Mid-term review 1 Chapter 1 1. Weather and Climate Climate: “average” weather conditions Weather: state of the atmosphere at a given time and place. It is constantly changing. Climate is what you expect, but weather is what you actually get. 2. Four “Spheres” in the Earth System: Geosphere, Atmosphere, Hydrosphere, Biosphere 3. Systems A group of interacting parts (components) that form a complex whole. Reading: P4-6 Reading: P12-P16

Open System: Open System: Energy and Matter can be exchanged between systems Closed System: Closed System: Exchange of Matter greatly restricted, but may allow exchange of energy Isolated System: Isolated System: No Energy or Matter can be transferred in or out of the system 4. Feedback Processes in one system influences processes in another interconnected system by exchange of matter and energy. Positive Feedback: Positive Feedback: Change in one system causes similar change in the other system. Can cause runaway instability. e.g., water vapor feedback, ice cover feedback Negative Feedback Negative Feedback: A positive change in one system causes a negative change in the other. e.g., cloud cover feedback Reading: P397

5. Composition of the Atmosphere Major components: Nitrogen (N 2 ), Oxygen (O 2 ), Argon (Ar), Carbon dioxide (CO 2 ), Minute trace gases: water vapor (H 2 O),Methane (CH 4 ), Ozone (O 3 ), Nitrous Oxide (N 2 O) Variable components: Water vapor, Aerosol, Ozone Aerosol: direct and indirect effect Ozone: depletion and ozone hole 6. Extent of the Atmosphere Pressure: Force F acting on unit area due to the weight of the atmosphere. Surface atmospheric pressure: 1000 hPa or 1000 mb Temperature Reading: P17-P24 Reading: P24-P25

Thermal Structure of the Atmosphere Troposphere Stratosphere Mesosphere Thermosphere Averaged Surface temperature is K, or 15C. Decreases 6.5C per km up to 11 km (lapse rate). Nearly all weather happens in this layer. Height of the tropopause varies with latitude with an average of 10 km. Inversion: Negative lapse rate, temperature increases with height. Temperature is constant in the lower part of the layer, and then, increases with height due to O 3 absorption of solar UV. ~ 99% of the atmosphere is below the stratopause. Temperature decreases with height in this layer Temperature increases greatly because air absorbs sunlight. Reading: P26-P30

Chapter 2 1. Sun-Earth relationship 2. Forms of energy Earth’s motion, Seasons, Earth’s orientation, Solstices and Equinoxes Kinetic energyPotential energy 3. Mechanisms of Energy Transfer Conduction, convection, and radiation 4. Laws of blackbody radiation Stefan-Boltzman law, Wien’s displacement law, Plank’s law Heat 6000K 300K Reading: P36-P42 Reading: P43-P44 Reading: P44-P47 Reading: P47-P48

5. Selective absorption and emission of atmospheric gases Electronic excitationPhotoionization M overlap Almost all solar radiations shorter than ultraviolet are used up in the upper layer for photoionization, electronic excitation, and molecule dissociation. Since most of solar energy is in the visible band, they have nothing to do with molecule vibration and rotation transition, so solar radiation can reach Earth's surface almost without any attenuation. On the other hand, terrestrial radiation in the infrared band, which is involved with atmospheric molecule vibration and rotation transitions, can be absorbed by the atmosphere to cause greenhouse effect.

6. Greenhouse Effect Shortwave solar radiation is nearly transparent to the atmosphere, but longwave terrestrial radiation is trapped by greenhouse gases, causing the increase of surface temperature. 7. Atmospheric window Highly un-reactive greenhouse gases containing bonds of fluorine-carbon or fluorine-sulfur, such as Perfluorocarbons (CF4, C2F6, C3F8) and Sulfur Hexafluoride (SF6). These trace gases have strong absorption lines right in the atmospheric window. Clouds can also absorb longwave radiation in the atmospheric window. Reading: P54-P55 Reading: P53-P54

8. Solar constant: incoming solar radiation per unit area at the top of the atmosphere 9. Radiative Equilibrium, Radiative-covection Equilibrium 10. Heat Budget of Earth’s Atmosphere Reading: P56

11. Latitudinal energy balance 12. Transport by atmospheric motion and ocean currents

Chapter 3 1. Air TemperatureIsotherms 2. Controls of Temperature Differential heating of land and water; Ocean currents; Altitude Geographic position; Cloud cover and albedo Temperature gradientReading: P66-P67 Reading: P68-P75

3. Daily Cycles of Air Tmperature (diurnal) 5. Temperature measurement Maximum and minimum temperature Instrument shelters 4. Heat island effect Buildings absorb and store more solar radiation. City surface results in reduction of evaporation. Heat sources from heating system, air-conditioning, and industry. Air pollution Heat stress is caused by high temperature and high humidity. Wind chill is the cooling power of moving air. 6. Heat stress and wind chill What controls the diurnal variation? Reading: P81-P82 Reading: P84-P85 Reading: P86-P90 Reading: P91-P94 7. Temperature Scale Reading: P89-P90 T=t+273

Chapter 4 1. Phase change and latent heat 2. Equation of state, gas law of dry air 3. Measuring water vapor in the air Water vapor pressure Mixing ratio, r Moist virtual effect Virtual temperature 4. Saturation Saturated water vapor pressure, E=E(T) Reading: P98-P102 Reading: P103 Reading: P104-P105

5. Relative humidity, h 6. Dew-point 9. First law of thermodynamics in the atmosphere The change in internal energy of a system is equal to the heat added to the system minus the work done by the system. 7. Internal energy U Energy associated with the random, disordered motion of molecules. U=U(T) 10. Dry adiabatic process Lifting mechanisms 11. Adiabatic lapse rate Lapse rate of ambient environment 12. Lifting condensation level (LCL) 8. Hydrostatic balance: the balance between upward pressure gradient force and downward gravitational force. Reading: P106-P108 Reading: P109-P111 Reading: P112-P116