to channel heat from Earth’s surface into the troposphere Heat Imbalance: Atmosphere vs. Earth’s Surface

28. Sensible Heating The Bowen Ratio compares how heat at the Earth’s surface is divided between sensible heating and latent heating Varies from one place to another Depends on amount of surface moisture Heat Imbalance: Atmosphere vs. Earth’s Surface Surface energy budget through the course of a year